JP2003153022A - Method and apparatus for processing image, image forming apparatus, program and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processor capable of correcting colors at a high speed in a direct conversion system. SOLUTION: The image processor having a color correction processor for converting first color image data in a first colorimetric system into second color image data in a second colorimetric system is provided with a color space conversion processing part for converting the color space of the first color image data. The color correction processing pant is provided with a sort/ inverse sort processor 12 which changes the configuration of the color image data in a color space converted by the color space conversion processing part to reference a lookup table having stored color correction data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lookup table (Luck Up Table: hereinafter referred to as "LUT") for input image data.
The present invention relates to an image processing method for converting output image data by using the above), an image processing apparatus, an image forming apparatus provided with this image processing apparatus, a program for executing the above image processing method, and a recording medium storing this program. . More specifically, the present invention relates to a technique for efficiently performing color correction processing by converting an array of input image data when performing color correction processing for converting input image data into output image data using a LUT.

[0002]

2. Description of the Related Art In a digital image forming apparatus such as a full-color digital copying machine, a color correction method for converting input image data from an image input apparatus into color-corrected output image data and input image data into uniform color space color data. Many proposals have heretofore been made regarding color coordinate conversion methods for conversion. Examples of such methods include the Color Science Handbook, new edition, pages 1137 to 1149 (edited by the Japan Color Association, published by the University of Tokyo Press), and the Journal of the Imaging Society of Japan, Volume 37, No. 4, (199).
8) As described on pages 555 to 559, LU
There is a table reference method for referring to T (hereinafter referred to as "LUT method").

The direct conversion method, which is one of the LUT methods, calculates color correction data or color conversion data for all combinations of input image data in advance, and stores the result in a color conversion table. This is a method of referring to a table value for input image data and outputting it as output image data. This direct conversion method obtains output image data by accessing the color conversion table, and can be applied to any nonlinear characteristic. However, the direct conversion method has a problem in that table values for all input image data need to be stored in the color conversion table, and the table size of the color conversion table becomes very large.

As a method for solving this problem, there is a table interpolation method. In this method, table values for a combination of some selected input image data are calculated in advance and stored in a color conversion table, and a table value in the vicinity of the input image data whose table values are stored in the color conversion table is calculated. With respect to the input image data, the output image data is calculated by interpolation using the table values stored in the color conversion table.

As an example of the table interpolation method, a three-dimensional interpolation method will be described below with reference to FIG. 12
Indicates that the input image data is represented by 8 bits, each axis of the 3 color input color space (input signal space) is divided into 16 (= 2 ⁴ ) and the coordinates of the grid points on each axis are represented by 4 bits. For example:
In this case, the input color space is divided into 4096 (= 16 ³ ) cubes, and the total number of grid points or tables is 4913 (= 17).
³ ). At each grid point p _i (i = 0, 1, ..., 7), color conversion data or color correction data corresponding to the upper 4-bit input image data is stored, and the lower 4-bit input image data is stored. Is used to perform the interpolation calculation. now,
If the relative ratio of the arbitrary input image data p to the grid width in each grid is a, b, and c, the interpolation value f (p) in 8-point interpolation (cubic interpolation) is the table value f at the grid point p _i . (p
_i ) is calculated by the following equation (1).

[0006] f (p) = (1- a) · (1-b) · (1-c) · f (p 0) + a · (1-b) (1-c) · f (p 1) + a・ B ・ (1-c) f (p ₂ ) + (1-a) ・ b ・ (1-c) ・ f (p ₃ ) + (1-a) ・ (1-b) ・ c ・ f ( _{p 4) + a · (1} -b) · c · f (p 5) + a · b · c · f (p 6) + (1-a) · b · c · f (p 7) ... (1) this The three-dimensional interpolation method can obtain color correction values and color conversion values for all combinations of input image data even when the number of input image data for which table values have to be calculated in advance is limited. The size of the table can be reduced.

[0007]

However, in the table interpolation method as described above, since the result is calculated by interpolation with respect to the data in the grid, the color coordinate conversion is non-linear due to the characteristics of the image output device. If it is necessary to express the sex, accurate conversion cannot be realized. In order to perform accurate conversion, it is necessary to use the direct conversion method.

However, in the direct conversion system, as described above, the table size of the color conversion table becomes very large. For example, if the input image data is luminance value (L), chromaticity
(a) and chromaticity (b) are expressed in 256 gradations (= 8-bit width), and if the color conversion table is accessed using 8 bits for luminance value and 7 bits for hue value, 16 megabytes (MB) storage area is required. Since a high-speed processing is required in a full-color copying machine or the like, a semiconductor memory is used as a storage device for this table. However, an image processing LSI incorporating a 16 MB memory is
The SI chip size becomes large and the cost becomes very expensive. Therefore, the system can be realized by combining an inexpensive large-capacity general-purpose memory and an image processing LSI.

