JP4104475B2 - Contour correction device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a contour correction device, and more particularly to a contour correction device that performs contour correction processing on image data such as a video signal.
[0002]
[Prior art]
In a video display device such as a monitor, the contour correction processing of an input video signal mainly includes contour enhancement for increasing sharpness and contour smoothing for removing jaggies (jagged pixels due to rough sampling). There is a purpose.
[0003]
Conventionally, for the enhancement and smoothing processing of video signals, it is common to perform spatial filtering within a local region. FIG. 7 shows a block diagram of spatial filtering, and FIG. An example of a typical filter coefficient used for the filtering process in the 3-pixel region and the 3-pixel region in the vertical direction is shown.
[0004]
However, since a single filter coefficient is used in these filter processes, the entire image is uniformly processed, and a portion that is excessive or undercorrected in the image is generated. Moreover, since enhancement and smoothing are contradictory processes, it is difficult to simultaneously perform a process of increasing sharpness while removing jaggies.
[0005]
As means for avoiding this, Patent Document 1 detects the direction of an edge present in a video signal and creates an edge image that is smoothed in a direction parallel to the edge and differentiated in a direction perpendicular to the edge. However, an edge emphasizing device is shown in which edges are effectively enhanced by combining with an input video signal.
[0006]
FIG. 9 is a block diagram in the embodiment of the above publication, in which 100 is an image input means, 101 is an input image switching means, 102 is a direction image generation means, 103 is an edge detection means, 104 is an image composition means, and 105 is an image. Storage / selection means, 106 a repeat control means, and 107 an image output means.
[0007]
Specifically, a direction image indicating the direction of the local edge is created from the input image, and based on this, Gaussian smoothing is performed in the direction parallel to the edge with respect to the original image, and two in the vertical direction. Creates an edge image by performing enhancement processing by second derivative, and obtains an enhanced image by combining it with the original image, and realizes appropriate enhancement processing by repeating this processing a specified number of times using this enhanced image as a new input image. Yes.
[0008]
Further, in Patent Document 2, the similarity of pixels in at least four directions with respect to the target pixel and the peripheral pixels of the image data is determined, and the weight ratio in the direction with strong similarity is increased, and then the peripheral pixels are compared. A direction-dependent low-pass filter process that removes jaggies without reducing the sharpness of an image by weighted averaging is shown.
[0009]
FIG. 10 is a flowchart of image processing in the embodiment of the above publication. S1 is an image file reading unit, S2 is an area setting unit, S3 is a dissimilarity calculating unit, S4 is a representative value calculating unit, and S5 is a similarity. The calculation means, S6 is a weight specific gravity calculation means, S7 is a weighted average means, and S8 is executed by an image output means.
[0010]
Specifically, pixel lines are set in at least four directions (vertical, horizontal, diagonally up, diagonally down) with respect to the local region including the target pixel of the input image, and a feature such as a level difference is set for each line. Detecting pixel similarity in each direction, increasing the weight specific gravity in the direction of strong similarity, and performing weighted averaging of the target pixel with surrounding pixels to correct jaggies without significantly damaging the image structure Is realized.
[0011]
[Patent Document 1]
JP-A-7-193716 [Patent Document 2]
Japanese Patent Laid-Open No. 2001-61157
[Problems to be solved by the invention]
However, since the edge enhancement device according to Patent Document 1 optimizes the enhancement degree by iterative processing, it cannot be applied to a moving image signal such as a television image whose input image changes one after another in time series, or An enormous buffer circuit for storing the input image is required. Furthermore, since only the direction of the edge information of the image is used, it is effective for binary images such as line drawings. However, a general natural image having gradations can be filtered regardless of the size of the edge. Since this process is performed, there is a problem that an optimal enhanced image cannot be obtained.
[0013]
Further, in the direction-dependent low-pass filter processing according to Patent Document 2, it is necessary to calculate feature amounts in at least four directions for similarity determination, and when it is desired to use the direction of weights that are further weighted and averaged, many directions are used. Therefore, there is a problem that the calculation of the feature amount becomes necessary and the amount of calculation increases.
[0014]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a contour correction device that suppresses an increase in calculation amount and is suitable for moving image signal processing.
