JPH0793563A - Image processor - Google Patents

Abstract

PURPOSE:To provide an image processor converting color image information of low resolution into image information of high resolution without blurring an edge and image quality. CONSTITUTION:Inputted color space is converted into color space which is capable of resolving luminance and color difference components by a RGB-YUV convertion circuit 1, the edge information of the color difference components is prepared based on the edge information of the luminance components in a color difference edge preparation part 3, the edge preparation of the only luminance components is performed in a luminance edge preparation part 2, the edge is converted into the original color space in a YUV-RGB conversion circuit 4 and the space is outputted. Therefore, the color image information of low resolution can be converted into the information of high resolution without blurring an edge part and image quality. Further, the color slippage due to the deviation of the edge preparation in each color is eliminated and excellent high resolution can be prepared.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus, for example, an image output apparatus such as a color printer for enlarging and scaling input color image information and outputting the low resolution information in communication between models having different resolutions. The present invention relates to an image processing apparatus which is effective in converting resolution from to high resolution information.

[0002]

2. Description of the Related Art Conventionally, various methods have been proposed as a method of converting input low resolution information into high resolution information. The proposed conventional method is based on a target image type (for example, a multi-valued image having gradation information for each pixel, a binary image binarized by pseudo halftone, and a binarized by a fixed threshold). The conversion processing method differs depending on the binary image, character image, etc.).

A conventional interpolation method, which mainly targets a multivalued image such as a natural image having gradation information for each pixel, arranges the same pixel value closest to the interpolation point as shown in FIG. Depending on the closest interpolating method and the distance of four points surrounding the interpolation point (pixel values of four points are A, B, C, and D) as shown in FIG. 7, the pixel value E is calculated by the following calculation. A co-temporal interpolation method for determining is generally used.

E = (1-i) (1-j) A + i. (1-
j) B + j · (1-i) C + ijD (However, when the inter-pixel distance is 1, it is assumed that there is a distance of i from A in the horizontal direction and j in the vertical direction. (i ≦ 1, j ≦
1))

[0005]

However, the above-mentioned conventional example has the following drawbacks. The recent interpolation method of arranging the same pixel value closest to the interpolation point has the advantage that the configuration is simple, but when the target image is naturally used, the pixel value is determined for each block to be enlarged. Therefore, the blocks are visually conspicuous and the image quality is poor.

Next, the linear interpolation method, which is calculated by the distances of four points surrounding the interpolation point, is a method that is generally used for enlarging a natural image. Is averaged and the image quality is smoothed, but the image quality is blurred at the edge part and the part where sharp image quality is required. Further, in the case of an image obtained by scanning a map or a natural image including a character portion, important information may not be transmitted to the recipient due to blurring due to interpolation.

[0007]

The present invention has been made for the purpose of solving the above-mentioned problems, and has the following structure as one means for solving the above-mentioned problems. That is, the first conversion means for converting the color space of the input image information into a color space capable of being decomposed into luminance and color difference components, and the color difference component based on the edge information of the luminance component in the converted color space by the first conversion means. Edge information creating means for creating edge information of
Guess the edges of the input image information.

[0008]

With the above arrangement, the low-resolution color image information can be converted into the high-resolution information without blurring the edges or the image quality. Therefore, for example, it is possible to output to a high-resolution output device or to perform communication between models having different resolutions at the resolution of the output device.

Further, it is possible to eliminate the color misregistration due to the misregistration at the time of edge creation for each color, and to create a good high resolution image.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described in detail below with reference to the drawings. [First Embodiment] The image processing apparatus of the present invention is effectively provided mainly in an image output apparatus such as a color printer, but image processing apparatuses other than the image output apparatus and application software in the host computer are effective. It is also possible to build in.

FIG. 1 is an overall view showing the configuration of an embodiment according to the present invention. Reference numeral 1 in the figure is RG which is a first color conversion means.
This is a B-YUV conversion circuit, which performs conversion into a color space with less redundancy than the input color space, particularly a color space decomposed into luminance and color difference. That is, the color space of the input image information is converted into a color space that can be decomposed into luminance and color difference components. For example,
Input R (red), G (green), B (blue)
Signal from another color space, for example, Y (luminance), U, V
Convert to (color difference) space. The RGB-YUV conversion circuit first may be based on calculation or may be a LUT (look-up table) using a ROM (read only memory).

Reference numeral 2 is a brightness edge creating unit for creating an edge from a Y (brightness) plane when the color components having the largest visual influence in the converted color space, for example, brightness and color difference, are created. A color difference edge creation unit that creates an edge part of another component (color difference component) based on the information of the edge part of the luminance component obtained by the creation unit 2 and YUV-RGB conversion that is a second color conversion unit. Circuit, RGB-
The color space changed by the YUV conversion circuit 1 is converted into the input color space. For example, it is a circuit for converting from the YUV color space to the RGB color space.

