JP3284827B2 - Image processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a GBTC (Generalize
The present invention relates to an image processing device that performs compression coding of image information using a d-block truncation coding (d Block Truncation Coding) method.

[0002]

2. Description of the Related Art In recent years, a GBTC method has been proposed as a method for compressing and expanding image data of a document. GBTC
In the method, image data of a document is extracted for each block of a predetermined pixel matrix, and for each block, an average value Q1 of data equal to or less than a parameter P1 defined by data in the block and a parameter P2 (where P1 <P2). The relationship is satisfied.) On the basis of the average value information LA obtained by dividing the sum of the average values Q4 of the data of the above values into two and the gradation width index LD which is the difference between the average value Q4 and the average value Q1, The data of each pixel in the block is compression-encoded into code data φij obtained by quantizing the data within the range of the gradation distribution in the block to a smaller number of gradation levels than the data. FIG. 1 is a diagram for explaining the flow of a general GBTC encoding process. In the GBTC method, as shown in (a), image data of a document image is extracted in units of 4 × 4 pixel blocks. The image data in the extracted 4 × 4 pixel block is subjected to a GBTC encoding process. As a result of the GBTC encoding process, one byte (= 8 bits) of data × 16 pixels of image data (16 bytes, that is, 128 bits) for each pixel is converted into a 1-byte data as shown in FIG. Width index LD, average value information LA of 1 byte, 2-bit code data assigned to each pixel data divided into four stages, and a total of 6 for 16 pixels
It is encoded into byte (= 48 bits) data. As a result, the data amount of the image is compressed to 3/8.
(C) is a diagram illustrating that the data amount of the encoded image data corresponds to six pixels of the image data before encoding. The decoding of the encoded data is executed by calculating 1-byte image data corresponding to each 2-bit code data based on the gradation width index LD and the average value information LA.

A pixel Xij in a 4 × 4 pixel block
(However, i and j are each one of the values 1, 2, 3, and 4.) The image data is 256 gradation data of four kinds of values by the encoding process and the decoding process of the GBTC system. Is replaced by Here, the decrypted data is
When compared with the data of the original image, it clearly contains errors. However, the error is at a level that is inconspicuous in human visual characteristics, and almost no image quality deterioration is recognized in a natural image. In the GBTC method, a parameter Q is obtained from a gradation width index LD and average value information LA included in encoded data.
1 and Q4 can be determined. That is, the parameter P
A character image composed of a black portion equal to or less than 1 and a white portion equal to or more than the parameter P2 can be reproduced from the encoded data. In the JPEG system in which data obtained by performing DCT conversion on image data is subjected to Huffman coding, the data compression ratio changes depending on the type of document. In other words, although data compression is higher for a certain document than for the GBTC method, compression may be hardly performed for another document. For this reason, it is difficult to set the capacity of the memory provided in the image processing apparatus. However, in the GBTC method, data can be compressed at a fixed compression ratio. Therefore, there is an advantage that the capacity of the memory provided in the image processing apparatus can be easily set.

[0004] An image processing apparatus that performs JPEG encoding processing performs DCT on image data of a document in units of a block composed of a predetermined pixel matrix. D
The CT-converted data includes the average value information LA and the gradation width index LD obtained by the encoding process of the GBTC method, and the average value and gradation width of the data of each pixel constituting the block, such as the code data φij. It is not data to reflect. For this reason, it is very difficult to change the density or color balance of an image reproduced by processing DCT-converted data. Therefore, determine the type of original,
In order to perform the editing / processing of the image reproduced on the paper based on the determination result, it is necessary to perform these processes before the encoding of the image data or after the decoding.

[0005]

As explained above,
Encoding of image data of the GBTC system always shows a constant data compression ratio (3/8). However, the compression ratio is J
The value is not so high when compared with the encoding of PEG image data. Further, in the image processing apparatus that performs the JPEG encoding process, the type of the document is determined before encoding the image data or after decoding the image data. Further, AE processing for optimizing the density distribution of an image, and image editing / processing processing such as color conversion and frame editing have also been performed before encoding or decoding image data. In this case, a hardware circuit for performing a high-speed operation and a large-capacity memory for storing all the image data are required to determine the attribute of the image, resulting in high cost.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image processing apparatus which performs more efficient image data compression and image processing.

[0007]

According to a first image processing apparatus of the present invention, a data conversion processing section for converting RGB image data of a document into lightness component data and chromaticity component data, a lightness component and a chromaticity component The component data is divided into blocks each having a predetermined pixel matrix, and for each block,
The average value Q1 of data having a value equal to or less than the parameter P1 determined from the data in the block and the parameter P2 (where P
1 <P2) Average value Q of data of values above
4 based on the average value information obtained by bisecting the sum of 4 and the gradation width index which is the difference between the average value Q4 and the average value Q1. An encoding processing unit that encodes into code data obtained by quantizing at a gradation level smaller than the data within the range of the tonal distribution, and an average of a lightness component and a chromaticity component of the encoded block. An attribute discrimination processing unit that discriminates an attribute of an image to which the block belongs based on the value information, the gradation width index, and the value of the code data; A storage unit that stores the result; and a decoding processing unit that decodes the code data in block units based on the average value information and the gradation width index stored in the storage unit.

[0008] In the second image processing apparatus of the present invention,
A data conversion processing unit for converting the RGB image data of the original into lightness component data and chromaticity component data; and dividing the lightness component and chromaticity component data into blocks each having a predetermined pixel matrix. The average value Q1 of data having a value equal to or less than the parameter P1 determined by the data in the block and the parameter P2 (where P1 <P2
Based on the average value information obtained by bisecting the sum of the average values Q4 of the data having the above values and the gradation width index which is the difference between the average value Q4 and the average value Q1. An encoding processing unit that encodes the data of each pixel in the code into code data obtained by quantizing the data at a gradation level smaller than the data within the range of the gradation distribution in the block; An attribute determination processing unit that determines an image attribute to which the block belongs based on the average value information of the lightness component and the chromaticity component, the gradation width index, and the value of the code data for the applied block; Average value information, a gradation width index, and a compression processing unit that performs a compression process of reducing data that can be always specified based on the attribute of the determined image among the code data, and data after the compression process, Attribute determination And a compressed data decompression unit that reads out the compressed data and the attribute determination result stored in the storage unit and stores the data reduced in the compression process based on the attribute determination result. A decoding unit that decodes the code data in block units based on the average value information of the brightness component and the chromaticity component expanded by the data expansion processing unit and the gradation width index.

In the first and second image processing apparatuses, the attribute discriminating processing unit may be arranged so that, when all values of the tone width index of the lightness component and the chromaticity component of the block to be discriminated are equal to or less than a predetermined value, The discriminating process of discriminating that the block belongs to a solid image, and if at least one of the tone width index values of the lightness component and the chromaticity component has a value equal to or greater than the predetermined value, the block image has two or more The discriminating process of discriminating that the block belongs to an image having a tone, and further, when the average value information of the chromaticity components of the block to be discriminated is both equal to or less than a predetermined value different from the above, it is determined that the block belongs to a monochrome image. A discriminating process for discriminating; a discriminating process for discriminating that the block belongs to a color image when the value of the average value information of the chromaticity component is equal to or more than a predetermined value different from the above; Assigned to ingredients If the value of the coded data is bipolarized, the block is determined to belong to a binary image. If not, the block is determined to belong to a multivalued image. , It is desirable to execute at least one determination process. In addition, before decoding the encoded data in block units in the encoding processing unit, according to the attribute of the block, a histogram of the brightness component of all blocks of the attribute or the average value information of the brightness component and the chromaticity component is generated. It is desirable to include an average value information conversion processing unit that converts the value of the average value information of each block into an appropriate value based on the obtained histogram. Further, from the storage unit, the average value information of the lightness component and the chromaticity component, the gradation width index, the code data, and the attribute determination result are read in block units, and based on the read attribute determination result, the average value information of the corresponding component, It is desirable to include an editing / processing unit that changes the values of the gradation width index and the sign data to predetermined values.

[0010]

In the first image processing apparatus, the attribute discriminating processing section includes:
The attribute of the image to which the block belongs is determined based on the average value information of the brightness component and the chromaticity component and the value of the gradation width index. Thus, the attribute of the image can be determined without using the image data before the encoding process and the image data after the decoding.
Further, since the attribute is determined for each block, more detailed information can be obtained.

[0011] In the second image processing apparatus, the compression processing section may include, among the data encoded by the encoding processing section,
The value of the average value information of the brightness component or the chromaticity component, the gradation width index, and the value of the code data which can be always specified based on the attribute of the image of the block are reduced. The storage unit stores the data after the compression processing and the attribute determination result. This allows
The compression ratio of image data can be greatly improved.

In the first and second image processing devices, the attribute discrimination processing unit may be configured to determine whether a value of a tone width index of a lightness component and a chromaticity component of a block to be discriminated is equal to or less than a predetermined value. The discriminating process of discriminating that the block belongs to a solid image, and if at least one of the tone width index values of the lightness component and the chromaticity component has a value equal to or greater than the predetermined value, the block image has two or more The discriminating process of discriminating that the block belongs to an image having a tone, and further, when the average value information of the chromaticity components of the block to be discriminated is both equal to or less than a predetermined value different from the above, it is determined that the block belongs to a monochrome image. A discriminating process for discriminating; a discriminating process for discriminating that the block belongs to a color image when the value of the average value information of the chromaticity component is equal to or more than a predetermined value different from the above; Assigned to ingredients If the value of the coded data is bipolarized, the block is determined to belong to a binary image. If not, the block is determined to belong to a multivalued image. By executing at least one determination process, the attribute of the image to which the block belongs can be determined more effectively. That is, depending on a combination of the above-described determination processes, the block image is a black-and-white solid image, a color solid image, a black-and-white binary image, a black-and-white multi-valued image, or a full-color image. Can be determined. Further, in the encoding processing unit, before decoding the encoded data in block units, according to the attribute of the block, the lightness components of all the blocks having the attribute or the average value information of the lightness component and the chromaticity component are obtained. A histogram is obtained, and based on the obtained minimum value, maximum value and average value of the histogram, average value information conversion processing means for converting the value of average value information of each block into an appropriate value is provided. Reads the average value information of the lightness component and the chromaticity component, the gradation width index, the sign data, and the attribute determination result. Based on the read attribute determination result, the average value information of the corresponding component, the gradation width index, and the value of the sign data. AE processing to optimize the density distribution of the original without processing the data before encoding or after decoding by providing an editing / processing unit for changing the It is possible to perform the editing / processing such as frame editing, it is possible to realize the phenomena of the storage unit and the processing time required for the process.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The digital color copying machine of this embodiment is a
After the encoding process of the C method is performed, the attribute of the image is determined for each processing block, and the encoded data is further compressed based on the determination result. The attributes of the above image are
There are five types: a black and white solid image, a color solid image, a black and white binary image, a black and white multivalued image, and a full color image. Also, GBTC
AE processing for optimizing the density distribution of the image using the gradation width index LD and the average value information LA included in the data encoded by the system, and image editing / processing processing such as color conversion and frame editing are executed. Hereinafter, regarding the image processing apparatus of the present embodiment,
Description will be made in the following order with reference to the attached drawings. (1) Encoding of image data by GBTC method (2) Configuration of digital color copier (2-1) Configuration of digital color copier (2-2) Operation panel (3) Description of image processing (3-1) Main routine (3-2) Key input processing (3-3) Recompression processing (3-3-1) Attribute determination processing <3-3-1-1> Solid image determination processing <3-3-1-2> Color / monochrome discrimination processing <3-3-1-3> Binary / multi-value discrimination processing (3-3-2) Feature extraction processing <3-3-2-1> Black and white solid image feature extraction processing <3 -3-2-2> Color solid image feature extraction processing <3-3-2-3> Black and white binary image feature extraction processing <3-3-2-4> Black and white multi-valued image feature extraction processing <3 -3-2-5> Full color image feature extraction processing (3-3-3) Recompression processing <3-3-3-1> Black and white solid image recompression processing <3-3-3-2> Color solid image Recompression processing <3-3-3-3> Black and white binary image recompression processing <3-3-3-4> Black and white multivalued image recompression processing (3-4) Decompression processing from recompression ( 3-4-1) Decompression processing from recompression <3-4-1-1> Decompression processing from black and white solid image recompression <3-4-1-2> Decompression processing from color solid image recompression <3 -4-1-3> Decompression processing from re-compression of monochrome binary image <3-4-1-4> Decompression processing from re-compression of monochrome multi-valued image <3-4-1-5> Re-compression of full-color image (3-4-2) AE processing <3-4-2-1> AE processing for monochrome multi-valued images <3-4-2-2> AE processing for full color images (3-4-3) Image editing / Processing <3-4-3-1> Black / white solid image editing / processing <3-4-3-2> Color solid image editing / processing <3-4-3-3> Black / white binary image editing / processing Processing <3-4-3-4> Black and white multi-value image editing / processing processing <3-4-3-5> Full color image editing / processing processing