As a general large-capacity general-purpose memory, SDR
There is an AM (Synchronous Dynamic Random Access Memory). This SDRAM has a feature that the memory cell structure is simple and inexpensive, but after giving a row address by using an active command and transitioning a target row to an active state, a column address is given in order. When accessing a memory cell and reading another row, it is necessary to close the currently active row using a precharge command and then transition the other row to the active state again. However, it has a drawback that it is fast for continuous address access but slow for random address access.

Generally, in the color correction processing, the color correction processing is performed in the pixel order of the image. However, in this state, noise included in the input image frequently causes random access even in an image area having the same pixel value. It will be. Therefore, there is a problem that the memory access speed becomes a bottleneck, the processing speed of the color conversion processing decreases, and the processing speed of the entire system decreases.

An object of the present invention is to solve the above problems and provide an image processing method, an image processing apparatus, an image forming apparatus, a program and a recording medium capable of performing a faster color correction process by a direct conversion method. is there.

[0012]

In the image processing apparatus according to the present invention, the first color image data having the first color system and the second color image data having the second color system are used. An image processing apparatus having a color correction means for converting into a color space is provided with a color space conversion means for converting a color space of the first color image data, and the color correction means is converted by the color space conversion means. LU that stores color correction data by changing the array of color image data in the color space
It is characterized by comprising a data array conversion means for referring to T.

According to the image processing apparatus of the present invention, the color correction unit changes the arrangement of the color image data of the color space converted by the color space conversion unit and refers to the LUT in which the color correction data is stored. Since the data array conversion means is provided, the frequency of continuous access to the position near the LUT is improved, and the average access speed to the LUT is improved. Therefore, the color correction processing by the direct conversion method can be performed at a higher speed.

In the image processing apparatus of the present invention, for example, the data array conversion means reversely converts the color correction data subjected to the color correction processing into the original data array before the array is changed.

According to this, by performing the inverse conversion to the original data array before changing the array, the image processing that handles a plurality of neighboring pixels with respect to the pixel after the color correction processing, for example, filter processing. Etc. can be carried out.

In the image processing apparatus of the present invention, for example, the color space conversion means converts the first color image data into a color space consisting of luminance information and color information, and the data array conversion means, the color space conversion means. The information is used to change the arrangement of the color image data whose color space has been converted.

According to this, by changing the array based on the color information that human visibility is low, the frequency of occurrence of pixels having the same key value at the time of changing the array, that is, sorting, becomes high. It is possible to simplify and speed up the processing by collectively handling the owned pixels.

In the image processing apparatus of the present invention, for example, the data array conversion means uses the color information to generate the L
A first address defining an approximate address for accessing the UT and a second address defining a detailed address for accessing the LUT using the luminance information and the color information are generated, and using the first address, The arrangement of the color image data whose color space has been converted is changed.

According to this, the first address, which is the key value, is generated mainly based on the pixel value indicating the color information, the sorting is performed based on the key value, and the key value has a wider range. Position or upper value of address (MSB (Most Signi
By reading the color correction value from the LUT in which the pixel values after color conversion are arranged so as to represent the fied Bit) side, the access concentrates on the closer position in the LUT, and the average access speed to the LUT To improve.

In the image processing apparatus of the present invention, for example, the data array conversion means extracts a block consisting of a plurality of pixels from the color image data representing color information, and color image data in which the color space is converted for each block. To change the array of.

One block is composed of 64 pixels, for example, 8 pixels in the main scanning direction and 8 pixels in the sub scanning direction.

According to this, by treating the neighboring pixels that are likely to have the same pixel value as one unit, that is, the block, and performing the sorting process, the frequency at which the neighboring positions in the LUT can be successively accessed is further improved, The average access speed to the LUT is further improved.

In the image processing apparatus of the present invention, for example, filter processing means for smoothing color image data representing color information is provided in front of the color correction means.

According to this, by performing the filtering process having the smoothing function on the color information whose human visual resolution is low, the noise of the color information included in the color image data is not affected by the human visual sense. The components are suppressed, the frequency with which the same key value can be obtained is further improved, and the access is concentrated in the near position in the LUT, so that the average access speed to the LUT is further improved.

The image forming apparatus according to the present invention comprises the above-described image processing apparatus.

