JP4533683B2 - Image processing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image processing apparatus of a digital device using an image compression technique such as a digital copying machine and a digital camera, and an image forming apparatus using the image processing apparatus.

  In image data including characters, for example, even if the gradation of the character data is reduced and the image data size is reduced, the description information of the characters can be transmitted. If the image data size is reduced, it is possible to realize the description information of the characters of the image data with a lower communication load even when transmitting the description information using communication. In addition, it is possible to store more information in a storage device such as a hard disk while maintaining the written information of characters.

Therefore, when reducing the resolution of the character color information in the character data, conventionally, the reduction / scaling process by the averaging process is performed regardless of whether the character area exists or not. An example of this conventional case is shown in FIG. Assume that the original image has a data value such as 1001 and is a single-color grayscale image. Since each pixel has a data value of 8 bits (1 byte), it can be seen that the data size of the original image is a data size of 1 × 16 = 16 bytes. When this image is compressed to a size of ¼, 4 bytes, it is common to reduce the size of the 2 × 2 block (the shaded portion of 1003) to the block of 1 × 1 (the shaded portion of 1004) with an average reduction. Is. When calculated, the shaded block of 1004 is (0 + 255 + 255 + 255) / 4 = 191
It becomes. By performing this processing, the original image 1001 should be compressed as 1004.

As a related technique, for example, the invention disclosed in Patent Document 1 or 2 is known.
JP 2002-368986 A JP 2003-169221 A

  By the way, when the image data 1004 and 1005 compressed to 1/4 size in this way are expanded (reverted) to the original 4 × 4 16-pixel image, it should be 1006. The image 1006 becomes an image 1007, which is different from the image 1002 of the original image 1001 before compression.

On the other hand, when the character area is small, for example, in the case of a thin line character, the color of the character may be light. This example will be described with reference to FIG.
In FIG. 7, when the original image data has a data value such as 4001 composed of 4 × 4 16 pixels, an image based on the data value becomes 4002. The original image can be separated like character color information data (gradation degree data) 4003 and character region information data 4004. When the character color information data 4003 has been reduced in resolution by 1/4 each in the vertical and horizontal directions according to the prior art, the average value of all 4 × 4 16 pixel values is taken and the value is replaced with the representative value of the character color. . When calculated from 4003 character color information data,
(0 + 250 + 0 + 0 + 254 + 255 + 250 + 253 + 0 + 250 + 0 + 0 + 0 + 250 + 0 + 0) / 16 = 110
It becomes. If an image is created based on the character color information 4005 and the character area information data 4006 with the reduced resolution, it should be as indicated by reference numeral 4007. When the image image indicated by the reference numeral 4007 is compared with the image image 4002 of the original image data, the result is that the color of the characters becomes lighter.

Accordingly, an object of the present invention is to prevent image deterioration including reducing the data size while maintaining the description information of characters.

To achieve the above object, the first means includes separating means for separating the image data into a character color information having a pixel value of the character region information and the multi-level pixel values of the multi-values of the character color information A resolution reducing means for reducing the resolution by averaging pixel values within the character area range in the character area information, and a data value of the character color information subjected to the resolution reducing process by the resolution reducing means On the other hand, by referring to a table in which the character color information is associated with the binarized information of each color, the character color information and the binarized information of each color are replaced and quantized. Quantizing means for determining the binarized information value of each color according to the information value of the character color information of each color , and the input color image data is converted into a character area by the separating means. information and each color Separating the first character color information, converting the first character information for each color in the second text color information of each color after resolution reduction processing by the resolution reduction means, the second character color information for each color Is converted into the binarized information value of each color after being quantized by the quantization means, and the original resolution is obtained by applying the binarized information value of each color after the quantization to the character area information. It is characterized in that an image is created.

The second means is characterized in that, in the first means, the resolution reduction process by the resolution reduction means is a reduction scaling process.

Third means includes separating means for separating the image data into a character color information having a pixel value of the character region information and the multi-level, the character area information a pixel value of a multi-value of the character color information Resolution reduction means for reducing the resolution by averaging the pixel values in the character area range in the character area , and the character color with respect to the data value of the character color information subjected to the resolution reduction processing by the resolution reduction means By referring to the table in which the information and the binarized information of each color are associated, the character color information and the binarized information of each color are replaced, and quantization is performed. Quantization means for determining the binarized information value of each color according to the information value of the information , and the input color image data from the character area information and the first color of each color by the separation means Separated into character color information , Converting the first character information for each color in the second text color information of each color after resolution reduction processing by the resolution reduction means, after quantizing the second character color information of each color by the quantization means An image processing method for generating an image image of the original resolution by converting the binarized information value of each color and applying the binarized information value of each color to the character area information It is characterized by.