(1) Encoding of image data by the GBTC method In the GBTC method, image data of a document is extracted for each block of a predetermined pixel matrix, and for each block, a parameter P1 or less defined by data in the block is determined. The average value information LA obtained by dividing the sum of the average value Q1 of the data and the average value Q4 of the data having a value equal to or larger than the parameter P2 (where P1 <P2 is satisfied) and the average value Q4
And the gradation width index LD which is the difference between the average value Q1 and
The data of each pixel in the block is compressed and coded into code data obtained by quantizing the data to a smaller number of gradation levels than the data within the range of the gradation distribution in the block.
FIG. 1 is a diagram illustrating a G executed by the digital color copying machine of the present embodiment.
It is a figure which shows the flow of the encoding processing of a BTC system. GBT
In the C method, as shown in FIG. 1A, image data of a document image is extracted in units of 4 × 4 pixel blocks. The extracted image data in the 4 × 4 pixel block is subjected to an encoding process according to a method described below with reference to FIG.
As shown in FIG. 1B, a byte (= 8 bits) data × 16 pixels of image data (16 bytes, that is, 128 bits) are converted into a 1-byte gradation width index LD and a 1-byte average value. The information LA and the data of each pixel are encoded into 2-bit code data x 16 pixels, which are classified into four stages and are assigned to a total of 6 bytes (= 48 bits) of data.
Thereby, the data amount is compressed to 3/8. FIG. 1 (c)
FIG. 4 is a diagram illustrating that the data amount of encoded image data corresponds to six pixels of image data before encoding. The decoding of the encoded data is executed by calculating 1-byte image data corresponding to each 2-bit code data based on the gradation width index LD and the average value information LA.
In this embodiment, the image data of the document is 4 × 4
The extraction is performed in units of pixel blocks, but is not limited thereto.
The image may be extracted in units of × 3 pixel blocks or 6 × 6 pixel blocks. Also, 2 of each pixel in the block
The present invention is not limited to the encoding of the 56-gradation data into the 4-gradation code data, but may be the encoding of the 2-gradation or 8-gradation code data. As described in order, in the image processing apparatus of the present invention, for each block, the image attribute determination is performed using the average value information LA and the gradation width index LD obtained from the parameters P1 and P2 determined from the data in the block. Also, it is characterized by executing various image processing based on the determination result.

FIGS. 2A and 2B are diagrams showing an encoding process and a decoding process of the GBTC system. FIG. 2A shows the relationship among the maximum value Lmax, the minimum value Lmin, the parameters P1 and P2, and the gradation width index LD.
From image data extracted in units of 4 × 4 pixel blocks, a predetermined feature amount required for encoding is obtained. The feature amount is obtained by the following calculation. First, a maximum value Lmax and a minimum value L of 8-bit image data in a 4 × 4 pixel block are set.
min is detected. Next, a parameter P1 obtained by adding 1/4 of the difference between the maximum value Lmax and the minimum value Lmin to the value of the minimum value Lmin, and 3/4 of the difference to the value of the minimum value Lmin.
And a parameter P2 to which is added. Note that the parameters P1 and P2 are obtained by the following calculations of "Equation 1" and "Equation 2".

P1 = (Lmax + 3Lmin) / 4

P2 = (3Lmax + Lmin) / 4 Next, of the image data of each pixel, the average value Q1 of the image data of the pixels equal to or less than the parameter P1 is obtained. Further, of the image data of each pixel, an average value Q4 of the image data of the pixels having the parameter P2 or more is obtained. Average values Q1 and Q4 obtained
Based on the average value information LA = (Q1 + Q4) / 2,
A gradation width index LD = Q4-Q1 is obtained. Next, "Equation 3"
And the calculation of "Equation 4" is performed to determine the reference values L1 and L2.

L3 = LA-LD / 4

L2 = LA + LD / 4 The above-mentioned reference values L1 and L2 are obtained together with the above-mentioned average value information LA.
It is used when encoding 1 byte (8 bits) of each pixel, that is, image data of 256 gradations, to 2 bits, that is, code data of 4 gradations. Next, code assignment is performed. In FIG. 2, (b) shows the i-th column (where i = 1, 2, 3, 4; the same applies hereinafter) and the j-th row (where j = 1) in a 4 × 4 pixel block. , 2, 3, and 4; the same applies hereinafter) indicating the value of the code data φij assigned according to the data value of the pixel Xij in the pixel Xij. More specifically, the pixel Xij
Are assigned 2-bit code data φij having the values shown in the following “Table 1”.

[Table 1] The data encoded by the GBTC method includes code data (16 × 2 bits) for 16 pixels, a gradation width index LD of one byte (8 bits), and average value information LA.

As shown in FIG. 2C, when decoding the encoded data, the gradation width index LD
And the average value information LA. That is, according to the value of the code data φij assigned to the pixel Xij on the j-th row of the i-th column, the data of Xij is changed to the value 2 shown in the following “Table 2”.
Replace with 56 gradation data.

[Table 2]

That is, in the GBTC system, the decoded 4
A pixel Xij in the × 4 pixel block (however, i and j
Is one of the values 1, 2, 3, and 4, respectively. ) Is replaced with 256 gradation data of four values. Therefore, the decoded data clearly includes an error when compared with the data of the original image. However, the error is a level that is inconspicuous in human visual characteristics,
In a natural image, image quality deterioration is hardly recognized. GBTC
In the method, the parameters Q1 and Q4 are completely restored from the gradation width index LD and the average value LA included in the encoded data. Therefore, in the character image, if the black portion is equal to or less than the parameter P1 and the white portion is equal to or more than the parameter P2, the character image can be completely restored. In the JPEG system in which encoding is performed using DCT transform, the data compression ratio changes depending on the type of document. That is, for a natural image, higher data compression is realized than in the GBTC system with less deterioration, but it may be hardly possible to compress a binary image, a CG image, and a character image. For this reason, it is difficult to set the capacity of the memory provided in the image processing apparatus. In the GBTC method, data can be compressed at a fixed compression ratio. Therefore, there is an advantage that the capacity of the memory provided in the image processing apparatus can be easily set.

(2) Configuration of Digital Color Copier (2-1) Configuration of Digital Color Copier FIG. 3 is a sectional view of the digital color copier of the present embodiment. The digital full-color copying machine is roughly divided into an image reading unit 100 for reading RGB image data of a document and a copying unit 200. In the image reading unit 100, a document placed on a platen glass 107 is exposed to an exposure lamp 101.
Irradiated by The reflected light of the original is reflected on three mirrors 10
The light is guided to the lens 104 by 3a, 103b, and 103c, and is imaged by the CCD sensor 105. Exposure lamp 101
The mirror 103a is moved by the scanner motor 102 in the direction of the arrow (sub-scanning direction) at a speed V according to the set magnification. Thus, the document placed on the platen glass is scanned over the entire surface. In addition, the mirror 103b, 1
Reference numeral 03c moves in the arrow direction (sub-scanning direction) at the speed of V / 2 with the movement of the exposure lamp 101 and the mirror 103a in the arrow direction. The multi-valued electrical signals of the three colors R, G, and B obtained by the CCD sensor 105 are read by a read signal processing unit 106 into yellow (Y), magenta (M),
After being converted into either 8-bit grayscale data of cyan (C) or black (BK), it is output to the external output port 108 and the copying unit 200. In the copying unit 200,
The image data correction unit 201 performs gradation correction (γ correction) on the inputted gradation data according to the gradation characteristics of the photoconductor. The printer exposure unit 202 converts the corrected image data into D
A / A conversion is performed to generate a laser diode drive signal, and the semiconductor laser is caused to emit light by this drive signal. The laser beam generated from the printer exposure unit 202 corresponding to the gradation data exposes the photosensitive drum 204 which is driven to rotate via the reflecting mirrors 203a and 203b. Photoconductor drum 2
04 is an eraser lamp 2 before receiving exposure for each copy.
Irradiated at 11 and charged uniformly by the charger 205. When exposure is performed in this state, an electrostatic latent image of the document is formed on the photosensitive drum 204. Only one of the cyan (C), magenta (M), yellow (Y), and black (BK) toner developing units 206a to 206d is selected to develop the electrostatic latent image on the photosensitive drum 204. I do. The developed toner image is transferred to a copy paper wound around a transfer drum 218 by a transfer charger 209 after an extra charge is removed by a pre-transfer eraser 208. The transfer drum 218 has a transfer film adhered to its surface, and rotates counterclockwise at the same speed as the rotation speed of the photoconductor. A reference plate 220a is provided inside the transfer drum 218 to synchronize the copy sheet holding position and the image transfer position. The reference position sensor 220b generates a predetermined reference signal every time the reference plate 220a crosses the sensor with the rotation of the transfer drum 218. The copy paper is transported from a paper cassette group 212 to a transport path by a paper feed roller 213, and is transported by a transport roller 214.
To the timing roller 217. When a copy sheet is inserted from the manual feed tray 216, the copy sheet is transported to the timing roller 217 by the transport roller 215. The timing roller 217 supplies the copy paper to the transfer drum 218 in synchronization with the reference signal, and
18 is held at a predetermined position. Timing roller 21
The copy paper supplied from 7 to the transfer drum 218 is electrostatically attracted to the transfer drum 218 by the attraction charger 219. The above printing process is repeatedly performed for four colors of yellow (Y), magenta (M), cyan (C), and black (BK). At this time, the photosensitive drum 2
The exposure lamp 101 and the mirrors 103a, 103b, and 103c repeat predetermined operations in synchronization with the operation of the transfer drum 218 and the transfer drum 218. Thereafter, the copy sheet is separated from the transfer drum 218 by removing the charge of the sheet that has been electrostatically attracted by the charge removing / separating charger pair 221. The copy paper separated from the transfer drum 218 is
After the fixing process is performed by No. 3, the sheet is discharged to a sheet discharge tray 224.