According to the image forming apparatus of the present invention, as described above, the access to the LUT becomes faster, so that it is possible to provide the image forming apparatus in which the processing speed is improved.

The image processing method according to the present invention is an image processing for performing color correction processing for converting the first color image data of the first color system into the second color image data of the second color system. The method includes a color space conversion process for converting the first color image data into a color space composed of luminance information and color information, and the color correction process includes a color obtained by converting the color space using the color information. The array of image data is changed, based on this array, the color correction data is read by referring to the LUT in which the color correction data is stored, and this color correction data is inversely converted into the order before the array change. Thus, color correction processing is performed.

According to the image processing method of the present invention, the color correction process changes the arrangement of the color image data whose color space has been converted using the color information, and the color correction data is stored based on this arrangement. Since the LUTs are referenced, the L
The frequency of access to the position near the UT is improved, and the LUT
The average access speed to is improved. Therefore, the color correction processing by the direct conversion method can be performed at a higher speed. In addition, by performing the inverse conversion to the original data array before changing the array, it is possible to perform image processing, such as filter processing, that handles a plurality of pixels in the vicinity of the pixels after color correction processing. It will be possible. Furthermore, by changing the arrangement based on color information that human visibility is low, the pixels having the same key value are frequently generated at the time of changing the arrangement, that is, sorting, and pixels having the same key value are treated collectively. As a result, the processing can be simplified and speeded up.

In the image processing method of the present invention, for example, the color correction processing uses the color information to perform the LUT.
To generate a first address that defines an approximate address for accessing the LUT and a second address that defines a detailed address for accessing the LUT using the luminance information and color information, and use the first address to generate The arrangement of the color image data whose color space has been converted is changed.

According to this, the first address which is the key value is generated mainly based on the pixel value indicating the color information, the sorting is performed based on the key value, and the key value has a wider range. Position or upper value of address (MSB (Most Signi
By reading the color correction value from the LUT in which the pixel values after color conversion are arranged so as to represent the fied Bit) side, the access concentrates on the closer position in the LUT, and the average access speed to the LUT To improve.

A program according to the present invention is characterized by causing a computer to execute the above image processing method.

According to the program of the present invention, the computer can read and execute the image processing method which has the same effect as that of the image processing method of the present invention and in which the speed of accessing the LUT is improved. The processing method can be general-purpose.

A recording medium according to the present invention is characterized by storing the above program in a computer-readable manner.

According to the recording medium of the present invention, the same effect as that of the image processing method of the present invention can be obtained, and the program of the image processing method capable of executing high-speed color correction processing can be easily supplied to the computer. You can

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a full-color digital copying machine which is one of image forming apparatuses will be described below with reference to the drawings.

FIG. 1 shows the structure of a digital copying machine.

As shown in FIG. 1, the digital copying machine includes a scanner unit (image input device) (1) and an ADC unit (Analog-Digi).
tal Converter: A / D converter) (2) and image processing device
(Image processing part) (3), controller (4), engine part
(Image output device) (5).

The scanner unit (1) includes a CCD (Charge Coupled
Device) line image sensor unit and a drive system in the sub-scanning direction, scans an original, and scans R for each main scanning line.
Outputs GB (R: red, G: green, B: blue) color analog signals.

The ADC section (2) includes an analog amplifier and an ADC.
And the RGB color analog signal from the scanner unit (1) is converted into a digital signal.

The image processing device (3) is a DSP (Digital Sign).
al Processor) -ASIC (6) and external data ROM (7)
And an external data memory (8). DSP-A
The SIC (6) has a DSP core (10), a built-in memory (11),
A sort / reverse sort processing device (1
2) and a DMA arbitrator (13). DSP core (1
0) includes software for the DSP including the front image processing unit (14), the main image processing unit (15) and the rear image processing unit (16). The DSP-ASIC (6) is a DSP core.
It has an interface (input buffer interface / output buffer interface) between (10) and the external data memory (8).

The built-in memory (11) is a low-capacity memory that can be accessed at high speed from the DSP core (10).
It is used as a work area for image processing work performed by.

The sorting / reversing sort processing device (12) sorts pixel values before performing color correction processing, sorts them so as to enable continuous access, and then sorts them in an external data memory (8 ) Rearranges the data read from () and outputs it.

The DMA arbitrator (13) is a DMA (Direct Memory Access) request between the external data memory (8) and the internal memory (11) required by the DSP core (10) and a sort / inverse sort processing device. External data memory required by (12) (8)
The DMA request between the sort / reverse sort processing device (12) is prioritized and the DMA is executed.

