JPH05324812A - Color data correcting system - Google Patents

Abstract

PURPOSE:To correct color disorder due to the mismatching of a dither pattern while maintaining features in a character or photograph area by recognizing an abnormal pixel whose color is disordered from the color state of peripheral normal pixels and correcting the abnormal pixel. CONSTITUTION:When a character written in a character area 22 where color 21 expected to appear is set to white and black is locally viewed, the character consists of a black pixel 24, a white pixel 25, a red pixel 26, and a yellow pixel 27 as shown by a process area 23. This results from that the red pixel 26 and yellow pixel 27 which are not expected to appear since the dither pattern at the time of the processing of the respective colors R, G, and B are discordant at the boundary of the character, etc. When this abnormal pixels are viewed in the order of R, G, and B, red pixel data is (100) and yellow pixel data 29 is (110). Black data 210 and white data 211 expected to appear in this area are compared by coincidence detection 212. Consequently, a corrected pixel 215 is selected as the red pixel data 28 by corrected pixel selection 213 and a corrected pixel 214 is selected as the yellow pixel data 29.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color data correction system when a color image is formed by performing dither processing for each of RGB color components.

[0002]

2. Description of the Related Art A conventional technique is disclosed in JP-A-63-12946.
There is No. 9 publication. A conventional technique will be described with reference to the flowchart of the conventional system shown in FIG. First, an abnormal pixel that needs to be corrected is detected. With respect to the detected abnormal pixel, a normal pixel is searched for in the order of decreasing distance among the non-adjacent peripheral pixels, and if there is, the abnormal pixel is replaced with the searched normal pixel. Further, if a plurality of normal pixels exist at equal distances, they are randomly selected. Further, if there is no normal image for a predetermined distance or more, the normal pixel is brought from the already corrected pixel.

[0003]

However, in the prior art, the abnormal pixel detecting means can detect only the pixel abnormality with respect to the abnormality of the input image, and the pixel abnormality detection caused by the image processing after the input is taken into consideration. Absent. Further, when correcting an abnormal pixel, since a normal pixel is searched for from an abnormal pixel that is not adjacent, there is a property that it is not suitable for correcting a pixel group in which pixels are adjacent and complicatedly gathered like a character.

In this system, the characteristic of the area in the character area or the photographic area of the image is determined against the color irregularity of the pixel due to the disagreement of the dither pattern which occurs when the color images of R, G, and B are dithered to form a color image. It is intended to be fixed while being retained.

[0005]

As means for solving the above-mentioned problems, an area in which a color appearing in a color dither image is limited, a means for designating the color, and a means for detecting an abnormal pixel after image processing are provided. It consists of means for correcting abnormal pixels.

[0006]

According to the color data correction method of the present invention, in order to correct the pixel disorder that appears due to the mismatch of the dither patterns when the input color image consisting of characters and photographs is dithered into RGB, the character area is first corrected. Is the location of the region,
Specify the size and the colors that make up the area. Thereby, the text area and the photo area can be modified by different means. First, the character region is basically composed of two colors, that is, the background color and the character color, so that the color can be limited and the fact that the pixel irregularity is likely to occur at the color boundary makes it possible to use the pixel to correct the adjacent normal pixel. .. Therefore, if a color other than the specified color appears, the means for detecting abnormal pixels
An abnormal pixel. The correction means detects the coincidence between the normal pixel and the abnormal pixel which are adjacent to each other, and corrects the normal pixel in which the primary colors of RGB constituting the pixel match more.

Next, with respect to the photographic area, locally, the color and density of the photographic area change smoothly, so that it is not necessary to strictly correct the color on a pixel-by-pixel basis. Use that the abnormal pixels must be searched for from the pixels in the area because the colors cannot be limited, and that the primary colors with different colors in the local area are considered to be composite colors because the primary colors are generated due to the mismatch of the dither patterns. .. That is,
The means for detecting an abnormal pixel detects a primary color within the processing area. The means for correction is to combine RGB in order from the primary color pixels that appear less in number of the primary colors in the area. "
Correct the pixel to one of the colors of "white", "yellow" that combines RG, "cyan" that combines GB, and "magenta" that combines RB, and eliminate the primary colors in the area as much as possible. Black pixels are placed in place of pixels, and the remaining primary colors remain unchanged.