FIG. 4 is a block diagram showing each signal processing executed by the read signal processing section 106. The R, G, and B image data of the original read by the CCD sensor 105 have variations due to individual differences of the CCD sensor 105 included in each copying machine. For this reason, even when the reference patches of the same color table are read, the value of the read data differs for each copying machine. In the reading device color correction processing unit 601,
The read RGB image data is corrected to standard RGB image data standardized by the NTSC standard, the Hi-Vision standard, and the like. The OR, OG, and OB image data corrected by the reading device color correction processing unit 601 are:
It is output to the next color space conversion processing unit 602 and also to the external input / output port 108. A peripheral device connected to the copier receives OR, OG, and OB image data of the original via the external input / output port 108. Further, in the copying machine of the present embodiment, the external input / output port 1
08, it is also possible to form an image using image data of OR, OG, and OB inputted.
The copier will function as a printer. this is,
This is because each processing unit after the reading device color correction processing unit 601 is set to use the standardized RGB image data. The color space conversion processing unit 602 converts the standardized RGB image data (OR, OG, OB) into the XYZ color system, and then converts the data into the L * a * b * color system data. FIG. 5 is a diagram illustrating an L * a * b * color system solid. Lightness 0 (black) to 255 (white) are expressed in units of L *, and hue and saturation are expressed in units of a * and b *. Chromaticity component a
* And b * represent the color direction, respectively, and the chromaticity component a *
Represents the direction from red to green, and the chromaticity component b * represents the direction from yellow to blue.
Here, the reason why the RGB image data is converted to the L * a * b * color system is as follows. As mentioned above, GBT
In the C system, each 8-bit image data Xij in a 4 × 4 pixel block is converted into 2-bit code data φij. At the time of decoding, the gradation width index LD and the average value information LA
Are replaced in accordance with the code data φij assigned to each pixel. As described above, image data obtained by decoding has a certain degree of error with respect to image data before encoding. When the color of each pixel is reproduced using the R, G, and B image data having these errors, a color shift occurs at the edge portion of the document. However, L * a
If each data of the * b * color system is used, even if an error occurs in the value of the data to be decoded, only a slight change in brightness or chromaticity will cause a color shift at the edge of the document. Absent. For this reason, in the copying machine of the present embodiment, when encoding and decoding the image data of the original, the RGB image data is temporarily converted into L * a * b * color system data. The data of the L * a * b * color system is used in the copying machine of this embodiment.
For the above reason, if the RGB image data is converted into hue, lightness, and saturation data, L * u * v
* The data may be converted into data of a color system or other color systems such as YCrCb and HVC. The color space optimization processing unit 603 converts the image data at the time of decoding before encoding each data of the image information L *, a *, and b * of the document represented by the L * a * b * color system. To reduce the deterioration of
The arithmetic processing based on the graphs (a) to (c) shown in FIG. 6 is performed on each data to change the distribution of the lightness component L * so as to be distributed in the range of 0 to 255 for each document. , The distribution of each component of chromaticity a * and b * is -127 to 1 for each document.
It is changed so as to be distributed in the range of 28. First, for each data of the image information L *, a *, b * of the original,
The maximum values L * max, a * max, b * max and the minimum values L * min, a * min, b * min are obtained. The color space optimization processing unit 603 executes the operation shown in the following “Equation 5” for the lightness component L * to obtain a lightness component L1 *.

L1 * = 255 / (L * max-L * min)
× (L * −L * min) The arithmetic processing is based on the graph shown in FIG. That is, in the calculation of Equation 5, L * max
The value of the lightness component L * distributed in the range of
Change to a value distributed in the range of 255. The chromaticity component a * is subjected to the calculation shown in the following “Equation 6” to obtain the chromaticity component a1 *. In Equation 6, when the value of a * is 0, processing is performed so that the value of a1 * after the optimization processing also becomes 0. This is because if the color of the pixel is an achromatic color in which the values of the chromaticity components a * and b * are both 0, this is maintained.

A1 * = 128 / a * max × a * where 0
≦ a * ≦ a * max a1 * = 127 / | a * min | × (a * −a * mi
n) -127 where a * min ≦ a * ≦ 0 The arithmetic processing is based on the graph shown in FIG. That is, in the calculation of the above “Equation 6,” 0 to a * m
Each value of a * distributed in the range of ax is changed to a value distributed in the range of 0 to 128, and each value of the chromaticity component a * distributed in the range of a * min to 0 is changed in the range of -127 to 0. To be distributed to Further, the following equation (7) is executed for the chromaticity component b * to obtain the chromaticity component b1 *.
In Equation 7, similarly to Equation 6, when the value of b * is 0, processing is performed so that the value of b1 * after the optimization processing is also 0. This is because if the color of the pixel is an achromatic color in which the values of the chromaticity components a * and b * are both 0, this is maintained.

B1 * = 128 / b * max × b * where 0
≦ b * ≦ b * max b1 * = 127 / | b * min | × (b * −b * mi
n) -127 where b * min ≦ b * ≦ 0 The arithmetic processing is based on the graph shown in FIG. That is, in the calculation of the above “Equation 7”, 0 to b * m
Each value of b * distributed in the range of ax is changed to a value distributed in the entire range of 0 to 128, and each value of the chromaticity component b * distributed in the range of b * min to 0 is changed to -127 to 0. Change to be distributed in the range. Note that the maximum values L * max, a * max,
b * max and minimum values L * min, a * min, b *
The min is stored in the hard disk 614 and used when performing the color space inverse conversion process. The above arithmetic processing is performed for the following reason. That is, GBTC
In the encoding process and the decoding process according to the method, as shown in the above “Equation 1” to “Equation 4” and “Table 2,” division is frequently used. For this reason, when the difference between the component data of each pixel is small, the difference is lost during the calculation, and the reproducibility of the image data obtained by the decoding process is reduced. In the color space optimization processing unit 603,
The distribution of the lightness component L * is changed to a value distributed in the range of 0 to 255 for each document, and the distribution of each component of the chromaticity a * and b * is distributed in the range of -127 to 128 for each document. Change to a value. This alleviates the above disadvantages. The encoding / decoding processing unit 604, after executing the encoding process of the GBTC method, determines the attribute of the image in units of each block, as described later in detail, and encodes the image based on the determined result. The data (gradation width index LD, average value information LA, code data φij) is compressed again. Here, the image attributes refer to five black and white solid images, color solid images, black and white binary images, black and white multivalued images, and full color images. The compressed data obtained by the recompression is stored in the compressed image memory 610, and the flags f1, f2, and f3 indicating the attributes of the image are stored in the hard disk 614. When performing the decoding process, the CPU 611 controls the compression image memory 610
The compressed data corresponding to each address is read out to the encoding / decoding processing unit 604 from the
, The flags f1, f2 and f3 indicating the attributes of the image are read. The encoding / decoding processing unit 604 encodes the recompressed data based on the values of the flags f1, f2, and f3 indicating the attributes of the image (the gradation width index LD,
It is expanded to the average value information LA and the code data φij). Then, the data encoded according to the GBTC method is decoded, and the brightness component L2 * and the chromaticity components a2 * and b2 * of the image data are output. In the color space inverse optimization processing unit 605,
The maximum values L * max, a * max, b * max and the minimum values L * min, a * min, b * min are read from the hard disk 614, and the read values are used to decode the decoded L2 *, a2 *. , B2 * to the original L * max to L * min, a * max to a * min, b
Return to * max to b * min. These processes are executed based on the graphs shown in FIGS. That is, with respect to the brightness component L2 *, the following calculation operation of Expression 8 is performed to return to the brightness component L3 * distributed in L * max to L * min.

L3 * = (L * max-L * min) / 255
× L2 * + L * min For the chromaticity component a *, the following arithmetic expression 9 is executed, and the chromaticity component a3 distributed from a * max to a * min
Return to *.

A3 * = a * max / 128 × a2 * where 0 ≦ a * ≦ 128 a3 * = 127 / | a * min | × (a * + 127) +
a * min However, for the chromaticity component b * of -127 ≦ a * ≦ 0, the arithmetic processing of the following “Equation 10” is executed, and the chromaticity component b distributed in b * max to b * min
Return to 3 *.

B3 * = b * max / 128 × b2 * where 0 ≦ b * ≦ 128 b3 * = 127 / | b * min | × (b * + 127) +
b * min However, -127 ≦ b * ≦ 0 In the color space inverse conversion processing unit 606, the L3 *, a3 *, b3 restored in the color space inverse optimization processing unit 605 are used.
Each data of * is inversely converted into RGB image data of OR1, OG1, and OB1. The reflection / density conversion processing unit 607
After subjecting the RGB image data of R1, OG1, and OB1 to a predetermined reflection / density conversion process, it outputs density data of DR, DG, and DB. The RGB image data converted into the density data is converted into image data of any one of cyan (C), magenta (M), yellow (Y), and black (BK) by the masking processing unit 608. Output to the image data correction unit 201. The image data correction unit 201 performs predetermined gradation correction (γ correction) processing on the gradation data output from the masking processing unit 608, and outputs the gradation data to the printer exposure unit 202. .

(2-2) Operation Panel FIG. 8 is a front view of an operation panel 300 provided in the digital full-color copying machine of the present embodiment. Operation panel 300
Is a numeric keypad 301 for inputting the number of copies, a start key 302 for starting a copying operation, a display unit 303 for displaying mode settings and copying status, and a selection for selecting a mode displayed on the display unit 303. Key 304, an enter key 305 for setting a mode displayed on the display unit 303, an image editing key 306 for selecting and setting an image editing mode, and a magnification setting key 307 for setting a copy magnification.
And a paper selection key 308 for selecting a copy paper size;
An automatic setting key 309 for setting an automatic paper selection function. In the copying machine according to the present embodiment, the editing / processing to be executed can be set according to the attribute of the image determined in units of 4 × 4 pixel blocks. The contents of the editing / processing processing are displayed in the display unit 303 in response to the pressing of the image editing key 306.
It is determined by the setting of the item displayed in. Selection and setting of items displayed on the display unit 303 are performed as follows. First, each item displayed on the display unit 303 is selected with the selection key 304 and inverted. Next, pressing the enter key 305 completes the setting of the selected item. With the setting of the editing / processing items, the mode flag MF of the set item is set as shown in Table 3 below.
Is set to "1".

[Table 3] For example, by inverting the item of “mono color” with the selection key 304 and pressing the enter key 305, the mono color conversion processing is set, and the entire flag MF1 and the mode flag MF51 for the full color image are set to “1”. Is done. In this case, in the editing / processing described later, the values of the gradation width indices LD, average value information LA, and code data of the chromaticity components a * and b * for the full-color image are all replaced with 0. For the mono-color conversion processing, the color conversion processing, the erasing processing, the negative / positive inversion processing, the background cutting processing, and the dpi conversion processing, data encoded by the GBTC method (gradation width index LD, average value information LA,
This is performed using the code data φij). For this reason, the memory required for the editing processing can be reduced as compared with the related art. Note that the sharpness processing, the gradation curve correction processing, and the outline trimming processing are performed after the RGB image data is decoded as in the related art.

