JP2003202848A - Method, device and program for image processing and computer-readable recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the picture quality of an image which is chromatically displayed on a liquid crystal display panel by making optimum dither matrixes correspond to planes of R, G, and B when pseudo-halftone processing by a binary or multi-valued systematic dither method is performed. <P>SOLUTION: When a image is displayed on an LCD panel 105 having an array of pixels each constituted by putting dots of the primary colors R, G, and B together in one, the pseudo-halftone processing by the multi-valued systematic dither method is performed while the matrixes are made to correspond to planes representing images of R, G, and B. In this case, an optimum matrix determining means 102 defines matrixes of one or two colors among R, G, and B made to correspond to the respective planes as basic matrixes used while a threshold array is fixed and determines the threshold array of the matrix of the color other than the colors of the basic matrixes according to a statistic value obtained by statistically processing the simultaneous ON probability that dots of R, G, and B turn on at the same time for one pixel. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, an EL display device and a PD mounted on electronic equipment such as mobile phones, personal digital assistants and personal computers.
Among various display devices such as P, an image processing method applied when displaying an image on a display device configured by arranging dots of a plurality of colors as one pixel and arranging the pixels, The present invention relates to an image processing program and a computer-readable recording medium.

[0002]

2. Description of the Related Art Conventionally, an image display unit of a mobile phone or the like has a monochrome or color liquid crystal display (LCD: Liquid).
Crystal Display) panel is used. This LC
In the D panel, the transmittance of the liquid crystal is changed by turning on / off the driving voltage to the liquid crystal cells arranged in a matrix, and characters or images of two gradations are displayed. Recently, as mobile phones have become more multifunctional such as the Internet function, it has been required to display more information including images with higher gradation and higher image quality on the LCD panel.

When an image is displayed in color on an LCD panel, input image data is divided into planes showing images of a plurality of colors which form one pixel, and a distributed dither matrix described later is provided for each of the planes of a plurality of colors. Pseudo-halftone processing by a binary or multivalued systematic dither method is performed by associating with a threshold matrix set based on Then, the image data after the pseudo halftone processing is collected and output to the LCD panel for color display.

A dither matrix (hereinafter, also simply referred to as a matrix) is a matrix in which a predetermined number of threshold values are arranged in the row / column direction and is associated with any one of a plurality of colors forming one pixel.

Next, a binary and multi-valued systematic dither method for a color image will be described. The dither method is
In a device with a small number of display gradations, this is a method of displaying intermediate gradations of display gradations in a pseudo manner. Binary dithers having a display gradation number of 3 and multi-value dithers having a display gradation number of 3 or more are used. Call. Multi-valued dither is composed of a combination of binary dithers.

First, the binary dither will be described.
First, the dither matrix showing the order of threshold values shown in FIG. 9E is determined, and the threshold matrix shown in FIG. 9B is calculated from the dither matrix. Next, the input image shown in (a) is compared with the threshold matrix shown in (b), and if the value of a pixel in the input image is greater than or equal to the corresponding threshold value, 255 is output, and if smaller, 0 is output. Threshold processing for output is performed, and a pseudo halftone image (output image) consisting of binary values of 0 and 255 shown in (d) is output. Now, even if the input image (a) is an image with 128 uniform densities, the average value of the pseudo halftone image shown in (d) which is the output image is 128, and the pseudo image is simulated by the binary pattern of 0, 255. Therefore, the halftone 128 is expressed.

The multi-value dither is executed by dividing the range of input gradation according to the multi-value used and performing binary dither within each range. When the multi-value is four-valued and the corresponding output gradation is 0,85,170,255, the input gradation is divided into three ranges of 0-85,86-170,171-255.

First, a threshold matrix shown in (b) to (d) is generated from the dither matrix shown in FIG. 10 (a) depending on which gradation range the input image belongs to. In the case of the input image shown in FIG. 9A, the gradation 128 is included in the range, so that the threshold matrix shown in FIG. 9C is generated. Next, using the matrix of (c), binary dither with gradations 85 and 170 is executed, and a pseudo halftone image as shown in (e) is output. Here, the threshold matrices shown in (b) to (d) do not have to be generated each time, and may be generated in advance. Further, other than this, a procedure for realizing multi-valued dither is known, but the present invention relates to a dither matrix and does not depend on a specific method of applying a dither threshold value.

The above is the case of performing dithering on an image in which one pixel is one color (gray). When dithering a color image, one pixel of the color image is R,
When it is composed of three colors of G and B, one pixel is divided into R, G, and B color components, and each image is regarded as an image of one color, and dithering is performed. At this time, the same matrix may be used for each of R, G, and B colors, or different matrices may be used.

Further, when associating different dither matrices with each color, as shown in FIG.
The G and B color matrices are individually stored in the memories 1101 to 11
03, and dither processing may be performed by the dither processing means 1104 to 1106. However, when the separate dither matrices are composed of a single matrix and a matrix shifted by a certain offset, one matrix is stored in the memory 1110 as shown in (b). Different dither matrices may be associated with the respective colors by the addressing means 1111 to 1113 which are independent for R, G, and B at the time of reading.

The addressing means 1111 to 1113 for shifting the matrix can be expressed by the following equations (0-1) and (0-2). Here, the matrix size is x_size in the x direction and y_size in the y direction.
The shift amount of the matrix is (x_size, y_size
In the case of e), it is sufficient to make the (m, n) threshold value of the matrix correspond to the (i, j) pixel of the input image. Also, addressing means 1111 to 11
If 13 is set to be the same, the same matrix can be associated with each color of R, G, and B.

[0012]   m = (i−x_shift)% x_size ... (0-1)   n = (j-y_shift)% y_size (0-2)

[0013]

By the way, in the conventional image processing method, when performing pseudo halftone processing by the binary or multivalued systematic dither method, each of the R, G, and B planes is processed. It is known that the image quality of the image displayed on the LCD panel is improved by associating R, G, and B dither matrices having different threshold arrangements. But R,
No technique has been found specifically showing what kind of policy the threshold arrangements of the G and B dither matrices should be made to differ, and by which effect the image quality is improved.