The external data memory (8) is a DSP core (10).
It is composed of an SDRAM having a capacity of 32 MB which can be directly connected to. The external data memory (8) is controlled by the DSP core (10) as shown in FIG.
A work buffer (memory area for image processing) (8a), an input buffer (8b), an image buffer (8c), an output buffer (8d) and a color correction table (color conversion table) (8e) which is a LUT are internally configured. .

The external data ROM (7) is a ROM (Read Only
Memory), which is a non-volatile memory and stores the original data of the color correction table to be transferred to the external data memory (8) according to the instruction from the DSP core (10) at the time of system initialization.

The controller (4) is a general-purpose CPU (Central CPU).
Processing unit), which controls the scanner unit (1), the image processing apparatus (3), and the engine unit (5) to control a series of copy operations. The controller (4) is provided with an operation panel (17).

The engine section (5) is CMYK (C: cyan
It is an inkjet type output engine using four color inks (M: magenta, Y: yellow, K: black), and outputs an image to an output sheet using CMYK data values output from the image processing device (3). .

Next, referring to FIG. 3, the image processing device (3)
The configuration and function of will be described.

As shown in FIG. 3, the image processing device (3) is
A pre-image processing unit (14), which is a series of processing units for image data,
A main image processing unit (1) including an input buffer interface (18) and a filter processing unit and a color correction processing unit according to the present invention (1
5), an output buffer interface (19), and a post-image processing unit (16).

The pre-image processing section (14) carries out the input format conversion processing in the input format conversion processing section, the shading correction processing in the shading correction processing section, and the input γ correction processing in the input γ conversion processing section. In the input format conversion processing unit, the CCD
The line gap between RGB is removed, and the data is converted into data that has no line gap and is easy to use internally. That is, since the CCDs provided with the R, G, and B filters are different in position, this positional deviation is corrected. The shading correction processing unit corrects input data having a light amount distribution in the main scanning direction and converts it into data having no light amount distribution. That is, the digital RGB signals sent from the ADC section (2) are subjected to processing for removing various distortions generated in the illumination system, the imaging system, and the imaging system of the scanner section (1). In the input γ correction processing unit, the scanner unit
The input characteristic of (1) is corrected so that the image data is linear to the sensitivity of the CCD so that it can be easily handled in the subsequent image processing.

The input buffer interface (18) temporarily stores the RGB multi-valued image data for which the pre-image processing has been completed in the external data memory (8) so that it can be read out as necessary in the post-stage image processing.

The main image processing unit (15) includes a color space conversion process in a color space conversion processing unit which is a color space conversion unit, a region separation process in a region separation processing unit, and a filter in a filter processing unit which is a filter processing unit. The processing, the color correction processing in the color correction processing unit that is the color correction unit, and the halftone processing in the halftone processing unit are performed. The color space conversion processing unit converts the color image data (first color image data of the first color system) input in color space coordinates of RGB 8-bit values into a luminance value (L) and a chromaticity (a). ), The Lab color space coordinates represented by the chromaticity (b) are converted into image data represented by 8-bit values (the color space may be YCrCb (Y: luminance, Cr · Cb: color difference signal)). In the area separation processing unit, the character / photo area is determined for each pixel in the input image,
Create an attribute for each pixel. In the filter processing unit, a two-dimensional FIR (Finite Impulse Respons
e) After filtering, using the attribute information for each pixel, the emphasis filter processing is performed for the L value in the character area and the smoothing filter processing is performed in the photo area, and the a value and the b value are processed. Smoothing filter processing is performed. In the color correction processing unit, Lab multi-valued data is converted into CMYK multi-valued color image data (second color image data based on the second color system). That is, in order to realize faithful color reproduction, a value based on the spectral characteristic of the CMYK color material including the unnecessary absorption component is directly converted from the Lab value to CMYK by referring to the table. In the halftone processing unit, CMY of 256 gradations for each color
The K data is converted into CMYK data of four gradations for each color.

The output buffer interface (19) temporarily stores the CMYK data of four gradations for each color, which has been subjected to the main image processing, in the external data memory (8) so that the CMYK data can be read out as necessary in the subsequent image processing.

The post-image processing section (16) performs the output format conversion processing in the output format conversion processing section. In the output format conversion processing unit, the engine unit (5)
The CMYK data of 4 gradations for each color is changed according to the input format of. For example, the output image data is converted according to the arrangement of the CMYK heads.

These individual image processes except for the color correction processing section are executed by the DSP core (10) using the built-in memory (11) as a work area.