(3) Description of Image Processing (3-1) Main Routine FIG. 9 shows a main routine of a copying process executed by the CPU 611 of the copying machine according to the present embodiment. First, the copier body is initialized (step S1000). Next, a key input process from the operation panel 300 is performed (step S200).
0). Next, pre-processing such as warm-up, shading, and image stabilization of the apparatus is performed (step S).
3000). Thereafter, the CPU 611 drives the scanner motor 102 to read the image data of the document placed on the document table 107, standardizes the RGB image data obtained by reading, and converts the standardized RGB image data to L. The data is converted into * a * b * color system data (step S4000). The image data of the document represented by the L * a * b * color system is subjected to an encoding process using the GBTC method, and then stored in the compressed image memory 610 (step S5000). In the copying machine of this embodiment, the encoded data (gradation width index L) stored in the compressed image memory 610 is used.
D, average value information LA, and code data φij),
The attribute of the image of the 4 × 4 pixel block to which the encoded data belongs is determined, and the encoded data is further compressed based on the determination result (step S6000).
Here, the attributes of the image are five of a black and white solid image, a color solid image, a black and white binary image, a black and white multi-valued image, and a full color image.
One. Flag f indicating the attribute of each determined block
1, f2 and f3 are stored in the hard disk 614. The re-compressed data is stored in the compressed image memory 6
10 is stored. In the next step S7000, the data stored in the compressed image memory 610 is read, and the flags f1, f2, and f indicating the attribute of the data are read.
3 is read from the hard disk 614, and the recompressed data is converted into the original coded data (average value information LA, gradation width index LD, code data φij) based on the attribute of the image determined from the value of each flag. To stretch. Based on the gradation width index LD of the coded data obtained by decompression and the average value information LA, execute AE processing for optimizing the density distribution of the image and editing / processing processing such as color conversion and frame editing. I do. The coded data (average value information LA, gradation width index LD,
The code data φij) is stored in the compressed image memory 610. In the next step S8000, the compressed image memory 61
The RGB image data is read by reading out the encoded data from 0, decoding the data into 256 gradation data for the lightness component L * and the chromaticity components a * and b *, and performing the inverse color space conversion process. Return to In step S9000, an image forming process for forming an image on a sheet based on the RGB image data obtained by the decoding process is executed.
After the image forming process, a process necessary for maintaining the condition of the apparatus, such as removal of residual toner on the photosensitive drum 204 after the image formation, is performed (step S9800). Finally, although not directly related to the image forming processing of the present embodiment, temperature control and communication control of the fixing device are performed (step S9900).

(3-2) Key Input Processing FIG. 10 shows key input processing (step S200 shown in FIG. 9).
It is a process flowchart of 0). If a key input is made on the operation panel 300 (step S20)
01 (YES), the following processing is executed according to the type of the input key. The entered key is an image editing key 306
(YES in step S2002), display unit 303
Then, an image editing menu screen shown in FIG. 8 is displayed (step S2003). The selection of 11 edit items displayed is
The operation is performed by operating the cursor key 304. The selected item is displayed in black and white reversed. On the screen shown in FIG. 8, the item of "mono color" is selected. Enter key 305
By pressing, the setting of the selected item is performed.
The set item remains black and white inverted even when another item is selected by operating the cursor key 304. If the mode has been set by the user (YES in step S2004), a flag setting process is executed (step S2005). In the flag setting process,
The mode flag MF of the set item is set to "1". The mode is not set (N in step S2004)
O) If the end item is selected (step S200)
Then, after returning the screen of the display unit 303 to the initial screen (step S2007), the process waits for a key input again (step S2001). If the input key is the print key 302 (YES in step S2008)
S), a predetermined image forming start process is executed (step S20)
09), and return. If the input key is neither the image editing key 306 nor the print key 302 (NO in step S2008), other processing is executed (step S2010), and the process waits for another key input (step S2010). S2001).

[Table 3] shows the types of flags that are set to "1" by the flag setting process (step S2005) in accordance with the items selected by the user and the set items. The mode flags are all set to "0" in the initial setting (step S1000). For example, when the item “mono color conversion” is set by the user, the overall flag MF1 indicating that the item is set and the mode flag MF51 of the full-color image to which the conversion process is applied are “1”. Is set to When the item “color conversion” is set, an overall flag MF2 indicating that the item is set, and a mode flag MF32 for a monochrome binary image and a full-color image to which the conversion process is applied. And MF52 are set to "1". When the "Erase" item is set, the entire flag MF3 indicating that the item is selected, and a black-and-white solid image, a color solid image, a black-and-white binary image, and a black-and-white multi-value image to which the process is applied The mode flags MF13, MF23, MF33, MF43 and MF53 for the full-color image are set to "1". Hereinafter, each item is also as shown in "Table 3".

(3-3) Recompression processing FIG. 11 is a flowchart relating to the recompression processing of the data encoded by the GBTC method (step S6000 shown in FIG. 9). Here, the attribute of the image is determined from the average value information LA of the data compressed and encoded by the GBTC method and the value of the gradation width index LD. Next, a recompression process is performed to reduce data that can be always specified based on the image attribute among the lightness component L, chromaticity components a * and b *, and code data φij. Thus, the compression ratio of the image data can be improved without sacrificing reproducibility. Further, even if the reproducibility is emphasized and the number of bits of the code data φij assigned to each pixel is increased, the compression ratio can be prevented from lowering by executing the recompression process. First, the code data stored in the compressed image data memory 610 is read (step S600).
1), execute an attribute determination process (step S600)
2). In this attribute discriminating process, for each code data, whether the 4 × 4 pixel block relating to the code data belongs to any of a black-and-white solid image, a color solid image, a black-and-white binary image, a black-and-white multi-valued image, and a full-color image And a flag f1 for a solid image, a flag f2 for a color / monochrome image, and a flag f for a binary / multi-valued image.
3 is set. The attribute determination processing will be described later using a flowchart. Next step S6
In 003, the value of each flag is checked, and the following processing is executed according to the type of each image. A 4 × 4 pixel block is a solid black and white image (flag f1 = 1, flag f2 = 1)
, A black-and-white solid image feature amount extraction process (step S6004) is executed. Here, histogram data of the average value information LA of the lightness component L * is created. next,
A black-and-white solid image recompression process is executed (step S600).
5). If the 4 × 4 pixel block belongs to a solid color image (flag f1 = 1, flag f2 = 0), a color solid image feature amount extraction process (step S6006) is performed. Here, the respective histogram data of the average value information LA of the lightness component L * and the chromaticity components a * and b * are created. Next, a color solid image recompression process is executed (step S6007). A 4 × 4 pixel block is a black and white binary image (flag f1 = 0, flag f2 = 1, flag f
3 = 1), a black-and-white binary image feature amount extraction process (step S6008) is executed. Here, 4 × 4
The black-and-white ratio of each pixel present in the pixel block is determined. Next, a black and white binary image recompression process is executed (step S6).
009) A 4 × 4 pixel block is a monochrome multi-valued image (flag f1 =
0, flag f2 = 1, and flag f3 = 0),
A black-and-white multivalued image feature amount extraction process (step S6010) is executed. Here, histogram data of the average value information LA of the lightness component L * and the gradation width information LD is created. Thereafter, the monochrome multi-valued image recompression process is executed (step S).
6011). A 4 × 4 pixel block is a full-color image (flag f1 = 0, flag f2 = 0, flag f3 = 1)
, A full-color image feature amount extraction process (step S6012) is executed. Here, the lightness components L *,
The average value information LA of the chromaticity components a * and b * and the histogram data of the gradation width index LD are formed. 4x4 above
After executing the processing according to the type of the image to which the pixel block belongs, the compressed data obtained by the recompression processing is stored in the compressed image memory 610 (step S6013). However,
The encoded data relating to the full-color image is stored in the compression code memory 611 as it is. The above processing (steps S6001 to S6013) is performed on the encoded data of all 4 × 4 pixel blocks of the document. If the above processing has been performed on the encoded data of all the 4 × 4 pixel blocks (step S6
(YES in 014), the process ends, and the process returns.

(3-3-1) Attribute Determination Process FIG. 12 shows an attribute determination process (step S60 shown in FIG. 11).
02) is a flowchart. First, it is determined whether the 4 × 4 pixel block corresponding to the encoded data belongs to a solid image (step S6020). In the solid image discriminating process, when it is determined that the 4 × 4 pixel block belongs to the solid image, the value of the flag f1 is set to 1, and when it is determined that the block does not belong to the solid image, the value of the flag f1 is set to 0.
Set to. After the solid image discriminating process is completed, the value of the flag f1 is checked (step S6021). Here, the flag f
When the value of 1 is 1, it is determined that the 4 × 4 pixel block corresponding to the code data belongs to the solid image, and the following processing is executed. First, a color / monochrome determination process is executed (step S6022). In the color / monochrome determination process, the value of the flag f2 is set to 1 when it is determined that the 4 × 4 pixel block belongs to the monochrome image, and the value of the flag f2 is set to 0 when it is determined that the block belongs to the color image. .
After the end of the color / monochrome image discrimination processing, the value of the flag f2 is checked (step S6023). Here, the flag f
If the value of 2 is 1, a process of writing an attribute signal representing a solid black and white image to the hard disk 614 in association with the code data is performed (step S6024). Also, the flag f
If the value of 2 is 0, a process of writing an attribute signal representing a solid color image to the hard disk 614 in association with the code data is performed (step S6025). If the value of the flag f1 is 0 in step S6020, it is determined that the 4 × 4 pixel block belongs to an image having two or more gradations (NO in step S6021), and the image is color / monochrome. Which image is the
In the case of a monochrome image, it is checked whether this is a binary image or a multi-valued image. First, a color / monochrome determination process is executed (step S6026). In the color / monochrome determination process, the value of the flag f2 is set to 1 when it is determined that the 4 × 4 pixel block belongs to the monochrome image, and the value of the flag f2 is set to 0 when it is determined that the block belongs to the color image. Set. The color / monochrome discrimination processing in step S6026 is performed in step S6022.
Is exactly the same as the processing in. After the end of the color / monochrome image discrimination processing, the value of the flag f2 is checked (step S6027). Here, when the value of the flag f2 is 1, a determination process is continuously performed as to whether the monochrome image is a binary image or a multi-valued image (step S).
6028). In the binary / multi-value discriminating process, the value of the flag f3 is set to 1 when it is determined that the 4 × 4 pixel block belongs to the binary image, and the value of the flag f3 is set when it is determined that the block belongs to the multi-value image. Set to 0. After the completion of the binary / multi-value discriminating process, the value of the flag f3 is checked (step S6029).
Here, when the value of the flag f3 is 1, a process of writing an attribute signal representing a black and white binary image to the hard disk 614 in association with the encoded data is performed (step S6).
030). If the value of the flag f3 is 0, a process of writing an attribute signal representing a monochrome multi-valued image to the hard disk 614 in association with the encoded data is performed (step S6031). If the value of the flag f2 set in the color / monochrome discrimination processing in step S6026 is 0, it is determined that the image is a full-color image (NO in step S6027). Therefore, an attribute signal representing a full-color image is written in the hard disk 614 in association with the encoded data (step S60).
32). After executing the above processing for all the encoded data stored in the compressed image memory 610 (YES in step S6033), the process returns.