Next, the operation procedure of this embodiment having the above configuration will be described. When RGB color image information is input to the RGB-YUV conversion circuit 1, the RGB-YUV conversion circuit 1 converts the input image into YUV color space information. Next, of the YUV image information converted by the luminance edge creation unit 2, an edge in the resolution direction is created based on the image information of the Y plane. Next, based on the edge information created by the luminance edge creation unit 2, the color difference edge creation unit 3
Create edges of U and V image information. The YUV image information created by the luminance edge creation unit 2 and the color difference edge creation unit 3 is converted by the YUV-RGB conversion circuit 4 into RGB image information that is the input color space.

Next, the luminance edge creating section 2 will be described with reference to FIG. In FIG. 2, the portion surrounded by the broken line corresponds to the luminance edge creating unit. Reference numeral 5 in FIG. 2 indicates low resolution information to be input, and 6 is an input terminal for this low resolution information. The luminance component information input via the input terminal 6 is transmitted to the linear interpolation means 7. An example of the information linearly interpolated by the linear interpolation means 7 is shown in FIG. In FIG. 3, a solid line indicates a block boundary centered on each low resolution pixel, and a portion surrounded by a thick line is a block for the target pixel E. Further, ◯ marks indicate pixels of low resolution information, and X marks indicate interpolation pixels. The information linearly interpolated by the linear interpolation means 7 is sent to the binarization means 10.

Further, the low resolution information input from the input terminal 6 is also sent to the MAX / MIN detecting means 8 where the maximum value and the minimum value in the window are detected. The detected maximum value (MAX) and minimum value (MIN) are transmitted to the threshold value determining means 9, and the threshold value quantized into two values is determined. In this embodiment, the threshold value (TH) is determined by the following formula.

[0016]

[Mathematical formula-see original document] TH = (MAX + MIN) / 2 The threshold information determined by the threshold determination means 9 and MAX.MI.
The maximum value (MAX) and the minimum value (MIN) detected by the N detection means 8 are transmitted to the binarization means 10. The binarization unit 10 binarizes the interpolation information of the block centered on the target pixel E, which has been linearly interpolated by the linear interpolation unit 7, according to the threshold value (TH) determined by the threshold value determination unit 9.
The binarizing means 10 assigns the maximum value to the interpolation pixels larger than the binarization threshold and assigns the minimum value to the small interpolation pixels. This binarization process corresponds to the creation of an edge.

The edge bitmap information of the Y component binarized by the binarizing means 10 is the information of the block as shown in 13, and the output terminal 14 to the color difference edge creating section 3 of FIG.
Is output to the color difference edge creating unit 3. The color difference edge creating unit 3 creates edges in U and V based on the binarized Y component edge bitmap information transmitted from the luminance edge creating unit 2.

Reference numeral 11 shown in FIG. 2 denotes an output terminal, and Y component information of the block allocated by the binarized representative values "MAX" and "MIN" as shown in 12 is output. Next in FIG.
The color difference edge creation unit 3 shown in FIG. 4 will be described with reference to FIG. In FIG. 4, the portion surrounded by the broken line corresponds to the color difference edge creation unit. Reference numeral 15 in FIG. 4 indicates low resolution information to be input, and 16 is an input terminal for this low resolution information. The color difference component information input via the input terminal 16 is
It is transmitted to the linear interpolation means 17. This linear interpolation means 17
The information linearly interpolated in (1) is, for example, as shown in FIG. The information linearly interpolated by the linear interpolation means 17 is sent to the error determination means 22.

The low resolution information input from the input terminal 16 is also sent to the MAX / MIN detecting means 18, where the maximum and minimum values in the window are detected. The maximum value (MAX) and minimum value (MIN) detected are MAX
The maximum value (MAX) and the minimum value (MIN) are arranged based on the Y component edge bit map transmitted to the MIN arranging means 21 and input from the 19 Y component edge bit map information input terminals. At this time, a pattern of a block in which the maximum value is placed at the position where the Y component edge bitmap value is "1" and a minimum value is placed in the position where it is "0", and two patterns opposite thereto are created. The created pattern is sent to the error determination means 22. The error determining unit 22 calculates the error between the data linearly interpolated by the linear interpolating unit 17 and the pattern of the two blocks created by the MAX / MIN arranging unit 21, and selects the pattern of the block with the smaller error. .

