JPH1155535A - Image processing device - Google Patents

Abstract

(57) [Summary] An image processing apparatus for obtaining binary image data used in an output device based on multi-valued input image data,
The color reproducibility of the entire output image is improved without increasing the processing load. SOLUTION: A multi-level input image data input for each pixel via an input / output unit 201 is subjected to a color difference addition circuit 203 to generate a color difference generated by binarization in a pixel having a predetermined positional relationship between a immediately preceding processed pixel and a previous line. Are added at predetermined ratios, and the address generation circuit 205 achieves an address based on the input image data to which the color difference has been added, whereby the color space between the input image data and the measurement data based on the binary data is obtained. The binary data used for printing in the recording unit is read from the output color table 2112 of the correspondence that minimizes the distance of.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus, and more particularly, to an image processing apparatus for performing a color correction process for color reproduction in a color image output device.

[0002]

2. Description of the Related Art Many output devices for outputting a color image express colors by a combination of binary primary colors, and color printers and color displays are known as specific examples. In an image processing apparatus that performs image processing for such a binary output device, first, for input color image data, a conversion relationship between an input color space created by these data and the like and an output color space of the output device is adjusted. The input color image data is converted into yellow, magenta, cyan, or primary color components obtained by adding black to these, or red, green,
Decomposed into each blue primary color component. In general, a binary image obtained by performing a pseudo gradation expression process on the color component data obtained by the color correction is output.

[0003]

However, in the above-described conventional image processing, since the colors to be output are obtained in pixel units, the above-described two-color output is limited in the number of combinations of colors that can be output.
The value output device has a problem that an error between a color actually output and a color corresponding to the input image data increases.

Further, in the binary output device, since the pseudo gradation expression processing is performed independently for each color component, there is a problem that the finally output color may not match the predicted color. .

On the other hand, the distance in the color space is calculated for each color of the combination so that the color closest to the color in the input image data is associated with the color combination reproducible by the output device. In addition to selecting the minimum color combination, a configuration in which the associated color difference is diffused to other pixels can be considered.

However, in this case, there is a problem that the load of calculation for selecting the color combination in the image processing apparatus becomes relatively large.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an image processing apparatus capable of improving the color reproducibility of the entire output image without increasing the processing load. It is to provide a device.

[0008]

According to the present invention, there is provided:
An image processing apparatus that converts multi-valued color data into binary data of a color that can be expressed by an output device, wherein a color difference adding unit that obtains color difference correction data by adding color difference data to the multi-valued color data; A data output unit that outputs, using a table, binary data of a color that can be represented by the output device and that corresponds to a color indicated by the color difference correction data, based on the color difference correction data obtained by the color difference addition unit; A color difference calculating means for calculating a color difference between multi-valued color point data corresponding to the binary data output from the data output means and color difference correction data relating to the output of the binary data; and a color difference calculated by the color difference calculating means. And storage means for storing as color difference data used by the color difference adding means.

According to the above arrangement, the color difference correction data is obtained by adding the color difference generated by the binarization of the other pixels to the multi-valued input color data, and the table is referred to based on the color difference correction data. Since the output of the value data, it is possible to omit the operation for obtaining the binary data in the image processing, in particular, the operation for obtaining the correspondence between the multi-valued color data and the binary data.
Color differences are diffused throughout the output image.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a facsimile apparatus according to one embodiment of the present invention.

In FIG. 1, a CPU 1 executes image processing of the present embodiment, which will be described later, according to a program stored in a ROM 6 and controls various functions of the facsimile apparatus.

The functions of the facsimile apparatus of this embodiment include the following.

Function as a Color Copier A document image is read by a reading unit 4 equipped with a CCD.
Outputs analog data of each color of R, G, B. The reading unit 4 may include a contact image sensor (CS) instead of the CCD, and the read data to be output may be for C, M, and Y colors.

The image processing unit 5 converts the analog data sent from the reading unit 4 into digital data, for example, for each color.
The data is converted into digital data capable of expressing 8 bits of pixels and 256 gradations and stored in the RAM 7. Further, by writing this data into the binarization processing unit 2, image processing of the present embodiment described later is performed, and the binary color data obtained thereby is read and stored in the RAM. Then, when the stored data reaches an amount necessary for the recording unit 11 to perform a predetermined amount of recording, the recording operation by the recording unit 11 is performed.