<3-3-1-1> Solid Image Discriminating Process FIG. 13 shows a solid image discriminating process (step S shown in FIG. 12).
6020) is a flowchart. The solid image is an image composed of only one color having a certain lightness component L * and chromaticity components a * and b *. Visually, lightness L
When the value of each gradation width index LD of *, chromaticity a * and b * is equal to or smaller than a predetermined value, the image is recognized as a solid image. However, when the value of the average value information LA of the lightness component L * is somewhat high (for example, 240 or more), the value of the gradation width index LD of the lightness L *, the chromaticity a *, and the b * is larger than the predetermined value. Even a value is recognized as a solid image. In the solid image discriminating process of this embodiment, the value of the average value information LA of the lightness component L * is less than 240, and the lightness L * and the chromaticity a
* When the value of the gradation width index LD of each component of * and b * is 2 or less (all YE in steps S6040 to S6043)
S) or the value of the average value information LA of the lightness component L * is 24
0 or more (NO in step S6040), and lightness L
When the value of the gradation width index LD of each of the *, chromaticity a * and b * components is 6 or less (YES in steps S6046 to S6048), it is determined that the 4 × 4 pixel block belongs to the solid image, and the flag f1 is set. Is set to 1 (step S60).
44 or S6049). Lightness component L *, chromaticity component a
When the value of each gradation width index LD of * and b * does not satisfy the above condition (the value of the average value information LA of the lightness component L * is 240
(YES in step S6040), when any one of steps S6041 to S6043 has NO, or when the value of average value information LA of lightness component L * is 240 or more (step S6040) NO in any of steps S6046 to S6048
If there is O), it is determined that the 4 × 4 pixel block does not belong to the solid image, and the value of the flag f1 is set to 0 (step S6045 or S6050).

<3-3-1-2> Color / Monochrome Determination Process FIG. 14 is a flowchart showing the color / monochrome determination process (steps S6022 and 6026 shown in FIG. 12). As illustrated, the processing executed in step S6022 is the same as the processing executed in step S6026. Here, the color / monochrome determination processing in step S6022 will be described in order. A black-and-white image is composed of an achromatic color in which the data values of the chromaticity components a * and b * are almost zero. For example, if the value of the average value information LA of each of the chromaticity components a * and b * is within ± 5, it can be determined that the image is an achromatic color. However, only with the above criterion, the average value information LA of the chromaticity components a * and b * is within ± 5, and the chromaticity component a *
If the data value of * is -120 and the data value of the chromaticity component a * of another pixel is 125, and the average value information LA is a small value, this is erroneously determined to be a monochrome image. Therefore, the CPU 611 of this embodiment uses the gradation width index L
Only when the value of D is within ± 5, it is determined that the 4 × 4 pixel block belongs to the monochrome image. Specifically, each average value information LA and gradation width information LD of the chromaticity components a * and b *
Are within ± 5 (steps S6051 to S6051).
(YES in S6054), and sets the value of flag f2 to 1 (step S6055). If at least one of the average value information LA and the gradation width information LD of the chromaticity components a * and b * is ± 5 or more (NO in any one of steps S6051 to 6054), 4 × 4 It is determined that the pixel block belongs to the color image, and the value of the flag f2 is set to 0 (step S6056).

<3-3-1-3> Binary / Multi-Valued Discrimination Processing FIG. 15 is a flowchart showing the binary / multi-valued discrimination processing (step S6028 shown in FIG. 12). The encoded data of the 4 × 4 pixel block of the binary image has a large value of the gradation width index LD of the lightness component L *, and 10 or 00 representing the halftone data is added to the code data φij of the lightness component L *. not exist. On the other hand, 4 × 4 belonging to the multi-valued image
The code data φij of the lightness component L * of the pixel block includes:
There are 10 or 00 representing halftone data. Therefore, in the binary / multi-value discriminating process, the value of the gradation width index LD of the lightness component L * is 200 or more (step S607).
If the value of all the code data φij of the lightness component L * is neither 10 nor 00 (step S60).
71 and NO in S6072, and YE in S6073
Only in S), it is determined that the 4 × 4 pixel block belongs to the binary image, and the value of the flag f3 is set to 1 (step S6).
074). On the other hand, the value of the gradation width index LD of the lightness component L * is 200 or less (NO in step S6070),
The value of the sign data φij of the lightness component L *
Or if there is 00 (steps S6071, S6
07 is YES), it is determined that the 4 × 4 pixel block belongs to the multi-valued image, and the value of the flag f3 is set to 0 (step S6075).

(3-3-2) Feature Amount Extraction Process The average value information LA and the gradation width index LD obtained for each block by the GBTC encoding process are the information amount of 1/16 of the original image data. , Average value information of all image data, and representative values of gradation width data. Therefore, the lightness component L * and the chromaticity components a * and b of the original image data are actually
The information that is almost the same as when the feature value for * is obtained is 1 /
It will be obtained from 16 data. As a result, it is possible to simplify the arithmetic circuit required for the characteristic amount extraction processing, and it is possible to reduce the time required for the characteristic amount extraction processing. In the copying machine of the present embodiment, a feature amount extraction process described below is executed, and each extracted feature amount is stored in the hard disk 614. Thus, when performing the AE process or the image editing / processing process described later, it becomes possible to read out the corresponding feature amount from the hard disk and execute each process based on the read out value. Therefore, the memory capacity required for processing can be reduced as compared with the case where AE processing or image editing / processing processing is performed based on image data before encoding and after image data after decoding. Further, the time required for the processing itself can be reduced.

<3-3-2-1> Solid Black and White Image Feature Extraction Processing FIG. 16 is a flowchart showing the black and white solid image feature extraction processing (step S6004 shown in FIG. 11). Here, after creating the histogram data of the average value information LA for all the blocks of the lightness component L * (step S6100), the process returns. The histogram data obtained here is stored in the hard disk 614, and is used when executing a background cutting process, which is one of editing / processing processes described later.

<3-3-2-2> Solid Color Image Feature Extraction Processing FIG. 17 is a flowchart showing the color solid image feature extraction processing (step S6006 shown in FIG. 11). First, histogram data of the average value information LA for all blocks of the lightness component L * is created (step S).
6110). Next, histogram data of the average value information LA for all blocks of the chromaticity component a * is created (step S6111). Next, histogram data of the average value information LA for all blocks of the chromaticity component b * is created (step S6112). Each histogram data obtained here is stored in the hard disk 614, and is used when executing a background cutting process which is one of editing / processing processes described later.

<3-3-2-3> Black and White Binary Image Feature Extraction Processing FIG. 18 is a flowchart of the black and white binary image feature extraction processing (step S6008 shown in FIG. 11). Here, the black-and-white ratio of each pixel existing in the 4 × 4 pixel block is obtained. If the value of the upper one bit of the code data of each pixel in the 4 × 4 pixel block is 1 (YES in step S6120), the pixel is determined to be white, and the white pixel is counted up (step S61).
21). If the value of the upper 1 bit of the code data is 0 (NO in step S6120), the pixel is determined to be black and the black pixel is counted up (step S6122). The determination in step S6120 is that code data φij = 11, 10 is assigned when the value of the 256 gradation data is larger than the value of the average value information LA, and φij = 00, 01 is assigned when the value is smaller. based on. After determining all the code data in the 4 × 4 pixel block (step S61)
23 (YES), the black-and-white ratio is calculated (step S61).
24). Here, the calculated black and white ratio is stored in the hard disk 614.

<3-3-2-4> Monochrome Multi-valued Image Feature Extraction Processing FIG. 19 is a flowchart showing the monochrome multi-valued image feature extraction processing (step S6010 shown in FIG. 11). First, histogram data of the average value information LA for all blocks of the lightness component L * is created (step S).
6130). Next, histogram data of the gradation width information LD for all blocks of the lightness component L * is created (step S6131). Each histogram data obtained here is stored in the hard disk 614 and used in the AE process described later.

<3-3-2-5> Full-Color Image Feature Extraction Processing FIG. 20 is a flowchart of the full-color image feature extraction processing (step S6012 shown in FIG. 11). First, histogram data of the average value information LA for all blocks of the lightness component L * is formed (step S).
6140). Next, histogram data of the gradation width index LD for all blocks of the lightness component L * is formed (step S6141). The histogram data of the average value information LA for all blocks of the chromaticity component a * is formed (step S6142). The histogram data of the gradation width index LD for all blocks of the chromaticity component a * is formed (step S6143). The histogram data of the average value information LA for all blocks of the chromaticity component b * is formed (step S6144). The histogram data of the gradation width index LD for all blocks of the chromaticity component b * is formed (step S6145). Each histogram data obtained here is stored in the hard disk 614 and used in the AE process described later.

(3-3-3) Recompression Processing In the copying machine of this embodiment, the average value information LA on the lightness component L *, the chromaticity components a * and b *, the gradation width index LD, and the code data φij Of the above, the attribute determination process (step S
Based on the attribute information determined in 6002), data that can always be specified is reduced, and image data is further compressed. Data obtained by the recompression processing is stored in the compressed image memory 610. Hereinafter, the recompression process executed for each attribute will be described.

<3-3-3-1> Solid Black and White Image Recompression Process FIG. 21 is a flowchart of the black and white solid image recompression process (step S6005 shown in FIG. 11). The black-and-white solid image is an achromatic image (the data values of the chromaticity components a * and b * are both 0) having a specific lightness component L *. That is, the solid black and white image can be reproduced from the value of the specific lightness component L *. Since the value of the lightness component L * is a specific value, all the values of the code data φij assigned to each pixel in the 4 × 4 pixel block have the same sign.
Further, the value of the gradation width index LD becomes 0. Therefore, only the average value information LA of the lightness component L * is extracted from the compressed image memory 610, and stored in the compressed image memory 610 as recompressed data relating to a solid black and white image (step S).
6200). FIG. 22 is a conceptual diagram showing the relationship between encoded data and recompressed data. The data after recompression is compressed to 1/18 of the encoded data before recompression. Since the compression ratio of encoded data obtained by the GBTC method is 3/8, the compression ratio of data after recompression is 1/48.

<3-3--3-2> Solid Color Image Recompression Process FIG. 23 is a flowchart of the color solid image recompression process (step S6007 shown in FIG. 11). The solid color image is an image of a single color (the data values of the chromaticity components a * and b * are constant) having a specific lightness component L *. That is, the solid color image can be reproduced from the average value information LA of the chromaticity components a * and b * and the average value information LA of the lightness component L *. Therefore, the compressed image memory 61
Only the average value information LA of the lightness component L * and the chromaticity components a * and b * is extracted from 0 and stored in the compressed image memory 610 as recompressed data for a solid color image (steps S6210, S6211, and S6212). ).
FIG. 24 is a conceptual diagram showing the relationship between code data and recompressed data. The data after recompression is compressed to 1/6 of the encoded data before recompression. Since the compression ratio of the encoded data obtained by the GBTC method is 3/8, the data after recompression is 1/16.