Next, with reference to FIG. 4, description will be given of a sort / reverse sort processing device (12) which constitutes a part of hardware for carrying out color correction processing according to the present invention.

As shown in FIG. 4, the sort / reverse sort processing device (12) includes a key generation / numbering unit (20), an address decoder (21), an input selector (22), and a target storage register (2).
3), a first target selector (24), a second target selector (25), a comparator (26), a DMA interface (27), an inverse sort register (28) and an output selector (29).

The key generation / numbering unit (20) is a DSP
Using the 64 Lab image data passed from the P core (10), it is converted into a 12-bit key value (first address), a 10-bit body value (second address), and a 6-bit permutation number. .

The key value is calculated by the following equation (2) using the upper 6 bits of the a value and the upper 6 bits of the b value.

Key value = a [7: 2] × 64 + b [7: 2] (2) where a [7: 2] is bit 7 which is the upper 6 bits of the a value.
To bit 2 are shown, and similarly b [7: 2] shows the value from bit 7 to bit 2 of the b value.

The body value is the second bit of the a value and the second bit of the b value.
It is calculated by the following equation (3) using the bit value and the L value.

Body value = a [1] × 512 + b [1] × 256 + L [7: 0] (3) where a [1] is the value of bit 1 of the a value, and b [1] is b
The value of bit 1 of the value is shown, and L [7: 0] shows an 8-bit value from bit 7 to bit 0 of the L value, that is, the L value itself. The key value is a value that indicates the row address of the SDRAM of the external data memory (8), is a value that is an upper value of the address, and is a sort target value. The body value is
It is a value indicating the column address of the SDRAM of the external data memory (8) and is a lower value of the address.

The permutation number is for later reverse sorting and is generated by sequentially allocating the numbers from 0 to 64 in the order passed from the DSP core (10).

The three values of the key value, the body value and the permutation number are input from the key generation / numbering unit (20) to the input selector.
Passed to (22).

The address decoder (21) is a DSP core (10).
Switch the input selector (22) according to the access from
When writing to the target storage register (23) from the DSP core (10), the input selector (22) is switched so that the output from the key generation / numbering unit (20) is connected to the target storage register (23). . Also, address decoder (21)
Switches the output selector (29) so that the target reverse sort register value is connected to the DSP core data bus when the DSP core (10) reads the value of the reverse sort register (28).

The input selector (22) has an address decoder (2
According to the outputs from 1) and the comparator (26), the value of the next target storage register value is determined.

The target storage register (23) stores a 12-bit key value, a 10-bit body value, and a 6-bit permutation number as 6.
It is a register that stores four sets and stores the data to be sorted.

The first target selector (24) selects 32 key values on one side to be sorted from the target storage register (23). The second target selector (25) selects 32 key values on the other side to be sorted from the target storage register (23).

The comparator (26) compares the key values of 32 sets of comparison targets from the first target selector (24) and the second target selector (25), and passes the result to the input selector (22).

After the sorting is completed, the DMA interface (27) reads out 64 sets of key values and body values from the target storage register (23), passes them to the DMA arbitrator (13), and then D
CM that is the result of memory access from the MA arbitrator (13)
The YK value is received and the reverse sort register (2
Store in 8).

The reverse sort register (28) is a set of 64 registers for storing CMYK values, and transfers data to the output selector (29).

5 to 9 are flowcharts showing an example of the above-mentioned image processing performed by the image processing apparatus (3). The processing judgment in these flowcharts is performed by the DSP core (10).

FIG. 5 is a flow chart schematically showing the whole image processing.

In FIG. 5, first, after the initialization processing (S1) is performed, the pre-image processing (S2), the main image processing (S3) and the post-image processing (S4) are performed, and whether the processing is completed or not. It is determined whether or not (S5). If the processing is not completed in S5, S2
The previous image processing (S2), the main image processing (S3) and the subsequent image processing (S4) are repeated until the processing is completed. Then, in S5, when the processing ends, the image processing ends.

In the initialization processing of S1, first, the area of the external data memory (8) is allocated, and the DSP work buffer (8a), input buffer (8b), image buffer (8c),
The output buffer (8d) and the color correction table (8e) are set to predetermined values as shown in FIG. continue,
In accordance with an instruction from the DSP core (10), the color correction table data is transferred from the external data ROM (7) to the external data memory (8) via the DMA arbitrator (13). Further, reset processing of the line counter is performed.

Details of the pre-image processing in S2 are shown in FIG.