Function as Monochrome Copier In the same manner as described above, the analog data output from the reading unit 4 is binarized into white and black in the image processing unit 5 and stored in the RAM.
7 is stored. Thereafter, monochrome recording is performed by the recording unit 11 in the same manner as described above.

Function as Scanner As described above, digital data obtained via the reading unit 4 and the image processing unit 5 is stored in the RAM 7, and thereafter, the PC I / F unit 12 is started, and a personal computer (hereinafter, referred to as PC) is started. Handover).

Function as Printer The recording section 11 outputs the data based on the data input from the PC via the PC I / F section 12.

Function of facsimile transmission As described above, R is transmitted via the reading unit 4 and the image processing unit 5.
The data stored in the AM 7 is encoded, modulated by the modem 15, and then output to the line via the NCU 16.

In the facsimile transmission of data by the PC, the transmission image transferred via the PC I / F unit 12 is encoded, and the data modulated by the modem 15 is converted into the PC data.
N based on the destination information transferred via the I / F unit 12
It controls the CU 16 and outputs it to the line.

Function of Facsimile Reception The analog waveform input via the line is demodulated through the NCU 16 and the modem 15, and the decoded data is stored in the RAM 77. Then, the data is output by the recording unit 11 according to the program stored in the ROM 6, or the stored data is read by the PC.

Further, in the configuration shown in FIG. 1, the nonvolatile RAM 8 stores the S
The RAM is used to store data such as a telephone number unique to the apparatus and a user abbreviation, communication results, and the like. The operation unit 9 is used to start copy keys for monochrome copying and color copying, and to start transmission and reception. The keys include a mode key for designating a mode such as a key, a fine mode for a transmitted image, a different image quality of a standard, a resolution mode for a copy, a stop key for stopping an operation, a registration key for one-touch registration, and the like. Then, the CPU 1 detects the pressed state of these keys, and controls each unit according to the detected state.

The display unit 10 includes a dot matrix type liquid crystal display (LCD) and an LCD driver.
Various displays are performed based on the control of U1. The recording unit 11
The CPU 1 includes a DMA controller, a bubble jet type inkjet head, a general-purpose IC, and the like.
With this control, the recording data stored in the RAM 7 can be read and printed out as a hard copy. The driving unit 14 includes a stepping motor for driving the feeding and discharging rollers in the reading operation and the recording operation of the reading unit 4 and the recording unit 11 described above, a gear for transmitting the driving force of the motor, and a motor. It is composed of a driver circuit for controlling and the like.

The modem 15 has a 34, V.I. 32, V.I.
32 bis, V.I. 17, V.I. 29, V.I. 27ter,
V. 23, V.I. 21 (H, L) modems and a clock generation circuit connected to these modems.
The transmission data stored in the RAM 7 is modulated based on the control of the PU 1 and output to the subscriber line via the NCU 16. Furthermore, the modem 11 introduces an analog signal from the subscriber line via the NCU 16, demodulates the analog signal, and stores it in the RAM 7 in binary form. NCU
Reference numeral 16 is provided with a DC capturing circuit, an AC supplementary circuit, a Ci / pole detection circuit, and a two-wire / four-wire conversion circuit, and connects a subscriber line to the modem 15. In addition, handset 18
Can also be connected to the NCU 16.

The sensor section 13 includes a recording paper width sensor, a recording paper presence / absence sensor, a document width sensor, and a document presence / absence sensor, and detects the state of the document and the recording paper under the control of the CPU 1.

FIG. 2 is a diagram showing details of the binarization processing section 2 shown in FIG. 1, and shows a main embodiment of the image processing apparatus of the present invention. As will be apparent from the description below, the binarization processing unit performs the input image data R of 8 bits each,
For G and B, pseudo-gradation processing is not performed on each of the Y, M, C, and K color component data obtained by color change as in the related art, and binarization is performed. A process of associating with binary Y, M, C, and K used in the direct recording unit 11 is performed.

