JP2011044090A - Image processing device and method, and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a magnified image having a sense of a resolution without causing an unnatural change of luminance in the vicinity of an edge. <P>SOLUTION: An input image (Din) is magnified to output a first magnified image (D2A)(2A), and a high-frequency component image (D1) of the input image (Din) is magnified to output a second magnified image (D2B)(2B). A high-frequency component of the second magnified image (D2B) is extracted to output a first intermediate image (D32A)(32A), and a second intermediate image (D32B) obtained by performing nonlinear processing on the second magnified image (D2B) is outputted (30). The device includes at least one of a first frequency component image correction means (33A) which outputs a third intermediate image (D33A) based on the second magnified image (D2B) and the first intermediate image (D32A), and a second high-frequency component image correction means (33B) which outputs a fourth intermediate image (D33B) based on the second magnified image (D2B) and the second intermediate image (D32B). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image processing apparatus and method for enlarging a digitized image, and an image display apparatus and method, and generates a high frequency component when enlarging an image, thereby providing a high resolution feeling. An enlarged image is obtained.

  In general, when the number of pixels of the output image is larger than the number of pixels of the input image, the image processing apparatus must enlarge the image. In a conventional image processing apparatus, an image is enlarged by weighting and adding pixel values of pixels in the vicinity of the pixel of interest.

  For example, in the image processing apparatus described in Patent Document 1, five adjacent pixel data in the main scanning direction output from each shift register are multiplied by a predetermined weighting constant, and the multiplication result in each pixel data is obtained. An arithmetic circuit for adding is provided, and when image data enlargement processing is performed, the arithmetic result in the arithmetic circuit is selected and output by the selector as pixel data at the center of these pixel data.

JP-A-6-31346 (FIG. 1)

  Weighting and adding pixel values of pixels in the vicinity of the target pixel is a low-pass filter process that passes only the low-frequency component of the input image. Therefore, the above-described conventional technique has a problem that the resolution of the enlarged image is lost because a high-frequency component cannot be sufficiently applied to the enlarged image.

The present invention has been made to solve the above-described problems, and the image processing apparatus of the present invention includes:
In an image processing apparatus for enlarging an input image,
First image enlarging means for enlarging the input image and outputting a first enlarged image;
First high frequency component image generation means for extracting a high frequency component of the input image and generating a first high frequency component image;
Second image enlarging means for enlarging the first high frequency component image and outputting a second enlarged image;
High-frequency component image processing means for receiving the second enlarged image and outputting a second high-frequency component image;
In the image processing apparatus having the first enlarged image and the first addition means for adding the second high-frequency component image,
The high frequency component image processing means includes
First correction component generation means including second high frequency component image generation means for extracting a high frequency component of the second enlarged image and outputting a first intermediate image;
Second correction component generation means including nonlinear processing image generation means for outputting a second intermediate image obtained by performing processing including nonlinear processing on the second enlarged image;
A second addition means for adding the output of the first correction component generation means and the output of the second correction component generation means;
The result of the addition in the second addition means is used as the output of the high frequency component image processing means,
The first correction component generation means further includes first high-frequency component image correction means for receiving the second enlarged image and the first intermediate image and outputting a third intermediate image,
The third intermediate image is used as an output of the first correction component generation means.

  According to the present invention, a high-frequency component can be sufficiently given without causing an unnatural change in luminance near the edge of the enlarged image with respect to the enlarged image, and an enlarged image with a sense of resolution can be obtained. it can.

It is a block diagram which shows the structure of the image processing apparatus of Embodiment 1 of this invention. FIG. 2 is a block diagram illustrating a configuration example of an image display device using the image processing device according to the first embodiment. It is a block diagram which shows the structure of the image processing apparatus of FIG. 1 in detail. (A)-(d) is a pixel arrangement | positioning figure which shows operation | movement of the image expansion means 2A. It is a block diagram which shows the structural example of 2 A of image expansion means. It is a block diagram which shows the structural example of the image expansion means 2B. It is a block diagram which shows the structural example of the horizontal direction nonlinear processing means 31h. It is a block diagram which shows the structural example of the vertical direction nonlinear processing means 31v. It is a block diagram which shows the structural example of 33 A of high frequency component image correction means. (A)-(d) is a figure which shows the pixel arrangement | positioning in enlarged image D2Bh, D2Bv, horizontal direction intermediate image D32Ah, and vertical direction intermediate image D32Av. It is a block diagram which shows the structural example of the high frequency component image correction means 33B. (A)-(d) is a figure showing the pixel arrangement | positioning in enlarged image D2Bh, D2Bv, horizontal direction intermediate image D32Bh, and vertical direction intermediate image D32Bv. (A)-(d) is a figure which shows the frequency spectrum and frequency response for demonstrating the process of obtaining enlarged image D2A. (A)-(f) is a figure which shows the frequency spectrum and frequency response for demonstrating the process of obtaining intermediate | middle image D32A. (A)-(c) is a figure which shows the frequency spectrum and frequency response for demonstrating the process of obtaining intermediate image D32B. (A)-(e) is a figure which shows the signal intensity | strength obtained when a step edge signal and a step edge signal are sampled with a different sampling frequency, and the signal strength of the high frequency component. (A)-(f) is a figure which shows the signal strength for demonstrating operation | movement of the nonlinear processing means 31 and the high frequency component image generation means 32B. (A)-(d) is a figure which shows the signal strength for demonstrating the effect which adds intermediate image D32A, D32B. (A)-(i) is a figure which shows the signal strength for demonstrating the effect of the high frequency component image correction means 33B. (A)-(i) is explanatory drawing of the effect of the high frequency component image correction means 33A. It is explanatory drawing of the frequency spectrum of the expansion image Dout. (A)-(e) is a figure which shows the signal intensity | strength obtained when a step edge signal and a step edge signal are sampled with a different sampling frequency, and the signal strength of the high frequency component. (A)-(f) is a figure which shows the strength of the signal for demonstrating operation | movement of the nonlinear processing means 31 and the high frequency component image generation means 32B. It is a block diagram which shows the structural example of the image processing apparatus of Embodiment 2 of this invention. 10 is a flowchart illustrating an image processing method according to Embodiment 2. FIG. It is a flowchart which shows high frequency component image generation step ST1. It is a flowchart which shows image expansion step ST2B. It is a flowchart which shows high frequency component image processing step ST3. It is a flowchart which shows horizontal direction nonlinear process step ST31h. It is a flowchart which shows vertical direction nonlinear processing step ST31v. It is a flowchart which shows high frequency component image correction step ST33A. It is a flowchart which shows high frequency component image correction step ST33B. FIG. 6 is a block diagram illustrating a modification of the image processing apparatus according to the first embodiment. FIG. 10 is a flowchart showing a modification of the image processing method according to the second embodiment.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration of an image processing apparatus according to Embodiment 1 of the present invention, and can be used as a part of the image display apparatus shown in FIG. 2, for example. Here, the image display apparatus shown in FIG. 2 includes an image processing apparatus U1 including the image processing apparatus shown in FIG. 1 and a display unit 9, and an image DU1 obtained as an output for the image DORG in the image processing apparatus U1. It is displayed on the display unit 9.

The image processing apparatus according to Embodiment 1 includes an image enlarging means 2A, a high frequency component image generating means 1, an image enlarging means 2B, a high frequency component image processing means 3, and an adding means 4.
The image enlarging means 2A enlarges the input image Din and generates an enlarged image D2A.
The high frequency component image generation means 1 extracts only the high frequency component of the input image Din and generates a high frequency component image D1.

The image enlarging means 2B enlarges the high frequency component image D1 output from the high frequency component image generating means 1 to generate an enlarged image (high frequency component enlarged image) D2B.
The high frequency component image processing means 3 performs a process described later on the enlarged image D2B output from the image enlargement means 2B, and generates a high frequency component image (high frequency component processed image) D3.

  The adding means 4 adds the high frequency component image D3 output from the high frequency component image processing means 3 to the enlarged image D2A output from the image enlarging means 2A, and the result is the final enlarged image, that is, the output Output as an image Dout. The output of the adding means 4 is supplied as, for example, an image DU1 to the display unit 9 of the image display device shown in FIG.

  In this specification, it is described that processing such as enlargement, high-frequency component generation, and high-frequency component processing is performed on an “image”. Specifically, it is performed on digital data representing an image. Is called. In addition, the description of “image” may specifically mean “image data”.

  Detailed operations of the image enlarging unit 2A, the high frequency component image generating unit 1, the image enlarging unit 2B, and the high frequency component image processing unit 3 will be described later. The frequency component of the high frequency component image D3 is obtained by the enlarged image D2A. The frequency component is higher than the frequency component. Therefore, by adding the high frequency component image D3 to the enlarged image D2A in the adding means 4, an enlarged image Dout containing a large amount of high frequency components can be obtained.

  FIG. 3 is a diagram showing details of the configuration of the image processing apparatus according to the first embodiment shown in FIG. Hereinafter, the configuration of the image enlarging means 2A, the high frequency component image generating means 1, the image enlarging means 2B, and the high frequency component image processing means 3 will be described in more detail with reference to FIG.

  The image enlarging means 2A is for enlarging an image in at least one of the horizontal direction and the vertical direction. For example, the image enlarging means 2A enlarges the image in the horizontal direction and the vertical direction at the same magnification, but instead has different magnifications in the horizontal direction and the vertical direction. It is also possible to perform enlargement with. Further, enlargement may be performed only in one of the horizontal direction and the vertical direction. For example, when the display screen is horizontally long with respect to the input image, enlargement may be performed only in the horizontal direction.

  The high frequency component image generation means 1 extracts a high frequency component (a component higher than the predetermined frequency Fb) of the input image Din and generates a high frequency component image D1. A horizontal high-frequency component image generating unit 1h and a vertical high-frequency component image generating unit 1v that generate a frequency component image D1h and a vertical high-frequency component image D1v are provided. The high frequency component image D1 is composed of the horizontal high frequency component image D1h and the vertical high frequency component image D1v.

  The image enlarging means 2B includes an image enlarging means 2Bh that generates an enlarged image D2Bh obtained by enlarging the horizontal high-frequency component image D1h, and an image enlarging means 2Bv that generates an enlarged image D2Bv obtained by enlarging the vertical high-frequency component image D1v. The enlarged image D2B is composed of the enlarged image D2Bh and the enlarged image D2Bv.

  When the image enlarging means 2A enlarges in both the horizontal and vertical directions, the image enlarging means 2Bh enlarges the horizontal high frequency component image D1h in both the horizontal and vertical directions, and the image enlarging means 2Bv The direction high frequency component image D1v is enlarged in both the horizontal direction and the vertical direction. The enlargement of the horizontal high-frequency component image D1h and the vertical high-frequency component image D1v by the image enlargement means 2Bh and 2Bv is performed at the same magnification for each of the enlargement by the image enlargement means 2A and the horizontal and vertical directions.

  The high frequency component image processing means 3 includes a first correction component generation means 3A, a first correction component generation means 3B, and an addition means 34. The first correction component generation unit 3A includes a high frequency component image generation unit 32A and a high frequency component image correction unit 33A, and the second correction component generation unit 3B includes a nonlinear processing image generation unit 30 and a high frequency component. Component image correcting means 33B.

  The high frequency component image generating means 32A extracts the high frequency component (component higher than the predetermined frequency Fd) of the enlarged image D2B and outputs an intermediate image (high frequency component image) D32A, which is included in the enlarged image D2Bh. A horizontal high-frequency component image generating unit 32Ah that generates a horizontal intermediate image D32Ah that extracts only the high-frequency component in the horizontal direction, and a vertical intermediate image D32Av that extracts only the high-frequency component in the vertical direction of the enlarged image D2Bv. A vertical high-frequency component image generating unit 32Av is generated, and an intermediate image D32A composed of a horizontal intermediate image D32Ah and a vertical intermediate image D32Av is output from the high-frequency component image generating unit 32A.

The nonlinear processed image generating means (edge sharpened image generating means) 30 outputs an intermediate image (edge sharpened image) D32B obtained by performing processing including nonlinear processing on the enlarged image D2B. And high frequency component image generation means 32B.
The nonlinear processing means 31 generates a nonlinear processed image D31 obtained by performing nonlinear processing for edge sharpening, which will be described later, on the enlarged image D2B.
The high frequency component image generating unit 32B outputs an intermediate image D32B obtained by extracting only the high frequency component (component higher than the predetermined frequency Ff) included in the nonlinear processed image D31.

  The non-linear processing means 31 generates a non-linear processed image D31h that is non-linearly processed with respect to the enlarged image D2Bh, and a vertical non-linear process that generates a non-linearly processed image D31v that is non-linearly processed with respect to the enlarged image D2Bv. Means 31v is provided, and the nonlinear processed image D31 is composed of a nonlinear processed image D31h and a nonlinear processed image D31v.

  The high frequency component image generation unit 32B extracts the high frequency component from the nonlinear processed image D31h, extracts the high frequency component from the horizontal processed high frequency component image generation unit 32Bh that generates the horizontal intermediate image D32Bh, and the nonlinear processed image D31v, A vertical high frequency component image generating means 32Bv for generating a vertical intermediate image D32Bv is provided, and the intermediate image D32B is composed of a horizontal intermediate image D32Bh and a vertical intermediate image D32Bv.

The high frequency component image correcting unit 33A receives the enlarged image D2B and the intermediate image D32A and outputs a third intermediate image (corrected image) D33A.
The high frequency component image correcting unit 33B receives the enlarged image D2B and the intermediate image D32B, and outputs an intermediate image (corrected image) D33B.
The adding means 34 adds the intermediate image D33A and the intermediate image D33B, and outputs the addition result as a high frequency component image D3.

  Hereinafter, the operation of each component will be described in more detail by taking as an example the case of generating an enlarged image Dout in which the input image Din is doubled in both the horizontal direction and the vertical direction. Through this description, the operation and effect of the present invention will become clearer.

  First, the operation of the image enlarging means 2A will be described. The image enlarging means 2A generates an enlarged image D2A obtained by enlarging the input image Din twice in both the horizontal direction and the vertical direction. FIGS. 4A to 4D are diagrams schematically showing an example of a procedure for generating the enlarged image D2A in the image enlarging unit 2A, and FIG. 5 is a diagram showing an example of the image enlarging unit 2A.

