JP2003078768A - Image compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image compressor that can match shapes of RGB image data in the case of implementing expansion processing so as to prevent color bleeding from being caused. SOLUTION: The image compressor includes; a luminance image data generating means 18 that obtains luminance image data from RGB image data; a compression window generating means 19 that generates respective compression windows from the RGB image data and the luminance image data, a bit map generating means 21 that obtains a luminance average in the compression windows and generates a bit map where 1 is set to pixels whose luminance value is greater than the luminance average and 0 is set to pixels whose luminance value is smaller than the luminance average, a high density representative value generating means 16 that obtains respective RGB average density values on the basis of density values of pixels in the compression windows in which the bit map is set to 1 to obtain a high density representative value, and a low density representative value generating means 17 that obtains respective RGB average density values on the basis of density values of pixels in the compression windows in which the bit map is set to 0 to obtain a low density representative value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a printer, a digital copying machine for reading image information of a document and copying and printing it on paper, and an image duplicating apparatus including an image reading apparatus and an image forming apparatus. The present invention relates to an image compression device that compresses image data handled by an (image copying device) or the like.

[0002]

2. Description of the Related Art In an image forming apparatus and an image duplicating apparatus, an intra-block 2 is used as a color image data compression apparatus.
Average value method (BTC (Block Trunoatio)
n Compression)) has been performed conventionally.

FIG. 1 is a schematic view showing a general image duplicating apparatus. In FIG. 1, 2 is an image reading device that reads an image, and 3 is an image forming device that copies the image onto paper or the like. As described above, the image duplicating apparatus 1 includes the image reading apparatus 2 and the image forming apparatus 3.

FIG. 2 is a block diagram showing a data processing device of the image duplicating apparatus 1 of FIG. As shown in FIG. 2, the data processing device includes an image reading unit 4, a line correction unit 5, a filter processing unit 6, an image compression device 7, a temporary storage unit 8, an expansion unit 9, a CMYK conversion unit 10, and a binarization process. Part 1
1. The image forming engine 12. Data processing including the image reading unit 4, the line correction unit 5, the filter processing unit 6, and the image compression device 7 illustrated in FIG. 2 is performed by the image reading device 2 illustrated in FIG. 1, and the temporary storage unit 8 and the expansion unit 9 illustrated in FIG. , The CMYK conversion unit 10, the binarization processing unit 11, and the image forming engine 12 perform data processing in the image forming apparatus 3.

FIG. 17 is a block diagram showing a conventional image compression apparatus.

In FIG. 17, 7 is an image compression device for compressing input image data, 8 is a temporary storage unit similar to FIG. 2, which temporarily stores image data, and 13 is a pixel matrix window for each color of RGB from RGB image data. RGB pixel matrix window generation means for generating a compressed window as a symbol, 14 is an RGB window density average value generation means for obtaining a density average value of each RGB compression window, and 15 is a bitmap generation means for generating a bitmap from the compression window. , 16 is a high density representative value generating means for generating a high density representative value of each RGB image, and 17 is a low density representative value generating means for generating a low density representative value of each RGB image.

The operation of the image compressing device 7 of the image duplicating device 1 configured as described above will be described with reference to FIGS. 3 and 18 to 20. FIG. 3 is a compression window diagram showing a compression window, FIG. 18 (a) is a pixel position diagram showing each pixel position of the compression window, FIG. 18 (b) is a bitmap diagram showing a bitmap of an image, and FIG. FIG. 20 is a data diagram showing bitmap data, and FIG. 20 is a data diagram showing decompression data.

First, a user scans a document with the image reading device 2
When an image duplicating print command of an original is issued from an external host computer (not shown), the image reading apparatus 2 starts the operation of reading the original and the image inside the image reading apparatus 2 is placed. Reading unit 4
The original is read line by line as RGB data. The line correction unit 5 performs line correction for correcting the delay of the RGB image data due to the RGB reading position shift of the image reading unit 4, and then the filter processing unit 6 removes noise and the like of the read image data. Filtering is applied to remove. RG of the image compression device 7 in the next stage
The B pixel matrix window generation means 13 generates a 4 × 4 pixel matrix window (compressed window) for each of the RGB colors shown in FIG. 3 from the RGB image data that has been filtered by the filter processing unit 6, and the density average value within the window. The generation unit 14 generates the density average value (Rave = 149, Gave = 157, Ba of each compression window of RGB in FIG. 3).
ve = 136) is calculated. The bitmap generation unit 15 in the next stage shows each pixel position (P0) of the compression window of FIG. 18 showing the relationship between each pixel position of the compression window and the bitmap.
0, P01, P02, ..., P33) and the density average value (R
ave, Gave, Bave) and compares the R image, G image, and B image corresponding to pixels with a density greater than the density average value.
Image bitmaps (Bit0, Bit1, Bit2,
.., Bit15) is set to "1" and the bit corresponding to a pixel having a density smaller than the density average value is set to "0" to indicate the shape of the image in the compression window. The bitmap data of the image, the G image, and the B image is obtained.

In the case of the R image compression window shown in FIG. 3A, the density value of P00 is "255", and Rav is Rav.
Since it is larger than e = 148, the bit indicated by P00 is "1", and the density value of P01 is "235" and Rave.
, The bit indicated by P01 is "1", P0
Since the density value of 2 is "230", which is larger than Rave,
The bit indicated by P02 is "1", and the density value of P03 is "10".
Since "0" is smaller than Rave, the bit indicated by P03 is "0". Similarly, the bits from P10 to P33 are determined to be "0" or "1" to obtain the bitmap data of the R image, the bitmap data of the G image, and the bitmap data of the B image of FIG.

The high-density representative value generating means 16 is the R of FIG.
The density average value of the pixels of each RGB compression window in which the bit of the image bitmap data, the G image bitmap data, and the B image bitmap data is “1” is calculated, and the high density representative value (Rmden, Gmden) is obtained. , Bmde
n). In the case of the R image compression window shown in FIG. 3A, the pixel positions where the bitmap data is “1” are P00, P01, P02, P10, P1.
There are 8 pixels of 1, P12, P20, and P21, and the average Rmden of the densities of these pixels is “208”. Similarly, when the average of the densities of the pixel positions where the bitmap data is “1” is calculated for the G image and the B image,
High concentration representative value is Gmden = 209, Bmden = 18
It becomes 8.

The low-density representative value generating means 17 is the R of FIG.
The average value of the densities at the pixel positions where the bit of the image bitmap data, the G image bitmap data, and the B image bitmap data is “0” is calculated, and the low-density representative value (Rlden, Glden, Blden) I am trying.
In the case of the R image compression window shown in FIG. 3A, the pixel position where the bitmap data is “0” is P
03, P13, P22, P23, P30, P31, P3
The average Rld of the densities of the two pixels P2 and P33
en becomes "89". Similarly, when the average of the densities at the pixel positions where the bitmap data is “0” is obtained for the G image and the B image, the high density representative value is Glden = 9.
4, and Blden = 69.

As described above, the RGB pixel matrix window generation means 13, the in-window density average value generation means 14, the bit map generation means 15, the high density representative value generation means 16 and the low density representative value generation means 17 are provided. The bitmap, high density representative value, and low density representative value of each RGB image obtained by the image compression device 7 are stored in the temporary storage unit 8 as compressed data.

The compressed data stored in the temporary storage unit 8 is
The data is read out by the decompression unit 9 and subjected to decompression processing.
The decompressed data of the RGB image of is generated. The CMYK conversion unit 10 converts the decompressed data of the RGB image into CMYK image data, then the binarization processing unit 11 performs error diffusion processing and dither processing, and the image forming engine 12 prints on paper or the like and outputs it. .