In the configuration shown in FIG. 2, reference numeral 201 denotes an input / output unit for inputting / outputting data via a data bus and a control data bus; a register unit for transferring data to / from the bus; It has a system counter unit for managing the processing timing of the processing unit 2.

Reference numeral 202 denotes a log table for converting input image data into CMY via the input / output unit 201, and reference numeral 203 denotes input image data CMY to be input after being log-converted.
A color difference addition circuit 204 for adding color difference data, which will be described later, is a selector / buffer circuit 204 for separating and holding input image data to which color differences have been added for each CMY. The input image data for each CMY is input to an address generation circuit 205 to generate an address of an output color table to be described later, and to a buffer 206 for calculating a color difference between the input image data and the output image data by a subtraction circuit 209. Stored temporarily.

A color difference distribution circuit 208 distributes the color difference obtained by the subtraction circuit 209 to each pixel. That is, the color difference is sent to the above-described color difference addition circuit 203 for addition to the input image data of the next pixel, as described later,
It is sent to the color difference conversion circuit 207 to diffuse to the pixels of the next line. The color difference conversion circuit 207 calculates the sum of the color differences for each pixel corresponding to each pixel of the next line and stores it in the previous line color difference memory 2110 as described later.

An R 210 manages an area of the RAM 211.
RAM management unit 21 which is an AM I / F unit and controls RAM addresses and write / read timings
00.

The RAM 211 is a RAM for binarization processing, and may be shared with the RAM 7. This RAM 211 is
The previous line color difference storage memory 2110 that stores the color difference of the previous line, the output color point table 2111 that associates the output color with the color actually output in the recording unit 11, and the input image data indicate It has an output color table indicating the output point closest to the input color in the color space.

FIG. 3 is a diagram mainly showing the binary processing performed by the binarization processing unit 2.
6 is a flowchart illustrating a binarization process, that is, a process for obtaining print data used by a recording unit.

Hereinafter, the processing will be described for each step in accordance with the flowchart shown in FIG.

Step S101: When color copy or color print is executed, the previous line color difference storage memory 21
Each buffer in the 10 and binarization processing section is cleared.

Step S102: A counter PIX indicating an input pixel to be processed is initialized to zero.

Step S103: The data stored in the RAM 7 is read, and the data is written to the registers 2010 allocated to the R, G, and B of the binarization processing unit.

The data format is RG as a color system.
It goes without saying that CMY and other colors may be used in addition to B.

If the CPU has a transfer mode in units of words (16 bits), for example, two addresses are assigned to each color, and R0, R1, G0, G1, B0, B1
The number of accesses can be reduced by writing data of 256 gradations (8 bits) to the address assigned with.

As a method of managing the processing of the binarization processing section, a method of counting the number of clocks can be used. The system counter 2011 starts counting when data is written from the CPU as a trigger, and the processing timing is controlled by the number of clocks, whereby an optimal processing circuit can be designed.

Note that circuits such as sum, difference, product, and quotient and circuits that can be used in common, such as an addition circuit, a color difference integration circuit, a subtraction circuit,
The circuit scale of the color difference distribution circuit and the log conversion table significantly increases as the bit width increases. By using these circuits in a time-division manner while managing a plurality of buffers by the system counter 2011, it is possible to realize a small-scale circuit. This is more effective as the output color is multi-valued. In addition, since it is a synchronous circuit, timing verification and the like become easy.

In step S103, the address R,
When data is written in the order of G and B, the system counter 2011 starts counting with the writing of the data at the address B as a trigger, and counts every clock. This counter 2011 is cleared by soft clear or when the next R data is written.

Steps S104 and S105: When the count value of the system counter 2011 is 0, the input data written in the register R is read. Incidentally, the data of the RJE registers G and B are read when the counter values are 10 and 20, respectively (steps S114 and S124).

Step S106: The read input data is converted into cyan data Ci by the log conversion table 202.

When the input data is represented by C, M, Y, it is needless to say that the conversion by the log table need not be performed. Further, the log table may be configured in the RAM 7 or may be configured together with various correction tables such as a reading system.

Step S107: The preceding line color difference data CL diffused to the present processing pixel is read from the storage memory 2110. This color difference data will be described later.