Reference numeral 23 is an output terminal for color difference information, and the information of the block to which MAX and MIN are assigned as shown in 24 is output. Y, U, V whose edges are created as described above
Image information of each of the YUV through the output terminal 23
-The image information is sent to the RGB conversion circuit 4 to be converted into the original RGB image, and the image information is magnified and scaled.

As described above, according to this embodiment, it is possible to convert low-resolution color image information into high-resolution information without blurring the edges or the image quality. Therefore, for example, it is possible to output to a high-resolution output device or to perform communication between models having different resolutions at the resolution of the output device. Further, it is possible to eliminate the color misregistration due to the misregistration at the time of edge creation for each color, and to create a good high resolution image.

[Second Embodiment] Next, a second embodiment according to the present invention will be described. FIG. 5 is an overall view showing the configuration of the second embodiment according to the present invention. In FIG. 5, 25 is RGB-Y
A UV conversion circuit, 26 is a luminance edge creation unit that creates an edge portion from Y plane image information, 27 is a linear interpolation circuit that performs linear interpolation from U and V image information, and 28 is YUV-.
It is an RGB conversion circuit.

In the second embodiment described above, FIG.
1 is different from the first embodiment shown in FIG. 1 in that in the first embodiment shown in FIG. 1, the edge information in the U and V planes is created based on the edge information created in the Y plane. In the second embodiment, the U and V planes are simply linearly interpolated without creating edges.

This is because when color image information is decomposed into YUV, visually important information such as edges mainly depends on the Y plane, and hardly depends on the U and V planes. is there. By taking this method,
The entire circuit can be simplified as compared with the first embodiment, and substantially the same effect as that of the first embodiment can be obtained.

In each of the embodiments described above, the color space separated into luminance and color difference was described by taking Y, U and V as an example, but it goes without saying that other luminance and color difference separated color spaces may be used. . Further, although the input / output color space has been described by taking RGB as an example, the present invention is not limited to RGB. Further, the luminance edge creating means has also been described as being binarized by the threshold value TH by (MAX + MIN) / 2, but it goes without saying that another method may be used.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0027]

As described above, according to the present invention, an input color space is converted into a color space that can be decomposed into luminance and color difference components, and edge information of color difference components is created based on edge information of luminance components. Alternatively, by creating an edge of only the luminance component, it is possible to convert low-resolution color image information to high-resolution information without blurring the edge part and image quality, and thus to a high-resolution output device. Output of
In communication between models having different resolutions, important information can be output at the resolution of the output device.

Further, it is possible to eliminate the color misregistration due to the misregistration at the time of edge creation for each color, and to create a good high resolution.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a color image resolution conversion system in an embodiment according to the present invention.

FIG. 2 is a diagram showing a detailed configuration of a luminance edge creation unit shown in FIG. 1 in the present embodiment.

FIG. 3 is a diagram showing a structure of linearly interpolated data in the present embodiment.

FIG. 4 is a diagram showing a detailed configuration of a color difference edge creation unit shown in FIG. 1 in the present embodiment.

FIG. 5 is a diagram showing a configuration of a color image resolution conversion system in a second embodiment according to the present invention.

FIG. 6 is a diagram illustrating a conventional interpolation method.

FIG. 7 is a diagram illustrating a conventional bi-linear interpolation method.

[Explanation of symbols]

 1,25 RGB, YUV conversion circuit 2,26 Luminance edge creation unit 3,27 Color difference edge creation unit 4,28 YUV-RGB conversion circuit 5 Low resolution information 6 Low resolution information input terminal 7 Linear interpolation circuit 8 MAX, MIN detection Circuit 9 Threshold value determination circuit 10 Binarization circuit 11 Luminance output terminal 12 Luminance block information 13 Y component edge bitmap information 14 Y component edge bitmap output terminal 15 Low resolution information 16 Low resolution information input terminal 17 Linear interpolation circuit 18 MAX, MIN detection circuit 19 Y component edge bitmap input terminal 20 Y component edge bitmap information 21 MAX, MIN arrangement circuit 22 error determination circuit 23 color difference information output terminal 24 color difference block information

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location H04N 1/409 8420-5L G06F 15/66 355 C 4226-5C H04N 1/40 101 D

Claims (3)

[Claims] 1. A first conversion means for converting a color space of input image information into a color space capable of being decomposed into a luminance and a color difference component, and based on edge information of a luminance component in the converted color space by the first conversion means. And an edge information creating means for creating edge information of the color difference component, and speculatively creates an edge of the input image information. 2. The image processing apparatus according to claim 1, wherein the edge information creating means creates an edge of only the luminance component. 3. The method according to claim 1, further comprising second conversion means for converting the color space of the image information in which the edges are estimated and created by the edge information creating means into the color space of the input image. The image processing device according to item 1.