<3-3-3-3> Monochrome Binary Image Recompression Process FIG. 25 is a flowchart of the monochrome binary image recompression process (step S6009 shown in FIG. 11). The black-and-white binary image is an image of achromatic color (both data values of chromaticity components a * and b * are 0) composed of black (lightness component L * is 0) or white (lightness component L * is 255). . That is, black and white 2
The value image can be reproduced from the code data φij for the lightness component L *. In the case of a black-and-white binary image, the code data φij assigned to each pixel is composed of only 11 or 01 codes. Therefore, the value of the code data φij for the lightness component L * is extracted from the compressed image memory 610, the extracted code data of each pixel is converted into 1-bit data φ'ij, and the converted 1-bit data is re-processed. Use compressed data. The value of 1-bit data φ′ij is, for example, 1 when φij = 11 and 0 when φij = 01. As the processing flow, first, one block of 6-byte data of the lightness component L * is read from the compressed image memory 610, and the 2-byte data of the average value information LA and the gradation width information LD is removed from the read data. Only 4-byte data indicating the code data assigned to each pixel is set (step S622)
0). Next, the first two bits of the 4-byte data are read out, and this data is used as code data φij (step S6221). In the case of a binary image, 11 or 01 code data φij is assigned to each pixel. Therefore, the value of the read 2-bit data φij is checked (step S6222). When φij = 01, φ′ij = 0 is assigned (step S622).
3). If φij = 11, φ′ij = 1 is assigned (step S6224). Next, the data of the first two bits of the 4-byte data is shifted, and the data of the next two bits of the two-bit data is made the first (step S6225). Step S6221 above
Steps S6225 to S6225 are performed for all 16 pixels. As a result, recompressed data φ′ij is obtained. The recompressed data φ′ij is stored in the compressed image memory 610.
When the first 2-bit data is again at the top by the shift operation in step S6225 (step S62
(YES at 26), ends the process, and returns. FIG.
FIG. 3 is a conceptual diagram showing a relationship between code data and recompressed data. The data after recompression consists of 1-bit code data φ'ij × 16 pixels = 16-bit data,
It is compressed to 1/9 of the code data before recompression. GBTC
Since the compression ratio of code data obtained by the method is 3/8, the compression ratio of data after recompression is 1/24.

<3-3-3-4> Monochrome Multivalued Image Recompression Process FIG. 27 is a flowchart of the monochrome multivalued image recompression process (step S6011 shown in FIG. 11). In the monochrome multi-valued image, achromatic color (both chromaticity components a * and b * are 0)
Where the brightness component L * changes in the range of 0 to 255. That is, the black-and-white multivalued image has a lightness component L
* Can be reproduced only. Thus, all information (average value information LA,
The gradation width index LD and the code data φij) are extracted and stored in the compressed image memory 610 as recompressed image data (step S6230). FIG. 28 is a conceptual diagram showing the relationship between code data and recompressed data. The data after recompression is compressed to 1/3 of the code data before recompression. The compression ratio of the code data obtained by the GBTC method is 3
/ 8, the data compression rate after recompression is 1/8.

(3-4) Decompression from Recompression The recompressed data is stored in the compressed image memory 610. When forming an image on a sheet, the CPU 611 reads out the recompressed data stored in the compressed image memory 610 and also reads out attribute information related to the data from the hard disk 614. The decompressed data is expanded based on the attribute of the recompressed data specified from the read attribute information.

<3-4-1> Decompression Process from Recompression FIG. 29 and FIG. 30 are flowcharts of the recompression and decompression process (step S7000 shown in FIG. 9). First, the attribute flags f1, f2, and f3 for the 4 × 4 pixel block to be expanded are read from the hard disk 614 (step S7001). The next attribute flag f1,
From the values of f2 and f3, the data regarding the 4 × 4 pixel block is a black and white solid image, a color solid image, a black and white binary image,
Whether the image belongs to a black-and-white multi-valued image or a full-color image is specified (step S7002). 4x4
When the data relating to the pixel block is data belonging to a monochrome solid image (solid image flag f1 = 1, color / color
A monochrome image flag f2 = 1), and a decompression process is performed from the black and white solid image recompressed data to create data that can be decoded by the GBTC method (step S7003).
Thereafter, an editing / processing process based on the setting by the user is executed (step S7004). After the above processing, the decompressed data is written to the compressed image memory 610 (step S7015). When the data relating to the 4 × 4 pixel block is data belonging to a solid color image (solid image flag f1 = 1, color / monochrome image flag f2 =
0), a decompression process is performed from the color solid image recompressed data, and data that can be decoded by the GBTC method is created (step S7005). Thereafter, the editing / processing process based on the setting by the user is executed (step S70).
06). After the above processing, the decompressed data is written to the compressed image memory 610 (step S7015). 4x4
When the data relating to the pixel block is data belonging to a monochrome binary image (solid image flag f1 = 0, color / monochrome image flag f2 = 1, binary / multi-valued image flag f3)
= 1), and executes decompression processing from the recompressed black and white binary image data to create data that can be decoded by the GBTC method (step S7007). Thereafter, the editing / processing is executed based on the setting by the user (step S7).
008). After the above processing, the decompressed data is written to the compressed image memory 610 (step S7015). 4x
When the data relating to the 4-pixel block is data belonging to a monochrome multi-valued image (solid image flag f1 = 0, color / color
Monochrome image flag f2 = 1, binary / multi-valued image flag f
3 = 0), and performs decompression processing from the recompressed black and white multi-valued image data to create data that can be decoded by the GBTC method (step S7009). The AE processing corresponding to the monochrome multivalued image is performed on the expanded data (step S7010). Thereafter, the editing / processing process based on the setting by the user is executed (step S7011). After the above processing, the decompressed data is written to the compressed image memory 610 (step S7015). If the data relating to the 4 × 4 pixel block is data belonging to a full-color image (solid image flag f1 = 0, color / monochrome image flag f2 = 0), a decompression process from the full-color image recompressed data is executed, and the GBTC method is used. Then, data that can be decrypted by is created (step S7012). An AE process corresponding to a full-color image is performed on the decompressed data (step S7013). Thereafter, the editing / processing process based on the setting by the user is executed (step S7).
014). After the above processing, the decompressed data is written to the compressed image memory 610 (step S7015).

<3-4-1-1> Decompression Processing from Re-Compression of Black and White Solid Image FIG.
9 shows a flowchart of step S7003) shown in FIG.
In the case of a black-and-white solid image, the data stored in the compressed image memory 610 is only 1-byte (8-bit) data which is the average value information LA of the lightness component L *, as shown in the upper part of FIG. First, recompressed data is read out from the compressed image memory 610 and is used as data A (step S
7100). Data A is converted to average value information L of lightness component L *.
A (step S7101). The black and white solid image is an achromatic image. Therefore, the data of the chromaticity components a * and b * are all 0. Based on the characteristics of the solid black and white image, the values of the average value information LA of the chromaticity components a * and b *, the gradation width index LD, and the code data φij are all set to 0 (steps S7102 and S7103). The lower part of FIG. 32 shows code data obtained in steps S7100 to S7103.

<3-4-1-2> Decompression Process from Color Solid Image Recompression FIG. 33 is a flowchart of the decompression process from color solid image recompression data (step S7005 shown in FIG. 29). In the case of a color solid image, the compressed image memory 610
As shown in the upper part of FIG. 34, each average value information LA (8 bits) of the lightness component L * and the chromaticity components a * and b * is sequentially stored. First, the first byte of the recompressed data is read from the compressed image memory 610, and is used as data A (step S7110). The data A is set as the average value information LA of the lightness component L * (step S7111).
0 is assigned to the gradation width index LD and the sign data φij of the lightness component L * (step S7112). Next, the next one byte of the recompressed data is read, and this is set as data B (step S7113). The data B is set as the average value information LA of the chromaticity component a * (step S7114). 0 is assigned to the gradation width index LD and the code data φij of the chromaticity component a * (step S7115). Next, the last one byte of the recompressed data is read, and this is set as data C (step S7116). The data C is set as the average value information LA of the chromaticity component b * (step S7117). 0 is assigned to all of the gradation width index LD and the code data φij of the chromaticity component b * (step S7118). The lower part of FIG. 34 shows code data obtained in steps S710 to S7118.

<3-4-1-3> Decompression Process from Recompression of Monochrome Binary Image FIG. 30 is a flowchart of the decompression process from the recompressed monochrome binary image data (step S7007 shown in FIG. 29). The monochrome binary image is composed of achromatic pixels having a lightness component L * of 255 or 0. Since the color of each pixel is binary black and white, the chromaticity components a * and b * are both 0.
The recompressed data φ'ij shown in the upper part of FIG. 37 is 2-byte data related to the lightness component L *, and each 1-bit data constituting the data is the color of each pixel in the 4 × 4 pixel block. Indicates white (the brightness component L * is 255) or black (the brightness component L * is 0). The expansion from the recompressed data to the code data is performed in the following procedure. First, 1-byte data indicating "127" in decimal is given to the average value information LA of the lightness component L * (step S7120). 10 is added to the gradation width information LD of the lightness component L *.
One-byte data indicating "255" in base is given (step S7121). The 2-byte data stored in the compressed image memory 610 is read, and the read data is used as data A (step S7122). Next, the first 1-bit data of the data A is read out, and is read as data B (step S7123). The value of data B is checked (step S7124). If the value of the data B is 0, φij of the corresponding lightness component L * is set to 01 (step S7125). If the value of the data B is 1, the corresponding φij is set to 11 (step S).
7126). The first one-bit data of the data A is shifted to the end, and the next one-bit data is set to the first (step S7127). The processes in steps S7123 to S7127 are executed 16 times, that is, for all data of 2 bytes (step S7128). Since the pixels in the block are achromatic, the average value information LA of the chromaticity components a * and b *, the gradation width index LD, and the sign data are all set to 0 (steps S7129 and S7130). FIG.
The lower part shows code data obtained by expanding the recompressed data stored in the compressed image memory 610.

<3-4-1-4> Decompression Processing from Re-Compression of Monochrome Multi-Valued Image FIG. 37 is a diagram showing a flowchart of decompression processing from re-compression data of monochrome multi-valued image (step S7009 shown in FIG. 30). It is. A monochrome multi-valued image is composed of achromatic pixels. As shown in the upper part of FIG. 38, the recompressed data of the black and white multi-valued image is composed of a total of 6 bytes of data. Specifically, the average value information LA (1 byte) of the lightness component L *,
The gradation width index LD (1 byte) and the code data φij (4
Bytes). First, 1 from the compressed image memory 610
The data for the byte is read, and this is set as data A (step S7140). The data A is set as the average value information LA of the lightness component L * (step S7141). The next 1-byte data is read from the compressed image memory 610, and is read as data B (step S7142). Data B
Is the gradation width information LD of the lightness component L * (step S7).
143). The remaining 4 bytes of data are read from the compressed image memory 610 and are used as data C (step S).
7144). The data C is converted to the sign data φi of the lightness component L *.
j (step S7145). Since each pixel of the black-and-white multi-valued image is achromatic, the average value data LA (1 byte), gradation width index LD (1 byte), and code data φij (4 bytes) of the chromaticity components a * and b * are Are set to 0 (steps S7146, S7147). 38 shows code data obtained by expanding the recompressed data stored in the compressed image memory 610.