Step S108: As described above, the input data Ci obtained as described above and the color difference data CL read out from the previous line color difference data storage memory 2110 in correspondence with the pixels shown in FIG. The error CP of the immediately preceding processing pixel is added by the adding circuit 203.

Step S109: Ci ₀ + CL + CP obtained by the above addition is stored in buffer 204 as data IL.
Latch as PC.

ILPC has a signed 11-bit width (−5).
12 to +512), and 5 so as not to overflow.
If the number exceeds 12, the addition circuit is rounded down to 512, so that the addition circuit can be realized on a small scale as long as the image is not affected.

Steps 114-118, 124-12
8: The same processing as in steps S104 to S109 described above is performed for G and B, and ILPM and ILPY are latched in the buffer 204. In this way, it is possible to obtain data obtained by adding the color difference between the predetermined pixel on the previous line and the immediately preceding processed pixel to the input image data.

Steps S110, S111: The input data (ILPC, ILPM, IL
PY), the addresses ILPC ', ILRM', I
LPY 'is created, and output color data (BO, MO, YO) closest to the input data in the color space is read out with reference to the output color table 2112 shown in FIG. 8 based on these addresses, and stored in the register.

The output color table 2112 is configured as follows.

In the color space, the color (I
LPC, ILPM, ILPY) and the color (CO, MO, YO) indicated by the measurement data actually recorded by the recording unit

[0053]

L ² = (ILPC-CO) ² + (ILPM-M
O) ² + (in the calculation of ^{ILPY-YO) 2, YO,} MO, the values of CO changed in the range shown in the output color point table in FIG. 4, CO when the value of L ² is minimized, A set of MO and YO is obtained, and binary (K, C, M, and Y) corresponding to the set of CO, MO, and YO are input data (ILP) in the relationship shown in FIG.
C, ILPM, ILPY) are tabulated as output colors. The binary data K for the output color is set to “0” when C, M, and Y are all “1”.
And K is obtained as "1".

As described above, performing the above calculation to obtain output color data for each pixel requires a considerable amount of software and hardware load and requires a long time for processing. By having the calculation results in a table, input data (ILPC, IPC,
Based on LPM, ILPY), output color data (K, C, M, Y) closest to the input data in the color space can be obtained at high speed.

Further, the table is configured in a memory,
It is possible to obtain optimum output color data (K, C, M, Y) at high speed by having a plurality of tables suitable for an output device, a recording method such as ink and toner, and a recording medium such as paper. .

Further, by changing the table,
An image can be represented by a plurality of dots or dots having different sizes. Further, by making the plurality of tables changeable under the control of the main and the PC, the optimum table can be selected without changing the hardware.

Regarding the output color table, the input data (I
LPC, ILPM, ILPY) are each 11 bits with a sign as described above, but the corresponding output color data is a total of 4 bits of (K, C, M, Y). On the other hand, 16 kinds of output color data correspond. Therefore, in the present embodiment, the output color data is obtained in a smaller table by extracting the upper multiple bits of the input data. in this case,
By setting the value to 0 when the component of the input data becomes negative, appropriate output color data can be obtained with a small table.

More specifically, in step S110, the input data (ILPC, ILPM, ILPY) as shown in FIG.
By combining the upper 3 bits obtained with the sign of (1) and forming 9-bit address data (ILPC ', ILPM', ILPY '), 512 tables can be obtained.

Steps S111, S112, A113:
The output color data (K,
C, M, Y) is stored in the register 2010, and then this data is read out and stored in the memory for one line. Here, the number of accesses from the CPU to the binarization processing unit 2 is reduced by allocating registers to C, M, Y, and K, respectively, and performing reading when eight pixels corresponding to the size of the data bus are stored. When the data processing method of the recording unit is a line unit of main scanning, the burden of data rearrangement by software is reduced.

If the CPU has a transfer mode in units of words (16 bits), two registers are allocated to C, M, Y, and K, respectively, and when 16 pixels are stored, C, M, Y, and K are stored.
You may make it read from PU.

As described above, the data for one line is binarized, the vertical position Y of the processing pixel is incremented, and the processing from step S102 is repeated, and the processing from step S101 is repeated due to a page break. It is.