[0014]

However, in the above image compression apparatus, since the bitmap is generated for each of the RGB image data, the shapes of the RGB image data do not match when the compressed data is expanded (for example, Figure 1
9. In FIG. 20, the value of Bit3 of R and G is changed to the value of Bit3 of B.
Values do not match each other), and there is a problem that color blur occurs at the character edge portion.

This image compression apparatus has the luminance image data generating means for generating the luminance image data from the RGB image data, and unifies the bitmap of each RGB image with the bitmap generated from the luminance image data. There is a demand for matching the shapes of the RGB image data when the decompression processing is performed so that the color bleeding that has occurred at the character edge portion or the like does not occur.

In order to meet this requirement, the present invention makes it possible to match the shapes of the RGB image data when the decompression processing is performed so that the color bleeding that has conventionally occurred in the character edge portion or the like does not occur. An object is to provide an image compression device.

[0017]

In order to solve the above problems, an image compression apparatus according to the present invention comprises a luminance image data generating means for obtaining luminance image data from RGB image data, and an RGB image data generating means.
R independent from image data and luminance image data
A compression window generating means for creating a compression window of each GB image and a luminance image and a luminance average value in the compression window of the luminance image are obtained, and the luminance value of each pixel in the compression window of the luminance image is compared with the luminance average value. Then, a pixel having a brightness value larger than the brightness average value is set to “1”, and a pixel having a brightness value smaller than the brightness average value is set to “0”, and a bitmap representing the shape of the brightness image in the compression window of the brightness image is set. The average density value of each RGB is obtained from the density values of the created bitmap and the density value of the pixel in the compression window of each RGB image where the bitmap created by the bitmap is “1”, and the average density value of each RGB is calculated. High density representative value generating means for setting the high density representative value of the compression window and RGB corresponding to the location of "0" in the bitmap generated by the bitmap generating means.
And a low-density representative value generating means for obtaining an average density value of each of RGB from the density values of pixels in the compression window of each image to obtain a low-density representative value of the compression window of each of the RGB images.

As a result, it is possible to obtain an image compressing device capable of matching the shapes of the RGB image data when the decompression processing is performed and preventing the blurring of the color which has been conventionally generated in the character edge portion.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image compression apparatus according to claim 1 of the present invention comprises a luminance image data generating means for obtaining luminance image data from RGB image data, and an RGB independent of the RGB image data and the luminance image data. A compression window generating means for creating a compression window of each image and the luminance image is obtained, and an average luminance value in the compression window of the luminance image is obtained, and the luminance value of each pixel in the compression window of the luminance image is compared with the luminance average value. Then, a pixel having a brightness value larger than the brightness average value is set to "1", and a pixel having a brightness value smaller than the brightness average value is set to "0" to create a bitmap showing the shape of the brightness image in the compression window of the brightness image. From the density value of the pixel in the compression window of each RGB image in which the bitmap created by the bitmap creating means and the bitmap created by the bitmap creating means is “1”. High density representative value generating means for obtaining the respective average density values and using them as the high density representative values of the compression windows of the RGB images, and each RGB image corresponding to the location of "0" of the bitmap generated by the bitmap generating means. The low density representative value generating means for obtaining the average density value of each of RGB from the density values of the pixels in the compressed window and using it as the low density representative value of the compressed window of each of the RGB images.

With this configuration, it is possible to generate the luminance image data from the RGB image data and unify the bitmaps of the RGB images with the bitmaps generated from the luminance image data. This has the effect of preventing the color bleeding that has occurred at the edge portion or the like from occurring.

An image compression apparatus according to a second aspect is RGB
Luminance image data generation means for obtaining luminance image data from image data, compression window generation means for generating independent compression windows for each RGB image and luminance image from RGB image data and luminance image data, and compression window for luminance image. The brightness average value in the brightness image is calculated, the brightness value of each pixel in the compression window of the brightness image is compared with the brightness average value, and the pixel having the brightness value larger than the brightness average value is set to “1”. And a place of "1" of the bitmap created by the bitmap creating means, which creates a bitmap representing the shape of the brightness image in the compression window of the brightness image with a pixel having a small brightness value as "0". R to hit
From the density value of the pixel in the compression window of each GB image to RGB
RGB high density representative value generating means for obtaining the n-th largest density value of each and making it the high density representative value of the compression window of each RGB image, and RGB corresponding to the location of “0” of the bitmap generated by the bitmap generating means. It has an RGB low density representative value generation means for obtaining the nth smallest density value of each RGB from the density values of the pixels in the compression window of each image and setting it as the low density representative value of the compression window of each RGB image. It is a thing.

With this configuration, it is possible to generate the luminance image data from the RGB image data and unify the bitmaps of the RGB images with the bitmaps generated from the luminance image data. This has the effect of preventing the color bleeding that has occurred at the edge portion or the like from occurring. Further, since the bitmaps of the RGB images can be unified into the bitmap generated from the luminance image data, there is an effect that the compression rate can be improved.

An image compression apparatus according to a third aspect is RGB
Luminance image data generation means for obtaining luminance image data from image data, compression window generation means for generating independent compression windows for each RGB image and luminance image from RGB image data and luminance image data, and compression window for luminance image. The brightness average value in the brightness image is calculated, the brightness value of each pixel in the compression window of the brightness image is compared with the brightness average value, and the pixel having the brightness value larger than the brightness average value is set to “1”. And a place of "1" of the bitmap created by the bitmap creating means, which creates a bitmap representing the shape of the brightness image in the compression window of the brightness image with a pixel having a small brightness value as "0". R to hit
From the density value of the pixel in the compression window of each GB image to RGB
High-density representative value generating means for obtaining an intermediate value of the respective densities and setting it as a high-density representative value of the compression window of each RGB image,
"0" of the bitmap generated by the bitmap generation means
RG by calculating the intermediate value of the respective densities of RGB from the density values of the pixels in the compression window of each RGB image corresponding to
B, a low-density representative value generating means for setting the low-density representative value of the compression window of each image.

With this configuration, the luminance image data can be generated from the RGB image data, and the bitmaps of the RGB images can be unified into the bitmap generated from the luminance image data. This has the effect of preventing the color bleeding that has occurred at the edge portion or the like from occurring. Further, since the bitmaps of the RGB images can be unified into the bitmap generated from the luminance image data, there is an effect that the compression rate can be improved.

An image compression apparatus according to a fourth aspect is the image compression apparatus according to any one of the first to third aspects,
The compression window generating means creates an m × m pixel matrix window of each RGB image and the luminance image, which is independent from the RGB image data and the luminance image data, as a compression window of each of the RGB image and the luminance image. .

With this configuration, m × of independent luminance images
Since it is possible to unify the bitmaps of the RGB images with the bitmap of the m-pixel matrix window, it is possible to prevent the color bleeding that has conventionally occurred in the character edge portion or the like when the expansion processing is performed. m
Has the effect that the image can be made fine by increasing the value of m, and m can be made small to simplify the processing when the definition may be low.

The image compression apparatus according to the fifth aspect is RGB
Luminance image data generating means for obtaining luminance image data from image data, compression window generating means for generating m × m compressed windows of each RGB image and luminance image independent from RGB image data and luminance image data, and luminance image The luminance intermediate value of each pixel in the m × m compression window of
The brightness value of each pixel in the m × m compression window of the brightness image is compared with the brightness intermediate value, and the pixel having the brightness value larger than the brightness intermediate value is set to “1” and the brightness value smaller than the brightness intermediate value. Bitmap generation means for creating a bitmap representing the shape of the brightness image in the m × m compression window of the brightness image with the pixel being “0”, and RGB corresponding to the location of “1” of the bitmap created by the bitmap generation means. M × m of each image
A high density representative value generating means for obtaining an average density value of each RGB from the density values of pixels of the compression window to obtain a high density representative value of the m × m compression window of each RGB image, and a bitmap generated by the bitmap generating means. Low density which is the low density representative value of the m × m compressed window of each RGB image by obtaining the average density value of each RGB from the density values of the pixels in the m × m compressed window of each RGB image corresponding to the “0” And a representative value generating means.