In FIG. 6, first, it is judged whether or not there is a free space in the input buffer (8b) (S201).
It is determined whether the scanner is scanning (S202). S2
In 02, if the scanner is scanning, it is determined whether input capture is possible (S203), and if it is possible, capture of one line in the main scanning direction (S204), depending on the processing content of the previous image processing. Input format conversion processing (S205),
Shading correction processing (S206) and input γ conversion processing (S
207) is performed, the image data is stored in the input buffer (8b) (S208), and the process is ended. In S203, if the input cannot be captured, the process ends as it is. If the scanner is not scanning in S202, scanning of the scanner carriage is restarted (S209), and the process ends. S201
If there is no space in the input buffer (8b), it is determined whether or not the scanner is scanning (S210) .If it is, the scanner carriage is temporarily stopped (S21
1), the processing ends. In S210, if the scanner is not scanning, the process ends.

When the input cannot be taken in S203, it means that the scanner is not at the position to scan, that is, the position to read the data. For example, for a scanner with an input resolution of 600 dpi (dot per inch), 600
This is a case where a main scanning pulse is generated for each dpi, and data is read when the pulse falls, but the main scanning pulse is not falling.
Therefore, in this case, the processing ends without doing anything.

When the scanner is not scanning in S202, as a result of the processing up to this point, the input buffer (8b) is full in the determination step of S201 before the previous time, S211 is executed, and the scan is temporarily stopped. It means that it is in the state. In this case, after the scanner carriage is stopped in S211, the scanner carriage is slightly returned. Then, after the next time, it is again determined in S201 whether or not there is a space in the input buffer (8b), and if there is space in the input buffer (8b), the process proceeds to S202, but initially the scanner is stopped. Therefore, the process proceeds from S202 to S209, the scanning of the scanner carriage is restarted, and the processing is ended, so that the scanning is performed again after the next time.

The details of the main image processing in S3 are shown in FIG.

In FIG. 7, first, it is judged whether or not there is image data in the input buffer (8b) (S301). If it is judged that there is image data, it is judged whether or not there is a space in the output buffer (8d). Is determined (S302). In S302, the output buffer (8
If it is determined that there is a space in d), the image data is taken out from the input buffer (8b) (S303), color space conversion processing (S304), which is the main image processing, area separation processing (S305), filter processing (S306). ), Color correction processing (S307) and halftone processing (S308) are performed, and after the above processing, data for four CMYK1 main scanning lines of each color is stored in the output buffer (8d) (S309).
The process ends. If it is determined in S301 that there is no image data in the input buffer (8b), or if it is determined in S302 that there is no space in the output buffer (8d), the processing ends.

The details of the color correction processing in S307 are shown in FIG. In addition, in FIGS. 11 to 14 used in the following description, the numbers with h added to the end are hexadecimal numbers.

In FIG. 9, first, initialization (S701) is performed, whereby the state of the sort / reverse sort device (12) and the SDRAM as the external data memory (8) are changed to the DSP core (10).
Initialized by instructions from. Next, the DSP core (10)
As shown in FIG. 10, from the image data to be color-corrected, block data of a total of 64 pixels with a length of 8 pixels in the main scanning direction and a length of 8 pixels in the sub-scanning direction is cut out, and the sorting / reversing sort device is executed.
Write to the target save register (23) in (12) (S
702). As a result, for example, as shown in FIG.
64 pixels are cut out. Next, in the key generation / numbering unit (20), the Lab write value from the DSP core (10) is converted into a 12-bit key value, a 10-bit body value, and a 6-bit permutation number, and the actual target storage is performed. The data is stored in the register (23) (S703). As a result, for example, as shown in FIG. 11B, the storage in the target storage register (23) is performed. The permutation number i is given to the pixel i (i = 0 to 63), and the key value, the body value, and the permutation number of the pixel i are stored in the target storage register i.

Then, sort processing is performed. The apparatus according to the present embodiment performs sort processing by a method generally called bubble sort. That is, the 64 key values stored in the target storage register (23) are to be sorted, and the key values of the 2xth and (2x + 1) th (x = 0, 1, ..., 31) are first compared with each other. If, as a result of the comparison, the key value of the target storage register (23) with the smaller number is larger, the input selector (22) is instructed to replace the target storage register values in which both are stored (S704). Then, (2x + 1) number
The key values of (2x + 2) th (x = 0, 1, ..., 30) are compared with each other, and as a result of the comparison, the target storage register with the smaller number
If the key value of (23) is larger, input selector (22) to replace the target storage register value where both are stored
To give instructions (S705). Next, the processing of S704 and S705 is 3
It is judged whether it has been performed twice, and if not, S7
Returning to 04, the processes of S704 and S705 are repeated 32 times, and the sorting process is completed. As a result, the target save register (23)
As shown in FIG. 11C, for example, the image data is stored in order from the smallest key value.