The present invention has been made in view of the above points, and is suitable for each plane of a plurality of colors forming one pixel when performing pseudo halftone processing by the binary or multivalued systematic dither method. An image processing method capable of improving the image quality of an image color-displayed on a display device configured by arranging dots of a plurality of colors as one pixel by making the matrices correspond to each other, An object is to provide an image processing device, an image processing program, and a computer-readable recording medium.

[0015]

In order to solve the above-mentioned problems, an image processing method of the present invention provides a display device configured by arranging dots of a plurality of colors as one pixel and arranging the pixels. When displaying an image, pseudo halftone processing is performed in which a dispersive matrix is associated with each plane showing each image of a plurality of colors forming one pixel, and pseudo halftone processing is performed. In an image processing method for displaying an image based on the generated image data, a basis of using a matrix of any one of a plurality of colors associated with each plane that is smaller than the number of the plurality of colors with a fixed threshold array A matrix is defined, and a threshold value array in a matrix of a color other than this basic matrix is statistically determined by determining a simultaneous ON probability that dots of two or more colors among a plurality of colors are simultaneously turned on adjacently. It is characterized by determining in accordance with the statistical value obtained by processing.

According to this method, the simultaneous ON probability (the lower the probability value, the more difficult it is for a plurality of ON dots to be adjacent to each other at the same time, therefore ON (ON) and OFF (OFF).
, Which indicates that the spatial frequency at which the dots alternate with each other becomes high, and the image quality is improved} is obtained, and the statistical value of the simultaneous ON probability is further obtained, and the threshold value array in the matrix of other colors to be combined with the basic matrix from this statistical value Since the determination is made, the image quality can be improved by obtaining the threshold value array corresponding to the statistical value that provides the best image quality and combining the matrix of this threshold value array with the basic matrix.

In the image processing method of the present invention,
The simultaneous ON probability is the matrix of each of a plurality of colors defined in any one of the basic matrices, and when the input gradation and the ON dot pattern correspond to each other, the matrix of the corresponding matrix is input for all the input gradations. By dividing the number of times each dot corresponding to each threshold is turned on by the total input gradation, the dot on probability that the above dots will be turned on is obtained, and the dot on probability of the matrix of each of the obtained plural colors is obtained. It is characterized by being obtained by multiplying by.

According to this method, the dot-on probability is obtained for each of the matrixes of a plurality of colors, each of which has a basic matrix defined for one pixel, and two or more colors among the plurality of colors are obtained from these dot-on probabilities. Since the simultaneous ON probability that the dots are simultaneously turned ON is obtained, the simultaneous ON probability can be obtained more appropriately.

In the image processing method of the present invention,
The statistic value is characterized in that it is obtained by any of the average value, standard deviation, maximum value, minimum value of each simultaneous ON probability in the corresponding matrix, alone, or in combination.

According to this method, since the statistic value is obtained by any of the average value, the standard deviation, the maximum value and the minimum value of the respective simultaneous ON probabilities in the matrix, alone or in combination, the image quality is added to the statistic value. The criteria for judging whether the quality is good or not are properly associated, and a more optimal threshold value array can be obtained by using this proper statistical value.

In the image processing method of the present invention,
The statistic value replaces the threshold value array in the matrix of other colors other than the basic matrix with the threshold value array of all patterns in this matrix, obtains the simultaneous ON probability in the threshold value array at the time of each replacement, and determines the individual simultaneous ON probability. It is characterized by what is required from.

According to this method, the threshold-value array in another color matrix combined with the basic matrix is replaced with all possible threshold-value arrays in this matrix, and the simultaneous ON probability in the threshold-value array at each replacement is calculated. , Because the statistical value of those simultaneous ON probabilities is obtained,
A statistic value indicating that the image quality is the best can be obtained from the simultaneous ON probabilities at each threshold value arrangement.

In the image processing method of the present invention,
It is characterized in that the color of the basic matrix is determined in the order of the size contributing to the luminance, or the colors other than the basic matrix are determined in the order of the size contributing to the brightness.

According to this method, since the colors of the basic matrix and the colors of the matrix other than the basic matrix are shifted from each other, ON dots (display sub-pixels) of the basic matrix or a matrix other than the basic matrix are OFF dots. Since the probability of intervening between the ON dots becomes higher, and the colors of the basic matrix or the colors of the matrix other than the basic matrix are determined in the order of the size that contributes to the luminance, the light of ON dots is larger than that of OFF dots. Since the light is illuminated, the darkness and darkness of the dot ON / OFF boundary becomes inconspicuous, so that even in an image of uniform density, the intensities of the image become inconspicuous and the image quality becomes high. In other words, the spatial frequency at which the ON and OFF dots alternate appears to increase the visual sensitivity, making it difficult to feel the contrast. In other words, it becomes easy to feel halftone (average gradation).

In the image processing method of the present invention,
The color of the basic matrix is the color that contributes most to the brightness, or the color other than the basic matrix is the color that contributes most to the brightness.

According to this method, since the colors of the basic matrix and the colors of the matrix other than the basic matrix are shifted from each other, ON dots (display sub-pixels) of the basic matrix or a matrix other than the basic matrix are OFF dots. Is more likely to be present, and the color of the basic matrix or the color of the matrix other than the basic matrix is the color that contributes the most to the luminance.
Since the light of N dots is irradiated more to the OFF dots, the lightness and darkness of the dot ON / OFF boundary is less noticeable, and the lightness and darkness of the image is less noticeable even for an image of uniform density, and high image quality is achieved. Become. In other words, O
The spatial frequency at which the N and OFF dots alternate appears to increase the visual sensitivity, making it difficult to feel the contrast. In other words, it becomes easy to feel halftone (average gradation).