With this configuration, the brightness intermediate value of each pixel in the compression window is used when the bitmap is generated, so that after the decompression treatment, the blurring of the color which has been conventionally generated in the character edge portion of the image or the like is prevented. It has an effect that the sharpness of the image can be improved without being generated.

An image compression apparatus according to a sixth aspect is RGB
Luminance image data generating means for obtaining luminance image data from image data, compression window generating means for generating m × m compressed windows of each RGB image and luminance image independent from RGB image data and luminance image data, and luminance image The luminance intermediate value of each pixel in the m × m compression window of
The brightness value of each pixel in the m × m compression window of the brightness image is compared with the brightness intermediate value, and the pixel having the brightness value larger than the brightness intermediate value is set to “1” and the brightness value smaller than the brightness intermediate value. Bitmap generation means for creating a bitmap representing the shape of the brightness image in the m × m compression window of the brightness image with the pixel being “0”, and RGB corresponding to the location of “1” of the bitmap created by the bitmap generation means. M × m of each image
Bits generated by a high density representative value generating means for obtaining an intermediate value of the respective RGB densities from the density values of the pixels of the compression window and setting it as the high density representative value of the m × m compression window of each RGB image, and the bit map generating means. From the density values of the pixels in the m × m compression window of each RGB image corresponding to the location of “0” in the map, the median value of the respective densities of RGB is obtained and used as the low density representative value of the m × m compression window of each RGB image. And a density representative value generating means.

With this configuration, when the bitmap is generated, the luminance intermediate value of each pixel in the compression window is used, so that after the decompression process, the blurring of the color that has conventionally occurred in the character edge portion of the image or the like is prevented. It has an effect that the sharpness of the image can be improved without being generated.

An image compression apparatus according to a seventh aspect is the image compression apparatus according to any one of the first to third aspects,
CMYK image data is used instead of RGB image data,
The compression window generation means creates m × m pixel matrix windows of the CMYK images and the luminance image, which are independent from the CMYK image data and the luminance image data, as m × m compression windows of the CMYK images and the luminance image, which are independent from each other. It was decided.

With this configuration, the luminance image data can be generated from the CMYK image data, and the bitmap of each CMYK image can be unified with the bitmap generated from the luminance image data. This has the effect of preventing the color bleeding that has occurred at the edge portion or the like from occurring.

An image compression apparatus according to claim 8 is the image compression apparatus according to claim 5 or 6, wherein CMYK image data is used in place of RGB image data, and the compression window generation means uses the CMYK image data and luminance. Mx of each CMYK image and luminance image independent of the image data
Independent CMY for each m-pixel matrix window
The K image and the luminance image are created as m × m compression windows.

With this configuration, by using the luminance intermediate value of each pixel in the compression window when generating the bitmap of the luminance image data generated from the CMYK image data,
After the decompression treatment, there is an effect that it is possible to improve the sharpness of the image without causing the blurring of the color that has been conventionally generated in the character edge portion of the image.

FIG. 1 shows an embodiment of the present invention.
~ It demonstrates using FIG.

(Embodiment 1) FIG. 4 is a block diagram showing an image compression apparatus according to Embodiment 1 of the present invention. The data processing device and the image duplicating device having the image compression device according to the present embodiment have the configurations of FIGS. This also applies to the following second to fifth embodiments.

In FIG. 4, an image compression device 7, a temporary storage unit 8, RGB pixel matrix window generation means 13,
High density representative value generation means 16 and low density representative value generation means 17
17 are the same as those in FIG. 17, the same reference numerals are given and description thereof is omitted. Reference numeral 18 is a brightness image data generation means for generating brightness image data from RGB image data, 19 is a brightness pixel matrix window generation means (compression window generation means) for generating a matrix window of a brightness image, and 20 is a compression window of the brightness image. In-window luminance average value generating means for calculating the luminance average value, and 21 is a luminance bitmap generating means for generating a bitmap of the luminance image.

The operation of the image compression apparatus having such a configuration will be described with reference to FIGS. FIG. 5 is a data diagram showing compressed window data of a luminance image, and FIG. 6 is a data diagram showing bitmap data of a luminance image. 7A is a data diagram showing the R image data after the decompression process, FIG. 7B is a decompression data diagram showing the G image data after the decompression process, and FIG. 7C is a B diagram after the decompression process. FIG. 6 is a data diagram showing image data, showing RGB image data after decompression processing of compressed data by a decompression unit 9.

First, the luminance image data generating means 18 to which the RGB image data is input performs the calculation expressed by the following equation (1) for the same pixel data of the RGB image in order to express the characteristics of the image well. The brightness image data is generated by applying the brightness image data.

Y = a × R + b × G + c × B (1) where Y is a brightness value, R is a density value of the R image, G is a density value of the G image, and B is a density value of the B image. Represents a value, and a, b, and c are constants, and in the present embodiment, a = 0.299, b = 0.5.
The following description will be made assuming that 87, c = 0.114.

The RGB pixel matrix window generating means 13 generates a compression window for each color of RGB shown in FIG. The luminance pixel matrix window generation means 19 generates a compression window of a luminance image (hereinafter, referred to as “luminance compression window”) as a 4 × 4 pixel luminance pixel matrix window shown in FIG. The in-window brightness average value generation means 20 divides the sum of the brightness values of the brightness compression window by the number of pixels to calculate the brightness average value (Yav) in the brightness compression window.
e = 152). Luminance bitmap generation means 21
Is the same as the conventional bitmap generation means 15 and the luminance value of each pixel of the luminance compression window and the average luminance value (Yav) obtained by the in-window luminance average value generating means 20.
From e), a luminance image bitmap representing the image shape of FIG. 6 is generated. The high-density representative value generating means 16 is the density of the pixel of the compression window (hereinafter, referred to as “RGB compression window”) of each RGB image in which the luminance image bitmap representing the image shape of FIG. 6 is “1”. An average value is obtained for each color, and a high density representative value (Rmden = 206, Gmden =
214, Bmden = 188), and the low-density representative value generation means 17 uses the density average value of the pixels of the RGB compression window whose bit on the luminance image bitmap representing the image shape of FIG. The low concentration representative value (R
lden = 93, Glden = 99, Blden = 8
4).

As described above, the RGB pixel matrix window generation means 13, the luminance image data generation means 18,
The image compression of the present embodiment, which includes the luminance pixel matrix window generation means 19, the in-window luminance average value generation means 20, the luminance bitmap generation means 21, the high density representative value generation means 16, and the low density representative value generation means 17. Compressed data (bit map of luminance image, R high density representative value, G high density typical value, B high density typical value, R low density typical value, G low density typical value, B low density typical value) obtained by the device is Temporary storage unit 8
Stored in. FIG. 7 shows decompression data obtained by decompressing RGB compression window data. In this embodiment, the input image data is RGB image data, but
The present invention is not limited to this, and can be applied even when CMYK image data is input, and has the same effect. CMYK
When image data is input, the CMYK conversion unit 1 shown in FIG.
0 becomes unnecessary.