<3-4-1-5> Decompression processing from full-color image recompression When data relating to a 4 × 4 pixel block belongs to a full-color image (solid image flag f1 = 0,
The color / monochrome image flag f2 = 0) and the compressed image memory 610 directly store 6-byte data of each of the lightness component L * and the chromaticity components a * and b *. For this reason, in a full-color image, the compressed image memory
Bytes, 1 byte, and 4 bytes are read in order as a set of 6-byte data, the first 1-byte data of the first set is used as the average value information LA of the brightness component L *, and the next 1-byte data is used as the brightness. The gradation width index LD of the component L * is used, and the next 4-byte data is code data φij assigned to each pixel. The first 1-byte data of the second set is the average value information LA of the chromaticity component a *, the next 1-byte data is the gradation width index LD of the chromaticity component a *, and the next 4-byte data is Is the code data φi assigned to each pixel.
j. Also, the first one-byte data of the third set, which is read first, is used as the average value information LA of the chromaticity component b *, and
The byte data is defined as a gradation width index LD of the chromaticity component b *,
The next 4-byte data is assumed to be code data φij assigned to each pixel.

(3-4-2) AE Processing <3-4-2-1> AE Processing for Monochrome Multi-Valued Image FIG. 39 is a processing flowchart of the AE processing (step S7010 shown in FIG. 30) for a monochrome multi-valued image. It is. Here, the value of the average value information LA of each block is converted into an appropriate value based on the histogram of the average value information LA of the brightness components of all the pixel blocks of the document, and the density distribution of the image is optimized. First, the histogram data of the average value information LA of the lightness component L * is read from the hard disk 614, and the minimum value M of the monochrome multi-valued image portion is read from the read data.
in, the maximum value Max, and the average value Ave are obtained (step S7200). Here, the minimum value Min is a frequency value accumulated in order from the high density side, and is a density value when the accumulated value exceeds 2% of the total frequency. The maximum value Max is obtained by accumulating frequencies in order from the high density side, and the accumulated value is 9 of the total frequencies.
The density value when it exceeds 8% is set. Thereby, the irregular data is removed. The average value Ave is the sum of the values obtained by multiplying the frequency at each density value,
Divide by all frequencies. Next, the minimum value Min,
The following AE process is executed using the maximum value Max and the average value Ave (step S7201). The AE process is executed based on the graph shown in FIG.
The value of the average value information LA distributed in the range of the maximum value Max is set to 0.
It is changed so as to be distributed in the range of 255. Specifically, the arithmetic processing shown in the following “Equation 11” is performed on the average value information LA. Average value information L obtained by calculation
A ′ is replaced with the value of the original average information LA.

LA ′ = 255 / (Max−Min) × (L
A-Min) Further, the graph of FIG. 41 shows the average value information LA and the average value information L after the AE processing when executing another AE processing.
A ". AE based on the graph shown in FIG.
In the processing, the value of the minimum value Min is corrected to 0, the value of the average value Ave is corrected to 128, and the value of the maximum value Max is corrected to 255. Specifically, the arithmetic processing shown in the following “Equation 12” is performed on the average value information LA. The average value information LA ″ obtained as a result of the operation is replaced with the original value of the average value information LA.

LA ”= 128 / (Ave−Min) × (L
A−Min) where Min ≦ LA ≦ Ave LA ”= 127 / (Max−Ave) × (LA−Av)
e) +128 However, according to the AE processing, Ave ≦ LA ≦ Max, the reproducibility of the halftone can be further improved as compared with the AE processing executed based on the graph shown in FIG. 42 (a) to (d) show FIG.
FIG. 13 is a diagram showing a result of the AE process executed based on the graph shown in FIG. FIG. 42A shows an original image (halftone image) before the AE processing. FIG. 42B shows histogram data of the average value information LA of the lightness component L * of the original image. The AE processing corrects that the image density of the original image is generally biased toward the low density side. FIG. 42C shows an image after the AE processing based on the graph shown in FIG. FIG.
(D) shows the histogram data after the AE processing. Comparing FIGS. 42A and 42C, it is understood that the bias of the data distribution is corrected.

<3-4-2-2> Full Color Image AE Processing FIG. 43 is a flowchart of the full color image AE processing (step S7013 shown in FIG. 30). here,
The value of the average value information LA of each block is converted into an appropriate value based on the histogram of the average value information LA of the brightness component and the chromaticity component of all the pixel blocks of the document, and the density distribution of the image is optimized. First, the lightness component L from the hard disk 614
* Read out the histogram data of the average value information LA,
The minimum value Min, the maximum value Max, and the average value Ave of the full-color image are obtained from the read histogram data (step S7210). Similarly, the hard disk 61
4, the histogram data of the average value information LA of the lightness components a * and b * is read, and the minimum value Min, the maximum value Max, and the average value Ave of the full-color image are obtained from the read histogram data (steps S7211, S72).
12). The AE process based on the graph in FIG. 40 or 41 is executed to rewrite the value of the average value information LA of the lightness component L * (step S7213). Similarly, the value of the average value information LA of the chromaticity components a * and b * is rewritten as necessary (steps S7214 and S7215).

<3-4-3> Image Editing / Processing Process FIGS. 44 to 48 show flowcharts of the editing / processing process for the attributes of each image. Here, average value information LA, gradation width index LD, and code data φij for each block
The editing / processing process is executed by converting the value of “.” Into the expected value. The contents of the editing / processing process are set in the key input process (step S2000). If the value of the mode flag MF for the editing / processing processing set for each image attribute is "1", the following processing is executed. (A) Mono-color conversion processing This processing is for a full-color image, and converts the image into a monochrome image. To convert a full-color image to a monochrome image, set the chromaticity components a * and b * to 0
However, if data encoded by the GBTC method is used, it is only necessary to convert both the average value information LA of the chromaticity components a * and b * and the value of the gradation width index LD to 0. Can be realized. This gives us another 4x
Without losing the color information for the four pixel block, the attribute discrimination processing determines that the 4
Only a × 4 pixel block can be converted to a monochrome image. In addition, since encoded data is used, the amount of memory required for conversion can be significantly reduced as compared with the case where the processing is performed using 256 gradation data. (B) Color conversion processing This processing targets a monochrome binary image such as a character image and a full-color image. The color conversion process in a black-and-white binary image refers to converting a black character portion and a white background into predetermined brightness and chromaticity. To convert the black and white portions of a black and white binary image to predetermined brightness and chromaticity,
This is realized by converting the average value information LA and the gradation width information LD of the lightness component L * and the chromaticity components a * and b *. As a result, color conversion of only the character image portion can be performed without changing the color information of the other 4 × 4 pixel blocks. In the case of a full-color image, color conversion is realized by similar processing. (C) Erase processing This processing is performed on all images, and the brightness component L of each 4 × 4 pixel block having the selected attribute is obtained.
*, The values of the average value information LA and the gradation width information LD of the chromaticity components a * and b * are both rewritten to 0 and converted to white data. Also, depending on the setting, each of the attributes other than the selected attribute
It is also possible to perform a trimming operation by converting data of a × 4 pixel block into white data. (D) dpi conversion processing This processing is performed on a monochrome multi-valued image and a full-color image, and encodes 4 × 4 pixel code data φij into 2 × 4 pixels.
By thinning out and storing data of 2 pixels or 1 × 1 pixel, the image resolution is reduced and the amount of data to be handled is reduced. (E) Negative / Positive Inversion Processing This processing is performed on a monochrome multi-valued image and a full-color image, and the brightness component L of the corresponding 4 × 4 pixel block is used.
The value of * is converted to a value obtained by subtracting it from 256, and the signs of the values of the chromaticity components a * and b * are inverted. This allows
Negative / positive reversal processing of a multi-value gradation image is realized. (F) Background cut processing This processing is performed on a black-and-white solid image and a color solid image, and the lightness component L of the corresponding 4 × 4 pixel block is used.
The background level is converted by rewriting the average value information LA of *. At this time, the feature amount extraction process (step S609)
0, and histogram data for the lightness component L * obtained in S6100).

<3-4-3-1> Monochrome Solid Image Editing / Processing Process FIG. 44 is a flowchart showing the black / white solid image editing / processing process (step S7004 shown in FIG. 29). For a black and white solid image, the value of the mode flag MF13 is "1"
Is set to (YES in step S7300).
S), an erase process (step S7301) is executed. If the value of the mode flag MF14 is set to "1" (YES in step S7302), negative / positive reversal processing (step S7303) is executed. If the value of the mode flag MF15 is set to "1" (YES in step S304), a background cutting process (step S7305) is performed.

<3-4-3-2> Color Solid Image Editing / Processing Process FIG. 45 is a flowchart showing the color solid image editing / processing process (step S7006 shown in FIG. 29). In the color solid image, the value of the mode flag MF23 is "
If "1" is set (YES in step S7310), an erase process (step S7311) is performed. If the value of mode flag MF24 is set to "1" (YES in step S7312). When the value of the mode flag MF25 is set to "1" (YES in step S7314), the background cutting process (step S731) is performed.
7315).

<3-4-3-3> Black / White Binary Image Editing / Processing Process FIG. 46 is a flowchart showing the black-and-white binary image editing / processing process (step S7008 shown in FIG. 29). In a monochrome binary image, the value of the mode flag MF32 is “1”.
Is set to (YES in step S7320).
S), a color conversion process (step S7321) is performed.
If the value of the mode flag MF33 is set to "1" (YES in step S7322), an erase process (step S7323) is performed. If the value of the mode flag MF34 is set to "1" (step S732)
4; YES), negative / positive reversal processing (step S732)
Execute 5).

<3-4-3-4> Monochrome Multi-Valued Image Editing / Processing Process FIG. 47 is a flowchart showing the black-and-white multi-valued image editing / processing process (step S7011 shown in FIG. 30). In a monochrome multi-valued image, the value of the mode flag MF43 is “1”.
Is set to (YES in step S7330).
S), an erase process (step S7331) is performed. If the value of the mode flag MF44 is set to “1” (YES in step S7332), negative / positive inversion processing (step S7333) is performed. Mode flag
If the value of MF46 is set to "1" (YES in step S7334), dpi conversion processing (step S7)
335).

<3-4-3-5> Full Color Image Editing / Processing Process FIG. 48 is a flowchart showing the full color image editing / processing process (step S 7014 shown in FIG. 30). If the value of the mode flag MF51 is set to "1" for a full-color image (step S73)
(YES at 40), mono-color conversion processing (step S73)
41) is executed. If the value of the mode flag MF52 is set to "1" (YES in step S7342)
S), a color conversion process (step S7353) is performed.
If the value of the mode flag MF53 is set to "1" (YES in step S7344), an erase process (step S7345) is performed. If the value of the mode flag MF54 is set to "1" (step S734)
6) (YES), negative / positive reversal processing (step S734)
Execute 7). If the value of the mode flag MF56 is set to "1" (YES in step S7348),
A dpi conversion process (step S7349) is executed.