Further, the image processing apparatus of the present invention collects dots of a plurality of colors into one pixel, and when displaying an image on a display device configured by arranging the pixels, each of the plurality of colors is displayed. In the image processing apparatus for displaying the image based on the image data that has been subjected to the pseudo halftone process for performing the binary or multi-valued process by associating the dispersive matrix with each plane showing the image, Of the multiple colors that are associated with each other, the matrix of any one of the colors that is less than the number of colors of the multiple colors is set as the basic matrix that uses the fixed threshold array, and the thresholds of the matrix of other colors other than this basic matrix are set. A determination means is provided for determining the array according to a statistical value obtained by statistically processing the simultaneous ON probability that dots of two or more colors among a plurality of colors are simultaneously turned on adjacently. It is characterized in that.

According to this device, the simultaneous ON probability is calculated,
Furthermore, the statistical value of the simultaneous ON probability is calculated, and the threshold value array in the other color matrix combined with the basic matrix is determined from this statistical value. Therefore, the threshold value array corresponding to the statistical value that gives the best image quality is calculated, and this threshold value array is calculated. The image quality can be improved by combining this matrix with the basic matrix.

Further, in the image processing apparatus of the present invention,
The simultaneous ON probability is the matrix of each of a plurality of colors defined in any one of the basic matrices, and when the input gradation and the ON dot pattern correspond to each other, the matrix of the corresponding matrix is input for all the input gradations. By dividing the number of times each dot corresponding to each threshold is turned on by the total input gradation, the dot-on probability that the dot is turned on is obtained, and the dot-on of each matrix of the obtained plural colors is obtained. It is characterized by being multiplied by the probability.

According to this apparatus, the dot-on probability is calculated for each of the matrixes of a plurality of colors, each of which has a basic matrix defined as one pixel, and two or more colors among the plurality of colors are calculated from these dot-on probabilities. Since the simultaneous on-probability that the dots of (2) are adjacently turned on at the same time is obtained, the simultaneous on-probability can be obtained more appropriately.

In the image processing apparatus of the present invention,
The statistic value is characterized in that it is obtained by any of the average value, standard deviation, maximum value, minimum value of each simultaneous ON probability in the corresponding matrix, alone, or in combination.

According to this apparatus, since the statistical value is obtained by the average value, the standard deviation, the maximum value, the minimum value of all of the simultaneous ON probabilities in the matrix, either alone or in combination, the image quality can be obtained as the statistical value. The criteria for judging whether the quality is good or not are properly associated, and a more optimal threshold value array can be obtained by using this proper statistical value.

In the image processing apparatus of the present invention,
The statistic value replaces the threshold value array in the matrix of other colors other than the basic matrix with the threshold value array of all patterns in this matrix, obtains the simultaneous ON probability in the threshold value array at the time of each replacement, and determines the individual simultaneous ON probability. It is characterized by what is required from.

According to this apparatus, while replacing the threshold array in the matrix of another color combined with the basic matrix with all the threshold arrays considered in this matrix, the simultaneous ON probability in the threshold array at each replacement is obtained. , Because the statistical value of those simultaneous ON probabilities is obtained,
A statistic value indicating that the image quality is the best can be obtained from the simultaneous ON probabilities at each threshold value arrangement.

Further, in the image processing apparatus of the present invention,
It is characterized in that the color of the basic matrix is determined in the order of the size contributing to the luminance, or the colors other than the basic matrix are determined in the order of the size contributing to the brightness.

According to this apparatus, the color of the matrix shifted from the basic matrix or the color of the basic matrix is determined in the order of the size that contributes to the brightness by changing the threshold array, so that dot ON / OFF Brightness and darkness of the boundary image are less noticeable, and the image quality becomes higher. Further, in the image processing device of the present invention, the color of the basic matrix is a color that most contributes to the brightness, or the color other than the basic matrix is a color that most contributes to the brightness. There is.

According to this apparatus, the color of the matrix shifted from the basic matrix or the color of the basic matrix when the threshold array is changed is the color that contributes most to the brightness, so that the image of the dot ON / OFF boundary is The brightness and darkness of the image becomes less noticeable, resulting in higher image quality.

Further, the image processing program of the present invention, when displaying dots on a display device constituted by arranging dots of a plurality of colors as one pixel and arranging the pixels,
An image displaying an image based on the image data that has been subjected to pseudo halftone processing in which binarized or multivalued processing is performed by associating a dispersive matrix with each plane showing each image of the plurality of colors In the processing program, a matrix of one of the colors that is less than the number of colors of the plurality of colors associated with each plane is defined as a basic matrix that uses a fixed threshold array, and a color other than this basic matrix is determined. A computer is executed to determine the threshold value array in the matrix according to the statistical value obtained by statistically processing the simultaneous ON probability that dots of two or more colors among a plurality of colors are simultaneously turned on adjacently. The feature is to let.

According to this program, the simultaneous ON probability is calculated, the statistical value of the simultaneous ON probability is calculated, and the threshold value array in the other color matrix combined with the basic matrix is determined from this statistical value. The image quality can be improved by obtaining the threshold value array corresponding to the improved statistical value and combining the matrix of this threshold value array with the basic matrix.

The recording medium of the present invention is characterized by recording the above-mentioned image processing program.

According to this recording medium, the simultaneous ON probability is calculated, the statistical value of the simultaneous ON probability is further calculated, and the threshold value array in the matrix of another color combined with the basic matrix is determined from this statistical value. The image quality can be improved by obtaining a threshold value array corresponding to a statistical value that improves the image quality and combining the matrix of the threshold value array with the basic matrix.

[0042]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings.

(Embodiment) FIG. 1 is a block diagram showing a configuration of an image processing apparatus according to an embodiment of the present invention.

The image processing apparatus 100 has an input means 10
1, a dither processing unit 104 having an optimum matrix determining unit 102, and an LCD panel 105 for color display.
And is configured.

The input means 101 takes in an image obtained by a scanner or an image pickup means as input image data.

The LCD panel 105 has a screen in which color filters of three primary colors of R, G, and B are arranged, and a color image is displayed on this screen by mixing the transmitted light that has passed through the color filters. Here, the LCD panel 105
2 is a pixel 2 in which subpixels (also referred to as dots) in which each of R, G, and B is a rectangle are grouped as shown in FIG.
01, and an image is displayed on a screen in which the same color of the pixel 201 is arranged in a line (arranged in a stripe shape).