As described above, according to this embodiment, the RG
Luminance image data generation means 18 for obtaining luminance image data from B image data, compression window generation means 19 for generating independent compression windows for each RGB image and luminance image from RGB image data and luminance image data, and luminance image The brightness average value in the compression window of is calculated, the brightness value of each pixel in the compression window of the brightness image is compared with the brightness average value, and the pixel having the brightness value larger than the brightness average value is set to “1”, A bitmap generation unit 21 that creates a bitmap that represents the shape of the luminance image in the compression window of the luminance image by setting the pixel having the luminance value smaller than the average value to “0”, and the bitmap created by the bitmap generation unit 21. The compression density of each RGB image is obtained by calculating the average density value of each RGB from the density values of the pixels in the compression window of each RGB image corresponding to the location of “1”. High density representative value generating means 16 for setting the high density representative value of the image and the density value of the pixel in the compression window of each RGB image corresponding to the location of “0” of the bitmap generated by the bitmap generating means 21 for each of RGB. By including the low-density representative value generating means 17 that obtains the average density value and sets it as the low-density representative value of the compression window of each RGB image, the brightness image data is generated from the RGB image data, and the bitmap of each RGB image is generated. Can be unified into the bitmap generated from the luminance image data, so that it is possible to prevent the color bleeding that has conventionally occurred in the character edge portion or the like when the expansion processing is performed.

Further, instead of RGB image data, CMYK
Using the image data, the compression window generation means 19 uses the CM
By creating m × m pixel matrix windows for each CMYK image and luminance image that are independent of each other from YK image data and luminance image data as an m × m compression window for each CMYK image and luminance image,
Luminance image data is generated from YK image data, and CMY is generated.
Since the bitmaps of the K images can be unified into the bitmaps generated from the luminance image data, it is possible to prevent the color bleeding that has conventionally occurred in the character edge portion or the like when the expansion processing is performed. it can.

(Embodiment 2) FIG. 8 is a block diagram showing an image compression apparatus according to Embodiment 2 of the present invention.

In FIG. 8, an image compression device 7, a temporary storage unit 8, an RGB image matrix window generation means 13,
Luminance image data generation means 18, luminance image matrix window generation means 19, in-window luminance average value generation means 2
0 and the luminance bitmap generation means 21 are the same as those in FIG. 4, and therefore, the same reference numerals are given and the description thereof is omitted. 22 is a high density representative value selecting means for selecting a high density representative value (Rmden, Gmden, Bmden), and 23 is a low density representative value (R
It is a low-concentration representative value selection means for selecting (lden, Glden, Blden).

The operation of the image compression apparatus having such a configuration will be described with reference to FIGS. 5, 6 and 9. FIG. 9 shows RGB after decompression processing of compressed data by the decompression unit 9.
It is a data figure which shows image data.

First, the RGB pixel matrix window generator 13 generates the compression windows of RGB colors shown in FIG. Luminance image matrix window generation means 19
Generates the 4 × 4 pixel luminance compression window shown in FIG. The in-window brightness average value generation means 20 divides the sum of brightness values in the brightness compression window by the number of pixels to obtain the brightness average value in the brightness compression window (Yave = 152). The luminance bitmap generation means 21 is the same method as the conventional bitmap generation means 15, and the luminance value of each pixel of the luminance compression window and the luminance average value (Yave) obtained by the in-window luminance average value generation means 20. Then, the luminance image bitmap representing the image shape of FIG. 6 is generated. The high-density representative value selecting means 22 obtains the n-th largest density value for each color from the pixels of the RGB compression window in which the luminance image bitmap of FIG. 6 is "1", and the high-density representative value (Rmde)
n = 235, Gmden = 233, Bmden = 220
(When n = 2)), the low-concentration representative value selection means 23
For each color, obtains the nth smallest density value among the pixels of the RGB compression window in which the bit on the luminance image bitmap of FIG. 6 is "0", and calculates the low density representative value (Rlde
n = 75, Glden = 75, Blden = 50 (n =
2))).

As described above, the RGB image matrix window generation means 13, the luminance data generation means 18, the luminance image matrix window generation means 19, the in-window luminance average value generation means 20, and the luminance bitmap generation means 2 are described.
1. Compressed data (bit image of luminance image, R high density representative value, G high density) obtained by the image compression apparatus of the present embodiment configured by the high density representative value selection means 22 and the low density representative value selection means 23. The representative value, B high density representative value, R low density representative value, G low density representative value, B low density representative value)
Stored in. Further, FIG. 9 shows expanded data obtained by expanding data obtained by expanding the RGB compression window data. In addition,
In the present embodiment, the image data input to the image compression device 7 is RGB image data, but the present invention is not limited to this, and can be similarly applied to CMYK image data, and similar effects can be obtained.

As described above, according to this embodiment, the RG
Luminance image data generation means 18 for obtaining luminance image data from B image data, compression window generation means 19 for generating independent compression windows for each RGB image and luminance image from RGB image data and luminance image data, and luminance image The brightness average value in the compression window of is calculated, the brightness value of each pixel in the compression window of the brightness image is compared with the brightness average value, and the pixel having the brightness value larger than the brightness average value is set to “1”, A bitmap generation unit 21 that creates a bitmap representing the shape of the luminance image in the compression window of the luminance image with a pixel having a luminance value smaller than the average value as “0”, and a bitmap generated by the bitmap generation unit 21. The n-th largest density value of each RGB is obtained from the density value of the pixel in the compression window of each RGB image corresponding to the location of “1”, and each RGB image is obtained. From the RGB high-density representative value generating means 22 for setting the high-density representative value of the compressed window of No. 2 and the density value of the pixel in the compression window of each RGB image corresponding to the location of “0” of the bitmap generated by the bitmap generating means 21 R is obtained by calculating the nth smallest density value of each of RGB.
RGB as the low density representative value of the compression window of each GB image
By having the low-concentration representative value generating means 23,
Since it is possible to generate the luminance image data from the B image data and unify the bitmaps of the RGB images with the bitmaps generated from the luminance image data, conventionally, when the decompression processing is performed, it occurs in a character edge portion or the like. It is possible to prevent the color bleeding from occurring. Also, R
Since the bitmaps of the GB images can be unified into the bitmaps generated from the luminance image data, the compression rate can be improved.

CMYK instead of RGB image data
Using the image data, the compression window generation means 19 uses the CM
By creating m × m pixel matrix windows for each CMYK image and luminance image that are independent of each other from YK image data and luminance image data as an m × m compression window for each CMYK image and luminance image,
Luminance image data is generated from YK image data, and CMY is generated.
Since the bitmaps of the K images can be unified into the bitmaps generated from the luminance image data, it is possible to prevent the color bleeding that has conventionally occurred in the character edge portion or the like when the expansion processing is performed. it can.

(Embodiment 3) FIG. 10 is a block diagram showing an image compression apparatus according to Embodiment 3 of the present invention.

In FIG. 10, an image compression device 7, a temporary storage unit 8, an RGB image matrix window generation means 1
3, the luminance image data generation means 18, the luminance image matrix window generation means 19, the in-window luminance average value generation means 20, and the luminance bitmap generation means 21 are the same as those in FIG. To do. 24 is a high concentration representative value (Rmden, Gmden, Bmden)
Is a high density representative value generating means, and 25 is a low density representative value generating means for generating a low density representative value (Rlden, Glden, Blden).

The operation of the image compression apparatus having such a configuration will be described with reference to FIGS. 3, 5, 6, and 11. FIG. 11 is a data diagram showing the RGB image data after the compressed data is expanded by the expansion unit 9.