  The image enlarging unit 2A includes a zero insertion unit 21A and a low frequency component passing unit 22A. Hereinafter, the operations of the zero insertion means 21A and the low frequency component passing means 22A will be described with reference to FIGS. 4A shows the input image Din (particularly, the arrangement of pixels constituting a part of the image), FIG. 4B shows the zero insertion image D21A generated by the zero insertion means 21A, and FIG. FIG. 4D shows the filter coefficient used when the enlarged image D2A is generated by the low frequency component passing means 22A, and FIG. 4D shows the enlarged image D2A generated by the low frequency component passing means 22A. 4A, 4B, and 4D show horizontal coordinates X and vertical coordinates Y corresponding to the positions of the pixels.

In the zero insertion means 21A, one pixel per pixel (in the input image Din) having a pixel value 0 with respect to the input image Din (one between two adjacent pixels) in the horizontal direction, and one in the vertical direction A zero-inserted image D21A is generated in which one (one between two adjacent lines) is inserted per line (of the input image Din).
If “PXY” represents the pixel value of the pixel at the coordinates (X, Y) of the input image Din, and “P′XY” represents the pixel value of the pixel at the coordinates (X, Y) of the zero-inserted image D21A, then zero. The pixel value represented by P ′ (2X−1) (2Y−1) in the insertion image D21A is equal to PXY in the input image Din, and P ′ (2X−1) (2Y), P ′ (2X) (2Y). ), P ′ (2X) (2Y−1), the pixel value is equal to zero.

The low frequency component passing means 22A performs the filter operation represented by the filter coefficient shown in FIG. 4C on the zero insertion image D21A, thereby generating the enlarged image D2A shown in FIG. .
For example, the pixel value QXY of the pixel at coordinates (X, Y) included in the enlarged image D2A is calculated as in the following equation (1).

QXY = (4/16) ×
{P ′ (X−1) (Y−1) + 2P′X (Y−1) + P ′ (X + 1) (Y−1)
+ 2P ′ (X−1) Y + 4P′XY + 2P ′ (X + 1) Y
+ P ′ (X−1) (Y + 1) + 2P′X (Y + 1) + P ′ (X + 1) (Y + 1)}
... (1)

  Since the filter coefficient represented in FIG. 4C represents a low-pass filter, the processing in the low-frequency component passing unit 22A represented by the equation (1) is performed by the low-frequency component (predetermined frequency Fa) of the zero insertion image D21A. This corresponds to taking out the following components).

  In the formula (1), P ′ (X−1) (Y−1), 2P′X (Y−1), P ′ (X + 1) (Y−1), 2P ′ (X−1) Y, Some of P′XY, 2P ′ (X + 1) Y, P ′ (X−1) (Y + 1), P′X (Y + 1), P ′ (X + 1) (Y + 1) have a value of 0, Otherwise, the pixel value itself of the input image Din is used. Therefore, the process of Expression (1) or the enlargement process is the same as the process of appropriately weighting and adding pixel values in the vicinity of the pixel of interest in the input image Din.

Next, operations of the horizontal direction high frequency component image generating unit 1h and the vertical direction high frequency component image generating unit 1v will be described.
The horizontal high-frequency component image generating means 1h applies a high-pass filter using, for example, a predetermined number of pixels in the vicinity of each pixel of the input image Din and the horizontal direction to the input image Din, and applies the horizontal high-frequency component image. D1h is generated.
On the other hand, the vertical high frequency component image generation unit 1v applies a high pass filter to the input image Din by applying a high pass filter using, for example, a predetermined number of pixels in the vicinity of each pixel of the input image Din and the vertical direction. A component image D1v is generated.

  Applying a high-pass filter corresponds to extracting a high-frequency component, and the horizontal high-frequency component image D1h includes a high-frequency component in the horizontal direction of the input image Din (consisting of a component higher than a predetermined horizontal frequency). The vertical high frequency component image D1v includes a high frequency component in the vertical direction of the input image Din (consisting of a component higher than a predetermined vertical frequency).

As a process for applying a high-pass filter performed by the horizontal high-frequency component image generating means 1h, for example, a low-frequency component in the horizontal direction (or a predetermined line aligned in the horizontal direction with respect to each pixel) from the input signal to the means 1h. By subtracting a simple average value or a weighted average value of pixel values in a local region composed of a number of pixels, it is possible to perform processing for extracting a high frequency component.
Similarly, as a process of applying a high-pass filter performed by the vertical high frequency component image generating means 1v, for example, from the input signal to the means 1v, the vertical low frequency component (or the vertical direction for each pixel). By subtracting a simple average value or a weighted average value of pixel values in a local region composed of a predetermined number of aligned pixels, it is possible to perform processing for extracting a high frequency component.

  Next, the operation of the image enlarging means 2Bh and 2Bv will be described. The image enlarging means 2Bh generates an enlarged image D2Bh obtained by enlarging the horizontal high-frequency component image D1h twice in both the horizontal and vertical directions, and the image enlarging means 2Bv converts the vertical high-frequency component image D1v in both the horizontal and vertical directions. An enlarged image D2Bv enlarged twice is generated.

Each of the image enlarging means 2Bh and the image enlarging means 2Bv can be configured in the same manner as the image enlarging means 2A described with reference to FIG. Therefore, the image enlarging means 2B composed of the image enlarging means 2Bh and the image enlarging means 2Bv can be shown as shown in FIG.
The input of the image enlarging means 2Bh is a horizontal high frequency component image D1h, and the output is an enlarged image D2Bh. The input of the image enlarging means 2Bv is a vertical high frequency component image D1v, and the output is an enlarged image D2Bv.

The image enlarging unit 2Bh includes a zero insertion unit 21Bh and a low frequency component passing unit 22Bh, and the image enlarging unit 2Bv includes a zero insertion unit 21Bv and a low frequency component passing unit 22Bv.
Each of the zero insertion means 21Bh and the zero insertion means 21Bv is the same as the zero insertion means 21A of FIG. 5, and each of the low frequency component passage means 22Bh and the low frequency component passage means 22Bv is a low frequency component of FIG. This is the same as the passing means 22A.

The zero insertion image D21B as the output of the zero insertion means 21B is composed of the zero insertion image D21Bh output from the zero insertion means 21Bh and the zero insertion image D21Bv output from the zero insertion means 21Bv.
The enlarged image D2B as the output of the low frequency component passing means 22B is composed of the enlarged image D2Bh outputted from the low frequency component passing means 22Bh and the enlarged image D2Bv outputted from the low frequency component passing means 22Bv. The output of the low frequency component passing means 22B is obtained by extracting the low frequency component (component below Fc) of the zero insertion image D21B.

Next, the operation of the high frequency component image generating means 32A will be described.
The horizontal high-frequency component image generating means 32Ah applies a horizontal high-pass filter to the enlarged image D2Bh to extract only high-frequency components composed of components of a predetermined horizontal frequency or more, and generates a horizontal intermediate image D32Ah.
On the other hand, the vertical high-frequency component image generation means 32Av applies a high-pass filter in the vertical direction to the enlarged image D2Bv to extract only the high-frequency components composed of components having a frequency equal to or higher than a predetermined vertical frequency, and generates a vertical intermediate image D32Av. To do.
Then, an intermediate image D32A composed of the horizontal intermediate image D32Ah and the vertical intermediate image D32Av is output from the high frequency component image generating means 32A.

The high-pass filter processing performed by the horizontal high-frequency component image generation unit 32Ah is performed in the same manner as the horizontal high-frequency component image generation unit 1h, and the high-pass filter performed by the vertical high-frequency component image generation unit 32Av. The processing to be applied can be performed in the same manner as the processing in the vertical high frequency component image generation means 1v.
That is, the processing for applying the high-pass filter performed by the horizontal high-frequency component image generation means 32Ah is, for example, from the input signal to the means 32Ah in the horizontal direction, as in the processing by the horizontal high-frequency component image generation means 1h. To extract a high frequency component by subtracting the low frequency component of (or a simple average value or a weighted average value of pixel values in a local region composed of a predetermined number of pixels aligned in the horizontal direction with respect to each pixel). it can.

  Similarly, as a process for applying a high-pass filter performed by the vertical high frequency component image generating means 32Av, for example, from the input signal to the means 32Av, a low frequency component in the vertical direction (or in a direction perpendicular to each pixel). By subtracting a simple average value or a weighted average value of pixel values in a local region composed of a predetermined number of aligned pixels, it is possible to perform processing for extracting a high frequency component.

  Next, the operation of the nonlinear processing means 31 will be described. The nonlinear processing means 31 includes a horizontal nonlinear processing means 31h and a vertical nonlinear processing 31v. The horizontal non-linear processing means 31h and the vertical non-linear processing means 31v are configured in the same manner. However, the horizontal non-linear processing means 31h performs horizontal processing, and the vertical non-linear processing means 31v performs vertical processing.

  FIG. 7 is a diagram showing the internal configuration of the horizontal nonlinear processing means 31h. The illustrated horizontal non-linear processing means 31h includes a zero-cross determining means 311h and a signal amplifying means 312h.

The zero cross determination means 311h confirms the change in the pixel value in the inputted enlarged image D2Bh along the horizontal direction. Then, a point where the pixel value changes from a positive value to a negative value or from a negative value to a positive value is regarded as a zero cross point, and pixels before and after the zero cross point by the signal D311h (in the illustrated example, each of the pixels immediately before and after 1 pixel) is transmitted to the signal amplifying means 312h.
In the horizontal non-linear processing means 31h, pixels located on the left and right of the zero cross point are recognized as pixels before and after the zero cross point.

The horizontal direction signal amplifying unit 312h amplifies the pixel value of the third enlarged image D2Bh with an amplification factor determined according to the determination result of the horizontal direction zero cross determining unit 311h. Specifically, the signal amplifying unit 312h specifies pixels before and after the zero cross point (pixels existing in a predetermined region including the zero cross point) based on the signal D311h, and regarding the pixels before and after the zero cross point. Only the pixel value is amplified (the absolute value is increased) to generate a nonlinear processed image D31h. That is, the amplification factor for the pixel values of the pixels before and after the zero cross point is set to a value larger than 1, and the amplification factors for the pixel values of the other pixels are set to 1.
By such processing, edge sharpening including stepwise changes in signal values of pixels arranged in the horizontal direction is performed.

  FIG. 8 is a diagram showing the internal configuration of the vertical nonlinear processing means 31v. The illustrated vertical non-linear processing means 31v includes a zero-cross determining means 311v and a signal amplifying means 312v.

The zero-cross determining unit 311v confirms the change of the pixel value in the input enlarged image D2Bv along the vertical direction. A point where the pixel value changes from a positive value to a negative value or from a negative value to a positive value is regarded as a zero cross point, and pixels before and after the zero cross point by the signal D311v (in the illustrated example, the respective pixels immediately before and after 1 pixel) is transmitted to the signal amplifying means 312v.
The vertical nonlinear processing means 31v recognizes pixels located above and below the zero cross point as pixels before and after the zero cross point.

The vertical direction signal amplifying unit 312v amplifies the pixel value of the fourth enlarged image D2Bv with an amplification factor determined according to the determination result of the vertical direction zero cross determining unit 311v. Specifically, the signal amplifying unit 312v identifies pixels (pixels existing within a predetermined region including the zero cross point) before and after the zero cross point based on the signal D311v, and detects the pixels before and after the zero cross point. Only the pixel value is amplified (the absolute value is increased) to generate a nonlinear processed image D31v. That is, the amplification factor for the pixel values of the pixels before and after the zero cross point is set to a value larger than 1, and the amplification factors for the pixel values of the other pixels are set to 1.
By such processing, edge sharpening including step-like changes in signal values of pixels arranged in the vertical direction is performed.

  In the example shown in the figure, the pixel value is amplified only for each one pixel immediately before and after the zero cross point, but a predetermined number of pixels before and after the zero cross point, in other words, the zero cross point is determined. It is also possible to amplify the pixel value for a pixel that exists in a predetermined region. Alternatively, the size of the “predetermined area” (the number of pixels included in the predetermined area) may be changed according to the image enlargement ratio in the image enlargement unit 2B (set to an appropriate value for the enlargement ratio). good.

Next, the operation of the high frequency component image generating means 32B will be described.
The horizontal high-frequency component image generating means 32Bh applies a high-pass filter in the horizontal direction to the non-linearly processed image D31h to extract only high-frequency components composed of components having a frequency equal to or higher than a predetermined horizontal frequency, and generates a horizontal intermediate image D32Bh. . On the other hand, the vertical high-frequency component image generation means 32Bv applies a high-pass filter in the vertical direction to the nonlinear processed image D31v to extract only the high-frequency component composed of components having a frequency equal to or higher than a predetermined vertical frequency, and outputs the vertical intermediate image D32Bv. Generate. An intermediate image D32B composed of the horizontal intermediate image D32Bh and the vertical intermediate image D32Bv generated in this way is output from the high frequency component image generating means 32B.

The high-pass filter processing performed by the horizontal high-frequency component image generation unit 32Bh is performed in the same manner as the processing by the horizontal high-frequency component image generation unit 1h, and the high-pass filter performed by the vertical high-frequency component image generation unit 32Bv. The processing to be applied can be performed in the same manner as the processing in the vertical high frequency component image generation means 1v.
That is, as a process for applying a high-pass filter performed by the horizontal high-frequency component image generating means 32Bh, for example, the horizontal low-frequency component (or the horizontal alignment for each pixel) from the input signal to the means 32Bh. By subtracting the simple average value or the weighted average value of the pixel values in the local area composed of the predetermined number of pixels, it is possible to perform processing for extracting the high frequency component.

  Similarly, as a process for applying a high-pass filter performed by the vertical high frequency component image generating means 32Bv, for example, from the input signal to the means 32Bv, the vertical low frequency component (or the vertical direction for each pixel). By subtracting a simple average value or a weighted average value of pixel values in a local region composed of a predetermined number of aligned pixels, it is possible to perform processing for extracting a high frequency component.