[0008]

EXAMPLES Examples of the present invention will be shown below. FIG. 1 is a flow chart of this system, FIG. 2 is a diagram showing a character region correction system, and FIG. 3 is a diagram showing a photo region correction system.

The present invention will be described with reference to FIG. First, for a color image that has been input and subjected to dither processing for each of RGB, a character region and a color that should appear therein are set. (S
1) Next, 25 pixels are read so as to form a 5 × 5 rectangle and set as a processing area. (S2) Next, it is determined whether or not the processing area belongs to the previously set character area.
(S3) When the determined result is the character area, the color of the pixel in the processing area is compared with the color that should appear, and the abnormal pixel is detected. (S4) Next, it is determined whether or not the pixel in the processing area is an abnormal pixel (S5), and if the pixel is an abnormal pixel, matching detection with an adjacent normal pixel is performed. (S6) From the result of the match detection, the abnormal pixel is corrected to the normal pixel having the larger number of matched primary colors.
(S7) When the processing area is not a character area, it is considered to be a photograph area. At this time, first, the pixels of the primary color in the processing area are detected as abnormal pixels. (S8) Next, it is determined whether the pixel in the processing area is an abnormal pixel. (S9) Next, the pixels of the primary color in the processing area are moved, and the "magenta" GB pixels that combine the "white" RG pixels that combine the RGB pixels and the "yellow" RB pixels that combine Correct the combined "cyan". (S10) A black pixel is arranged at the position where the moved pixel was originally located. (S11) When there is no abnormal pixel in the processing area, or after completion of correction, it is determined whether or not all pixels have finished (S12). If not completed, the pixel of the next processing area is read, and if all pixels have finished. If it ends.

Next, a method of correcting a character area consisting of black characters on a white background will be described with reference to FIG. "A" is written in the character area 22 where the color 21 that should appear is set to white and black.
As seen in the processing area 23, the black pixel 24, the white pixel 25, the red pixel 26, and the yellow pixel 27 are locally viewed.
It consists of This is especially for character boundaries.
The red pixel 26 and the yellow pixel 2 that are not colors that should not appear because the dither patterns when processing each GB color do not match
This is because 7 appears. When these abnormal pixels are viewed in the order of RGB, the red pixel data 28 becomes "100" and the yellow pixel data 29 becomes "110". Therefore, the black data 210 and the white data 211 that are the colors that should appear in this area.
And match detection 212 respectively. From the result, in the correction pixel selection 213, the correction pixel 215 is selected for the red pixel data 28, and the correction pixel 214 is selected for the yellow pixel data 29. As a result, the black corrected pixel 217 and the white corrected pixel 218 are displayed on the corrected processing area 216.
Is placed.

Next, a method of correcting the photographic area will be described with reference to FIG.

When the image of the face in the photograph area 31 is viewed locally, it is composed of black pixels 33, yellow pixels 34, red pixels 35 and green pixels 36 as in the processing area 32. Here, since the dither patterns when processing the RGB colors do not match, red pixels 35 are present in the area representing the skin color.
And the green pixel 36 appears as an abnormal pixel. In order to correct this abnormal pixel, first, the pixels of the primary color are counted, and the pixels of the primary color in which the number of appearances are small are moved. In this case, as shown in Table 37 showing the number of abnormal pixels, the number of green pixels that appear is one, and since it is the smallest, it is moved from the green pixels.
Looking at the processing area 31 including this abnormal pixel for each RGB, R plane data 38, G plane data 39, B
It becomes like the plain data 310. In this case, in order to correct the green primary color pixel 311, the R plane data 38,
A search is performed around pixels having the same position on the B plane data 310. The B plane data 310 has no "1" pixels, and the R plane data 38 has "1" pixels on the left and right. The method of moving and combining pixels is (1)
The pixels are selected in order from the most recent pixel. (2) For equidistant pixels,
Select left, right, up, and down. Therefore, as the pixel for combining the green primary color pixel 311 of the G plane data 39, the pixel 312 on the left is selected. In the combination method, the green primary color pixel 311 is moved to obtain a logical sum, and the pixel 313 of “0” is placed at the position before the movement. Next, another abnormal pixel is tried to be corrected, but since the pixels of the primary colors cannot be combined, the correction ends. As a result, the corrected black pixel 315 and the corrected yellow pixel 315 are placed in the corrected processing area 314.