First, the RGB image matrix window generation means 13 generates the compression window shown in FIG. 3 for each of the RGB images. The luminance image matrix window generation means 19 generates the luminance compression window of FIG. The in-window brightness average value generation means 20 divides the sum of brightness values in the brightness compression window by the number of pixels to obtain the brightness average value in the brightness compression window (Yave = 152). The luminance bitmap generation means 21 is the same method as the conventional bitmap generation means 15, and the luminance value of each pixel of the luminance compression window and the luminance average value (Yave) obtained by the in-window luminance average value generation means 20. Then, the luminance image bitmap representing the image shape of FIG. 6 is generated. The high-density representative value generating means 24 obtains, for each color, the density intermediate value of the pixels of the RGB compression window in which the luminance image bitmap of FIG. 6 is "1", and the high-density representative value (Rmden = 205, Gmden).
= 205, Bmden = 190), the low-density representative value generating means 25 obtains the density intermediate value of the pixels of the RGB compression window for which the bit on the luminance image bitmap of FIG. 6 is "0" for each color. , Low concentration representative value (Rlden = 1
01, Glden = 113, and Blden = 115).

As described above, the RGB image matrix window generation means 13, the luminance data generation means 18, the luminance image matrix window generation means 19, the in-window luminance average value generation means 20, and the luminance bitmap generation means 2 are described.
1. Compressed data (bit image of luminance image, R high density representative value, G high) obtained by the image compression apparatus of the third embodiment configured by the high density representative value generation means 24 and the low density representative value generation means 25. The density representative value, the B high density representative value, the R low density representative value, the G low density representative value, and the B low density representative value are stored in the temporary storage unit 8.
Stored in. Further, FIG. 11 shows decompression data obtained by decompressing data obtained by decompressing RGB compression window data. Note that, in the present embodiment, the image data input to the image compression device 7 is RGB image data, but the present invention is not limited to this, and can also be applied to CMYK image data with similar effects. .

As described above, according to this embodiment, the RG
Luminance image data generation means 18 for obtaining luminance image data from B image data, compression window generation means 19 for generating independent compression windows for each RGB image and luminance image from RGB image data and luminance image data, and luminance image The brightness average value in the compression window of is calculated, the brightness value of each pixel in the compression window of the brightness image is compared with the brightness average value, and the pixel having the brightness value larger than the brightness average value is set to “1”, A bitmap generation unit 21 that creates a bitmap representing the shape of the luminance image in the compression window of the luminance image with a pixel having a luminance value smaller than the average value as “0”, and a bitmap generated by the bitmap generation unit 21. Compressing each RGB image corresponding to the location of "1" Compressing each RGB image by obtaining the intermediate value of each RGB density from the density value of the pixel in the window A high density representative value generating unit 24, high concentration typical of India, the bitmap generation means 21
RGB corresponding to the location of "0" in the bitmap created in
By providing an intermediate value of the densities of R, G and B from the densities of the pixels in the compressed window of each image, and having a low-density representative value generation means 25 for setting the low-density representative value of the compressed window of each of the RGB images, the RGB image Since the luminance image data can be generated from the data and the bitmaps of the RGB images can be unified into the bitmap generated from the luminance image data, the color that has conventionally been generated in the character edge portion when the decompression process is performed. Bleeding can be prevented. Moreover, since the bitmaps of the RGB images can be unified into the bitmaps generated from the luminance image data, the compression rate can be improved.

Further, instead of RGB image data, CMYK
Using the image data, the compression window generation means 19 uses the CM
By creating m × m pixel matrix windows for each CMYK image and luminance image that are independent of each other from YK image data and luminance image data as an m × m compression window for each CMYK image and luminance image,
Luminance image data is generated from YK image data, and CMY is generated.
Since the bitmaps of the K images can be unified into the bitmaps generated from the luminance image data, it is possible to prevent the color bleeding that has conventionally occurred in the character edge portion or the like when the expansion processing is performed. it can.

(Embodiment 4) FIG. 12 is a block diagram showing an image compression apparatus according to Embodiment 4 of the present invention.

In FIG. 12, an image compression device 7, a temporary storage unit 8, an RGB image matrix window generation means 1
3, luminance image data generating means 18, luminance image matrix window generating means 19, luminance bitmap generating means 2
1, the high density representative value generating means 16 and the low density representative value generating means 17 are the same as those in FIG. Reference numeral 26 is an in-window luminance intermediate value generating means for generating an intermediate value in the luminance compression window.

The operation of the image compression apparatus thus configured will be described with reference to FIGS. 3, 5, 13, and 14. FIG. 13 is a data diagram showing bitmap data of a luminance image, and FIG. 14 is a data diagram showing RGB image data after decompression processing of compressed data by the decompression unit 9.
In this embodiment, m × m of the RGB image matrix window and the luminance image matrix window will be described as 4 × 4 in order to simplify the description.

First, the RGB image matrix window generating means 13 generates the compression window shown in FIG. 3 for each image of RGB. The luminance image matrix window generation means 19 generates the luminance compression window shown in FIG. The in-window luminance intermediate value generating means 26 calculates an intermediate value (Ymi from the maximum luminance value and the minimum luminance value in the luminance compression window).
d = 151) is calculated. Luminance bitmap generation means 21
Is the same as the conventional bitmap generation means 15, and the luminance intermediate value (Ymi) obtained by the luminance value of each pixel of the luminance compression window and the in-window luminance intermediate value generating means 26.
From d), a luminance image bitmap representing the image shape of FIG. 13 is generated. The high-concentration representative value generating means 16 is shown in FIG.
The density average value of the pixels of the RGB compression window in which the luminance image bit map of is 1 is obtained for each color, and the high density representative value (Rmden = 198, Gmden = 208, B
mden = 187), and the low-density representative value generating means 17
Indicates that the bit on the luminance image bitmap in FIG. 13 is "0".
The density average value of the pixels of the RGB compression window, which has become, is calculated for each color, and the low density representative value (Rlden = 87, Gl
den = 91, Blden = 65).

As described above, the RGB image matrix window generating means 13, the luminance image data generating means 18,
The image compression of the present embodiment, which includes the luminance image matrix window generation means 19, the in-window luminance intermediate value generation means 26, the luminance bitmap generation means 21, the high density representative value generation means 16, and the low density representative value generation means 17. Compressed data (bit map of luminance image, R high density representative value, G high density typical value, B high density typical value, R low density typical value, G low density typical value, B low density typical value) obtained by the device is Temporary storage unit 8
Stored in. FIG. 14 shows decompressed data obtained by expanding data obtained by expanding the RGB compression window data. Note that, in the present embodiment, the image data input to the image compression device 7 is RGB image data, but the present invention is not limited to this, and can also be applied to CMYK image data with similar effects. .

As described above, according to the present embodiment, RG
Luminance image data generation means 18 for obtaining the luminance image data from the B image data, and each RGB image and luminance image m × independent of the RGB image data and the luminance image data.
Compression window generation means 19 for creating m compression windows
And the luminance intermediate value of each pixel in the m × m compression window of the luminance image is obtained, and the luminance value of each pixel in the m × m compression window of the luminance image is compared with the luminance intermediate value. A bitmap that creates a bitmap showing the shape of the luminance image in the m × m compression window of the luminance image by setting the pixel having the larger luminance value as “1” and the pixel having the luminance value smaller than the intermediate luminance value as “0”. The generating means 21 and the average density value of each RGB are obtained from the density value of the pixel of the m × m compression window of each RGB image corresponding to the location of “1” of the bitmap created by the bitmap creating means 21, and the average density value of each RGB is calculated. m
High density representative value generating means 16 for setting the high density representative value of the × m compression window, and the density of the pixel in the m × m compression window of each RGB image corresponding to the location of “0” of the bitmap generated by the bitmap generating means. By including the low-density representative value generation means 17 for obtaining the average density value of each RGB from the values and setting it as the low-density representative value of the m × m compression window of each RGB image, the inside of the compression window is generated when the bitmap is generated. By using the intermediate luminance value of each pixel of
It is possible to improve the sharpness of an image without causing the color bleeding that has conventionally occurred in the character edge portion of the image.