Next, the detailed operation of the high frequency component image correcting unit 33A will be described.
FIG. 9 is a diagram showing the configuration of the high frequency component image correcting unit 33A. The high frequency component image correcting unit 33A shown in FIG.
A code comparison unit 33A1 and a pixel value changing unit 33A2 are provided.

  The sign comparison unit 33A1 compares the signs of the pixel values of the enlarged image D2B and the intermediate image D32A, and outputs the result as a signal D33A1. Here, the enlarged image D2B is made up of the enlarged image D2Bh and the enlarged image D2Bv, and the intermediate image D32A is made up of the horizontal intermediate image D32Ah and the vertical intermediate image D32Av. This is performed for the pixels, and for each pixel of the enlarged image D2Bv and the vertical intermediate image D32Av. That is, for the enlarged image D2Bh and the horizontal intermediate image D32Ah, the horizontal direction code comparison means 33A1h compares the sign of each pixel, and the comparison result is output as a signal D33A1h. The enlarged image D2Bv and the vertical intermediate image D32Av Is compared in the vertical direction code comparison means 33A1v, and the comparison result is output as a signal D33A1v. Then, the signal D33A1h and the signal D33A1v are output as the signal D33A1.

  10A to 10D are diagrams showing the arrangement of pixels. FIG. 10A shows the enlarged image D2Bh, FIG. 10B shows the enlarged image D2Bv, and FIG. 10C shows the horizontal direction. FIG. 10D shows the intermediate image D32Ah, and FIG. 10D shows the vertical intermediate image D32Av. 10A to 10D show horizontal coordinates, vertical coordinates, and coordinate values according to the horizontal and vertical directions of the image. For the enlarged image D2Bh, the pixel value of the pixel at the position of the horizontal coordinate x and the vertical coordinate y is represented by the symbol D2Bh (xy). For the enlarged image D2Bv, the horizontal coordinate x and the vertical coordinate y The pixel value of the pixel at the position is represented by the symbol D2Bv (xy). For the horizontal intermediate image D32Ah, the pixel value of the pixel at the position of the horizontal coordinate x and the vertical coordinate y is the symbol D32Ah (xy). In the vertical intermediate image D32Av, the pixel value of the pixel at the position of the horizontal coordinate x and the vertical coordinate y is represented by the symbol D32Av (xy).

  The operations of the horizontal direction code comparison unit 33A1h and the vertical direction code comparison unit 33A1v will be described in more detail.

  The horizontal direction code comparison unit 33A1h compares the signs of pixel values at the same coordinates in the enlarged image D2Bh and the horizontal direction intermediate image D32Ah. That is, comparison of codes for pixel values at the same coordinates, such as comparison of the sign of pixel value D2Bh (11) and pixel value D32Ah (11), comparison of sign of pixel value D2Bh (12) and pixel value D32Ah (12). Is performed, and the code value of each pixel is checked for coincidence and non-coincidence, and the result is output as a signal D33A1h. Further, the vertical direction code comparison unit 33A1v compares the signs of the pixel values at the same coordinates of the enlarged image D2Bv and the vertical direction intermediate image D32Av. That is, comparison of codes for pixel values at the same coordinates, such as comparison of the sign of pixel value D2Bv (11) and pixel value D32Av (11), comparison of sign of pixel value D2Bv (12) and pixel value D32Av (12). Is performed, and the code value of each pixel is checked for coincidence and non-coincidence, and the result is output as signal D33A1v.

  The above is the operation of the sign comparison means 33A1, and the high frequency component image correction means 33A then causes the pixel value changing means 33A2 to display the pixels of the intermediate image D32A based on the signal D33A1 (indicating the comparison result by the sign comparison means 33A1). An intermediate image D33A with a changed value is generated. The pixel value changing unit 33A2 sets the pixel value of each pixel value of the intermediate image D32A that is different from the sign of each pixel value of the enlarged image D2B by the signal D33A1 to zero, and sets the pixel values of the other pixels. The pixel value is output without being changed. This process is performed for each of the horizontal intermediate image D32Ah and the vertical intermediate image D32Av.

That is, for the horizontal intermediate image D32Ah, the horizontal pixel value changing unit 33A2h changes the pixel value of the same pixel in the horizontal intermediate image D32Ah based on the comparison result for each pixel in the horizontal direction code comparing unit 33A1h. . Specifically, in the horizontal direction pixel value changing unit 33A2h, an image D33Ah in which the pixel value of a pixel having a different sign from that of the enlarged image D2Bh is generated based on the signal D33A1h, and the vertical direction intermediate image D32Av is The pixel value changing unit 33A2v changes the pixel value of the same pixel in the vertical intermediate image D32Av based on the comparison result for each pixel in the vertical direction code comparison unit 33A1v. Specifically, in the vertical direction pixel value changing unit 33A2v, based on the signal D33A1v, a vertical direction intermediate image D33Av in which the pixel value of a pixel having a sign different from that of the enlarged image D2Bv is zero is generated.
The pixel value changing unit 33A2 outputs an intermediate image D33A including a horizontal intermediate image D33Ah and a vertical intermediate image D33Av.
Then, the intermediate image D33A is output from the high frequency component image correcting means 33A.

Next, a detailed operation of the high frequency component image correcting unit 33B will be described.
FIG. 11 is a diagram showing the configuration of the high frequency component image correcting unit 33B. The high frequency component image correcting unit 33B shown in the figure includes a code comparison unit 33B1 and a pixel value changing unit 33B2.

  The sign comparison unit 33B1 compares the signs of the pixel values of the enlarged image D2B and the intermediate image D32B, and outputs the result as a signal D33B1. Here, the enlarged image D2B is made up of the enlarged image D2Bh and the enlarged image D2Bv, and the intermediate image D32B is made up of the horizontal intermediate image D32Bh and the horizontal intermediate image D32Bv. This is performed for the pixels, and for each pixel of the enlarged image D2Bv and the vertical intermediate image D32Bv. That is, for the enlarged image D2Bh and the horizontal intermediate image D32Bh, the sign of each pixel is compared in the horizontal code comparison means 33B1h, and the comparison result is output as a signal D33B1h, and the enlarged image D2Bv and the vertical intermediate image D32Bv Is compared with the sign of each pixel in the vertical direction code comparison means 33B1v, and the result of the comparison is output as a signal D33B1v. Then, the signal D33B1h and the signal D33B1v are output as the signal D33B1.

  12 (a) to 12 (d) are diagrams showing the arrangement of pixels. FIG. 12 (a) shows the enlarged image D2Bh, FIG. 12 (b) shows the enlarged image D2Bv, and FIG. 12 (c) shows the horizontal direction. The intermediate image D32Bh is shown, and FIG. 12D shows the vertical intermediate image D32Bv. 12A to 12D show horizontal coordinates, vertical coordinates, and coordinate values in accordance with the horizontal and vertical directions of the image. For the enlarged image D2Bh, the pixel value of the pixel at the position of the horizontal coordinate x and the vertical coordinate y is represented by the symbol D2Bh (xy). For the enlarged image D2Bv, the horizontal coordinate x and the vertical coordinate y The pixel value of the pixel at the position is represented by the symbol D2Bv (xy). For the horizontal intermediate image D32Bh, the pixel value of the pixel at the position of the horizontal coordinate x and the vertical coordinate y is the symbol D32Bh (xy). In the vertical direction intermediate image D32Bv, the pixel value of the pixel at the position of the horizontal coordinate x and the vertical coordinate y is represented by the symbol D32Bv (xy).

  The operations of the horizontal direction code comparison unit 33B1h and the vertical direction code comparison unit 33B1v will be described in more detail.

  The horizontal direction code comparison unit 33B1h compares the signs of pixel values at the same coordinates in the enlarged image D2Bh and the horizontal direction intermediate image D32Bh. That is, comparison of codes for pixel values at the same coordinates, such as comparison of the sign of pixel value D2Bh (11) and pixel value D32Bh (11), comparison of sign of pixel value D2Bh (12) and pixel value D32Bh (12). And confirms whether the pixel values of each pixel match or not, and outputs the result as a signal D33B1h. Further, the vertical direction code comparison unit 33B1v compares the signs of the pixel values at the same coordinates of the enlarged image D2Bv and the vertical direction intermediate image D32Bv. That is, the comparison of the sign for the pixel value of the same coordinate, such as the comparison of the sign of the pixel value D2Bv (11) and the pixel value D32Bv (11), the comparison of the sign of the pixel value D2Bv (12) and the pixel value D32Bv (12). And confirms whether the pixel values of each pixel match or not, and outputs the result as a signal D33B1v.

  The above is the operation of the sign comparison unit 33B1, and the high frequency component image correction unit 33B then uses the pixel value changing unit 33B2 to display the pixels of the intermediate image D32B based on the signal D33B1 (indicating the comparison result by the sign comparison unit 33B1). An image D33B whose value has been changed is generated. The pixel value changing unit 33B2 zeros the pixel value of the pixel value of the intermediate image D32B that is indicated by the signal D33B1 to have a sign different from that of the pixel value of the enlarged image D2B. The pixel value is output without being changed. This process is performed for each of the horizontal intermediate image D32Bh and the vertical intermediate image D32Bv.

That is, for the horizontal intermediate image D32Bh, the horizontal pixel value changing unit 33B2h changes the pixel value of the same pixel in the horizontal intermediate image D32Bh based on the comparison result for each pixel in the horizontal code comparison unit 33B1h. . Specifically, in the horizontal pixel value changing unit 33B2h, based on the signal D33B1h, a horizontal intermediate image D33Bh in which the pixel value of a pixel having a sign different from that of the enlarged image D2Bh is zero is generated, and for the vertical intermediate image D32Bv, The vertical direction pixel value changing unit 33B2v changes the pixel value of the same pixel in the vertical direction intermediate image D32Bv based on the comparison result for each pixel in the vertical direction code comparison unit 33B1v. Specifically, in the vertical direction pixel value changing unit 33B2v, based on the signal D33B1v, a vertical direction intermediate image D33Bv in which the pixel value of a pixel having a sign different from that of the enlarged image D2Bv is zero is generated.
The pixel value changing unit 33B2 outputs an intermediate image D33B composed of a horizontal intermediate image D33Bh and a vertical intermediate image D33Bv.
Then, the intermediate image D33B is output from the high frequency component image correcting unit 33B.

  Next, the operation of the adding means 34 will be described. The adding means 34 outputs the result of adding the intermediate image D33A and the intermediate image D33B as a high frequency component image D3.

  Here, since the intermediate image D33A is composed of the horizontal intermediate image D33Ah and the vertical intermediate image D33Av, and the intermediate image D33B is composed of the horizontal intermediate image D33Bh and the vertical intermediate image D33Bv, the intermediate image D33A and the intermediate image D33B are added together. , Horizontal intermediate image D33Ah, vertical intermediate image D33Av, horizontal intermediate image D33Bh, and vertical intermediate image D33Bv. The addition process here is not limited to simple addition, and may be a process of adding each image with an individual weight.

  Finally, the operation of the adding means 4 will be described. The adding means 4 adds the enlarged image D2A and the high frequency component image D3. Then, an image obtained as a result of adding the enlarged image D2A and the high frequency component image D3 in the adding means 4 is output from the image processing apparatus as a final enlarged image Dout. The addition process here is not limited to simple addition, and may be a process of adding each image with an individual weight.

The operation and effect of the image processing apparatus according to the present invention will be described below.
In the embodiment of the present invention, the intermediate images D32A and D32B are not added as they are, but the high frequency component image D3 is generated and added to the enlarged image D2A. The intermediate images D32A and D32B are not added to the high frequency component image correcting unit 33A. Are added to the enlarged image D2A by adding after correcting at 33B, and hereinafter, the intermediate images D32A and D32B are added as they are to generate the high frequency component image D3. Then, the effect obtained when adding to the enlarged image D2A will be described, and then the effect obtained by adding the intermediate images D33A and D33B instead of the intermediate images D32A and D32B will be described.

  The enlarged image D2A includes a frequency component corresponding to a frequency lower than the Nyquist frequency Fn of the input image Din, and the high frequency component image D3 includes a frequency component corresponding to a frequency equal to or higher than the Nyquist frequency Fn of the input image Din. Therefore, the magnified image Dout generated by adding the magnified image D2A and the high frequency component image D3 has frequency components over all frequency regions that reach the Nyquist frequency after the image is magnified.

  First, it will be described that the enlarged image D2A has a frequency component corresponding to a frequency lower than the Nyquist frequency Fn of the input image Din.

  FIGS. 13A to 13D are diagrams schematically showing the action when the enlarged image D2A is generated from the input image Din. FIG. 13A shows the frequency spectrum of the input image Din. b) shows the frequency spectrum of the zero insertion image D21A, FIG. 13 (c) shows the frequency response of the low-frequency component passing means 22A, and FIG. 13 (d) shows the frequency spectrum of the enlarged image D2A.

  The frequency spectrum of the input image Din will be described. Normally, natural images and the like are input from the input image Din, but the spectral intensities of these images are concentrated around the origin of the frequency space. Therefore, the frequency spectrum of the input image Din can be expressed as shown in FIG. Here, the vertical axis in FIG. 13A represents the spectral intensity, the horizontal axis represents the spatial frequency, and Fn represents the Nyquist frequency of the input image Din.

  Since the normal input image Din is a two-dimensional image, its frequency spectrum is also represented in a two-dimensional frequency space, but its shape is isotropic with the frequency spectrum shown in FIG. It will spread to. Therefore, in order to describe the frequency spectrum, it is only necessary to show the shape of one dimension at a minimum. In the future, unless otherwise specified, the shape of the frequency space will be described by showing only one dimension.

  Next, the frequency spectrum of the zero insertion image D21A will be described. By inserting one pixel per pixel (of the input image Din) and a pixel value of 0 with respect to the input image Din by the zero insertion means 21A, folding around the frequency Fn occurs in the frequency space. As a result, the frequency spectrum of the zero insertion image D21A is as shown in FIG.

  Next, the frequency response of the low frequency component passing means 22A will be described. As described above, since the calculation in the low frequency component passing means 22A is low pass filter processing, the frequency response of the low frequency component passing means 22A becomes lower as the frequency becomes higher as shown in FIG. . In the example shown in the figure, the low frequency component passing means 22A mainly passes the frequency component equal to or lower than the first frequency Fa (= Fn).