Next, the process of diffusing the color difference generated in the above-described binarization processing will be described in detail with reference to the flowchart shown in FIG.

Step S201: The vertical position Y of the input pixel to be processed is initialized to zero.

Step S202: The horizontal position X of the input pixel to be processed is initialized to zero.

Step S203: The output color data (C, M, and C) obtained from the output color table 2112 as described above.
Y, K), the multi-value data (CO, MO, YO) is obtained by referring to the output color point table 2111 of FIG. Here, the data (CO, MO, YO) is (C, M,
(Y, K) indicates the density of each color when printing is performed.

Step S204: Pixel (X,
Y) of the color difference E (Ce, Me, Ye)
i, Mi, Yi) and output color point data (Co, Mo, Y)
In the subtraction circuit 209, the following is obtained from o).

[0067]

## EQU2 ## Ce = Co-Ci, Me = Mo-Mi, Ye =
Yo-Yi Step S205: In the color difference distribution circuit 208, the color difference E obtained above is added to the neighboring input pixels at a predetermined ratio. Specifically, as shown in FIG. 6, the color difference is diffused to the lower right, lower, and lower right diagonal pixels in the right and next line pixels of the processing target pixel. ,
The diffusion of the next line to the above three pixels is achieved by sending the color difference data to the color difference addition circuit 203, and by sending the color difference data to the previous line color difference memory. That is, the color difference of the processing pixel (x, y) is 2/16 (x, y + 1) in (x-1, y + 1) and 5/16 (x + 1, y + 1) in 1/16 (x + 1, y). Distribute at a rate of (1/2). The remainder when divided by 16 is (x
+1 and y) can be reflected without losing the color difference information.

Thus, the addition in the adding circuit 203 is performed as follows.

Yi (X + 1, Y) → Yi (X + 1, Y) + (Ye / 2) Mi (X + 1, Y) → Mi (X + 1, Y) + (Me / 2) Yi (X + 1, Y) → Ci ( X + 1, Y) + (Ce / 2) Step 206: On the other hand, from the above, the color difference diffused to the processing pixel (x, y) is: E (x, y) → 1 / 16E (x−1, y) -1) +5/1
5E (x, y-1) + 2 / 16E (x + 1, y-1) +
8 / 16E (x-1, y) +, of which the data E of the previous line ((y-1)) is stored in the previous line color difference memory 2110. In this case, the color difference integration circuit 207 as described above. Is the sum of the color differences for each pixel set on the previous line

[0070]

## EQU3 ## CL = 1 / 16E (x-1, y-1) +5/1
6E (x, y-1) + 2 / 16E (x + 1, y-1). Thus, the RAM can be effectively used.

The color difference to be stored is 8 bits (−12 bits) in order to reduce the number of accesses by utilizing the RAM chip.
The distribution shown in FIG. 6 may be determined so as to fall within the range of 8 to 128). Further, by further expanding the area to be distributed, more faithful color reproduction can be obtained. Further, since the color difference is distributed to unprocessed pixels, if the processing direction is alternately left and right, the color difference is not reflected only in a specific direction, and there is an effect of suppressing the occurrence of moiré and the like.

Thereafter, the horizontal position counter X is updated in step S207, and it is determined in step S208 whether the processing for one line has been completed. When one line has been completed, the vertical position counter Y is updated in step S209,
In step S210, it is determined whether or not the processing for all lines has been completed.

Determination of Output Color Point Table 2111 The color data of the input / output system of the apparatus of this embodiment is correlated.

In a system design such as the present apparatus having color reading and output, improvement of reproducibility of input / output colors is one of relatively important matters.

The patches are printed in eight colors by the combinations of the CMYK inks shown in FIG. At this time, for each patch, a patch printed with a dot duty corresponding to the type of ink to be used and the type of paper is prepared. That is, in printing, a linear relationship is not always obtained between the amount of ink applied and the density of dots formed by ink bleeding, overlapping dots, and internal scattering of paper. For this reason, a non-linear relationship, such as 50% that can maintain a linear relationship rather than a 100% duty-free "solid" print, so that the patch reading result is accurately reflected in the contents of the table.
For example, a checkered dot pattern is used.