The dither processing means 104 is the input means 101.
The input image data taken in by is separated into planes showing R, G, B images, and each R, G, B plane is associated with a threshold matrix set based on a distributed dither matrix. In addition, pseudo-halftone processing by the binary or multivalued systematic dither method is performed. The LCD panel 10 collects the image data after the pseudo halftone processing.
Output to 5. Since the threshold matrix is set based on the dither matrix, the dither matrix may be referred to for each of the R, G, and B planes.

In the optimum matrix determining means 102, the dither processing means 104 uses R, G, B in pseudo halftone processing.
When associating a dither matrix for each plane of, the dither matrix associated with each plane is
An optimum matrix that gives a high quality display image is used. This defines a dither matrix of one color or two colors of R, G, and B as a basic matrix, and a dither matrix of another color combined with this basic matrix provides a high quality display image when combined with the basic matrix. The optimal matrix is such that the thresholds are arranged so that

This optimum matrix has a threshold array different from that of the basic matrix. An example of a matrix having different threshold arrays is shown in FIGS. 3 (a) and 3 (b).
(A) shows that R, G, and B are all the same dither matrix of the threshold array, and (b) shows that R and B are the dither matrix of the same threshold array as (a) and G is the same. This shows that the dither matrices have different threshold arrays. If the G dither matrix shown in (b) is an optimum matrix, the other R and B dither matrices are the same basic matrix of the threshold array shown in (a).

Such a dither matrix is shown in FIG.
As shown in (a), the image 401 is laid out in a grid pattern 402. At this time, if R, G, and B shown in FIG. 3A are all dither matrices having the same threshold value array, as shown in FIG. 4B by Rm, Gm, and Bm, a grid pattern is shown in the image 401. 3 are all arranged at the coordinate position (0,0) representing the position of the upper left pixel of each of FIG.
In the dither matrix shown in (b), as shown in FIG. 4 (c), only the G dither matrix Gm has the other Rm,
It will be arranged at a position (0, 1) deviating from Bm. However, the arrangement position of the matrix is represented by coordinates (x, y), the position of the basic matrix that coincides with the checkerboard is set to (0, 0), and in this position, the dither matrix shifts to the right by one pixel. x becomes a positive 1, and y becomes a positive 1 at a position shifted by one pixel in the downward direction, (0,
The number of pixels deviated from 0) is represented by adding a positive or negative sign to the deviated direction.

In addition, FIG. 3C shows a case where R, G, and B shown in FIG. 8 shows a dot-ON pattern when data of uniform density such that 8 dots) are lit is input. FIG. 3D shows a case where R and B shown in FIG. 3B have the same threshold value array as that of FIG. 3A and G has a threshold value array different from that of other R and B. B shows a dot ON pattern in the case where data of uniform density such that half of the dots (8 dots) of the whole are turned on are inputted. Comparing (c) and (d), in (d), R
Since B and B are the same as the dither matrix in (a), the position of the ON dot is the same as in (c), but in G, the position of the dither matrix is (0, 1), so the ON dot is shifted downward by one pixel. It becomes a state. Since the matrix repeatedly corresponds to the image in a grid pattern, (0,
The matrix of G at the position 1) is (0,
0) The bottom line of the dither matrix at position “15, 7, 1
"3, 5" is shifted to the top row.

In this way, when the optimum matrix is combined with the basic matrix, as shown in FIG.
The spatial frequency of the pattern due to ON / OFF dots in the direction becomes high. Generally, the relationship between spatial frequency and visual sensitivity is
As shown by a curve 501 in FIG. 5, as the spatial frequency becomes higher, the visual sensitivity is lowered and the contrast is less likely to be felt, so that the ON dot pattern of (d) having a higher spatial frequency is more likely to have ON dot clusters and OFF dots. The lumps of dots are not perceived as separate lumps, but are felt more uniformly, and are perceived by the human eye as halftones of the average density. Since the input was assumed to be uniform gray data such that half of the dots would light up, the image quality would be better if it were felt as a halftone of the smoothed average density. It can be seen that the image quality is improved by combining the optimum matrices. Here, the optimum matrix is particularly effective when it is applied to G, which has the highest brightness indicating the intensity of brightness, among R, G, and B. Further, since the matrix shift is a relative problem between colors, the same effect can be obtained by applying it to R and B instead of G.

That is, the relationship between the pattern of ON / OFF dots and the spatial frequency is as follows:
As shown in (b), the larger the number of R, G, B three-color subpixels that are simultaneously turned ON in one pixel, the lower the spatial frequency and the lower the image quality. , The higher the spatial frequency, the higher the image quality.

For this reason, in the present embodiment, the optimum matrix determining means 102 has a probability that the R, G, B three-color sub-pixels are simultaneously turned ON in one pixel (hereinafter, R, G, B).
The dot simultaneous ON probability) is calculated, a statistical value is calculated from the R, G, B dot simultaneous ON probability, and the optimal matrix is determined by using this statistical value as an evaluation value.

Here, based on the dither matrix (basic matrix without displacement) shown in FIG. 3A, as shown in FIG. 6, the input gradation (17 gradations) and the output pattern (ON dot pattern). And correspond to 0 to 16 gradations, one of the dots of the pixels corresponding to each threshold is O
If the number of times of N = N, then N / 17 (1 of 17 gradations)
7) indicates the probability that a dot of any one of R, G, and B will be ON for all the input gradation inputs (hereinafter referred to as dot ON probability). The dot ON probability increases as the threshold value of the dither matrix decreases, and decreases as the threshold value increases.

This dot ON probability is calculated by the following equation (1) for each of the R, G, B dither matrices, and the product of these R, G, B dot ON probabilities is calculated based on equation (2). Simultaneously turning on the R, G, B dots by calculating
Probability is calculated.

[0057]

[Equation 1]

[0058]

[Equation 2] However, Xmat: dither matrix for X (X = R, G, B), THmax: maximum threshold, THmat (i,
j): threshold of dither matrix mat, Pmat_on
(I, j): dot ON probability of mat, PRGB_on
(I, j): R, G, B dot simultaneous ON probability.