  Finally, the frequency spectrum of the enlarged image D2A will be described. An enlarged image D2A is generated by passing the zero insertion image D21A having the frequency spectrum shown in FIG. 13B through the low frequency component passing means 22A having the frequency response shown in FIG. 13C. Accordingly, the frequency spectrum of the enlarged image D2A is obtained by removing the high frequency side region (region having a frequency higher than Fa = Fn) R2AH indicated by hatching from the frequency spectrum of D21A.

  Therefore, the enlarged image D2A mainly has a frequency component corresponding to a frequency lower than the Nyquist frequency Fn of the input image Din.

  Next, it will be described that the high frequency component image D3 mainly has a frequency component corresponding to a frequency equal to or higher than the Nyquist frequency Fn of the input image Din. If correction by the high frequency component image correction means 33A and 33B is not performed, the high frequency component image D3 is obtained by adding the intermediate image D32A and the intermediate image D32B. The intermediate image D32A is particularly Nyquist of the input image Din. The intermediate image D32B has a frequency component corresponding to a frequency higher than the Nyquist frequency Fn of the input image Din, and the high-frequency component image D3 has the frequencies of the intermediate images D32A and D32B. Since the components are added, the input image Din has a frequency component equal to or higher than the Nyquist frequency Fn.

First, the frequency spectrum of the intermediate image D32A will be described.
14 (a) to 14 (f) are diagrams schematically showing the action when the intermediate image D32A is generated, and FIG. 14 (a) shows the frequency response of the high-frequency component image generating means 1 as shown in FIG. b) shows the frequency spectrum of the high frequency component image D1 (or D1h or D1v), and FIG. 14C shows the zero insertion image D21B (or D21Bh or D21Bv) generated by the zero insertion means 21B in the image enlargement means 2B. 14D shows the frequency spectrum of the enlarged image D2B (or D2Bh or D2Bv), FIG. 14E shows the frequency response of the high-frequency component image generation means 32A (or 32Ah or 32Av), and FIG. (F) shows the frequency spectrum of the intermediate image D32A (or D32Ah or D32Av) output from the high frequency component image generating means 32A. It represents the torque.

  First, the frequency response of the high frequency component image generation means 1 and the frequency spectrum of the high frequency component image D1 will be described. Since the high-frequency component image generation means 1 generates the high-frequency component image D1 using a high-pass filter that passes a component of the input image Din that is equal to or higher than the predetermined frequency Fb, the high-frequency component image generation unit 1 generates a high-frequency component image D1 as shown in FIG. The frequency response of the component image generation unit 1 increases as the frequency increases. The input image Din having the frequency spectrum shown in FIG. 13A passes through the high-pass filter having the frequency response shown in FIG. 14A, so that a high frequency component image D1 is obtained. In the illustrated example, the frequency spectrum of the high frequency component image D1 is small in a low frequency region (a region lower than the frequency Fb) as shown in FIG. 14B, and a high frequency region (a region higher than the frequency Fb). It will have a certain level of strength only.

  Next, the frequency spectrum of the zero insertion image D21B in the image enlarging means 2B will be described. In the same manner as described for the zero insertion means 21A of the image enlargement means 2A, the zero insertion means 21B causes folding, and the frequency spectrum of the zero insertion image D21B in the image enlargement means 2B is as shown in FIG. become.

  Next, the frequency spectrum of the enlarged image D2B will be described. When the enlarged image D2B is generated, the frequency spectrum on the high frequency component side of the zero insertion image D21B (for example, a component in a region higher than the predetermined frequency Fc) is removed by the low frequency component passage unit 22B. As shown in FIG. 14D, the frequency spectrum is obtained by removing the high frequency side region (region higher than the frequency Fc) R32AH.

  Finally, the frequency response of the high frequency component image generating means 32A and the frequency spectrum of the intermediate image D32A will be described. Since the high-frequency component image generating means 32A is a high-pass filter that mainly passes components of a predetermined frequency Fd or higher, the frequency response becomes higher as the frequency becomes higher as shown in FIG. The intermediate image D32A is generated by passing the enlarged image D2B having the frequency spectrum shown in FIG. 14D through the high-pass filter having the frequency response shown in FIG. Accordingly, the frequency response of the intermediate image D32A is, as shown in FIG. 14 (f), the lower frequency side region (region lower than the frequency Fd) R32AL is removed from the frequency spectrum of the enlarged image D2B shown in FIG. 14 (d). It will be.

  Accordingly, the intermediate image D32A mainly has a frequency component (frequency component from the frequency Fd to the frequency Fc) corresponding to the frequency close to the Nyquist frequency Fn of the input image Din.

Next, the frequency spectrum of the intermediate image D32B will be described.
FIGS. 15A to 15C are diagrams schematically showing the action when the intermediate image D32B is generated. FIG. 15A shows a high frequency component generated by the nonlinear processing means 31 (or 31h or 31v). FIG. 15 (b) shows the frequency response of the high-frequency component image generation means 32B, and FIG. 15 (c) shows the frequency spectrum of the intermediate image D32B.

  As will be described later, a high frequency component corresponding to a frequency higher than the Nyquist frequency Fn of the input image Din is generated in the nonlinear processed image D31. FIG. 15A is a diagram schematically showing the state. In the example shown in the figure, components having a frequency of Fe or higher are mainly generated. The intermediate image D32B is generated when the nonlinear processed image D31 passes through the high frequency component image generating means 32B. The high-frequency component image generating means 32B is a high-pass filter that passes components of the frequency Ff or higher, and the frequency response becomes higher as the frequency becomes higher as shown in FIG. Accordingly, as shown in FIG. 15C, the frequency spectrum of the intermediate image D32B is higher than the Nyquist frequency Fn of the input image Din because the low-frequency region R32BL is removed from the frequency spectrum of the nonlinear processed image D31. It corresponds to the frequency.

  The frequency spectrum of the intermediate image D32B will be described in more detail with reference to FIGS. 16 (a) to 16 (e) and FIGS. 17 (a) to 17 (f). In addition, in order to simplify description, each is described as a one-dimensional signal.

  16A to 16E show a step edge signal representing an image (step image) in which component values such as luminance and saturation change stepwise, and when the step edge signal is sampled at different sampling frequencies. The signal strength of the obtained signal and its high frequency component signal are shown. FIG. 16A shows a step edge signal.

FIG. 16B shows a signal obtained by sampling the step edge signal at the sampling interval S1, and FIG. 16C shows a high frequency component of the signal obtained by sampling the step edge signal at the interval S1, and FIG. d) shows a signal obtained by sampling the step edge signal at the sampling interval S2, and FIG. 16E shows a high frequency component of the signal obtained by sampling the step edge signal at the interval S1.
Note that the sampling interval S1 is shorter than the sampling interval S2, and shortening the sampling interval is the same as enlarging the image.

  As shown in FIGS. 16B, 16C, 16D, and 16E, the center of the edge appears as a zero cross point Z in the high frequency component signal (FIGS. 16C and 16E). Further, as is apparent from a comparison between FIGS. 16B and 16C and FIGS. 16D and 16E, the slope of the high-frequency component signal before and after the zero-cross point Z decreases as the sampling interval decreases ( Alternatively, the position of the point giving the local maximum and minimum values of the high-frequency component near the zero-cross point Z also approaches the zero-cross point Z (according to the enlargement of the image).

  Therefore, when enlarging the image, the high frequency component of the input image Din is taken out, the change is made steep near the zero cross, and the point giving the local maximum and minimum values near the zero cross is brought close to the zero cross point. A high-frequency component that is not included in the resolution of Din (or higher than the Nyquist frequency of the input image Din) is generated, thereby making it possible to sharpen the edge.

  FIGS. 17A to 17F are diagrams schematically illustrating a procedure of high frequency component generation by the high frequency component image generation unit 1, the image enlargement unit 2B, the nonlinear processing unit 31, and the high frequency component image generation unit 32B. FIG. 17A shows an image (step image) in which component values such as luminance and saturation change stepwise, FIG. 17B shows an input image Din corresponding to the step image, and FIG. FIG. 17D shows an enlarged image D2B, FIG. 17E shows a nonlinear processed image D31, and FIG. 17F shows an intermediate image D32B.

  The input image Din and the high-frequency component image D1 corresponding to the step image are as described in FIGS. 16A to 16E, and the description thereof is omitted. First, the enlarged image D2B will be described.

  The enlarged image D2B (or D2Bh or D2Bv) is passed through the low-frequency component after inserting one pixel per pixel (image D1) with a pixel value of 0 into the high-frequency component image D1 by the zero insertion means 21B. It is obtained by extracting the low frequency component by means 22B. Extracting the low frequency component is the same as obtaining the average pixel value in the local region for the high frequency component image D1 (FIG. 17C), and the enlarged image D2B (or D2Bh or D2Bv) is shown in FIG. As shown in d), the signal has the same shape as the high-frequency component image D1 and has an increased sampling number.

  Next, the nonlinear processed image D31 will be described. The nonlinear processed image D31 is output as a result of the nonlinear processing means 31 detecting the zero cross point Z in the enlarged image D1 and amplifying the pixel values of the pixels before and after the zero cross point Z. Accordingly, the nonlinear processed image D31 (or D31h or D31v) becomes a signal as shown in FIG.

  Finally, the intermediate image D32B will be described. The intermediate image D32B (FIG. 17 (f)) is obtained by extracting the high frequency component of the nonlinear processed image D31 (FIG. 17 (e)) by the high frequency component image generating means 32B. The high frequency component can be extracted by subtracting the low frequency component of the input signal (or a simple average value or a weighted average value of pixel values in the local region) from the input signal.

  In the nonlinear processed image D31 (FIG. 17 (e)), the pixel values of the pixels before and after the zero cross point Z are amplified by the signal amplifying units 312h and 312v. The difference grows. On the other hand, since the pixel values of other pixels near the zero cross point are not amplified, the difference from the average pixel value in the local region is a small value. Therefore, compared with the enlarged image D2B (FIG. 17D), in the intermediate image D32B (FIG. 17F), the point giving the local maximum value and minimum value in the vicinity of the zero-cross point Z is further to the zero-cross point Z. And get closer. In addition, since the point that gives the local maximum and minimum values approaches the zero-cross point Z, the signal change near the zero-cross point also becomes abrupt.

  As described above, this means that the intermediate image D32B includes high frequency components that are not included in the resolution of the input image Din. In other words, the nonlinear processing means 31 amplifies pixel values around the zero cross point of the enlarged image D2B, thereby generating a high frequency component corresponding to a frequency higher than the Nyquist frequency Fn of the input image Din.

  Further, since the intermediate image D32B is generated by extracting the high frequency component generated by the nonlinear processing means 31 by the high frequency component image generating means 32B, the high frequency component corresponding to a frequency higher than the Nyquist frequency Fn of the input image Din is obtained. It becomes an image with.

  FIG. 21 shows frequency components of the enlarged image D2A, the intermediate image D32A, and the intermediate image D32B. The enlarged image D2A mainly includes a frequency component corresponding to a region RL corresponding to a frequency lower than the Nyquist frequency Fn of the input image Din. On the other hand, the intermediate image D32A includes a frequency component corresponding to a region RM corresponding to a frequency close to the Nyquist frequency Fn of the input image Din, and the intermediate image D32B corresponds to a frequency higher than the Nyquist frequency Fn of the input image Din. The frequency component corresponding to the area | region RH to be included is contained.

  If the high frequency component image D3 is generated by adding the intermediate image D32A and the intermediate image D32B, the high frequency component image D3 includes both the frequency component of the intermediate image D32A and the frequency component of the intermediate image D32B. become. The intermediate image D32A includes a frequency component corresponding to a frequency close to the Nyquist frequency Fn of the input image Din, and the intermediate image D32B includes a frequency component corresponding to a frequency higher than the Nyquist frequency Fn of the input image Din. Therefore, the high frequency component image D3 includes frequency components equal to or higher than the Nyquist frequency Fn of the input image Din. Then, by adding the high frequency component image D3 to the enlarged image D2A to obtain the output image Dout, it becomes possible to give the output image Dout a frequency component equal to or higher than the Nyquist frequency Fn of the input image Din. The resolution can be increased.

  FIGS. 18A to 18D are diagrams for explaining the above effect from another viewpoint. FIG. 18A shows a step edge signal. In the edge shown in FIG. 18A, the luminance on the left side of the edge center is lower than that on the right side. In the following description, an area where the luminance is low with respect to the center of the edge is sometimes called a low level side, and a high area is called a high level side. FIG. 18B shows an input image Din obtained by sampling the step edge signal at the sampling interval S2.

  FIG. 18C shows an enlarged image D2A obtained for the input image Din shown in FIG. Since the enlarged image D2A is obtained by performing an interpolation operation on the input image Din, the sampling interval becomes S1, which is twice as long as S2, but the change in the signal in the vicinity of the edge remains gentle.

  FIG. 18D shows an image obtained by sampling the step edge signal at the sampling interval S1 (indicated by the symbol Din as in the image of FIG. 18B). Compared with the enlarged image D2A, the change of the signal near the edge is steep.

  By adding the intermediate image D32A and the intermediate image D32B, the inclination of the signal in the vicinity of the edge of the enlarged image D2 is corrected, and an image close to the image obtained by sampling the step edge signal shown in FIG. 18D at the sampling interval S1 is obtained. It can be obtained and the resolution of the image can be enhanced.

  As described above, by adding the intermediate images D32A and D32B to the enlarged image D2A, the sharpness of the image can be increased and the image quality can be improved. However, the image quality may be deteriorated. Therefore, in the image processing apparatus of the present invention, the high-frequency component image correction means 33A and 33B are used to prevent the deterioration of the image quality.

  FIGS. 19A to 19I are views for explaining the operation and effect of the high-frequency component image correcting unit 33B. FIG. 19A shows the step edge signal as in FIG. 18A, and FIG. 19B shows the input image Din obtained for the step edge signal, as in FIG. 18B. Yes.

  FIG. 19C shows a high frequency component image D1 obtained for the input image Din shown in FIG. The pixel value of the high frequency component image D1 takes a positive value on the high level side (right side of the zero cross point Z) near the edge, and takes a negative value on the low level side (left side of the zero cross point Z).