The color patch is read by the reading unit, and lo
The data of YO, MO, and CO is obtained by performing g conversion. This is determined for each combination of the above colors, and the input color corresponding to the output measurement color is associated.

As described above, it is possible to obtain an output color that is faithful to the input color of the type of ink used and the combination thereof.

According to the color difference diffusion method (CD method) of the present embodiment, all input colors are replaced with the input colors of the nearest used ink and the combination thereof, and the difference is diffused to peripheral pixels. How to take is the basis for improving the color reproducibility of a color copy using the CD method.

2. Determination of Output Color Point Table In order to diffuse the difference between the input color and the output color to peripheral pixels, it is necessary to determine how much the output color differs from the input color in the present processing system. Here, the difference between the output color and the input color obtained in step 1 can be obtained as a table and stored in a memory or the like.

Since the correspondence obtained in the above 1 is different depending on the type of ink used and the type of paper, if the table is changed according to the supported ink and paper, high color reproducibility can be obtained. RAM does not have multiple types, each copy,
Alternatively, the table may be copied from the ROM or the like to the RAM every time the setting is changed. Of course, having an average table may simplify the table to have.

It is also possible to optimize the selected recording medium such as paper and toner and ink in the following procedure.

A color patch is printed on paper used for copying with at least one type of duty for each color. This is because the range of the duty that can achieve the linear relationship between the ink ejection amount and the reading density may vary depending on the type of paper as described above, and thus a patch having the optimal linear relationship can be used. Because. An output color point table is created by reading this patch with the input device.

As described above, depending on the combination of paper and ink, the intended density may not be obtained due to differences in the amount of ink, bleeding, and absorption depending on the combination of paper and ink. Further, depending on the combination of inks, there may be a case where a density suitable for ink ejection cannot be obtained. When such an output point is detected, a table may be created using output points of other parts except for the output point.

3. Output Pattern Table The input color is converted to the closest output color by the output color table determined by the above method.

That is, when the input is 256 gradations, 25
6 × 256 × 256 tables are required, but 25
The points in the 6 × 256 × 256 spatial coordinates have a many-to-one correspondence corresponding to 16 combinations of output patterns. Therefore, the input color data can be discarded as long as this correspondence is not lost. By using this, as shown in the present embodiment, it is possible to convert to the closest output color with a small table using only the necessary bits of the upper few bits.

This table is also changed in accordance with the change of the output color point table, and is written in the RAM.

If the output color table is calculated from the output color point table and the table is created at least before image processing, it is not necessary to have the output color table in a memory such as a ROM.

<Other Embodiments> Even if the present invention is applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), it is possible to use a single device (for example, a copying machine, a facsimile machine) May be applied to such a device.

Further, software for realizing the functions of the above-described embodiments is installed in an apparatus or a computer in a system connected to the various devices so as to operate the various devices so as to realize the functions of the above-described embodiments. The present invention also includes a program that is provided by supplying a program code and causing a computer (CPU or MPU) of the system or apparatus to operate the various devices according to a stored program.

Further, in this case, the program code itself of the software realizes the function of the above-described embodiment, and the program code itself and means for supplying the program code to the computer,
For example, a storage medium storing such a program code constitutes the present invention.

As a storage medium for storing such a program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, magnetic tape, nonvolatile memory card, ROM or the like can be used.

When the computer executes the supplied program code, not only the functions of the above-described embodiment are realized, but also the program code can be executed by an OS (Operating System) running on the computer or another operating system. Needless to say, even when the functions of the above-described embodiments are realized in cooperation with application software and the like, such program codes are included in the embodiments of the present invention.

Further, the supplied program code is
After being stored in the memory provided in the function expansion board of the computer or the function expansion unit connected to the computer, the CPU or the like provided in the function expansion board or the function storage unit may perform a part of the actual processing or It goes without saying that the present invention also includes a case where the functions of the above-described embodiments are realized by performing the entire process.

[0094]

As described above, the color difference correction data is obtained by adding the color difference generated by the binarization of other pixels to the multi-valued input color data, and the table is referred to based on the color difference correction data. Since the binary data is output, it is possible to omit the operation for obtaining the binary data in the image processing, in particular, the calculation for finding the correspondence between the multi-valued color data and the binary data, and the color difference is diffused throughout the output image.