After the sorting is completed, the data in the target storage register (23) is passed to the DMA arbitrator (13) via the DMA interface (S707).

The DMA arbiter (13) judges whether or not the data in the same row in the external data memory (8) was accessed immediately before (S708), and if the same row was not accessed immediately before, the external data A row active command is issued to the SDRAM, which is the memory (8), waits until the row becomes active (S709), and proceeds to S710. If the row is active in S708, the process directly proceeds to S710. In S710,
Whether the next access is the same row or not is determined. If the rows are the same row, a read command is issued together with the column address, and the target data is read while the row is in the active state (S711).
If the next access is not the same row in S710, a read precharge command is issued together with the column address to read the target data and close the row (S
712). When the processing of S711 or S712 is completed, the target data output from the external data by the read command is fetched (S713). Next, it is judged whether or not the above processing is executed 64 times (S714). If it is not executed 64 times, S708 is executed.
Return to and repeat it 64 times.

When the above processing is repeated 64 times, from S714
Proceeding to S715, the DMA arbitrator (13) sends back the read result to the DMA interface (27) in the sort / inverse sort processing device (12) (S715). DMA interface (27)
The received data is stored again in the reverse sort register (28) based on the permutation number. That is, the color correction values (CMYK values) are read out in the order of FIG. 11 (c) and rearranged in the original order using the permutation numbers. As a result, the contents of the reverse sort register (28) are as shown in FIG. 11 (d), and the contents of the reverse sort register i (i = 0 to 63) become the color correction value of the pixel i.

Thereafter, the DSP core (10) reads the contents of the reverse sort register (28), receives the color correction result, and writes it back to the original block position (S716). Next, it is determined whether or not the block cutout is completed (S717), and if it is not completed, the process returns to S702 and the above process is repeated until there is no block data to be cut out, and the color correction process is ended.

Details of the post-image processing in S4 are shown in FIG.

In FIG. 8, first, it is judged whether or not there is image data in the output buffer (8d) (S401), and if there is, it is possible to output to the engine section (5) which is an image output device. It is determined whether or not (S402). When the output is not possible in S402, it is when the head is cleaned in the case of the engine section (5) of the inkjet system, or when the image processing side is fast and the output side processing is not catching up.

In S402, if output is possible,
Image data is taken out from the output buffer (8d) (S403), output format conversion processing which is the content of post-image processing is performed (S404), and the result is output to the engine unit (5) (S405),
The line counter is incremented (S406), and the post-image processing ends. Since line-by-line processing is performed in the increment of the line counter in S406,
When the processing of one line is completed, the line counter is incremented by 1.

When there is no image data in the output buffer (8d) in S401, or in S402 the engine unit (5)
If the output is not possible, the post-image processing is ended as it is.

In the present invention, the image processing method may be recorded on a computer-readable recording medium recording a program to be executed by a computer. As a result, it is possible to provide a recording medium on which a program for performing the above-described image processing method is recorded so as to be portable.

As the recording medium, a memory (not shown) such as a ROM itself may be a program medium because the microcomputer performs the processing in the above-described embodiment. Although not shown, a program medium that is provided with a program reading device as an external storage device and is readable by inserting a recording medium therein may be used.

In any case, the stored program may be accessed and executed by a microprocessor, or in any case, the program is read and the read program is read by a microcomputer. The program may be downloaded to a program storage area (not shown) and the program may be executed. It is assumed that this download program is stored in the main body device in advance.

Here, the program medium is a recording medium which can be separated from the main body, and is a tape system such as a magnetic tape or a cassette tape, or a floppy (registered trademark).
Magnetic disks such as disks and hard disks, and CD-Rs
Disk systems for optical discs such as OM, MO, MD, DVD, card systems such as IC cards (including memory cards), optical cards, etc., mask ROM, EPROM (Erasable)
Programmable Read Only Memory), EEPROM (Elect
rically Erasable Programmable Read Only Memory),
It may be a medium that fixedly carries the program, including a semiconductor memory such as a flash ROM.

Further, in the above embodiment, a medium having a system configuration capable of connecting a communication network including the Internet and fluidly carrying the program so as to download the program from the communication network may be used. When the program is downloaded from the communication network in this way, the program for downloading may be stored in the main body device in advance, or may be installed from another recording medium.

The recording medium is read by a program reading device provided in the image forming apparatus or the computer system to execute the above-described image processing method.