As described above, in the present embodiment, only the case where the character area is monochrome with white and black has been described, but the case where the character area is composed of other colors can be applied. Further, the present invention can be applied to not only the printing and displaying of pixels but also the pre-processing of image accumulation.

[0014]

The present invention has the following effects. It is possible to automatically correct the disturbance of the pixel in dot unit due to the disagreement of the dither pattern which performs the dither processing after the image input. By adopting different correction methods for the text area and the photo area, the characteristics of the area are not impaired.

[Brief description of drawings]

FIG. 1 is a diagram showing a flowchart of the present system.

FIG. 2 is a diagram illustrating an example of a correction method of a character area.

FIG. 3 is a diagram showing an example of a correction method for a photographic area.

FIG. 4 is a diagram showing a flow chart of Japanese Patent Laid-Open No. 63-129469, which is a conventional method.

[Explanation of symbols]

21 ... Color to appear, 22 ... Character area, 23 ... Processing area, 24 ... Black pixel, 25 ... White pixel, 26 ... Red pixel, 27
... yellow pixel, 28 ... red pixel data, 29 ... yellow pixel data,
210 ... Black data, 211 ... White data, 212 ... Match detection, 213 ... Correction pixel selection, 214 ... Correction pixel, 215
... corrected pixel, 216 ... corrected processing region, 217 ... black corrected pixel, 218 ... white corrected pixel, 31 ... photographic region, 3
2 ... Processing area, 33 ... Black pixel, 34 ... Yellow pixel, 35 ... Red pixel, 36 ... Green pixel, 37 ... Table showing the number of abnormal pixels,
38 ... R plane data, 39 ... G plane data, 3
10 ... B plane data, 311 ... Green primary color pixel, 31
2 ... Pixel on the left side, 313 ... Pixel of "0", 314 ... Processing area after correction, 315 ... Black pixel after correction, 316 ... Yellow pixel after correction.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenichi Nishikawa Inventor Kenichi Nishikawa 292 Yoshida-cho, Totsuka-ku, Yokohama Hitachi, Ltd. Microelectronics Device Development Laboratory

Claims (4)

[Claims] 1. A device in which a color image is dithered for each of the RGB color components, accumulated in a storage device, displayed on a color display or a color printer, and printed in a device, and a pixel in which a color is disturbed caused by a mismatch of dither patterns is regarded as an abnormal pixel,
When a pixel in which the color is not disturbed is regarded as a normal pixel, the abnormal pixel is recognized from the color condition of the surrounding normal pixel, and the abnormal pixel is corrected from the color condition of the normal pixel. Color data correction method. 2. The color data correction method according to claim 1, wherein a pixel of a primary color appearing in an m × m area is set as the abnormal pixel, and the pixel of the primary color is moved to select any of white, yellow, magenta, and cyan. A color data correction method characterized in that the pixels of the primary colors are eliminated as much as possible by combining the above-described ones so that the areas where the pixels disappear by moving are made black. 3. A monochrome image or a multicolor image is converted into RGB.
In a device that performs dithering for each color component and displays and prints on a color display or color printer, set the color that should appear in a region such as a character region where the color that appears in advance is limited, and set the other colors. Is the abnormal pixel, and the abnormal pixel is corrected from the state of the surrounding normal pixels. 4. The color data correction method according to claim 3, wherein the color of the abnormal pixel is separated into primary colors, and the primary color forming the color that should appear is detected to be coincident. Color data correction method characterized by correcting to many colors.