  FIG. 19D shows an enlarged image D2B obtained for the high frequency component image D1 shown in FIG. Since the pixel value of the enlarged image D2B is obtained by weighted addition of the pixel value of the high frequency component image D1, the pixel value of the high frequency component image D1 basically matches the sign. Accordingly, the pixel value of the enlarged image D2B also takes a positive value on the high level side (right side of the zero cross point Z) near the edge, and takes a negative value on the low level side (left side of the zero cross point Z).

FIG. 19 (e) is a diagram schematically showing the nonlinear processed image D31 output from the nonlinear processing means 31 in the nonlinear processed image generating means 30, and particularly shows the nonlinear processed image D31 near the zero cross point Z. ing. As described above, in the non-linearly processed image D31, the points giving maximum and minimum values near the zero cross point Z (represented by coordinates P2 and P1, respectively) are closer to the zero cross point Z than the enlarged image D2B. . This means that a high frequency component corresponding to the sampling interval S1 has been generated.
Further, in FIG. 19 (e), of the regions included on the low level side near the edge, a region having a certain distance from the zero cross point Z is defined as a region R1, and the region included on the high level side near the edge Among these, a region where the distance from the zero cross point Z is separated to some extent is indicated as a region R2. Hereinafter, description will be made with attention to these regions R1 and R2.

  FIG. 19F is an enlarged view of the nonlinear processed image D31 in the vicinity of the region R2 shown in FIG. 19E in the horizontal axis direction, and the data indicated by the solid line in the white circle is the nonlinear processed image. D31 is represented, and the data indicated by the dotted line with the “x” mark represents the low frequency component of the nonlinear processed image D31.

  The low frequency component of the nonlinear processed image D31 is calculated as a local weighted average value of the pixel values of the nonlinear processed image D31. In the vicinity of the region R2, some of the pixel values are positive, but most of the pixel values are zero, so the value of the low frequency component is slightly larger than zero. When the pixel value of the nonlinear processed image D31 is compared with the value of the low frequency component, the value of the low frequency component becomes slightly larger. On the other hand, in the vicinity of the coordinate P2 in the nonlinear processed image D31, the pixel value of the pixel located outside the coordinate P2 is smaller than the pixel value of the pixel located at the coordinate P2, so the value of the low frequency component is the nonlinear processed image D31. It becomes a value smaller than the pixel value. That is, as a result, the magnitude relationship between the pixel value of the nonlinear processed image D31 and the value of the low frequency component is switched between the vicinity of the region R2 and the coordinate P2.

  FIG. 19 (g) is an enlarged view of the nonlinear processed image D31 in the vicinity of the region R1 shown in FIG. 19 (e) in the horizontal axis direction, and the data indicated by the solid line in the white circle is the nonlinear processed image. D31 is represented, and the data indicated by the dotted line with the “x” mark represents the low frequency component of the nonlinear processed image D31.

  The low frequency component of the nonlinear processed image D31 is calculated as a local weighted average value of the pixel values of the nonlinear processed image D31. In the vicinity of the region R1, some of the pixel values are negative, but most of the pixel values are zero, so the value of the low frequency component is slightly smaller than zero. When comparing the pixel value of the nonlinear processed image D31 and the value of the low frequency component, the value of the low frequency component is slightly smaller (the absolute value is larger and becomes a negative value). On the other hand, in the vicinity of the coordinate P1 in the nonlinear processed image D31, the pixel value of the pixel located outside the coordinate P1 is larger than the pixel value of the pixel located at the coordinate P1, so the value of the low frequency component is the nonlinear processed image D31. It becomes a value larger than the pixel value. That is, as a result, the magnitude relationship between the pixel value of the nonlinear processed image D31 and the value of the low frequency component is switched between the vicinity of the region R1 and the coordinate P1.

  FIG. 19 (h) is a diagram schematically showing the intermediate image D <b> 32 </ b> B output from the high frequency component image generation unit 32 </ b> B in the nonlinear processed image generation unit 30. The intermediate image D32B is obtained by extracting the high frequency component of the nonlinear processed image D31. In order to extract the high frequency component from the nonlinear processed image D31, the low frequency component may be subtracted from the nonlinear processed image D31. That is, the difference between the non-linearly processed image D31 shown in FIGS. 19F and 19G and the low frequency component becomes the intermediate image D32B. As described above, in the vicinity of the region R1, the nonlinear processed image D31 has a larger value than the low frequency component, and in the vicinity of the coordinate P1, the low frequency component has a larger value than the nonlinear processed image D31. In the vicinity of the coordinate P2, the nonlinear processed image D31 has a larger value than the low frequency component, and in the vicinity of the region R2, the low frequency component has a larger value than the nonlinear processed image D31. Looking at the value of the intermediate image D32B in the order of the vicinity of P1, the vicinity of the coordinate P2, and the vicinity of the region R2, the value once changes from a positive value to a negative value, and after taking a local minimum value at the coordinate P1, a negative value is obtained. The value changes from positive to positive. And after taking the local maximum value by the coordinate P2, it changes from a positive value to a negative value.

  Consider a case where the intermediate image D32B shown in FIG. 19 (h) is added to the enlarged image D2A. As described above, the edge can be sharpened by adding the intermediate image D32B. However, since the sign of the pixel value of the intermediate image D32B is negative in the region R2, the luminance of the image is reduced by adding the intermediate image D32B. As described above, since the region R2 is included on the high level side near the edge, the luminance on the high level side is reduced by adding the intermediate image D32B. On the contrary, in the region R1, the luminance on the low level side is increased by adding the intermediate image D32B.

  This means that by adding the intermediate image D32B, when the luminance on the high level side near the edge decreases or the luminance on the low level side increases, an unnatural luminance change is observed in the vicinity of the edge. Since the normal edge has a certain length along a certain direction such as the horizontal or vertical direction of the image, this unnatural luminance change appears with a certain length alongside the edge. An unnatural line or outline pattern appears in the vicinity of the edge.

  On the other hand, when the change in the pixel value of the enlarged image D2B shown in FIG. 19D is seen, it changes only once from negative to positive. Therefore, the sign of the enlarged image D2B is positive in the region R2 and negative in the region R1. In other words, when the enlarged image D2B and the intermediate image D32B are compared, the signs of both are inverted in the vicinity of the region R1 and the region R2. In other words, it can be said that a portion where the sign of the pixel value does not match between the enlarged image D2B and the intermediate image D32B causes an unnatural luminance change in the vicinity of the edge.

  FIG. 19 (i) is a diagram schematically showing an intermediate image D33B output from the high frequency component image processing means 33B. The sign comparison means 33B1 in the high frequency component image processing means 33B compares the signs of the enlarged image D2B and the intermediate image D32B. If the signs of the two are opposite, the pixel value changing means 33B2 detects the corresponding pixel of the intermediate image D32B. The value is set to zero. Accordingly, as shown in FIG. 19 (i), in the intermediate image D33B, the pixel values near the regions R1 and R2 become zero while maintaining the local minimum and maximum values at the coordinates P1 and P2. In the intermediate image D33B, the local minimum value and maximum value in the vicinity of the zero cross point Z are kept in the pixels at the positions represented by the coordinates P1 and P2. This means that the high frequency component corresponding to the sampling interval S1 generated by the nonlinear image generating means 30 is also maintained in the intermediate image D33B. Further, when the enlarged image D2B and the intermediate image D33B are compared, the signs in the vicinity of the region R1 and the region R2 are the same, and even if the intermediate image D33B is added, an unnatural luminance change near the edge It does not appear. Therefore, by adding the intermediate image D33B, it is possible to enhance the edge without causing an unnatural luminance change in the vicinity of the regions R1 and R2.

20A to 20I are diagrams for explaining the operation and effect of the high-frequency component image correcting unit 33A.
20A shows a step edge signal as in FIG. 19A, and FIG. 20B shows an input image Din obtained for the step edge signal as in FIG. 19B. Yes.

  FIG. 20C shows a high frequency component image D1 obtained for the input image Din shown in FIG. The pixel value of the high frequency component image D1 takes a positive value on the high level side (right side of the zero cross point Z) near the edge, and takes a negative value on the low level side (left side of the zero cross point Z).

  FIG. 20D shows an enlarged image D2B obtained for the high frequency component image D1 shown in FIG. Since the pixel value of the enlarged image D2B is obtained by weighted addition of the pixel value of the high frequency component image D1, the pixel value of the high frequency component image D1 basically matches the sign. Accordingly, the pixel value of the enlarged image D2B also takes a positive value on the high level side (right side of the zero cross point Z) near the edge, and takes a negative value on the low level side (left side of the zero cross point Z).

  FIG. 20E shows the enlarged image D2B shown in FIG. Further, in FIG. 20 (e), among the regions included on the low level side near the edge, a region with a certain distance from the zero cross point Z is defined as region R3, and among the regions included on the high level side near the edge A region having a certain distance from the zero cross point Z is shown as a region R4. Hereinafter, description will be made with attention paid to these regions R3 and R4.

  FIG. 20F is an enlarged view of the enlarged image D2B in the vicinity of the region R4 shown in FIG. 20E in the horizontal axis direction, and the data indicated by the solid line in the white circle represents the enlarged image D2B. The data indicated by the dotted line in the “x” mark represents the low frequency component of the enlarged image D2B. The region R4 is included on the high level side near the edge.

  The low frequency component of the enlarged image D2B is calculated as a local weighted average value of the pixel values of the enlarged image D2B. In the vicinity of the region R4, although some of the pixel values are positive, most of the pixel values are zero, so the value of the low frequency component is slightly larger than zero. When the pixel value of the enlarged image D2B is compared with the value of the low frequency component, the value of the low frequency component becomes slightly larger. On the other hand, in the enlarged image D2B, in the vicinity of the coordinate P4, the pixel value of the pixel located outside the coordinate P4 is smaller than the pixel value of the pixel located at the coordinate P4. Therefore, the value of the low frequency component is the pixel of the enlarged image D2B. The value is smaller than the value. That is, as a result, the magnitude relationship between the pixel value of the enlarged image D2B and the value of the low frequency component is interchanged in the vicinity of the region R4 and the coordinate P4. Note that the coordinate P4 is a coordinate of a point giving a local maximum value in the vicinity of the zero cross point Z with respect to the enlarged image D2B.

  FIG. 20G is an enlarged view of the enlarged image D2B in the vicinity of the region R3 shown in FIG. 20E in the horizontal axis direction, and the data indicated by the solid line in the white circle represents the enlarged image D2B. The data indicated by the dotted line in the “x” mark represents the low frequency component of the enlarged image D2B. The region R3 is included on the low level side near the edge.

  The low frequency component of the enlarged image D2B is calculated as a local weighted average value of the pixel values of the enlarged image D2B. In the vicinity of the region R3, although some of the pixel values are negative, most of the pixel values are zero, so the value of the low frequency component is slightly smaller than zero. When the pixel value of the enlarged image D2B is compared with the value of the low frequency component, the value of the low frequency component is slightly smaller (the absolute value is larger and becomes a negative value). On the other hand, in the enlarged image D2B, in the vicinity of the coordinate P3, the pixel value of the pixel located outside the coordinate P3 is larger than the pixel value of the pixel located at the coordinate P3. Therefore, the value of the low frequency component is the pixel of the enlarged image D2B. The value is larger than the value. That is, as a result, the magnitude relationship between the pixel value of the enlarged image D2B and the value of the low frequency component is interchanged in the vicinity of the region R3 and the coordinate P3. Note that the coordinate P3 is a coordinate of a point that gives a local minimum value in the vicinity of the zero cross point Z with respect to the enlarged image D2B.

  FIG. 20H is a diagram schematically showing the intermediate image D32A output from the high frequency component image generating unit 32A. The intermediate image D32A is obtained by extracting the high frequency component of the enlarged image D2A, but in order to extract the high frequency component from the enlarged image D2A, the low frequency component may be subtracted from the enlarged image D2B. That is, the difference between the enlarged image D2A shown in FIGS. 20F and 20G and the low frequency component becomes the intermediate image D32A. As described above, the enlarged image D2A has a larger value than the low frequency component in the vicinity of the region R3, and the low frequency component in the region close to the zero cross point Z on the low level side than the nonlinear processed image D31. The enlarged image D2A has a larger value than the low frequency component in the region close to the zero cross point Z on the high level side, and the low frequency component has a larger value than the enlarged image D2A near the region R4. Since it is a large value, when looking at the value of the intermediate image D32A in the order of the region R3, the zero cross point Z, and the region R4 in this order, after changing from a positive value to a negative value once, from the negative value It changes to a positive value, and further changes from a positive value to a negative value.

  Consider a case where the intermediate image D32A shown in FIG. 20 (h) is added to the enlarged image D2A. As described above, the edge can be sharpened by adding the intermediate image D32A. However, since the sign of the pixel value of the intermediate image D32A is negative in the region R4, the luminance of the image is reduced by adding the intermediate image D32A. As described above, since the region R4 is included on the high level side near the edge, the luminance on the high level side is reduced by adding the intermediate image D32A. On the contrary, in the region R3, the luminance on the low level side is increased by adding the intermediate image D32A.

  This means that by adding the intermediate image D32A, when the luminance on the high level side near the edge decreases or the luminance on the low level side increases, an unnatural change in luminance is observed in the vicinity of the edge. Since the normal edge has a certain length along a certain direction such as the horizontal or vertical direction of the image, this unnatural luminance change appears with a certain length alongside the edge. An unnatural line or outline pattern appears in the vicinity of the edge.

  On the other hand, looking at the change in the pixel value of the enlarged image D2B shown in FIG. 20 (d), it changes only once from negative to positive. Therefore, the sign of the enlarged image D2B is positive in the region R4 and negative in the region R3. In other words, when the enlarged image D2B and the intermediate image D32A are compared, the signs of both are inverted near the region R3 and the region R4. In other words, it can be said that a portion where the sign of the pixel value does not match between the enlarged image D2B and the intermediate image D32A causes an unnatural luminance change in the vicinity of the edge.