According to the present invention, it is possible to prevent image degradation by compressing the data size by reducing the resolution of the second character color information and storing it, and returning to the original resolution using the character area information. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
FIG. 1 is a block diagram showing a main part of an image processing apparatus according to the first embodiment of the present invention. This image processing apparatus includes a character area information / character color information separation means (hereinafter abbreviated as a separation unit) 101 for separating input image data 100 from character area information and character color information, and a character color separated by the separation unit 101. Character color information resolution reducing means (hereinafter referred to as a resolution reduction unit) 102 that performs processing for reducing the resolution of information data is included. Note that the character area information data 103 is output from the separation unit 101, and the character color information data 104 is output from the resolution reduction unit 102. Note that the configuration for separating the character area information from the input image data 100 is a well-known technique as an image area separation circuit, and is not particularly described here.

FIG. 2 is a diagram for explaining the processing contents processed by the image processing apparatus of FIG. In this embodiment, the data value “0” is white and the data value “255” is black. The original image, in other words, the image indicated by the input image data 100 has a data value as indicated by reference numeral 5001 by the separation unit 101 and is a single-color grayscale image. Each pixel can have a data value of 8 bits (1 byte), and the data size of the original image is 1 × 16 = 16 bytes. The original image should be a black image as indicated by reference numeral 5002. The image data can be separated into character area information 5004 (each pixel is 1 bit) and character color information 5003 by the separation unit 101 described above. When the character color information 5003 after separation is reduced by a resolution reduction means to 1/4 each of vertical and horizontal by resolution reduction processing, the sum of all the pixel values of the character color information 5003 is 1/4 × 1 / 4
(0 + 255 + 255 + 0 + 255 + 255 + 255 + 255 + 255 + 255 + 255 + 255 + 0 + 255 + 255 + 0) / 16 = 191
Thus, the character color information is indicated by reference numeral 5005 after the resolution reduction processing is performed by the resolution reduction unit 102.

  When the character color information 5005 after the resolution reduction processing is used as a representative value of the character color and an image is created from the character area information 5006, an image as indicated by reference numeral 5007 can be obtained. Also, the size of the original image is 16 bytes, but the character color information (1 byte) and the character area information (16 bits = 2 bytes) after the resolution is reduced to only 3 bytes. It is possible to obtain the same image diagram.

<Second Embodiment>
FIG. 3 is a block diagram showing the configuration of the image processing unit of the second embodiment. In this embodiment, the resolution reduction unit 102 that reduces the resolution of the character color information with respect to the image processing unit of the first embodiment uses the character region information data 103 from the separation unit 101 to perform the character in the character region. Only the color information data value 105 is set as an effective data value, and reduction scaling is performed based on the effective data value.

  FIG. 4 is a diagram for explaining the processing contents processed by the image processing apparatus of FIG. Also in the second embodiment, the data value “0” is white and the data value “255” is black. The original image has a data value such as 6001 and is a single-color grayscale image. Assume that the image is a very thin line such as reference numeral 6002.

When the original image data 6001 is separated from the character area information / character color information by the separation unit 101, the character color information becomes 6003 and the character area information 6004. When the resolution reduction processing is performed by the low resolution unit 102 on the separated character color information 6003, the character region information 6004 is referred to and the resolution reduction processing is performed by averaging the character color information 6003 within the character region range. If you do
(0 + 250 + 0 + 0 + 0 + 255 + 0 + 0 + 0 + 250 + 0 + 0 + 0 + 250 + 0 + 0) / (1 + 1 + 1 + 1) = 251
And character color information 6005 is obtained.

  When an image is created from the character area information 6006 for the character color information 6005 after the resolution reduction process, an image as indicated by reference numeral 6007 can be obtained. Since the density of this image is “251” in terms of 8-bit, it is possible to improve the color fading as shown in the previous figure.

  In other words, when the resolution of conventional character color information is reduced, the character area is small in order to perform reduction scaling processing by averaging all pixels regardless of where the character area does not exist in the character data. As described with reference to the above-described figure, for example, in the case of a thin line character, the color of the character may be light. According to this embodiment, the density is averaged only in the character region. Therefore, the thinness of the characters can be improved.

<Third Embodiment>
FIG. 5 is a block diagram showing the configuration of the image processing unit of the third embodiment. In this embodiment, character color information quantization means (hereinafter referred to as a quantization unit) that quantizes data values for character color information data whose resolution has been lowered by the resolution reduction unit 102 in the second embodiment. ) 106 is provided. The quantization unit 106 determines the information value of each color after quantization according to the information value of each color when the character color is a color image of two or more colors.