The computer system displays an image input device such as a flatbed scanner, a film scanner, a digital camera, etc., a computer on which various processes such as the above image processing method are performed by loading a predetermined program, and a processing result of the computer. An image display device such as a CRT display or a liquid crystal display, and a printer that outputs the processing result of a computer to paper or the like. Furthermore, a modem or the like is provided as a communication means for connecting to a server or the like via a network.

Further, the present invention may be applied to a printer. In this case, the program of the image processing method may be provided in the printer driver of the computer,
Alternatively, it may be provided on the printer side.

[Brief description of drawings]

FIG. 1 is a block diagram of a full-color digital copying machine showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an example of a configuration of the external data memory shown in FIG.

FIG. 3 is a block diagram showing a detailed configuration of the image processing apparatus shown in FIG.

FIG. 4 is a block diagram showing a detailed configuration of the sort / reverse sort processing apparatus shown in FIG.

FIG. 5 is a flowchart showing an example of an image processing method of the present invention.

FIG. 6 is a flowchart showing details of a pre-image processing method of the image processing method shown in FIG.

7 is a flowchart showing details of a main image processing method of the image processing method shown in FIG.

8 is a flowchart showing details of a post-image processing method after the image processing method shown in FIG.

9 is a flowchart showing details of color correction processing of the main image processing shown in FIG.

FIG. 10 is an explanatory diagram showing an example of block cutout from image data.

FIG. 11 is an explanatory diagram showing an example of the contents of one block of image data cut out from the image data, the storage register, and the reverse sort register when the color correction processing is executed.

FIG. 12 is an explanatory diagram showing color conversion processing by a conventional interpolation method.

[Explanation of symbols]

(3) Image processing device (10) DSP core (12) Sort / reverse sort processing device (15) Main image processing unit

Continued front page    F-term (reference) 2H030 AA02 AA03 AD11                 5B057 CA01 CA08 CA12 CA16 CB01                       CB08 CB12 CB16 CC01 CE05                       CE06 CE17 CE18 CH07 CH08                       CH11 CH12 DB02 DB06 DB09                 5C077 LL18 MM03 MP08 NN02 PP02                       PP06 PP32 PP33 PP36 PP37                       PQ12 PQ22 PQ23 SS01 TT06                 5C079 HB01 HB03 HB08 HB12 JA23                       LA12 LA19 MA04 MA11 NA11                       PA02

Claims (11)

[Claims] 1. An image processing apparatus comprising color correction means for converting first color image data of a first color system into second color image data of a second color system. Of the color image data is converted into a color space, and the color correction means changes the arrangement of the color image data of the color space converted by the color space conversion means to obtain the color correction data. An image processing apparatus comprising a data array conversion means for referencing a stored look-up table. 2. The data array conversion means reversely converts the color correction data subjected to the color correction processing into the original data array before the array is changed. Image processing device. 3. The color space conversion means converts the first color image data into a color space composed of luminance information and color information,
3. The image processing apparatus according to claim 1, wherein the data array conversion means uses the color information to change an array of color image data whose color space has been converted. 4. The data array conversion means accesses the look-up table using a first address that defines an approximate address for accessing the look-up table using color information and the luminance information and color information. A second address that defines a detailed address is generated, and the first address is generated.
The image processing apparatus according to any one of claims 1 to 3, wherein the array of the color image data whose color space has been converted is changed using the address of. 5. The data array conversion means extracts a block consisting of a plurality of pixels from color image data representing color information, and changes the array of color image data in which the color space is converted for each block. The image processing apparatus according to any one of claims 1 to 4, characterized in that. 6. A filter processing means for smoothing color image data representing color information is provided before the color correction means.
The image processing device according to any one of 1. 7. An image forming apparatus comprising the image processing apparatus according to claim 1. Description: 8. An image processing method for performing color correction processing for converting first color image data of a first color system into second color image data of a second color system, comprising: A color space conversion process for converting color image data into a color space composed of luminance information and color information is provided, and the color correction process changes the array of color image data whose color space has been converted using the color information. Then, based on this array, the color correction data is read by referring to the look-up table in which the color correction data is stored, and the color correction data is inversely converted to the order before the array is changed to An image processing method characterized by performing correction processing. 9. The color correction processing uses a first address that defines an approximate address for accessing the look-up table using the color information, and accesses the look-up table using the luminance information and color information. Generate a second address that defines the detailed address to
9. The image processing method according to claim 8, wherein the array of the color image data whose color space has been converted is changed using the address of. 10. A program for causing a computer to execute the image processing method according to claim 8 or 9. 11. A recording medium on which the program according to claim 10 is stored so that it can be read by a computer.