[0015]
[Means for Solving the Problems]
The present invention provides an edge correction device that performs edge correction of a video signal, extracts an edge of a video using an attention pixel and its peripheral pixels from an input video signal, and outputs an edge component; and A coefficient calculating unit that calculates a coefficient of a local filter depending on an edge direction as a parameter; a filter calculating unit that performs a local filter operation on an input image using the filter coefficient and outputs a contour correction component; and a contour correction component On the other hand, it is a contour correction device including a normalization calculation unit that performs normalization based on the size of an edge, and an addition unit that synthesizes and outputs a contour correction component after the normalization calculation and an input signal.
[0016]
Further, the present invention is the contour correction device, wherein the edge calculating means has means for calculating a pixel value gradient from the peripheral pixels of the target pixel and outputting two components of a horizontal component and a vertical component.
[0017]
In the present invention, the coefficient calculating means can calculate the filter coefficient from only an edge component that is an output of the edge calculating means, wherein the filter coefficient is expressed by a trigonometric function having the edge direction as a parameter, and the filter coefficient is the edge coefficient. It is a contour correction apparatus having means for outputting so as to perform a smoothing process depending on a direction.
[0018]
Further, according to the present invention, the coefficient calculation means can calculate the filter coefficient from only an edge component that is an output of the edge calculation means, wherein the filter coefficient is expressed by a trigonometric function having the edge direction as a parameter. It is an outline correction device having means for outputting so as to perform enhancement processing depending on the direction.
[0019]
Further, according to the present invention, the coefficient calculation means can be calculated from only the edge component that is an output of the edge calculation means, wherein the filter coefficient is expressed by a trigonometric function with the edge direction as a parameter, and the filter coefficient is the edge coefficient. The contour correction apparatus has means for outputting so as to perform smoothing processing in the direction and enhancement processing in the vertical direction.
[0020]
In the present invention, the normalization calculation means calculates an edge size (edge strength) using an edge component which is an output of the edge calculation means, and the maximum edge strength that can be theoretically calculated, or attention This is a contour correction apparatus having means for normalizing by the maximum edge strength calculated from the maximum value and the minimum value in a local region such as a pixel peripheral region and outputting the contour correction component depending on the edge strength.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
An embodiment of a contour correcting device of the present invention will be described based on the drawings.
[0022]
Embodiment 1 will be described. The contour correction apparatus of this embodiment is configured as shown in the block diagram of FIG. 1, for example. In the configuration of FIG. 1, 1 is an edge calculator that extracts a contour of a video using the target pixel and its peripheral pixels from the input video INPUT and outputs edge components EH and EV, and 2 is an edge component EH and EV as parameters. A coefficient calculator that calculates local filter coefficients F1 to F9, 3 is a filter calculator that performs INPUT and local filter operations using the filter coefficients F1 to F9 and outputs a contour correction component DE, and 4 is an edge from the edge components EH and EV. A normalization computing unit that calculates the intensity, performs a normalization operation on the contour correction component DE, and outputs a standardized contour correction component NE, 5 is an addition that combines the contour correction component NE and INPUT after the normalization calculation and outputs It is a vessel.
[0023]
In this apparatus, the edge calculator 1 extracts the outline of the video using the target pixel of INPUT and its peripheral pixels, and two edge components orthogonal to each other, for example, an edge component EH parallel to the video and a vertical edge component EV is calculated and output.
[0024]
FIG. 2 is a block diagram showing an example of the configuration of the edge calculator 1, wherein 6 is a local region setting unit that sets a peripheral region of a pixel of interest for INPUT, and 7 is a horizontal component EH of a pixel value gradient from the peripheral region. A horizontal component calculator 8 for calculating a vertical component EV for calculating a vertical component EV of a pixel value gradient from the peripheral region.
[0025]
The coefficient calculator 2 calculates filter coefficients F1 to F9 for smoothing or enhancement processing depending on the edge direction expressed by a trigonometric function having the edge direction θ as a parameter.
[0026]
FIG. 3 is a table showing an example of the filter coefficient for performing the smoothing process in the edge direction. The value in the 3 × 3 square represents the local filter coefficient, the center is the weighting coefficient for the pixel of interest, and the surroundings are It represents the weighting factor for the surrounding pixels. Looking at the change of the coefficient value at the upper left position F1 among the filter coefficients, it is 1 only when θ = 135 [deg]. In other words, by using a periodic function that takes 1 when θ = 135 [deg] and takes 0 otherwise, the filter processing depending on the edge direction is possible without preparing a plurality of filters.