Further, instead of RGB image data, CMYK
Using the image data, the compression window generation means 19 uses the CM
By creating m × m pixel matrix windows for each CMYK image and luminance image that are independent of each other from YK image data and luminance image data as an m × m compression window for each CMYK image and luminance image,
By using the luminance intermediate value of each pixel in the compression window when generating the bitmap of the luminance image data generated from the YK image data, the color that has conventionally occurred in the character edge portion of the image after decompression processing. Bleeding does not occur and the sharpness of the image can be improved.

(Embodiment 5) FIG. 15 is a block diagram showing an image compression apparatus according to Embodiment 5 of the present invention.

In FIG. 15, an image compression device 7, a temporary storage unit 8, an RGB image matrix window generation means 1
3, the luminance image data generating means 18, the luminance image matrix window generating means 19, the in-window luminance intermediate value generating means 26, the luminance bitmap generating means 21, the high density representative value generating means 24, and the low density representative value generating means 25 are shown in FIG. The configuration is the same as that of FIG. 10 and FIG. 12, so the same reference numerals are given and description thereof is omitted.

The operation of the image compression apparatus thus configured will be described with reference to FIGS. 3, 5, 13, and 16. FIG. 16 is a data diagram showing the RGB image data after the compressed data is expanded by the expansion unit 9. In this embodiment, m × m of the RGB image matrix window and the luminance image matrix window will be described as 4 × 4 in order to simplify the description.

First, the RGB pixel matrix window generation means 13 generates the compression window shown in FIG. 3 for each image of RGB. The luminance image matrix window generation means 19 generates the luminance compression window shown in FIG. The in-window luminance intermediate value generating means 26 calculates an intermediate value (Ymi from the maximum luminance value and the minimum luminance value in the luminance compression window).
d = 151) is calculated. Luminance bitmap generation means 21
Is the same as the conventional bitmap generation means 15, and the luminance intermediate value (Ymi) obtained by the luminance value of each pixel of the luminance compression window and the in-window luminance intermediate value generating means 26.
From d), a luminance image bitmap representing the image shape of FIG. 13 is generated. The high-concentration representative value generating means 24 is shown in FIG.
The density intermediate value of the pixels of the RGB compression window in which the luminance image bit map of is 1 is obtained for each color, and the high density representative value (Rmden = 186, Gmden = 196, B
mden = 190), and the low-density representative value generating means 25
Indicates that the bit on the luminance image bitmap in FIG. 13 is "0".
The density intermediate value of the pixels of the RGB compression window, which has become, is calculated for each color, and the low density representative value (Rlden = 88, Gl
den = 90, Blden = 75).

As described above, the RGB image matrix window generation means 13, the luminance data generation means 18, the luminance image matrix window generation means 19, the in-window luminance intermediate value generation means 26, and the luminance bitmap generation means 2 are described.
1. Compressed data (bit image of luminance image, R high density representative value, G high density) obtained by the image compression apparatus of the present embodiment configured by the high density representative value generation means 24 and the low density representative value generation means 25. The representative value, B high density representative value, R low density representative value, G low density representative value, B low density representative value)
Stored in. FIG. 16 shows decompression data obtained by decompressing data obtained by decompressing RGB compression window data. Note that, in the present embodiment, the image data input to the image compression device 7 is RGB image data, but the present invention is not limited to this, and can also be applied to CMYK image data with similar effects. .

As described above, according to this embodiment, the RG
Luminance image data generation means 18 for obtaining the luminance image data from the B image data, and each RGB image and luminance image m × independent of the RGB image data and the luminance image data.
Compression window generation means 19 for creating m compression windows
And the luminance intermediate value of each pixel in the m × m compression window of the luminance image is obtained, and the luminance value of each pixel in the m × m compression window of the luminance image is compared with the luminance intermediate value. A bitmap that creates a bitmap showing the shape of the luminance image in the m × m compression window of the luminance image by setting the pixel having the larger luminance value as “1” and the pixel having the luminance value smaller than the intermediate luminance value as “0”. Generating means 21 and each RGB image by obtaining an intermediate value of the respective densities of RGB from the density value of the pixel of the m × m compression window of each RGB image corresponding to the location of “1” of the bitmap created by the bitmap creating means 21. M × m m of each RGB image corresponding to the position of “0” of the bitmap generated by the bitmap generation means 21 and the high-density representative value generation means 24 that is the high-density representative value of the compressed window.
By including the low-density representative value generating means 25 for obtaining an intermediate value of the respective densities of RGB from the density values of the pixels in the × m compression window and setting it as the low-density representative value of the m × m compression window of each RGB image, By using the brightness intermediate value of each pixel in the compression window when generating the map, after the decompression process, the blurring of the color that was conventionally generated at the character edge part of the image etc. does not occur, and the sharpness of the image is felt. Can be improved.

CMYK instead of RGB image data
Using the image data, the compression window generation means 19 uses the CM
By creating m × m pixel matrix windows for each CMYK image and luminance image that are independent of each other from YK image data and luminance image data as an m × m compression window for each CMYK image and luminance image,
By using the luminance intermediate value of each pixel in the compression window when generating the bitmap of the luminance image data generated from the YK image data, the color that has conventionally occurred in the character edge portion of the image after decompression processing. Bleeding does not occur and the sharpness of the image can be improved.

[0073]

As described above, according to the image compression apparatus of the first aspect of the present invention, the luminance image data generating means for obtaining the luminance image data from the RGB image data, and the RGB image data and the luminance image data are used. Independent RGB
A compression window generating means for creating a compression window of each image and the luminance image is obtained, and an average luminance value in the compression window of the luminance image is obtained, and the luminance value of each pixel in the compression window of the luminance image is compared with the luminance average value. Then, a pixel having a brightness value larger than the brightness average value is set to "1", and a pixel having a brightness value smaller than the brightness average value is set to "0" to create a bitmap showing the shape of the brightness image in the compression window of the brightness image. Bit map generating means and the compression of RGB images in which the bitmap created by the bitmap generating means corresponds to the location of "1" is calculated from the density values of pixels in the window to compress each RGB image. High density representative value generating means for setting the high density representative value of the window, and compression windows for each RGB image corresponding to the location of "0" in the bitmap generated by the bitmap generating means. Luminance density data is generated from the RGB image data by including the low density representative value generating means for obtaining the average density value of each of RGB from the density values of the pixels and making it the low density representative value of the compression window of each RGB image. Thus, since the bitmaps of the RGB images can be unified into the bitmaps generated from the luminance image data, it is possible to prevent the color blur that has been conventionally generated in the character edge portion or the like when the expansion processing is performed. That is an advantageous effect.

According to the image compression apparatus of the second aspect,
Luminance image data generation means for obtaining luminance image data from RGB image data, compression window generation means for generating independent compression windows for each RGB image and luminance image from RGB image data and luminance image data, and compression of luminance image. The brightness average value in the window is calculated, the brightness value of each pixel in the compression window of the brightness image is compared with the brightness average value, and the pixel having the brightness value larger than the brightness average value is set to “1”, and the brightness average value is set. A bitmap generation unit that creates a bitmap representing the shape of the brightness image in the compression window of the brightness image by setting the pixel having a smaller brightness value to “0”, and the bitmap “1” created by the bitmap generation unit. From the density value of the pixel in the compression window of each RGB image corresponding to the place, the n-th largest density value of each RGB is obtained and R
RGB as the high density representative value of the compression window of each GB image
The high density representative value generating means and the nth smallest density value of each RGB are obtained from the density values of the pixels in the compression window of each RGB image corresponding to the location of "0" of the bitmap generated by the bitmap generating means By having RGB low-density representative value generating means for setting the low-density representative value of the compression window of each image, the luminance image data is generated from the RGB image data, and the bitmap of each RGB image is generated from the luminance image data. Since the bitmaps can be unified, it is possible to obtain the advantageous effect of preventing the color bleeding that has conventionally occurred in the character edge portion or the like when the expansion processing is performed. Moreover, since the bitmaps of the RGB images can be unified into the bitmap generated from the luminance image data, the advantageous effect that the compression rate can be improved can be obtained.