Further, a method of obtaining the R, G, B dot simultaneous ON probability will be specifically described with reference to FIG. This Figure 7
In a matrix of size 4 × 4, when the threshold value of the G dither matrix, which is the optimum matrix, is shifted downward by one pixel (0, 1) from the basic matrix, R, G, B The state of the matrix for obtaining the dot simultaneous ON probability is shown.

First, the R dither matrix which is the basic matrix shown in FIG. 7A, the B dither matrix which is the basic matrix shown in FIG. 7B, and the threshold array shown in FIG. 0, 1) Dot O in each of the G dither matrix which is the shifted optimal matrix
Find N probabilities.

Since this dot ON probability is N / 17 described above, the dot ON probability of the pixel corresponding to each threshold value of the R dither matrix shown in (a) is, as shown in (d),
Each number N = 1 to 16 described in the matrix 1/17
It is the value multiplied by. For example, the dot ON probability of the pixel corresponding to the threshold 0 shown in (a) is 16/17, the dot ON probability of the pixel corresponding to the threshold 2 is 14/17, and the dot ON probability of the pixel corresponding to the threshold 15 is 1/17. Becomes

The dot ON probability of the B dither matrix shown in (b) is the same as that of the above R dither matrix. The dot ON probability of the G dither matrix shown in (c) is different from the above R and B in the arrangement of the respective threshold values, but similarly, each threshold value has the same number N as the number of times described in the matrix shown in (f).
= 1 to 16 multiplied by 1/17.

The R, G, B dot simultaneous ON probabilities can be obtained by multiplying the R, G, B dot ON probabilities thus obtained by those at the same pixel position in the matrix. That is, the value obtained by multiplying the number of times N = 16, 16, 1 at the position at the upper left (0, 0) of the matrix of (d), (e), (f) is the upper left (0, 0) of the matrix of (g). 0)
Since the value of the position of 256 is 256, this can be multiplied by (1/17) ³ to obtain a simultaneous ON probability of R, G, B dots of 256/4913.

Next, in order to calculate an evaluation value representing the likelihood of simultaneous ON of R, G, and B dots, from the probability of simultaneous ON of R, G, and B dots, the average value, maximum value, minimum value, standard deviation, etc. Calculate the statistical value of. The evaluation value is the following formula (3), the average value is the formula (4), the standard deviation is the formula (5), and the maximum value is the formula (6).
The minimum value is calculated by the equation (7).

[0065]

[Equation 3]

[0066]

[Equation 4]

[0067]

[Equation 5]

[0068]

[Equation 6]

[0069]

[Equation 7] However, Eval: evaluation value, αn: weighting coefficient (n =
1, ..., 4), M: size of matrix in x direction, N:
Size of matrix in y direction, Pave (Gmat, G
mat, Bmat): standard deviation of PRGB_on (i, j), Pmax (Gmat, Gmat, Bmat): P
The maximum value of RGB_on (i, j), Pmin (Gma
t, Gmat, Bmat): PRGB_on (i, j)
Is the minimum value of.

Although the evaluation value is a total value obtained by weighting a plurality of statistical values in the equation (3), one statistical value may be used alone or in combination. When only the average value is used alone as the evaluation value, the local high probability and the variation in the value are not considered, but if the maximum value and the standard deviation are added to form a linear sum of them, they are considered. The evaluation value, which is the total value, represents the likelihood of simultaneous ON of the R, G, and B dots, and the smaller the value, the better the image quality. In other words, the smaller the value, the more R, G,
It means that simultaneous ON of B dots is unlikely to occur and the image quality is improved.

Further, as shown in the following table (1), the smaller the average value, the maximum value and the standard deviation of each statistic value, the smaller the value of the average value, the maximum value and the standard deviation. , The larger the minimum value is, the R, G, B dots are turned on at the same time.
Is less likely to occur and the image quality is good. Since the minimum value tends to be opposite to the other statistical values as it is, it may be used as a value indicating that the smaller the value is, the less likely the simultaneous ON of R, G, and B dots occurs.

[0072]

[Table 1] Next, an image processing method by the image processing apparatus 100 having such a configuration will be described with reference to the flowchart shown in FIG. However, the matrix of size 4 × 4 shown in FIG. 7 described above is applied to this image processing.

(Step S801) First, when the dither processing means 104 separates the input image data obtained by the input means 101 into planes showing images for R, G, and B, the optimum matrix determining means 102. , R, G, B
It is determined whether the dither matrix of any one or two colors is used as the basic matrix. Here, it is assumed that it is determined that the R and B dither matrices are used as the basic matrix.

(Step S802) R is determined by the determination.
The dither matrix of each of B and B becomes the basic matrix of the threshold value array shown in FIGS. 7A and 7B.

(Step S803) The optimum matrix determination means 102 generates a G matrix (this is called an optimum candidate matrix) having all threshold arrays different from R and B defined as the basic matrix. . Here, for simplicity, it is assumed that the optimum candidate matrix is obtained by translating the basic matrix as shown in FIG.

(Step S804) The optimum matrix determination means 102 selects one of all the generated optimum candidate matrices.

(Step S805) The optimum matrix determination means 102 calculates a dot-ON probability matrix based on the selected optimum candidate matrix (G dither matrix). That is, as described above, the number N of times when any of the dots of the pixels corresponding to each threshold value is turned ON with respect to the input of all the input gradations is as shown in the relationship between (c) and (f) of FIG. , G corresponding to the respective threshold values of the dither matrix, and each N is multiplied by 1/17 to calculate the dot-ON probability matrix.

(Step S806) The optimum matrix determination means 102 calculates a dot-ON probability matrix based on the R and B dither matrices, which are basic matrices. That is, the number of times N is as shown in FIGS.
As shown in the relationships between (d) and (e), R and B are applied corresponding to the respective threshold values of the dither matrix, and N of each is multiplied by 1/17 to obtain R and B.
Each dot ON probability matrix is calculated.