  FIG. 20 (i) is a diagram schematically showing the intermediate image D33A output from the high frequency component image processing means 33A. The sign comparison means 33A1 inside the high-frequency component image processing means 33A compares the signs of the enlarged image D2B and the intermediate image D32A. If the signs of both are opposite, the pixel value changing means 33A2 selects the corresponding pixel of the intermediate image D32A. The value is set to zero. Accordingly, as shown in FIG. 20 (i), in the intermediate image D33A, the pixel values in the vicinity of the regions R3 and R4 become zero, and when the enlarged image D2B and the intermediate image D33A are compared, in the vicinity of the regions R3 and R4. The sign mismatch between the two is eliminated, and even if the intermediate image D33A is added, an unnatural luminance change does not appear in the vicinity of the edge. Therefore, by adding the intermediate image D33A, it is possible to enhance the edge without causing an unnatural luminance change in the vicinity of the regions R3 and R4.

  As described above, the high-frequency component image processing unit 3 processes the image enlarging unit 2B obtained by enlarging the high-frequency component image D1 generated by the high-frequency component image generating unit 1 with the image enlarging unit 2B. A high frequency component image D3 including a frequency component corresponding to a frequency equal to or higher than the Nyquist frequency Fn of the image Din can be obtained. Then, in the adding means 4, an enlarged image D2A including a frequency component in a region corresponding to a frequency lower than the Nyquist frequency Fn of the input image Din and a high frequency including a frequency component in a region corresponding to a frequency equal to or higher than the Nyquist frequency Fn of the input image Din. Since the enlarged image Dout is generated by adding the frequency component images D3, a high frequency component can be sufficiently given to the enlarged image Dout, and an enlarged image Dout with a sense of resolution can be obtained.

Further, the high frequency component image generation means 1 generates a horizontal high frequency component image D1h obtained by extracting the horizontal high frequency component and a vertical high frequency component image D1v obtained by extracting the vertical high frequency component. It is possible to generate a frequency component corresponding to a frequency equal to or higher than the Nyquist frequency Fn of the input image Din in any one of the horizontal direction and the vertical direction of the image. That is, by applying a horizontal high-pass filter to the enlarged image D2Bh obtained by enlarging the horizontal high-frequency component image D1h by the image enlarging means 2Bh by the horizontal high-frequency component image generating means 32Ah, the input image Din An intermediate image D32Ah having a frequency component corresponding to a frequency close to the Nyquist frequency Fn is generated, and a vertical high frequency component image generating unit is generated with respect to the enlarged image D2Bv obtained by enlarging the vertical high frequency component image D1v by the image enlarging unit 2Bv. By applying a high-pass filter in the vertical direction at 32 Av, an intermediate image D32Av having a frequency component corresponding to a frequency close to the Nyquist frequency Fn of the input image Din in the vertical direction is generated.
Further, by applying high-pass filters having different characteristics in the horizontal direction and the vertical direction, frequency components corresponding to frequencies close to the Nyquist frequency Fn can be included in different levels in the horizontal direction and the vertical direction.

Further, by applying a high-pass filter to the non-linearly processed image D31h generated by performing non-linear processing on the enlarged image D2Bh by the horizontal non-linear processing unit 31h, the horizontal direction high-frequency component image generating unit 32Bh applies an input in the horizontal direction. An intermediate image D32Bh having a frequency component corresponding to a frequency higher than the Nyquist frequency Fn of the image Din is generated, and the non-linearly processed image D31v generated by performing non-linear processing on the enlarged image D2Bv by the non-linear processing means 31v in the vertical direction. By applying a high-pass filter in the vertical high frequency component image generation means 32Bv, an intermediate image D32Bv having a frequency component corresponding to a frequency higher than the Nyquist frequency Fn of the input image Din in the vertical direction is generated.
Further, by applying non-linear processing and a high-pass filter having different characteristics in the horizontal direction and the vertical direction, frequency components corresponding to frequencies higher than the Nyquist frequency Fn can be included in different levels in the horizontal direction and the vertical direction. .

  The intermediate image D32A is compared with the high frequency component correcting unit 33A, and the intermediate image D32B is compared with the high frequency component correcting unit 33B. The sign of the enlarged image D2B is compared. It is possible to prevent an unnatural line or pattern from appearing near the edge.

  Further, the high frequency component image D3 is obtained by adding the intermediate image D33A and the intermediate image D33B by the adding means 34, whereby a high frequency having a frequency component corresponding to a frequency equal to or higher than the Nyquist frequency Fn of the input image Din in any direction. A component image D3 can be obtained.

Note that the description has been made assuming that the enlargement ratio when generating the enlarged image Dout from the input image Din is double in both the horizontal direction and the vertical direction, but the enlargement ratio is not limited to double. That is, the image enlargement unit 2A generates an enlarged image D2A obtained by enlarging the input image Din to a desired magnification both in the horizontal direction and the vertical direction, and the high frequency component generation unit 1 generates the high frequency component image D1 based on the input image Din. The image enlarging means 2B generates an enlarged image D2B obtained by enlarging the high frequency component image D1 to a desired magnification (the same magnification as the magnification in the image enlarging means 2A) in both the horizontal direction and the vertical direction. The processing means 3 generates the high frequency component image D3 based on the enlarged image D2B, and the adding means 4 adds the enlarged image D2A and the high frequency component image D3 to obtain the final enlarged image Dout.
Furthermore, as described above, the horizontal enlargement factor and the vertical enlargement factor may not be the same, and enlargement may be performed only in one of the horizontal direction and the vertical direction.

  In the above description, the amplification factor is increased only for one pixel before and after the zero cross point in both the horizontal direction and the vertical direction. However, the example of the amplification factor control is not limited to this, and is appropriately changed according to, for example, the enlargement factor ( It can also be set to a value according to the enlargement ratio).

Hereinafter, the case where the enlargement ratio is different from the above example will be described with reference to FIGS. 22 (a) to 22 (e) and FIGS. 23 (a) to 23 (f).
FIG. 22A shows a step edge signal, FIG. 22B shows a signal obtained by sampling the step edge signal at the sampling interval S1, and FIG. 22C shows that obtained by sampling the step edge signal at the sampling interval S1. FIG. 22D shows a signal obtained by sampling a step edge signal at an interval S3 that is three times the interval S1, and FIG. 22E shows a step edge signal sampled at an interval S3. Represents the high frequency component of the resulting signal. In FIGS. 22D and 22E, pixel positions PL1 and PR1 represent step edge signal boundaries (points at which brightness brightness changes). Usually, in a signal representing a high-frequency component of an image obtained by sampling the step edge signal, the position of the pixel that gives the local maximum value and minimum value in the vicinity of the zero cross point Z substantially coincides with the position of the boundary of the step edge signal. .

  23A to 23F show high frequency component generation by the high frequency component image generation means 1, the image enlargement means 2B, the non-linear processing means 31, and the high frequency component image generation means 32B when the enlargement ratio is three times. FIG. 23A is an image (step image) in which component values such as luminance and saturation change stepwise, and FIG. 23B is an input corresponding to the step image. Image Din, FIG. 23C shows the high-frequency component image D1, FIG. 23D shows the enlarged image D2B, FIG. 23E shows the nonlinear processed image D31, and FIG. 23F shows the intermediate image D32B. In addition, in order to simplify description, each is described as a one-dimensional signal.

As shown in FIG. 23D, pixel positions PL1 and PR1 that give local maximum and minimum values near the zero-cross point Z in the enlarged image D2B are the positions of the boundary of the step edge signal in the enlarged image D2B. Almost matches. Normally, in the enlargement method used in the description of the present embodiment, the positions of PL1 and PR1 do not change, and the number of pixels existing between the positions represented by PL1 and PR1 and the zero-cross point Z increases. Further, the number of pixels existing between the positions represented by PL1 and PR1 and the zero-cross point Z increases as the enlargement ratio when generating the enlarged image D2B is increased (or the sampling interval is shortened).
On the other hand, in the signal representing the high frequency component of the image obtained by sampling the step edge signal at a short sampling interval, the position of the pixel giving the local maximum value and minimum value near the zero cross point Z is closer to the zero cross point Z, and the zero cross A pixel closer to the point than Z has a larger amplitude of a signal representing a high frequency component.

Accordingly, when generating the nonlinear processed image D31 by amplifying only the signals before and after the zero cross point Z, it is preferable to perform processing so that the amplitude becomes larger as the pixel is closer to the zero cross point Z than PL1 and PR1, for example, positions PL1, PR1 By amplifying the pixel value of the enlarged image D2B at a pixel closer to the zero cross point Z with a larger amplification factor as the pixel closer to the zero cross point Z and with a gain of 1 for pixels farther from the zero cross point Z than PL1 and PR1, FIG. As shown in (e), it is possible to generate a nonlinear processed image D31 having a larger amplitude as the pixel is closer to the zero cross point Z.
Then, by extracting only the high frequency component from the enlarged image D2B generated in this way by high-pass filter processing, an intermediate image D32B corresponding to the sampling interval S1 as shown in FIG. 23 (f) can be generated.

  In summary, since the number of pixels existing between the positions PL1 and PR1 and the zero cross point Z varies depending on the enlargement ratio at the time of generating the enlarged image D2B, the zero cross point Z is generated when generating the nonlinear processed image D31 from the enlarged image D2B. The number of pixels whose amplification factor is greater than 1 before and after may be changed in accordance with the enlargement factor of the image. Further, the amplification factors for these pixels may be changed according to the pixels, for example, according to the distance from the zero cross point Z. For example, the amplification factor may be increased as the pixel is closer to the zero cross point Z.

  In the above embodiment, the high frequency component image processing means 3 includes both the high frequency component image correction means 33A and 33B, but only one of them may be provided. For example, the second correction component generation unit 3B does not include the high-frequency component image correction unit 33B, and the intermediate image D32B output from the nonlinear processed image generation unit 30 may be used as the output of the second correction component generation unit 3B. Even if the first correction component generation means 3A does not include the high frequency component image correction means 33A, the intermediate image D32A output from the high frequency component image generation means 32A may be used as the output of the first correction component generation means 3A. good.

  Further, even by adding the intermediate image D33B to the enlarged image D2A, a high-frequency component in a region higher than the Nyquist frequency Fn can be given, so that the resolution of the image can be increased. That is, the high-frequency component image processing means 3 only needs to include means for performing non-linear processing in its interior, and for example, the configuration shown in FIG. 33 is also conceivable as such a configuration. In the configuration shown in FIG. 33, the high frequency component image processing means 3 outputs an intermediate image D33B as a high frequency component image D3. Note that the operation of each component in FIG. 33 is the same as that shown in FIG.

Embodiment 2. FIG.
In the first embodiment, the present invention has been described as being realized by hardware. However, part or all of the configuration shown in FIG. 1 may be realized by software, that is, by a programmed computer. Processing in that case will be described with reference to FIG. 24 and FIGS.

FIG. 24 shows an image processing apparatus according to the second embodiment. The illustrated image processing apparatus includes a CPU 11, a program memory 12, a data memory 13, and a bus 14 for connecting them.
The CPU 11 operates according to a program stored in the program memory 12. Various data are stored in the data memory 13 in the course of operation. The enlarged image Dout generated as a result of the processing is supplied to the display unit 9 via the interface 15 and used for display by the display unit 9.
Hereinafter, processing performed by the CPU 11 will be described with reference to FIGS.

  25 is a diagram illustrating a flow of an image processing method performed by the image processing apparatus in FIG. 24. The image processing method illustrated in FIG. 16 includes an image enlargement step ST2A, a high-frequency component image generation step ST1, and an image enlargement. Step ST2B, high frequency component image processing step ST3, and addition step ST4 are included.

  In the image enlarging step ST2A, an enlarged image D2A is generated by enlarging the input image Din input in the image input step (not shown) by the same processing as the image enlarging means 2A in FIGS.

  As shown in FIG. 26, the high frequency component image generation step ST1 includes a horizontal direction high frequency component image generation step ST1h and a vertical direction high frequency component image generation step ST1v. In the horizontal direction high frequency component image generation step ST1h, the input image Din is processed in the same manner as the horizontal direction high frequency component image generation unit 1h in FIG. 3 to generate a horizontal direction high frequency component image D1h. On the other hand, in the vertical direction high frequency component image generation step ST1v, the input image Din is processed in the same manner as the vertical direction high frequency component image generation means 1v in FIG. 3 to generate the vertical direction high frequency component image D1v.

As shown in FIG. 27, the image enlargement step ST2B includes an image enlargement step ST2Bh and an image enlargement step ST2Bv.
In the image enlarging step ST2Bh, the horizontal direction high frequency component image D1h generated in the horizontal direction high frequency component image generating step ST1h is subjected to the same processing as the image enlarging means 2Bh in FIG. 3 to generate an enlarged image D2Bh.
In the image enlarging step ST2Bv, the vertical high frequency component image D1v generated in the vertical high frequency component image generating step ST1v is subjected to the same processing as the image enlarging means 2Bv in FIG. 3 to generate an enlarged image D2Bv.

Next, the operation of the high frequency component image processing step ST3 will be described.
As shown in FIG. 28, the high frequency component image processing step ST3 includes a high frequency component image generation step ST32A, a non-linear processing image generation step ST30, a high frequency component image correction step ST33A, a high frequency component image correction step ST33B, and an addition step. It has ST34.
The high frequency component passing step ST32A includes a horizontal high frequency component image generation step ST32Ah and a vertical high frequency component image generation step ST32Av.

The nonlinear processed image generation step ST30 has a nonlinear processing step ST31 and a high frequency component image generation step ST32B.
The non-linear processing step ST31 includes a horizontal non-linear processing step ST31h and a vertical non-linear processing step ST31v.
The high frequency component image generation step ST32B includes a horizontal direction high frequency component image generation step ST32Bh and a vertical direction high frequency component image generation step ST32Bv.

In the horizontal high-frequency component passing step ST32Ah, the enlarged image D2Bh generated in the image enlargement step ST2Bh is subjected to the same processing as the horizontal high-frequency component image generating unit 32Ah in FIG. 3 to generate the horizontal intermediate image D32Ah. . In the vertical high-frequency component passing step ST32Av, the enlarged image D2Bv generated in the image enlargement step ST2Bv is subjected to the same processing as the vertical high-frequency component image generating means 32Av in FIG. 3 to generate the vertical intermediate image D32Av. .
In the high frequency component image generation step ST32A, an intermediate image D32A composed of the horizontal direction intermediate image D32Ah and the vertical direction intermediate image D32Av is generated.
Thus, in the high frequency component passing step ST32A, the same operation as the high frequency component image generating means 32A of FIG. 3 is performed.