According to the image compression device of the third aspect,
Luminance image data generation means for obtaining luminance image data from RGB image data, compression window generation means for generating independent compression windows for each RGB image and luminance image from RGB image data and luminance image data, and compression of luminance image. The brightness average value in the window is calculated, the brightness value of each pixel in the compression window of the brightness image is compared with the brightness average value, and the pixel having the brightness value larger than the brightness average value is set to “1”, and the brightness average value is set. A bitmap generation unit that creates a bitmap representing the shape of the brightness image in the compression window of the brightness image by setting the pixel having a smaller brightness value to “0”, and the bitmap “1” created by the bitmap generation unit. The intermediate value of the densities of RGB is obtained from the density values of the pixels in the compression windows of the RGB images corresponding to the location, and the compression window height of the RGB images is increased. The high-density representative value generating means for setting the degree representative value, and the intermediate value of the respective densities of RGB from the density value of the pixel in the compression window of each RGB image corresponding to the position of “0” of the bitmap generated by the bitmap generating means. By including a low-density representative value generating unit that obtains the low-density representative value of the compression window of each RGB image,
Since it is possible to generate luminance image data from the image data and unify the bitmaps of the RGB images with the bitmaps generated from the luminance image data, conventionally, when the decompression process is performed, the image is generated in the character edge portion or the like. An advantageous effect is obtained in that color bleeding can be prevented. Moreover, since the bitmaps of the RGB images can be unified into the bitmap generated from the luminance image data, the advantageous effect that the compression rate can be improved can be obtained.

According to the image compression device of the fourth aspect,
The image compression apparatus according to any one of claims 1 to 3, wherein the compression window generation means converts each RGB image and luminance image m × m pixel matrix window independent from RGB image data and luminance image data into RGB. By creating a compressed window of each image and the luminance image, the bitmap of each RGB image can be unified with the bitmap of the m × m pixel matrix window of the independent luminance image. It is possible to prevent the color bleeding that has occurred at the character edge portion, etc., and to make the image finer by increasing m, and reduce the m to simplify the processing when the fineness may be low. The advantageous effect that it can be achieved is obtained.

According to the image compression device of the fifth aspect,
Luminance image data generation means for obtaining the luminance image data from the RGB image data, and m × of each RGB image and the luminance image independent of the RGB image data and the luminance image data.
A compression window generating means for creating an m compression window and a luminance intermediate value of each pixel in the m × m compression window of the luminance image are obtained, and the luminance value and the luminance intermediate value of each pixel in the m × m compression window of the luminance image are obtained. And a pixel having a luminance value larger than the luminance intermediate value is set to “1”, and a pixel having a luminance value smaller than the luminance intermediate value is set to “0”, and the pixel of the luminance image in the m × m compression window of the luminance image is A bitmap generation means for generating a bitmap showing a shape, and the average density of each RGB from the density value of the pixel of the m × m compression window of each RGB image corresponding to the location of “1” of the bitmap created by the bitmap generation means. A high-density representative value generating unit that obtains a value and sets it as a high-density representative value of the m × m compression window of each RGB image, and each RGB image corresponding to the “0” position of the bitmap generated by the bitmap generating unit. RG is calculated by calculating the average density value of each RGB from the density values of the pixels in the m × m compression window of the image.
By using the low-density representative value generating means for setting the low-density representative value of the m × m compression window of each B image, the brightness intermediate value of each pixel in the compression window is used when the bitmap is generated, After the decompression treatment, there is an advantageous effect that it is possible to improve the sharpness of the image without causing the color bleeding that has conventionally occurred in the character edge portion of the image.

According to the image compression apparatus of the sixth aspect,
Luminance image data generation means for obtaining the luminance image data from the RGB image data, and m × of each RGB image and the luminance image independent of the RGB image data and the luminance image data.
A compression window generating means for creating an m compression window and a luminance intermediate value of each pixel in the m × m compression window of the luminance image are obtained, and the luminance value and the luminance intermediate value of each pixel in the m × m compression window of the luminance image are obtained. And a pixel having a luminance value larger than the luminance intermediate value is set to “1”, and a pixel having a luminance value smaller than the luminance intermediate value is set to “0”, and the pixel of the luminance image in the m × m compression window of the luminance image is A bitmap generation means for generating a bitmap showing a shape and a density value of each RGB from the density value of the pixel of the m × m compression window of each RGB image corresponding to the position of “1” of the bitmap created by the bitmap generation means. A high-density representative value generating means for obtaining an intermediate value and setting it as a high-density representative value of the m × m compression window of each RGB image, and each RGB corresponding to the “0” position of the bitmap generated by the bitmap generating means. From the density values of the pixels in the m × m compression window of the image, the intermediate values of the respective RGB densities are calculated and R
By using the low-density representative value generating means for setting the low-density representative value of the m × m compression window of each GB image, by using the luminance intermediate value of each pixel in the compression window when generating the bitmap, After the decompression treatment, there is an advantageous effect that it is possible to improve the sharpness of the image without causing the color bleeding that has conventionally occurred in the character edge portion of the image.

According to the image compression apparatus of the seventh aspect,
The image compression apparatus according to any one of claims 1 to 3, wherein CMYK image data is used instead of RGB image data, and the compression window generation unit is independent of CMYK image data and luminance image data. The brightness image data is generated from the CMYK image data by creating m × m pixel matrix windows of the CMYK image data and the brightness image as independent CMYK images and m × m compression windows of the brightness image, respectively. Can be unified into the bitmap generated from the luminance image data, so that there is an advantageous effect that it is possible to prevent the color bleeding that has conventionally occurred in the character edge portion or the like when the expansion processing is performed.

According to the image compression device of claim 8,
The image compression device according to claim 5 or 6, wherein RG
The CMYK image data is used in place of the B image data, and the compression window generation means sets the CMYK images that are independent of the CMYK image data and the luminance image data, and the CMYK images that are independent of the m × m pixel matrix window of the luminance image. And the brightness image are created as m × m compression windows, the brightness intermediate value of each pixel in the compression window is used when the bitmap of the brightness image data generated from the CMYK image data is used. The advantageous effect that the sharpness of the image can be improved without causing the color blur that has been conventionally generated in the character edge portion of the image or the like can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic view showing a general image duplicating apparatus.

FIG. 2 is a block diagram showing a data processing device of the image duplicating apparatus of FIG.

FIG. 3 is a compression window diagram showing a compression window.

FIG. 4 is a block diagram showing an image compression apparatus according to the first embodiment of the present invention.

FIG. 5 is a data diagram showing compressed window data of a luminance image.

FIG. 6 is a data diagram showing bitmap data of a luminance image.

7A is a data diagram showing R image data after decompression processing, FIG. 7B is a decompression data diagram showing G image data after decompression processing, and FIG. 7C is a data diagram showing B image data after decompression processing.

FIG. 8 is a block diagram showing an image compression device according to a second embodiment of the present invention.

FIG. 9: RGB after decompression processing of compressed data by the decompression unit
Data diagram showing image data

FIG. 10 is a block diagram showing an image compression device according to a third embodiment of the present invention.

FIG. 11 is an RG after decompressing the compressed data by the decompression unit.
Data diagram showing B image data

FIG. 12 is a block diagram showing an image compression apparatus according to Embodiment 4 of the present invention.

FIG. 13 is a data diagram showing bitmap data of a luminance image.