(Step S807) The optimum matrix determination means 102 multiplies the values of the dot ON probabilities of R, G, and B obtained above by those at the same pixel positions in this matrix, An R, G, B dot simultaneous ON probability matrix shown in 7 (g) is calculated.

(Step S808) The optimum matrix determination means 102 calculates an evaluation value from each value of the R, G, B dot simultaneous ON probability matrix. This is because the statistical values of the average value, the standard deviation, the maximum value, and the minimum value are calculated by the above equations (4) to (7), and the evaluation value is calculated by the equation (3) using these statistical values. To be done. Here, for simplicity of explanation, it is assumed that only the average value is used as the evaluation value.

(Step S809) The optimum matrix determination means 102 determines whether or not the calculation of evaluation values for all optimum candidate matrices has been completed. As a result,
If not completed, the procedure returns to step S803 and step S803.
The processes up to 808 are repeated. Here, for example, it is limited that all the optimum candidate matrices have the patterns shown in Table 2. In Table 2, for example, (0, 1) indicates that the threshold array of the optimum candidate matrix is as shown in FIG.
It shows that it is the sequence shown in (c). If the calculation of the evaluation values (= average values) in all the optimum candidate matrices in Table 2 is completed, the process proceeds to step S810.

[0082]

[Table 2] (Step S810) The optimum matrix determination means 102 detects the best evaluation value from all evaluation values (= all average values) in Table 2 corresponding to all the calculated optimum candidate matrices. As can be seen from the results in Table 2, the average value = 9.15 at which the average value is the minimum value is detected as the optimum matrix.

(Step S811) That is, the optimum matrix determination means 102 determines the optimum candidate matrix of the threshold value array indicated by (0, 1) corresponding to the best evaluation value = 9.15 as the optimum matrix.

However, the above steps S801 to S811
In the processing of, the R and B dither matrices are defined as basic matrices, and the optimum matrix is determined.
Any one of G and B or any two colors can be defined as the basic matrix, and the optimum matrix can be determined by similar processing.

Next, in the dither processing means 104, the R and B planes are associated with the R and B dither matrices, which are basic matrices, and the G plane is associated with the G dither matrix, which is the optimum matrix. Attached. That is, when the pseudo halftone process is performed, the process of associating the G matrix with the G plane as the optimum matrix is performed. Then, the dither processing means 104
Then, the image data subjected to the pseudo halftone processing is collected and output to the LCD panel 105.
In FIG. 5, an image with good image quality corresponding to the image data is displayed.

As described above, according to the image processing apparatus of the present embodiment, when the dots of the three primary colors of R, G and B are collectively set as one pixel and the image is displayed on the LCD panel 105 in which the pixels are arranged, In addition, a matrix is associated with each plane showing each image of R, G, and B, and pseudo halftone processing by a binary or multivalued systematic dither method is performed, and an image based on the image data on which this processing is performed is performed. Is displayed. In this case, the optimal matrix determination means 102 determines a matrix of one color or two colors of R, G, and B associated with each plane as a basic matrix to be used with a fixed threshold array, and other than this basic matrix. The threshold array in the matrix of another color is determined according to the statistical value obtained by statistically processing the simultaneous ON probability that the R, G, and B dots are simultaneously turned ON in one pixel.

According to this structure, R, G, B all-dots simultaneous ON probability {The lower the probability value, the more difficult it is for a plurality of ON dots to be adjacent to each other at the same time.
N) and OFF (OFF) dots indicate that the spatial frequency at which the dots alternate becomes higher, and the image quality is improved}, and a statistical value of the R, G, B all-dots simultaneous ON probability is calculated. From the values the threshold array in the matrix of other colors to be combined into the base matrix is determined. That is, since the threshold value array corresponding to the statistical value that gives the best image quality is obtained, the image quality can be improved by combining the optimum matrix of this threshold value array with the basic matrix. Therefore, the image quality of the image displayed in color on the LCD panel 105 can be improved by using the basic matrix in combination with the optimum matrix. continue,
An image processing program according to the present embodiment and a computer-readable recording medium recording the image processing program will be described. The recording medium is capable of transmitting the data content of the program to the reading function of the computer, and is, for example, various magnetic disks, optical disks, or R that are built in, externally attached to, or detached from the computer.
OM, RAM, etc. correspond.

An image processing program is recorded in the program recording area of such a recording medium. This program collects dots of three primary colors of red, green and blue into one pixel on a computer, and displays each image of red, green and blue when displaying an image on a liquid crystal display panel in which the pixels are arranged. A matrix is associated with each plane shown to perform a pseudo halftone process by a binary or multivalued systematic dither method, and a process for displaying an image based on the image data subjected to this process is executed. A matrix of one color or two colors of red, green, and blue associated with each plane of is defined as a basic matrix with a fixed threshold array, and a threshold array in a matrix of colors other than this basic matrix is set. , The red, green, and blue dots are simultaneously turned on by one pixel, and a process of determining the simultaneous on probability according to a statistical value obtained by statistically processing is executed.

Further, the simultaneous on-probability obtained by the above-mentioned processing is the red color for which the basic matrix is set to either
In each of the green and blue matrices, when the input gradation and the on-dot pattern correspond to each other, the dots corresponding to the respective thresholds of the matrix are turned on for the input of all the input gradations. The number of times may be divided by all the input gradations to obtain the dot-on probability that a dot will be on, and the dot-on probabilities of the respective red, green, and blue matrices may be multiplied to obtain the dot-on probability. .

The statistical value obtained by the above processing is
Average value of each simultaneous ON probability in the corresponding matrix,
The standard deviation, the maximum value, the minimum value, all of them, alone, or in combination may be used. Further, the statistic value replaces the threshold value array in the matrix of other colors other than the basic matrix with the threshold value array of all patterns in this matrix, obtains the simultaneous ON probability in each replaced threshold value array, and determines the simultaneous ON You may make it calculated | required from each probability. Further, the colors of the base matrix or colors other than the base matrix are determined in the order of contributing to luminance, or the colors of the base matrix or colors other than the base matrix are
It is preferable that the color contributes most to the brightness.