In the above-mentioned editing / processing, the values of the average value information LA and the gradation width index LD are changed to scheduled values in accordance with the set editing / processing, based on the attribute determination result. The present invention is not limited to this, and the value of the decoded data may be changed to a predetermined value.

[0056]

According to the first image processing apparatus of the present invention, the attribute of the image of the block can be determined by the attribute determining means based on the average value information of the encoded data and the gradation width index. . For this reason, the determination process can be performed with a simpler operation and with less memory than in the case where the attribute of the image is determined from the image data before encoding. Further, the second image processing apparatus further compresses and encodes the encoded data based on the determination result,
The compression ratio of image data can be improved, and the memory required to store the code data can be reduced.
In any one of the above image processing apparatuses, based on the histogram of the average value information of all the blocks, the value of the brightness component or the average value information of the brightness component and the chromaticity component of each block is set to an appropriate value in accordance with the determination result. , The density distribution of the reproduced image can be optimized without using data before encoding. As a result, it is possible to save the memory required for the processing and reduce the processing time.
Also, based on the determination result, average value information, gradation width index,
By converting the value of the code data φij into a predetermined value, the image can be edited / processed without using data before coding. As a result, it is possible to save the memory required for the processing and reduce the processing time.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the flow of a general GBTC encoding process.

FIG. 2 is a diagram illustrating an encoding process of the GBTC system.

FIG. 3 is a sectional view of the configuration of a digital color copying machine according to the present embodiment.

FIG. 4 is a block diagram showing each signal processing executed by a read signal processing unit 106.

FIG. 5 is a diagram showing an L * a * b * color system solid;

FIG. 6A shows the distribution of the lightness component L * is set to 0 for each document.
(B) and (c) are chromaticity a * and b
It is a figure which shows the graph used when changing the distribution of each component of * to -127-128 for every original.

7 (a) to 7 (c) show the decoded L2 *, a
The distribution of each data of 2 * and b2 * is calculated from the original L * max to L *
min, a * max to a * min, b * max to b * m
It is a figure showing the graph used when returning to in.

FIG. 8 is a front view of the operation panel 300.

FIG. 9 is a diagram showing a main routine of a copying process executed by a CPU 611 of the copying machine.

FIG. 10 is a diagram illustrating a processing flowchart of key input processing (step S2000).

FIG. 11 is a diagram showing a flowchart relating to recompression processing (step S6000) of data encoded by the GBTC method.

FIG. 12 is a diagram illustrating a flowchart of an attribute determination process (step S6002).

FIG. 13 is a solid image discriminating process (step S6020).
FIG. 4 is a diagram showing a flowchart of the above.

FIG. 14 is a color / monochrome determination process (step S6)
022, S6026).

FIG. 15 shows a binary / multi-value discriminating process (step S602).
It is a figure which shows the flowchart of 8).

FIG. 16 shows a black-and-white solid image feature extraction process (step S).
FIG. 6004 is a diagram showing a flowchart of (6004).

FIG. 17 is a diagram illustrating a flowchart of a color solid image feature amount extraction process (step S6006).

FIG. 18 is a flowchart of a black-and-white binary image feature extraction process (step S).
FIG. 6008 is a diagram showing a flowchart of (6008).

FIG. 19 is a black-and-white multivalued image feature amount extraction process (step S);
FIG. 6010 is a view showing a flowchart of (6010).

FIG. 20 is a diagram showing a flowchart of a full-color image feature amount extraction process (step S6012).

FIG. 21 is a black-and-white solid image recompression process (step S60).
It is a figure which shows the processing flowchart of 05).

FIG. 22 is a conceptual diagram showing a relationship between encoded data and recompressed data formed by a black and white solid image recompression process.

FIG. 23 is a color solid image recompression process (step S6).
007) is a diagram showing a processing flowchart of FIG.

FIG. 24 is a conceptual diagram illustrating a relationship between code data and recompressed data formed by a solid color image recompression process.

FIG. 25: Black and white binary image recompression processing (step S60)
FIG. 09 is a diagram showing a flowchart of (09).

FIG. 26 is a conceptual diagram showing the relationship between code data and recompressed data formed by a black and white binary image recompression process and 2.

FIG. 27 is a process for recompressing a monochrome multi-valued image (step S6).
It is a figure which shows the flowchart of 011).

FIG. 28 is a conceptual diagram showing a relationship between code data and recompressed data formed by recompression processing of a monochrome multivalued image.

FIG. 29 is a view showing a flowchart of recompression / expansion processing (step S7000).

FIG. 30 is a view showing a flowchart of recompression / expansion processing (step S7000).

FIG. 31 is a diagram illustrating a flowchart of a decompression process (step S7003) from recompression of a black-and-white solid image.

FIG. 32 is a diagram showing recompressed data in the upper part and code data obtained by expanding the recompressed data in the lower part.

FIG. 33 is a diagram illustrating a flowchart of a decompression process (step S7005) from color solid image recompression.

FIG. 34 is a diagram showing recompressed data in the upper part and code data obtained by expanding the recompressed data in the lower part.

FIG. 35 is a diagram showing a flowchart of a decompression process from black and white binary image recompressed data (step S7007).

FIG. 36 is a diagram showing recompressed data in the upper part and code data obtained by expanding the recompressed data in the lower part.

FIG. 37 is a diagram illustrating a flowchart of a decompression process from recompression of a monochrome multi-valued image (step S7009).

FIG. 38 is a diagram illustrating recompressed data in the upper part and code data obtained by expanding the recompressed data in the lower part.

FIG. 39 is a view showing a processing flowchart of AE processing (step S7010) for a monochrome multi-valued image.

FIG. 40 is a graph showing a relationship between average value information LA and average value information LA ′ after AE processing.

FIG. 41 is a graph showing a relationship between average value information LA and average value information LA ″ after another AE process.

42A shows a document image (halftone image) before AE processing, FIG. 42B shows histogram data of average value information LA of the lightness component L * of the image shown in FIG.
(C) shows the image after AE processing, and (d) shows the histogram data of the document image after AE processing.

FIG. 43 is a view illustrating a flowchart of a full-color image AE / color adjustment process (step S7013).

FIG. 44: Black and white solid image editing / processing (step S)
FIG. 7004 is a diagram showing a flowchart of (7004).

FIG. 45 is a view showing a flowchart of color solid image editing / processing processing (step S7006).

FIG. 46: Black / white binary image editing / processing (step S)
FIG. 7007 is a diagram showing a flowchart of (7008).

FIG. 47: Black-and-white multi-valued image editing / processing (step S)
FIG. 7011 is a diagram showing a flowchart of (7011).

FIG. 48 is a view showing a flowchart of full color image editing / processing processing (step S7014).

[Explanation of symbols]

 106: read signal processing unit 300: operation panel 601: reading device color correction processing unit 602: color space conversion processing unit 603 ... color space optimization processing unit 604 ... encoding / decoding processing unit 605: color space inverse optimization processing Unit 606: Color space inverse conversion processing unit 607: Reflection / density conversion processing unit 608: Masking processing unit 610: Compressed image memory 611: CPU 614: Hard disk

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-164950 (JP, A) JP-A-4-96575 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 1/41-1/419

Claims (5)

(57) [Claims] 1. A data conversion processing unit for converting RGB image data of a document into lightness component data and chromaticity component data, and divides the lightness component and chromaticity component data into blocks each having a predetermined pixel matrix. Then, for each block, a parameter P1 determined from data in the block
Average value information obtained by dividing the sum of the average value Q1 of data having the following values and the average value Q4 of data having a value equal to or greater than the parameter P2 (where P1 <P2) into two, and the average value Based on Q4 and a gradation width index which is a difference between the average value Q1, the data of each pixel in the block is quantized at a gradation level smaller than the data within the range of the gradation distribution in the block. An encoding processing unit for encoding the encoded data to be encoded, and for the encoded block, an image to which the block belongs based on the average value information of the brightness component and the chromaticity component, the gradation width index, and the value of the encoded data. An attribute discrimination processing unit for discriminating the attribute of the image;
The image processing apparatus characterized by comprising a storage unit that stores a compression processor for compressing the encoded data, the attribute discrimination result and compressed data by the compression processing section. 2. A data conversion processing unit for converting RGB image data of a document into lightness component data and chromaticity component data, and divides the lightness component and chromaticity component data into blocks each having a predetermined pixel matrix. and, for each block, the parameters P1 to be pRESCRIBED bY data in the block
Average value information obtained by dividing the sum of the average value Q1 of data having the following values and the average value Q4 of data having a value equal to or greater than the parameter P2 (where P1 <P2) into two, and the average value Based on Q4 and a gradation width index which is a difference between the average value Q1, the data of each pixel in the block is quantized at a gradation level smaller than the data within the range of the gradation distribution in the block. An encoding processing unit that encodes the encoded data to be encoded, and, for the encoded block, an image to which the block belongs based on the average value information of the brightness component and the chromaticity component, the gradation width index, and the value of the encoded data. and attribute determination processing unit for determining the attributes, the average information of luminance component and a chromaticity component, and tone width index,
A compression processing unit that performs a compression process of reducing data that can always be specified based on the determined image attribute among the code data; a storage unit that stores the data after the compression process and an attribute determination result; A compressed data decompression processing unit that reads out the data after compression processing and the attribute determination result stored in the storage unit and restores the data reduced in the compression processing based on the attribute determination result; An image processing apparatus comprising: a decoding processing unit that decodes code data in block units based on average value information of a lightness component and a chromaticity component and a gradation width index. 3. The image processing apparatus according to claim 1, wherein the attribute determination processing unit determines that the values of the tone width index of the brightness component and the chromaticity component of the block to be determined are all less than or equal to a predetermined value. In a certain case, the discriminating process of discriminating that the block belongs to a solid image, and if at least one value of the gradation width index of the brightness component and the chromaticity component has a value equal to or more than the predetermined value, the block image is If the discriminating process of discriminating that the block belongs to an image having two or more gradations and the average value information of the chromaticity components of the discriminating block are both equal to or less than a predetermined value different from the above, the block is black and white. A determination process of determining that the image belongs to an image;
If the value of the average information of the chromaticity component is different than the predetermined value and above, encoded data the block is assigned to the luminance component of the determination process and the discrimination block to determine that belong to the color image If the value is 2 poling, determines that the block belongs to a binary image, if not the two poled, among the block of determination processing to determine that belong to multi-level image, at least one determination An image processing apparatus for performing processing. 4. The image processing apparatus according to claim 1, further comprising: a decoding unit that decodes the encoded data before decoding the encoded data in block units. According to the attribute, a histogram of the lightness component or the average value information of the lightness component and the chromaticity component of all the blocks of the attribute is obtained, and the value of the average value information of each block is converted into an appropriate value based on the obtained histogram. An image processing apparatus comprising: an average value information conversion processing unit. 5. The image processing apparatus according to claim 1, further comprising: a storage unit configured to output average value information of a lightness component and a chromaticity component in block units, a gradation width index, The code data and the attribute determination result are read, and based on the read attribute determination result,
An image processing apparatus comprising: an editing / processing unit configured to change a value of average value information, a gradation width index, and code data of a corresponding component to a predetermined value.