As shown in FIG. 29, the horizontal non-linear processing step ST31h includes a zero cross determination step ST311h and a signal amplification step ST312h.
The operation of the horizontal nonlinear processing step ST31h is as follows.
First, in the zero cross determination step ST311h, a change in the pixel value in the enlarged image D2Bh generated in the image enlargement step ST2Bh is confirmed along the horizontal direction. A location where the pixel value changes from a positive value to a negative value or from a negative value to a positive value is regarded as a zero cross point, and pixels located on the left and right sides of the zero cross point are specified. In the signal amplification step ST312h, the pixel values of the pixels located on the left and right of the zero cross point specified in the zero cross determination step ST311h in the enlarged image D2Bh are amplified, and an image obtained as a result is generated as the nonlinear processed image D31h.

As shown in FIG. 30, the vertical nonlinear processing step ST31v includes a zero cross determination step ST311v and a signal amplification step ST312v.
The operation of the vertical nonlinear processing step ST31v is as follows.
First, in the zero cross determination step ST311v, a change in pixel value in the enlarged image D2Bv generated in the image enlargement step ST2Bv is confirmed along the vertical direction. A portion where the pixel value changes from a positive value to a negative value or from a negative value to a positive value is regarded as a zero cross point, and pixels located above and below the zero cross point are specified. In the signal amplification step ST312v, the pixel values of the pixels located above and below the zero-cross point specified in the zero-cross determination step ST311v in the enlarged image D2Bv are amplified, and the resulting image is generated as the nonlinear processed image D31v.

In the high frequency component image generation step ST31, a nonlinear processed image D31 including a horizontal direction nonlinear processed image D31Ah and a vertical direction nonlinear processed image D32Av is generated.
Thus, in the non-linear processing step ST31, the same operation as that of the non-linear processing means 31 of FIG. 3 is performed.

In the horizontal high-frequency component passing step ST32Bh, a high-pass filter is applied to the nonlinear processed image D31h generated in the horizontal nonlinear processing step ST31h to generate a horizontal intermediate image D32Bh. In the vertical direction high frequency component passing step ST32Bv, a high-pass filter is applied to the nonlinear processed image D31v generated in the vertical nonlinear processing step ST31v to generate a vertical intermediate image D32Bv.
In the high frequency component image generation step ST32B, an intermediate image D32B composed of the horizontal direction intermediate image D32Bh and the vertical direction intermediate image D32Bv is generated.
Thus, in the high frequency component passing step ST32B, the same operation as that of the high frequency component image generating unit 32B in FIG. 3 is performed.

The high frequency component image correction step ST33A includes a code comparison step ST33A1 and a pixel value change step ST33A2 as shown in FIG.
The code comparison step ST33A1 includes a horizontal direction code comparison step ST33A1h and a vertical direction code comparison step ST33A1v.
The pixel value changing step ST33A2 includes a horizontal direction pixel value changing step ST33A2h and a vertical direction pixel value changing step ST33A2v.
The operation of the high frequency component image correction step ST33A is as follows.

First, the sign comparison step ST33A1 compares the signs of the pixel values of the enlarged image D2B and the intermediate image D32A, and outputs the result as a signal D33A1. Here, the enlarged image D2B is made up of the enlarged image D2Bh and the enlarged image D2Bv, and the intermediate image D32A is made up of the horizontal direction intermediate image D32Ah and the vertical direction intermediate image D32Av. It is performed for each pixel of the enlarged image D2Bv and the vertical intermediate image D32Av. That is, for the enlarged image D2Bh and the horizontal intermediate image D32Ah, the codes of the respective pixels are compared in the horizontal code comparison step ST33A1h, and the comparison result is output as a signal D33A1h. The enlarged image D2Bv and the vertical intermediate image D32Av Is compared in the vertical direction code comparison step ST33A1v, and the result of the comparison is output as a signal D33A1v. From the code comparison step ST33A1, the signal D33A1h and the signal D33A1v are output as the signal D33A1.
Thus, the code comparison step ST33A1 performs the same operation as the code comparison unit 33A1 in FIG.

Next, the pixel value changing step ST33A2 generates an intermediate image D33A in which the pixel value of the intermediate image D32A is changed based on the signal D33A1. The pixel value changing step ST33A2 sets the pixel value of each pixel value of the intermediate image D32A that is indicated by the signal D33A1 to be different from the pixel value of the enlarged image D2B to zero. This process is performed for each of the horizontal intermediate image D32Ah and the vertical intermediate image D32Av. That is, for the horizontal intermediate image D32Ah, in the horizontal pixel value changing step ST33A2h, based on the signal D33A1h, an image D33Ah in which the pixel value of a pixel having a different sign from the enlarged image D2Bh is generated is generated. In the vertical pixel value changing step ST33A2v, based on the signal D33A1v, a vertical intermediate image D33Av in which the pixel value of a pixel having a sign different from that of the enlarged image D2Bv is zero is generated. From the pixel value changing step ST33A2, an intermediate image D33A composed of a horizontal intermediate image D33Ah and a vertical intermediate image D33Av is output.
Thus, the pixel value changing step ST33A2 performs the same operation as the pixel value changing unit 33A2 of FIG.

  The above is the operation of the high frequency component image correction step ST33A, and the operation is the same as that of the high frequency component image correction means 33A of FIG.

The high frequency component image correction step ST33A includes a code comparison step ST33B1 and a pixel value change step ST33B2, as shown in FIG.
The code comparison step ST33B1 includes a horizontal direction code comparison step ST33B1h and a vertical direction code comparison step ST33B1v.
The pixel value changing step ST33B2 includes a horizontal direction pixel value changing step ST33B2h and a vertical direction pixel value changing step ST33B2v.
The operation of the high frequency component image correction step ST33B is as follows.

First, the sign comparison step ST33B1 compares the signs of the pixel values of the enlarged image D2B and the intermediate image D32B, and outputs the comparison result as a signal D33B1. Here, the enlarged image D2B is made up of the enlarged image D2Bh and the enlarged image D2Bv, and the intermediate image D32B is made up of the horizontal direction intermediate image D32Bh and the vertical direction intermediate image D32Bv. This is performed for the pixels, and for each pixel of the enlarged image D2Bv and the vertical intermediate image D32Bv. That is, for the enlarged image D2Bh and the horizontal intermediate image D32Bh, the sign of each pixel is compared in the horizontal code comparison step ST33B1h, and the comparison result is output as a signal D33B1h, and the enlarged image D2Bv and the vertical intermediate image D32Bv Is compared in the vertical direction code comparison step ST33B1v, and the result of the comparison is output as a signal D33B1v. From the code comparison step ST33B1, the signal D33B1h and the signal D33B1v are output as the signal D33B1.
Thus, the code comparison step ST33B1 performs the same operation as the code comparison unit 33B1 of FIG.

Next, the pixel value changing step ST33B2 generates an intermediate image D33B in which the pixel value of the intermediate image D32B is changed based on the signal D33B1. The pixel value changing step ST33B2 sets the pixel value of each pixel value of the intermediate image D32B that is indicated by the signal D33B1 to be different from the pixel value of the enlarged image D2B to zero. This process is performed for each of the horizontal intermediate image D32Bh and the vertical intermediate image D32Bv. That is, for the horizontal intermediate image D32Bh, in the horizontal pixel value changing step ST33B2h, based on the signal D33B1h, an image D33Bh in which the pixel value of a pixel having a different sign from the enlarged image D2Bh is generated is generated. In the vertical pixel value changing step ST33B2v, based on the signal D33B1v, a vertical intermediate image D33Bv in which the pixel value of a pixel having a sign different from that of the enlarged image D2Bv is zero is generated. From the pixel value changing step ST33B2, an intermediate image D33B composed of a horizontal intermediate image D33Bh and a vertical intermediate image D33Bv is output.
Thus, the pixel value changing step ST33B2 performs the same operation as the pixel value changing unit 33B2 of FIG.

  The above is the operation of the high frequency component image correction step ST33B, and the operation is the same as that of the high frequency component image correction means 33B of FIG.

  The combination of the high frequency component image generation step ST32A and the high frequency component image correction step ST33A corresponds to the operation of the first correction component generation means 3A, and the combination of the nonlinear processing image generation step ST30 and the high frequency component image correction step ST33B This corresponds to the operation of the second correction component generation means 3B.

  In the addition step ST34, the intermediate image D33A generated in the high frequency component image correction step ST33A and the intermediate image D33B generated in the high frequency component image correction step ST33B are added to obtain a high frequency component image D3. Thus, in step ST34, the same operation as that of the adding means 34 in FIG. 3 is performed.

  The above is the operation of the high frequency component image processing step ST3, and this operation is the same as that of the high frequency component image processing means 3 of FIGS.

The adding step ST4 generates an image Dout obtained by adding the enlarged image D2A generated in the image enlarging step ST2A and the high frequency component image D3 generated in the high frequency component image processing step ST3. Then, the generated image Dout is output as a final enlarged image through a step (not shown).
This operation is the same as that of the adding means 4 in FIGS.

  The above is the operation of the image processing method according to the second embodiment. As is clear from the above description, the image processing method according to the second embodiment can also enlarge an image by the same processing as that of the image processing device according to the first embodiment, so that the same effect as the image processing device according to the first embodiment can be obtained. It is done. Also, the image processing method according to the second embodiment can be modified in the same manner as the image processing apparatus according to the first embodiment, and the effect obtained in that case is the same as that of the image processing apparatus according to the first embodiment. .

  For example, an example in which the high frequency component image processing step ST3 is modified to the configuration shown in FIG. 34 can be considered. The operation of each step in FIG. 34 is the same as that described in FIG. 28, and the description thereof will be omitted. However, in the configuration shown in FIG. 34, the intermediate image D33B has a high frequency from the high frequency component image processing step ST3. It is output as a component image D3. Even by only adding the intermediate image D33B, a high frequency component in a region higher than the Nyquist frequency Fn can be provided, so that an effect of increasing the resolution of the image can be obtained. In other words, since high frequency components in a region higher than the Nyquist frequency Fn are generated by non-linear processing, the high frequency component image processing step ST3 only needs to include a step of performing non-linear processing therein.

  Note that the modifications are not limited to those described above, and all modifications applied to the image processing apparatus according to the first embodiment can be applied to the image processing method according to the second embodiment. At that time, how to modify each step of the image processing method according to the second embodiment can be easily considered by those skilled in the art.

  In addition, since the image processing apparatus according to the second embodiment can be used as a part of the image display apparatus similar to the image processing apparatus described in the first embodiment, the image Dout generated by the image processing apparatus according to the second embodiment. The image display apparatus that displays the same effect as the image processing apparatus described in the first embodiment can also be obtained. Further, the image processing method implemented using the image processing apparatuses of the first and second embodiments and the image display method using the same can obtain the same effects.

  DESCRIPTION OF SYMBOLS 1 High frequency component image generation means, 2A Image expansion means, 2B Image expansion means, 3 High frequency component image processing means, 3A Correction component generation means, 3B Correction component generation means, 4 Addition means, 30 Nonlinear image generation means, 31 Nonlinear Processing means, 32A high frequency component image generation means, 32B high frequency component image generation means, 33A high frequency component image correction means, 33B high frequency component image correction means, 34 addition means, Din input image, D1 high frequency component image, D2A Enlarged image, D2B enlarged image, D3 high frequency component image, D32A intermediate image, D32B intermediate image, D33A intermediate image, D33B intermediate image, Dout output image.

Claims (32)