Although the embodiments of the present invention have been described above, the present invention is not limited to such embodiments, and various embodiments can be carried out without departing from the scope of the invention. Is possible. For example, the following modifications are possible.

Modification 1: In the above-mentioned embodiment, the LCD panel is applied as the image display means, but it is not limited to this as long as it is an image display means in which one pixel is composed of sub-pixels of a plurality of colors. . For example, EL panel or P
It can also be applied to a display panel such as a DP.

Modification 2 In the above embodiment, the image display means is applied to an LCD panel having a stripe type array in which color filters of the same color are vertically arranged in a line, but one pixel is a subpixel of a plurality of colors. However, the present invention is not limited to this as long as the color display is performed by the mixed colors. For example, it can be applied to a self-luminous panel that does not use a color filter, or can be applied to a panel in which sub-pixels of a plurality of colors forming one pixel are arranged in a zigzag pattern.

Modified Example 3 In the above embodiment, the case where a plurality of colors forming one pixel are R, G and B is applied, but the present invention is not limited to this. For example, if multiple colors are C,
It can also be applied to cases such as M, Y, and K.

Modified Example 4 In the above-mentioned embodiment, the sub-pixel has a rectangular shape, but the present invention is not limited to this. Need not be an exact rectangle,
It can also be applied to a panel in which the vertical and horizontal directions are not uniform, for example, a panel having elliptical subpixels.

Modification 5: In the above embodiment, the dot simultaneous ON probability is applied as a target for calculating the statistic value for obtaining the optimum shift amount, but the present invention is not limited to this. Since the dot ON probability and the dot OFF probability have a complementary relationship of 1 when added together, the statistical values obtained from the dot simultaneous ON probability and the dot simultaneous OFF probability are always the same, and the dot simultaneous OFF probability is replaced by the dot simultaneous OFF probability. You may use.

Modification 6: In the above embodiment, the case where all the colors of a plurality of colors forming one pixel are simultaneously turned on by one pixel is applied as the simultaneous ON probability, but the present invention is not limited to this, for example, 1 Dots of two or more colors among a plurality of colors forming a pixel may be adjacent to each other at the boundary of the pixel and turned on at the same time.

Modification 7: In the above embodiment, the average value is applied as the statistical value of the dot simultaneous ON probability, but the present invention is not limited to this. For example, all the statistical values such as the average value, standard deviation, variance, maximum value, minimum value, and the like, which are obtained from the dot simultaneous ON probability, may be obtained as the sum of any one of them, or any combination thereof. It may be an inverse number or a weighting coefficient may be applied to each statistical value.

Modification 8: In the above embodiment, the optimum candidate matrix generating means applies the method of generating the optimum candidate matrix by translating the basic matrix, but the present invention is not limited to this. For example, the threshold value of the matrix may be replaced with all possible threshold value array patterns in the matrix.

In addition, in the image processing device and the image processing program described in the embodiments of the present invention, the basic matrix and the optimum matrix corresponding to at least one of the plurality of colors forming one pixel are stored in the memory. Alternatively, the case where the matrix is recorded in the recording medium has been illustrated, but the matrix does not need to be fixedly stored, and may be acquired through a communication system or the like by a user operation. Alternatively, the matrix may be attached to the image data by incorporating it in the header portion of the image file, and the matrix may be acquired each time the image is browsed, without the user's conscious operation. Further, the information transmitted / received in the communication system and the information incorporated in the header may be the basic matrix or the optimum matrix itself, or may be the information on the process of generating the optimum matrix from the basic matrix.

Finally, the present invention records the configuration as the invention of the image processing method, the configuration as the image processing apparatus, the program for realizing these, the data provided for the program, and the program as described above. The present invention can be realized in various forms such as a recording medium, a program, or a data signal including data provided for the program and embodied in a carrier wave.

[0102]

As described above, according to the present invention,
The dots of the three primary colors of red, green, and blue are collected into one pixel, and when displaying an image on a liquid crystal display panel in which these pixels are arranged, a matrix is associated with each plane showing each image of red, green, and blue. In the image processing method of displaying the image based on the image data on which the pseudo-halftone processing by the binary or multivalued systematic dither method is performed, red, green, and blue that are associated with each plane are associated. One of the two colors is defined as a basic matrix with a fixed threshold array, and the threshold array in a matrix of other colors other than this basic matrix is defined as one pixel of red, green, and blue dots. The simultaneous ON probabilities of being ON at the same time are determined according to the statistical value obtained by statistically processing.

That is, the simultaneous ON probability (the lower the probability value, the more difficult it is for a plurality of ON dots to be adjacent to each other at the same time, so the spatial frequency at which the ON (ON) dots and the OFF (OFF) dots alternate becomes high. It is determined that the image quality is improved}, and the statistical value of the simultaneous on-probability is determined, and from this statistical value, the threshold value array in the matrix of another color to be combined with the basic matrix is determined. In other words, since the threshold value array corresponding to the statistical value that provides the best image quality is obtained, the image quality can be improved by combining the optimal matrix having this threshold value array with the basic matrix. Therefore, the quality of the image displayed in color on the liquid crystal display panel can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an image processing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing pixels of an LCD panel in the image processing apparatus.

FIG. 3 is a diagram showing a threshold array and R, G, B dot ON patterns in a 4 × 4 Bayer matrix.

FIG. 4 is a diagram showing a state in which only the G dither matrix is displaced when the R, G, and B dither matrix are spread over the image and the threshold arrays of the dither matrix only for G are different.

FIG. 5 is a characteristic diagram of spatial frequency and visual sensitivity.

FIG. 6 is a dot ON for input of all input gradations when an input gradation corresponds to an output pattern (ON dot pattern) in a 4 × 4 Bayer type matrix without shifting.
It is a figure which shows a state.

FIG. 7 is an explanatory diagram of a process of obtaining an R, G, B dot simultaneous ON probability matrix when the G dither matrix of R, G, B is shifted.

FIG. 8 is a flowchart for explaining an optimum matrix determination process by the optimum matrix determination means.