[0027]
Furthermore, by expressing the periodic function as a trigonometric function with θ as a parameter, it is not necessary to perform a trigonometric function calculation from the edge components EH and EV which are the outputs of the edge calculating means 1 in the calculation of the periodic function. In other words, between θ and EH and EV,
EH = sqrt (EH * EH + EV * EV) * cos θ (Formula 1)
EV = sqrt (EH * EH + EV * EV) * sin θ (Formula 2)
Therefore, the trigonometric function can be replaced with EH and EV for calculation.
[0028]
FIG. 4 shows an example in which the filter coefficient is represented by a trigonometric function having θ as a parameter, and FIG. 5 shows a case where this is replaced with edge components EH and EV. Thereby, the filter coefficient depending on the edge direction can be obtained only from the edge component without calculating a complicated periodic function.
[0029]
In the coefficient value, the filter processing for emphasizing the position F5 of the target pixel in the edge direction and emphasizing the other in the edge direction by reversing the sign, F1 and F3, F2 and F4, F6 and F8, and F7 and F9 are replaced As a result, the filter processing can be performed in the direction perpendicular to the edge, so that the edge enhancement can be performed while suppressing jaggies by performing smoothing in the edge direction and enhancement processing in the vertical direction.
[0030]
The filter calculator 3 performs an INPUT and local filter calculation using the filter coefficients F1 to F9 that are the outputs of the coefficient calculator 3, and outputs a contour correction component DE.
[0031]
The normalization computing unit 4 calculates the edge size (edge strength) from the edge components EH and EV for the DE calculated only from the edge direction, and divides it by the maximum edge strength that can be theoretically calculated. Using the factor, normalization is performed by multiplying DE. Thereby, the contour correction component NE depending on the size of the edge is calculated. In addition to using the maximum and minimum values that can theoretically be taken by the input video as the maximum edge strength, normalization calculation should be performed using the maximum and minimum values in the local area such as the peripheral pixel area of the target pixel. Thus, contour correction applicable to a relatively small edge component can be performed.
[0032]
FIG. 6 is a block diagram showing an example of the configuration of the normalization computing unit 4. The edge strength calculator 10 calculates and outputs the edge strength from the edge components EH and EV, and uses the value that can be taken by the INPUT as the maximum edge strength. A selector 12 that selects whether to use a value in the local region, a maximum edge strength calculator 13 that calculates and outputs the maximum edge strength using the output of the selector 12, and a divider that divides the edge strength and the maximum edge strength. 11 is a multiplier 9 for standardizing DE.
[0033]
The adder 5 adds the INPUT and the contour correction component NE, and then outputs it as an output video OUTPUT.
[0034]
As described above in the first embodiment, the contour correction apparatus according to the present invention calculates the edge component of the video signal regarding the contour enhancement processing for increasing the sharpness and the contour smoothing processing for removing jaggies. By emphasizing and smoothing according to the direction and intensity, there is an effect that an appropriate contour correction process can be performed without the need for repeated processes.
[0035]
In addition, the contour correction apparatus of the present invention can calculate the filter coefficient from only the horizontal edge component and the vertical edge component by expressing the filter coefficient for emphasizing and smoothing by a trigonometric function with the edge direction as a parameter. The filter coefficient depending on the edge direction can be calculated without requiring a complicated calculation.
[0036]
The contour correction device of the present invention has an effect of removing jaggy contained in the video signal while maintaining the contour structure by performing the smoothing process only in the direction parallel to the edge direction. .
[0037]
Furthermore, the contour correction apparatus according to the present invention is suitable for a relatively small edge component by using the maximum value and the minimum value in the local region when the contour correction component is normalized by the size of the edge component. There is an effect that a correct contour correction can be performed.
[0038]
【The invention's effect】
According to the present invention, it is possible to obtain a contour correction device that suppresses an increase in the amount of computation and is suitable for moving image signal processing.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an example of a configuration of a contour correction apparatus according to a first embodiment.
FIG. 2 is a block diagram showing an example of the configuration of an edge calculator in the first embodiment.
FIG. 3 is an explanatory diagram of an example of a filter coefficient for performing a smoothing process in an edge direction by a general filter process.