  FIG. 6 is a diagram for explaining the processing contents processed by the image processing apparatus of FIG. In the third embodiment, the data value “0” is black and the data value “255” is white. In this embodiment, as described with reference to FIG. 4, the color character information is subjected to the resolution reduction processing by the resolution reduction unit 102 for each color, and a character color information value as indicated by reference numeral 7001 is obtained for each RGB color. To do. If the character area information value 7002 at this time is a thin line of one pixel as shown in FIG. 6, the image image should be a red line image as indicated by reference numeral 7003. When data value replacement processing is performed on the original image based on a table such as reference numeral 7004, the values such as R = 170, G = 20, and B = 20 illustrated in FIG. Assuming that the quantization threshold is “128”, it can be seen from the table that R = 255, G = 0, and B = 0. By replacing this data value, it is possible to convert it into a clearer red color character.

  That is, according to this embodiment, the black character can be changed into a clear black character, and the color character can be changed into a clearer color character, and the readability of the character can be improved.

<Image forming apparatus>
The image processing apparatus according to the first to third embodiments configured and functioning as described above is mounted, for example, in an image forming apparatus having the following configuration.

  FIG. 9 is a diagram schematically showing an overall configuration of an image forming system according to an embodiment of the present invention. 9, the image forming system according to the present embodiment includes a color image forming apparatus PR having a scanner and a printer function, host computers PC1, PC2, and PC3 such as a PC, a LAN and a parallel I / F (PI / F). Print data from the host computers PC1, PC2, and PC3 can be transmitted to the image forming apparatus PR via the LAN and parallel I / F (PI / F), and an image can be output from the image forming apparatus PR. It is configured as follows.

  The color image forming apparatus PR forms, for example, an independent image forming station for each color of the tandem YMCK, and superimposes each color image on the intermediate transfer belt so that the full color is applied to the sheet fed from the sheet feeding device. Is formed, and the paper is discharged on the sorter side.

  Image data is input from PC1 and PC2 connected via LAN, PC3 connected locally, or a scanner provided in the upper part of the color image forming apparatus PR main body.

It is a block diagram which shows the principal part of the image processing apparatus which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the processing content processed by the image processing apparatus of FIG. It is a block diagram which shows the structure of the image process part of the 2nd Embodiment of this invention. It is a figure for demonstrating the processing content processed by the image processing apparatus of FIG. It is a block diagram which shows the structure of the image process part of the 3rd Embodiment of this invention. It is a figure for demonstrating the processing content processed by the image processing apparatus of FIG. It is a figure for demonstrating the problem of a prior art. It is a figure for demonstrating the problem of a prior art. 1 is a diagram schematically showing an overall configuration of an image forming system according to an embodiment of the present invention.

Explanation of symbols

100 input image data 101 character area information / character color information separation means (separation unit)
102 Character color information reduction means (resolution reduction part)
103 Character area information data 104 Character color information data 105 Character color information data value 106 Character color information quantization means (quantization unit)

Claims (3)

Separation means for separating image data into character area information and character color information having multi-value pixel values;
And resolution reduction means for reducing the resolution by averaging the pixel values in the character region range in the character area information a pixel value of a multi-value of the character color information,
By referring to a table in which the character color information and the binarized information of each color are associated with the data value of the character color information subjected to the resolution reduction processing by the resolution reduction unit, Quantization is performed by replacing character color information with the binarized information of each color, and determining the binarized information value of each color according to the information value of the character color information of each color And
With
The input color image data is separated into character area information and first character color information of each color by the separating means,
Converting the first character information for each color in the second text color information of each color after resolution reduction processing by the resolution reduction means,
Converting the second character color information of each color into the binarized information value of each color after quantization by the quantization means;
An image processing apparatus, wherein an image image having an original resolution is created by applying the binarized information value of each color after the quantization to the character area information.   The image processing apparatus according to claim 1, wherein the resolution reduction process by the resolution reduction unit is a reduction scaling process. Separation means for separating image data into character area information and character color information having multi-value pixel values;
And resolution reduction means for reducing the resolution by averaging the pixel values in the character region range in the character area information a pixel value of a multi-value of the character color information,
By referring to a table in which the character color information and the binarized information of each color are associated with the data value of the character color information subjected to the resolution reduction processing by the resolution reduction unit, Quantization is performed by replacing character color information with the binarized information of each color, and determining the binarized information value of each color according to the information value of the character color information of each color And
With
The input color image data is separated into character area information and first character color information of each color by the separating means,
Converting the first character information for each color in the second text color information of each color after resolution reduction processing by the resolution reduction means,
Converting the second character color information of each color into the binarized information value of each color after quantization by the quantization means;
An image processing method, wherein an image image having an original resolution is created by applying the binarized information value of each color after the quantization to the character area information.

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