In an image processing apparatus for enlarging an input image,
First image enlarging means for enlarging the input image and outputting a first enlarged image;
First high frequency component image generation means for extracting a high frequency component of the input image and generating a first high frequency component image;
Second image enlarging means for enlarging the first high frequency component image and outputting a second enlarged image;
High-frequency component image processing means for receiving the second enlarged image and outputting a second high-frequency component image;
In the image processing apparatus having the first enlarged image and the first addition means for adding the second high-frequency component image,
The high frequency component image processing means includes
First correction component generation means including second high frequency component image generation means for extracting a high frequency component of the second enlarged image and outputting a first intermediate image;
Second correction component generation means including nonlinear processing image generation means for outputting a second intermediate image obtained by performing processing including nonlinear processing on the second enlarged image;
A second addition means for adding the output of the first correction component generation means and the output of the second correction component generation means;
The result of the addition in the second addition means is used as the output of the high frequency component image processing means,
The first correction component generation means further includes first high-frequency component image correction means for receiving the second enlarged image and the first intermediate image and outputting a third intermediate image,
The image processing apparatus, wherein the third intermediate image is used as an output of the first correction component generation unit. In an image processing apparatus for enlarging an input image,
First image enlarging means for enlarging the input image and outputting a first enlarged image;
First high frequency component image generation means for extracting a high frequency component of the input image and generating a first high frequency component image;
Second image enlarging means for enlarging the first high frequency component image and outputting a second enlarged image;
High-frequency component image processing means for receiving the second enlarged image and outputting a second high-frequency component image;
In the image processing apparatus having the first enlarged image and the first addition means for adding the second high-frequency component image,
The high frequency component image processing means includes
First correction component generation means including second high frequency component image generation means for extracting a high frequency component of the second enlarged image and outputting a first intermediate image;
Second correction component generation means including nonlinear processing image generation means for outputting a second intermediate image obtained by performing processing including nonlinear processing on the second enlarged image;
A second addition means for adding the output of the first correction component generation means and the output of the second correction component generation means;
The result of the addition in the second addition means is used as the output of the high frequency component image processing means,
The second correction component generation means includes second high-frequency component image correction means for receiving the second enlarged image and the second intermediate image and outputting a fourth intermediate image;
The image processing apparatus, wherein the fourth intermediate image is used as an output of the second correction component generation unit.
Image processing device. The second correction component generation unit includes a second high-frequency component image correction unit that receives the second enlarged image and the second intermediate image and outputs a fourth intermediate image. The image processing apparatus according to claim 1, wherein the intermediate image is used as an output of the second correction component generation unit. The first high frequency component image correction means includes:
First sign comparison means for comparing signs of pixel values of the second enlarged image and the first intermediate image;
The image processing apparatus according to claim 1, further comprising: a first pixel value changing unit that changes a pixel value of the first intermediate image based on a result of comparison by the first code comparison unit. The first pixel value changing means includes
If it is determined by the first code comparison means that the sign of the pixel value of the second enlarged image is different from the sign of the pixel value of the first intermediate image, the pixel value of the first intermediate image is set to zero. The image processing apparatus according to claim 4, wherein: The second high frequency component image correcting means includes:
Second sign comparison means for comparing signs of pixel values of the second enlarged image and the second intermediate image;
The image processing apparatus according to claim 2, further comprising: a second pixel value changing unit that changes a pixel value of the second intermediate image based on a result of comparison by the second code comparison unit. The second pixel value changing means includes
If the second code comparison means determines that the sign of the pixel value of the second enlarged image and the sign of the pixel value of the second intermediate image are different, the pixel value of the second intermediate image is set to zero. The image processing apparatus according to claim 6. The first high frequency component image correction means includes:
First sign comparison means for comparing signs of pixel values of the second enlarged image and the first intermediate image;
First pixel value changing means for changing a pixel value of the first intermediate image based on a result of comparison by the first code comparison means;
The second high frequency component image correcting means includes:
Second sign comparison means for comparing signs of pixel values of the second enlarged image and the second intermediate image;
The image processing apparatus according to claim 3, further comprising: a second pixel value changing unit that changes a pixel value of the second intermediate image based on a result of comparison by the second code comparison unit. The first pixel value changing means includes
If it is determined by the first code comparison means that the sign of the pixel value of the second enlarged image is different from the sign of the pixel value of the first intermediate image, the pixel value of the first intermediate image is set to zero. ,
The second pixel value changing means includes
If the second code comparison means determines that the sign of the pixel value of the second enlarged image and the sign of the pixel value of the second intermediate image are different, the pixel value of the second intermediate image is set to zero. The image processing apparatus according to claim 8. The nonlinear processed image generation means includes:
Nonlinear processing means for generating a first nonlinear processed image obtained by performing nonlinear processing on the second enlarged image;
10. The image processing apparatus according to claim 8, further comprising third high-frequency component image generation means that extracts a high-frequency component from the first non-linearly processed image and sets the second intermediate image as the second intermediate image. The first high frequency component image generation means includes:
First horizontal high-frequency component image generation means for generating a first horizontal high-frequency component image using pixel values of pixels existing in the vicinity in the horizontal direction for each pixel of the input image;
The second image enlargement means includes:
A third image enlarging means for enlarging the first horizontal high-frequency component image and outputting a third enlarged image;
The second enlarged image includes the third enlarged image,
The second high frequency component image generating means includes:
A second horizontal high frequency component image generating means for extracting only the high frequency component of the third enlarged image and outputting the first horizontal intermediate image;
The nonlinear processed image generation means includes:
A horizontal nonlinear processing means for outputting a second nonlinear processed image obtained by performing nonlinear processing on the third enlarged image;
A third horizontal high frequency component image generating means for extracting a high frequency component from the second nonlinear processed image and outputting a second horizontal intermediate image;
The first intermediate image includes the first horizontal intermediate image;
The second intermediate image includes the second horizontal intermediate image;
The first code comparison means includes:
First horizontal direction code comparison means for comparing the sign of the pixel values of the third enlarged image and the first horizontal intermediate image;
The first pixel value changing means includes
First horizontal pixel value changing means for changing a pixel value of the first horizontal intermediate image based on a result of comparison by the first horizontal code comparison means;
The second code comparison means includes:
Second horizontal direction code comparison means for comparing the sign of the pixel values of the third enlarged image and the second horizontal intermediate image;
The second pixel value changing means includes
The second horizontal direction pixel value changing means for changing a pixel value of the second horizontal direction intermediate image based on a result of comparison by the second horizontal direction code comparison means. Image processing apparatus. The horizontal nonlinear processing means includes:
A horizontal direction zero cross determining means for determining a point where the pixel value of the third enlarged image changes from positive to negative or from negative to positive as a zero cross point;
Horizontal signal amplification means for amplifying the pixel value of the third enlarged image at an amplification factor determined according to the determination result of the horizontal direction zero-cross determination means;
The image processing apparatus according to claim 11, wherein the third horizontal high-frequency component image generation unit extracts a high-frequency component from an image output from the horizontal signal amplification unit. The horizontal direction signal amplification means includes
The amplification factor for the pixel value of the pixel existing in the first region including the zero-cross point determined by the horizontal zero-cross determination unit is set to a value larger than 1, and the amplification factor for the pixel values of the other pixels is set to 1. The image processing apparatus according to claim 12. The image processing apparatus according to claim 13, wherein the first area is determined according to an enlargement ratio of the second image enlargement unit. The image processing apparatus according to claim 13 or 14, wherein an amplification factor for a pixel existing in the first region is determined according to the pixel. The first horizontal pixel value changing means is
When the first horizontal direction code comparison means determines that the sign of the pixel value of the third enlarged image is different from the sign of the pixel value of the first horizontal direction intermediate image, the first horizontal direction intermediate image The image processing apparatus according to claim 11, wherein the pixel value is set to zero. The second horizontal pixel value changing means is
If the second horizontal direction code comparison means determines that the sign of the pixel value of the third enlarged image and the sign of the pixel value of the second horizontal direction intermediate image are different, the second horizontal direction intermediate image The image processing apparatus according to claim 11, wherein the pixel value of the image data is zero. The first high frequency component image generation means includes:
First vertical high-frequency component image generation means for generating a first vertical high-frequency component image using a pixel value of a pixel existing near the vertical direction for each pixel of the input image;
The second image enlargement means includes:
A fourth image enlarging means for enlarging the first vertical high-frequency component image and outputting a fourth enlarged image;
The second enlarged image includes the fourth enlarged image,
The second high frequency component image generating means includes:
A second vertical high frequency component image generating means for extracting only the high frequency component of the fourth enlarged image and outputting the first vertical intermediate image;
The nonlinear processed image generation means includes:
Vertical direction nonlinear processing means for outputting a third nonlinear processed image obtained by performing nonlinear processing on the fourth enlarged image;
A third vertical high frequency component image generating means for extracting a high frequency component from the third nonlinear processed image and outputting a second vertical intermediate image;
The first intermediate image includes the first vertical intermediate image;
The second intermediate image includes the second vertical intermediate image;
The first code comparison means includes:
First vertical direction code comparison means for comparing the sign of pixel values of the fourth enlarged image and the first vertical intermediate image;
The first pixel value changing means includes
First vertical pixel value changing means for changing a pixel value of the first vertical intermediate image based on a result of comparison by the first vertical code comparison means;
The second code comparison means includes:
Second vertical direction code comparison means for comparing the signs of the pixel values of the fourth enlarged image and the second vertical intermediate image;
The second pixel value changing means includes
The second vertical pixel value changing means for changing a pixel value of the second vertical intermediate image based on a result of the comparison by the second vertical code comparison means. Image processing apparatus. The vertical nonlinear processing means includes:
Vertical zero-cross determination means for determining a point where the pixel value of the fourth enlarged image changes from positive to negative or from negative to positive as a zero-cross point;
Vertical direction signal amplification means for amplifying the pixel value of the fourth enlarged image at an amplification factor determined according to the determination result of the vertical direction zero cross determination means;
The image processing apparatus according to claim 18, wherein the third vertical high-frequency component image generation unit extracts a high-frequency component from an image output from the vertical signal amplification unit. The vertical signal amplification means includes
The amplification factor for the pixel value of the pixel existing in the second region including the zero-cross point determined by the vertical zero-cross determination unit is set to a value larger than 1, and the amplification factor for the pixel values of other pixels is set to 1. The image processing apparatus according to claim 19. 21. The image processing apparatus according to claim 20, wherein the second area is determined in accordance with an enlargement ratio in the second image enlargement unit. The image processing apparatus according to claim 20 or 21, wherein an amplification factor for a pixel existing in the second region is determined according to the pixel. The first vertical pixel value changing means is
When the first vertical direction code comparison unit determines that the sign of the pixel value of the fourth enlarged image is different from the sign of the pixel value of the first vertical direction intermediate image, the first vertical direction intermediate image The image processing apparatus according to claim 18, wherein the pixel value of the image data is zero. The second vertical pixel value changing means is
When the second vertical direction code comparison unit determines that the sign of the pixel value of the fourth enlarged image is different from the sign of the pixel value of the second vertical direction intermediate image, the second vertical direction intermediate image The image processing apparatus according to claim 18, wherein the pixel value of is set to zero. The first high frequency component image generation means includes:
First horizontal high-frequency component image generation means for generating a first horizontal high-frequency component image using pixel values of pixels existing in the vicinity in the horizontal direction for each pixel of the input image;
First vertical high-frequency component image generation means for generating a first vertical high-frequency component image using a pixel value of a pixel existing near the vertical direction for each pixel of the input image;
The second image enlargement means includes:
Third image enlarging means for enlarging the first horizontal high-frequency component image and outputting a third enlarged image;
A fourth image enlarging means for enlarging the first vertical high-frequency component image and outputting a fourth enlarged image;
The second enlarged image includes the third enlarged image and the fourth enlarged image,
The second high frequency component image generating means includes:
A second horizontal high frequency component image generating means for extracting only the high frequency component of the third enlarged image and outputting a first horizontal intermediate image;
A second vertical high frequency component image generating means for extracting only the high frequency component of the fourth enlarged image and outputting the first vertical intermediate image;
The nonlinear processed image generation means includes:
A horizontal nonlinear processing means for outputting a second nonlinear processed image obtained by performing nonlinear processing on the third enlarged image;
Third horizontal high frequency component image generation means for extracting a high frequency component from the second non-linearly processed image and outputting a second horizontal intermediate image;
Vertical direction nonlinear processing means for outputting a third nonlinear processed image obtained by performing nonlinear processing on the fourth enlarged image;
A third vertical high frequency component image generating means for extracting a high frequency component from the third nonlinear processed image and outputting a second vertical intermediate image;
The first intermediate image includes the first horizontal intermediate image and the first vertical intermediate image;
The second intermediate image includes the second horizontal intermediate image and the second vertical intermediate image;
The first code comparison means includes:
First horizontal direction code comparison means for comparing the sign of pixel values of the third enlarged image and the first horizontal intermediate image;
First vertical direction code comparison means for comparing the sign of pixel values of the fourth enlarged image and the first vertical intermediate image;
The first pixel value changing means includes
First horizontal pixel value changing means for changing a pixel value of the first horizontal intermediate image based on a result of comparison by the first horizontal code comparison means;
First vertical pixel value changing means for changing a pixel value of the first vertical intermediate image based on a result of comparison by the first vertical code comparison means;
The second code comparison means includes:
Second horizontal direction code comparison means for comparing the signs of the pixel values of the third enlarged image and the second horizontal intermediate image;
Second vertical direction code comparison means for comparing the signs of the pixel values of the fourth enlarged image and the second vertical intermediate image;
The second pixel value changing means includes
Second horizontal pixel value changing means for changing a pixel value of the second horizontal intermediate image based on a result of comparison by the second horizontal code comparison means;
The second vertical pixel value changing means for changing a pixel value of the second vertical intermediate image based on a result of the comparison by the second vertical code comparison means. Image processing apparatus.   An image display apparatus comprising the image processing apparatus according to claim 1. In an image processing method for enlarging an input image,
A first image enlargement step of enlarging the input image and outputting a first enlarged image;
A first high-frequency component image generation step of extracting a high-frequency component of the input image and generating a first high-frequency component image;
A second image enlargement step of enlarging the first high frequency component image and outputting a second enlarged image;
A high-frequency component image processing step for receiving the second enlarged image and outputting a second high-frequency component image;
In the image processing method comprising the first addition step of adding the first enlarged image and the second high frequency component image, the high frequency component image processing step includes:
A second high-frequency component image generating step for extracting a high-frequency component of the second enlarged image;
A non-linearly processed image generating step for performing processing including non-linear processing on the second enlarged image;
An addition step of adding the image obtained by the second high-frequency component image generation step and the image obtained by the nonlinear processing image generation step,
At least one of the image obtained by the second high-frequency component image generation step and the image obtained by the nonlinear processing image generation step is increased based on the second enlarged image before addition by the addition step. An image processing method, further comprising: a high frequency component image correction step for correcting the frequency component image. The high frequency component image correction step includes:
The pixel value of the image to be corrected is changed based on a result of the comparison by comparing signs of pixel values of the image to be corrected and the second enlarged image. Item 27. The image processing method according to Item 27.   29. An image display device that displays an image processed by the image processing method according to claim 27 or 28. In an image processing apparatus for enlarging an input image,
First image enlarging means for enlarging the input image and outputting a first enlarged image;
First high frequency component image generation means for extracting a high frequency component of the input image and generating a first high frequency component image;
Second image enlarging means for enlarging the first high frequency component image and outputting a second enlarged image;
High-frequency component image processing means for receiving the second enlarged image and outputting a second high-frequency component image;
In the image processing apparatus having the first enlarged image and the first addition means for adding the second high-frequency component image,
The high frequency component image processing means includes
An image processing apparatus comprising correction component generation means including non-linear processing image generation means for outputting an intermediate image obtained by performing processing including non-linear processing on the second enlarged image. In an image processing method for enlarging an input image,
A first image enlargement step of enlarging the input image and outputting a first enlarged image;
A first high-frequency component image generation step of extracting a high-frequency component of the input image and generating a first high-frequency component image;
A second image enlargement step of enlarging the first high frequency component image and outputting a second enlarged image;
A high-frequency component image processing step for receiving the second enlarged image and outputting a second high-frequency component image;
In the image processing method comprising the first addition step of adding the first enlarged image and the second high frequency component image, the high frequency component image processing step includes:
A non-linearly processed image generating step for performing processing including non-linear processing on the second enlarged image;
An image processing method comprising: a high frequency component image correction step for correcting the image obtained by the nonlinear processed image generation step.   An image display device that displays an image processed by the image processing device according to claim 30 or the image processing method according to claim 31.

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