FIG. 4 is a table for explaining filter coefficient values showing an example in which filter coefficients obtained by the coefficient calculator according to the first embodiment are expressed by a trigonometric function with an edge direction as a parameter.
FIG. 5 is a table for explaining filter coefficient values showing an example in which filter coefficients obtained by the coefficient calculator according to the first embodiment are expressed by horizontal edge components and vertical edge components;
FIG. 6 is a block diagram showing an example of the configuration of a normalization calculator in the first embodiment.
FIG. 7 is a block diagram showing a basic configuration of conventional spatial filter processing.
FIG. 8 is an explanatory diagram of an example of a filter coefficient in conventional spatial filter processing.
FIG. 9 is a block diagram showing a basic configuration of a conventional contour emphasizing apparatus.
FIG. 10 is a flowchart showing a processing procedure in a conventional contour emphasizing apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Edge calculator 2 Coefficient calculator 3 Filter calculator 4 Normalization calculator 5 Adder 6 Local region setter 7 Horizontal component calculator 8 Vertical component calculator 9 Multiplier 10 Edge strength calculator 11 Divider 12 Selector 13 Maximum edge strength calculator 100 Image input means 101 Input image switching means 102 Direction image generation means 103 Edge detection means 104 Image composition means 105 Image storage / selection means 106 Repeat control means 107 Image output means

Claims (5)

In a contour correction device that performs contour correction of a video signal,
Edge calculation means for extracting the edge of the video using the target pixel and its surrounding pixels from the input video signal and outputting an edge component, and a coefficient for calculating the coefficient of the local filter depending on the edge direction using the edge component as a parameter A calculation means; a filter calculation means for performing a local filter operation on the input image using the filter coefficient and outputting a contour correction component; and a normalization calculation means for normalizing the contour correction component with an edge size. And an adding means for combining and outputting the contour correction component after normalization calculation and the input signal ,
The coefficient calculating means is expressed by a trigonometric function whose filter coefficient is an edge direction as a parameter, can be calculated only from an edge component that is an output of the edge calculating means, and an enhancement process in which the filter coefficient depends on the edge direction contour correcting device according to claim Rukoto to have a means for outputting so as to. In a contour correction device that performs contour correction of a video signal,
Edge calculation means for extracting the edge of the video using the target pixel and its surrounding pixels from the input video signal and outputting an edge component, and a coefficient for calculating the coefficient of the local filter depending on the edge direction using the edge component as a parameter A calculation means; a filter calculation means for performing a local filter operation on the input image using the filter coefficient and outputting a contour correction component; and a normalization calculation means for normalizing the contour correction component with an edge size. And an adding means for combining and outputting the contour correction component after normalization calculation and the input signal,
The coefficient calculating means is expressed by a trigonometric function whose filter coefficient is an edge direction as a parameter, can be calculated only from an edge component that is an output of the edge calculating means, and an enhancement process in which the filter coefficient depends on the edge direction A contour correction apparatus having means for outputting so that In a contour correction device that performs contour correction of a video signal,
Edge calculation means for extracting the edge of the video using the target pixel and its surrounding pixels from the input video signal and outputting an edge component, and a coefficient for calculating the coefficient of the local filter depending on the edge direction using the edge component as a parameter A calculation means ; a filter calculation means for performing a local filter operation on the input image using the filter coefficient and outputting a contour correction component; and a normalization calculation means for normalizing the contour correction component with an edge size. And an adding means for combining and outputting the contour correction component after normalization calculation and the input signal,
The coefficient calculation means is expressed by a trigonometric function whose filter coefficient is the edge direction as a parameter, can be calculated only from an edge component that is an output of the edge calculation means, and the filter coefficient is smoothed in the edge direction. A contour correcting apparatus comprising means for outputting so as to perform enhancement processing in a vertical direction . The contour correction apparatus according to any one of claims 1 to 3, wherein the edge calculation means includes means for calculating a pixel value gradient from peripheral pixels of the target pixel and outputting two components of a horizontal component and a vertical component . The normalization calculation means calculates an edge size (edge strength) using an edge component that is an output of the edge calculation means, and calculates the maximum edge strength that can be theoretically calculated or a local area such as a region around the target pixel. The contour according to any one of claims 1 to 3, further comprising means for normalizing by a maximum edge strength calculated from a maximum value and a minimum value in the region and outputting the result to be a contour correction component depending on the edge strength. Correction device.

Images