FIG. 9 is a matrix diagram for explaining binary dither.

FIG. 10 is a matrix diagram for explaining multi-valued dither.

FIG. 11 is a block diagram of an apparatus for associating different dither matrices with R, G, and B colors.

[Explanation of symbols]

100 image processing apparatus 101 input means 102 optimal matrix determination means 103 matrix moving means 104 dither processing means 105 LCD panel 201 1 pixel 501 by a group of sub-pixels of three primary colors of red, green and blue Spatial frequency-visual sensitivity characteristic curves 1101 to 1103 1110 memories 1104-1106 dither processing means 1111-1113 addressing means Rm red dither matrix Gm green dither matrix Bm blue dither matrix

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 1/405 H04N 1/46 B 5C082 1/52 1/40 C 1/60 DF Term (reference) 5B057 AA20 BA29 CA01 CA08 CA12 CA16 CB01 CB07 CB12 CB16 CE13 CE16 CH01 DA16 5C006 AA12 AA21 BB11 FA56 5C077 LL19 MP08 NN09 PP32. 5C082 AA00 AA01 BA12 BA34 BA35 BB16 BD02 CA11 CA81 DA53 MM10

Claims (14)

[Claims] 1. When displaying an image on a display device configured by arranging dots of a plurality of colors as one pixel, the dots are dispersed for each plane showing each image of the plurality of colors. In an image processing method of performing pseudo halftone processing, which performs binary or multi-valued processing by associating a type matrix, and displaying an image based on the image data on which the processing is performed, Among the colors, a matrix of any one of the colors less than the plurality of colors is defined as a basic matrix to be used with a fixed threshold array, and the threshold arrays in the matrix of other colors other than this basic matrix are An image processing method, characterized in that two or more dots among colors are determined in accordance with a statistical value obtained by statistically processing the simultaneous ON probability that adjacent dots are simultaneously ON at the same time. . 2. The simultaneous on-probability is the total input gradation when the input gradation and the on-dot pattern correspond to each other in the matrix of the plurality of colors in which the basic matrix is defined. For each input, the number of times each dot corresponding to each threshold value of the matrix is turned on is divided by the total input gradation to obtain the dot-on probability that the dot is turned on. The image processing method according to claim 1, wherein the image processing method is obtained by multiplying dot-on probabilities of matrices of each of the plurality of colors. 3. The statistical value is obtained by any one of an average value, a standard deviation, a maximum value and a minimum value of respective simultaneous ON probabilities in the corresponding matrix, alone or in combination. 1. The image processing method described in 1. 4. The statistical value replaces a threshold value array in a color matrix other than the basic matrix with a threshold value array of all patterns in the matrix, and calculates the simultaneous ON probability in each of the replaced threshold value arrays. The image processing method according to claim 1 or 3, wherein the image processing method is obtained from each of the simultaneous ON probabilities. 5. The color of the basic matrix is determined in order of magnitude contributing to luminance, or the colors other than the basic matrix are determined in order of magnitude contributing to luminance. The image processing method according to any one of claims 1 to 4, which is characterized in that. 6. The color of the basic matrix is a color that contributes most to brightness, or the color other than the basic matrix is a color that contributes most to brightness. 4. The image processing method according to any one of 4 above. 7. When displaying an image on a display device configured by arranging dots of a plurality of colors as one pixel, the pixels are dispersed for each plane showing each image of the plurality of colors. In an image processing apparatus that performs pseudo halftone processing that performs binary or multi-valued processing by associating a type matrix with each other, and displays an image based on the image data on which the processing has been performed, Among the colors, a matrix of any one of the colors less than the plurality of colors is defined as a basic matrix to be used with a fixed threshold array, and the threshold arrays in the matrix of other colors other than this basic matrix are It is characterized in that a determination means for determining the simultaneous ON probability that two or more dots among the colors are adjacently turned ON at the same time according to a statistical value obtained by statistically processing is provided. The image processing apparatus. 8. The simultaneous on-probability is the total input gradation when the input gradation corresponds to an on-dot pattern in each matrix of the plurality of colors in which the basic matrix is defined. For each input, the number of times each dot corresponding to each threshold value of the matrix is turned on is divided by the total input gradation to obtain the dot-on probability that the dot is turned on. 8. The image processing apparatus according to claim 7, wherein the image processing apparatus is obtained by multiplying dot-on probabilities of matrices of each of the plurality of colors. 9. The statistical value is obtained by any one of an average value, a standard deviation, a maximum value, a minimum value of the respective simultaneous ON probabilities in the corresponding matrix, alone or in combination. 7. The image processing device according to 7. 10. The statistical value replaces a threshold value array in a matrix of colors other than the basic matrix with a threshold value array of all patterns in the matrix, and calculates the simultaneous ON probability in each of the replaced threshold value arrays. 10. The image processing device according to claim 7, wherein the image processing device is obtained from each of the simultaneous ON probabilities. 11. The color of the basic matrix is determined in order of magnitude contributing to luminance, or the colors other than the basic matrix are determined in order of magnitude contributing to luminance. The image processing apparatus according to any one of claims 7 to 10, which is characterized in that. 12. The color of the basic matrix is a color that contributes most to brightness, or the color other than the basic matrix is a color that contributes most to brightness. The image processing device according to any one of 10. 13. When displaying an image on a display device configured by arranging dots of a plurality of colors as one pixel, the dots are dispersed for each plane showing each image of the plurality of colors. In an image processing program for performing pseudo halftone processing in which a type matrix is associated with binary or multivalued processing, and an image based on image data subjected to this processing is displayed, Of the colors, a matrix of any one of the colors less than the plurality of colors is defined as a basic matrix that uses a fixed threshold array, and the threshold array in a matrix of a color other than this basic matrix is defined as the plurality of colors. The process of determining the simultaneous ON probability that two or more dots in the same area are simultaneously turned on adjacently is determined according to the statistical value obtained by statistically processing. The image processing program for causing performed. 14. A computer-readable recording medium on which the image processing program according to claim 13 is recorded.