FIG. 14 is an RG after decompressing the compressed data by the decompression unit.
Data diagram showing B image data

FIG. 15 is a block diagram showing an image compression device according to a fifth embodiment of the present invention.

FIG. 16 is an RG after decompressing the compressed data by the decompression unit.
Data diagram showing B image data

FIG. 17 is a block diagram showing a conventional image compression device.

18A is a pixel position diagram showing each pixel position of the compression window, and FIG. 18B is a bitmap diagram showing a bitmap of an image.

FIG. 19 is a data diagram showing bitmap data.

FIG. 20 is a data diagram showing decompressed data.

[Explanation of symbols]

1 image duplicating device 2 image reading device 3 image forming device 4 image reading unit 5 line correction unit 6 filter processing unit 7 image compression device 8 temporary storage unit 9 expansion unit 10 CMYK conversion unit 11 binarization processing unit 12 image forming engine 13 RGB pixel matrix window generation means 16 and 24 High density representative value generation means 17 and 25 Low density representative value generation means 18 Luminance image data generation means 19 Luminance pixel matrix window generation means (compression window generation means) 20 In-window luminance average value Generating means 21 Luminance bitmap generating means (bitmap generating means) 22 High density representative value selecting means 23 Low density representative value selecting means 26 In-window brightness intermediate value generating means

Claims (8)

[Claims] 1. Luminance image data generating means for obtaining luminance image data from RGB image data, and compression window generating means for generating independent compression windows for RGB images and luminance images from the RGB image data and the luminance image data, respectively. A luminance average value in the compression window of the luminance image, and compares the luminance value of each pixel in the compression window of the luminance image with the luminance average value, a pixel having a luminance value larger than the luminance average value. Is set to "1", and a pixel having a brightness value smaller than the brightness average value is set to "0" to create a bitmap representing the shape of the brightness image in the compression window of the brightness image; RG from the density value of the pixel in the compression window of each of the RGB images in which the bitmap created by the generation means corresponds to the location of "1"
High density representative value generating means for obtaining the average density value of each of the B images and using it as the high density representative value of the compression window of each of the RGB images, and the RGB corresponding to the location of "0" in the bitmap generated by the bitmap generating means. An image characterized by comprising: low-density representative value generating means for obtaining an average density value of each of RGB from the density values of pixels in the compression window of each image to obtain a low-density representative value of the compression window of each of the RGB images. Compressor. 2. Luminance image data generation means for obtaining luminance image data from RGB image data, and compression window generation means for generating independent compression windows for each RGB image and luminance image from the RGB image data and luminance image data. , A brightness average value in the compression window of the brightness image is obtained, and the brightness value of each pixel in the compression window of the brightness image is compared with the brightness average value, and a pixel having a brightness value larger than the brightness average value. Is set to "1", and a pixel having a brightness value smaller than the brightness average value is set to "0" to create a bitmap representing the shape of the brightness image in the compression window of the brightness image, and the bitmap generation means. From the density value of the pixel in the compression window of each of the RGB images corresponding to the location of "1" of the bitmap created by the generation means, RG
The nth largest density value of each B
RGB high-density representative value generating means for setting the high-density representative value of the compressed window of each image, and the density of the pixel in the compression window of each RGB image corresponding to the location of "0" of the bitmap generated by the bitmap generating means. An image compression apparatus comprising: an RGB low-density representative value generating unit that obtains the n-th smallest density value of each RGB from the values and sets it as the low-density representative value of the compression window of each of the RGB images. 3. Luminance image data generation means for obtaining luminance image data from RGB image data, and compression window generation means for generating independent compression windows for each RGB image and luminance image from the RGB image data and luminance image data. A luminance average value in the compression window of the luminance image, and compares the luminance value of each pixel in the compression window of the luminance image with the luminance average value, a pixel having a luminance value larger than the luminance average value. Is set to "1", and a pixel having a brightness value smaller than the brightness average value is set to "0" to create a bitmap representing the shape of the brightness image in the compression window of the brightness image; From the density value of the pixel in the compression window of each of the RGB images corresponding to the location of "1" of the bitmap created by the generation means, RG
The high density representative value generating means for obtaining the intermediate value of the respective densities of B to obtain the high density representative value of the compression window of each of the RGB images, and the bit corresponding to "0" in the bitmap generated by the bitmap generating means. Low density representative value generating means for obtaining an intermediate value of the respective densities of RGB from the density values of pixels in the compression window of each of the RGB images to obtain a low density representative value of the compression window of each of the RGB images. Image compression device. 4. The compression window generating means is an RGB signal independent of RGB image data and luminance image data.
The image compression apparatus according to claim 1, wherein an m × m pixel matrix window of each image and the luminance image is created as a compression window of each of the RGB images and the luminance image. 5. A luminance image data generating means for obtaining luminance image data from RGB image data, and a compression window for generating m × m compression windows for each RGB image and luminance image independent from the RGB image data and the luminance image data. The generation means and the brightness intermediate value of each pixel in the m × m compression window of the brightness image are obtained, and the brightness value of each pixel in the m × m compression window of the brightness image is compared with the brightness intermediate value. , "1" for a pixel having a brightness value larger than the brightness intermediate value
And a bitmap generation means for generating a bitmap representing the shape of the luminance image in the m × m compression window of the luminance image by setting the pixel having the luminance value smaller than the intermediate luminance value to “0”, and the bitmap generation. The average density value of each RGB is calculated from the density value of the pixel of the m × m compression window of each RGB image corresponding to the location “1” of the bitmap created by the means, and the height of the m × m compression window of each RGB image is increased. High-concentration representative-value generating means for setting the concentration representative value,
Mxm of each RGB image corresponding to the location of "0" in the bitmap generated by the bitmap generating means, the average density value of each RGB is calculated from the density value of the pixel in the compression window, and mx of each RGB image is obtained. An image compression apparatus comprising: a low-density representative value generating unit that sets a low-density representative value of an m-compression window. 6. A luminance image data generating means for obtaining luminance image data from RGB image data, and a compression window for generating an m × m compression window of each RGB image and luminance image independent from the RGB image data and the luminance image data. The generation means and the brightness intermediate value of each pixel in the m × m compression window of the brightness image are obtained, and the brightness value of each pixel in the m × m compression window of the brightness image is compared with the brightness intermediate value. , "1" for a pixel having a brightness value larger than the brightness intermediate value
And a bitmap generation means for generating a bitmap representing the shape of the luminance image in the m × m compression window of the luminance image by setting the pixel having the luminance value smaller than the intermediate luminance value to “0”, and the bitmap generation. The intermediate value of the respective densities of RGB is obtained from the density value of the pixel of the m × m compression window of each RGB image corresponding to the location of “1” of the bitmap created by the means, and the m × m compression window of each RGB image is calculated. A high-density representative value generating means for setting a high-density representative value, and a density value of a pixel in the m × m compression window of each RGB image corresponding to a position of “0” of the bitmap generated by the bitmap generating means from each of the RGB values. An image compression apparatus comprising: a low-density representative value generating unit that obtains an intermediate value of densities and sets it as a low-density representative value of the m × m compression window of each of the RGB images. . 7. The CMYK image data is used in place of the RGB image data, and the compression window generating means is the CMY.
An m × m pixel matrix window of each CMYK image and luminance image independent from the K image data and the luminance image data is created as an m × m compression window of each independent CMYK image and luminance image. The image compression device according to any one of items 1 to 3. 8. CMYK image data is used instead of RGB image data, and the compression window generation means is the CMYK image data.
An m × m pixel matrix window of each CMYK image and luminance image independent from the K image data and the luminance image data is created as an m × m compression window of each independent CMYK image and luminance image. Item 7. The image compression device according to Item 5 or 6.