As a result, the processing load required for obtaining the output color can be extremely reduced, and the image quality can be prevented from deteriorating due to binarization.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a facsimile apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a detailed configuration of a binarization processing unit illustrated in FIG. 1;

FIG. 3 is a flowchart showing a procedure of a binarization process in the apparatus shown in FIGS. 1 and 2;

FIG. 4 is a schematic diagram showing the contents of an output color point table used for color difference diffusion in the binarization processing.

FIG. 5 is a flowchart illustrating a procedure of the color difference diffusion processing.

FIG. 6 is a diagram showing pixels to be diffused in the color difference diffusion.

FIG. 7 is a diagram showing a diffusion source pixel in the color difference diffusion.

FIG. 8 is a schematic diagram showing contents of an output color table used in the binarization processing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CPU 4 Reading part 5 Image processing part 6 ROM 7 RAM 8 Non-volatile RAM 9 Operation part 10 Display part 11 Recording part 14 Drive part 15 Modem 16 CPU 18 Telephone (handset) 201 Input / output part 202 log (logarithmic) circuit 203 Color difference Addition circuit 204 Selector / buffer 205 Address generation circuit 206 Buffer 207 Color difference integration circuit 208 Color difference distribution circuit 209 Subtraction circuit 211 RAM unit 2110 Front line color difference memory 2111 Output color point table 2112 Output color table

Claims (12)

[Claims] An image processing apparatus for converting multi-valued color data into binary data of a color that can be expressed by an output device, wherein the color-difference data is added to the multi-valued color data.
A color difference addition unit that obtains color difference correction data; and a table that stores, based on the color difference correction data obtained by the color difference addition unit, binary data of a color that can be expressed by the output device and that corresponds to the color indicated by the color difference correction data. Data output means for outputting using the color data; and color difference calculation means for calculating a color difference between multi-valued color point data corresponding to the binary data output by the data output means and color difference correction data relating to the output of the binary data. An image processing apparatus comprising: a storage unit configured to store the color difference calculated by the color difference calculation unit as color difference data used by the color difference addition unit. 2. The image processing apparatus according to claim 1, wherein the data output unit uses the table based only on valid bits of the color difference correction data obtained by the color difference addition unit. 3. A recording medium selecting unit for selecting a recording medium to be used in an output device from a plurality of recording media, wherein the data output unit stores a table corresponding to the recording medium selected by the recording medium selecting unit. 3. The image processing apparatus according to claim 1, wherein the image processing apparatus is selected from a plurality of tables corresponding to the plurality of recording media and used. 4. The color difference calculation means has an output point table that defines multi-valued color points corresponding to the binary data, and the output point table is used in an output device based on the binary data. 4. The image processing apparatus according to claim 1, wherein a patch is output, and the patch is created based on colorimetric data of the output color patch. 5. The image processing apparatus according to claim 1, wherein the table is created at least before the start of the image processing. 6. The image processing apparatus according to claim 5, wherein the table created at least until the start of the image processing is stored in a memory. 7. A method according to claim 1, wherein a plurality of multi-valued output points within a predetermined distance in the color space are not used as the multi-valued color points if a large amount of ink is applied. The image processing device according to claim 4. 8. The method according to claim 4, wherein the color patch is output to a recording medium used in the output device, and the contents of the output point table are changed based on the colorimetric data of the color patch on the recording medium. An image processing apparatus according to claim 1. 9. The color difference calculation means according to claim 1, wherein the sum of at least a part of the color differences in peripheral pixels corresponding to the pixel involved in the processing is calculated and stored in a memory as the color difference. An image processing device according to any one of the above. 10. The image processing apparatus according to claim 4, wherein for colorimetric data of each ink dot forming a color patch, a color patch whose colorimetric output of each dot does not interfere with each other is used. 11. The image processing apparatus according to claim 4, wherein, of the colorimetric data of the color patches, only colorimetric data valid for the density to be measured is used. 12. An image processing program for converting multi-valued color data into binary data of a color that can be expressed by an output device, wherein the color-difference data is added to the multi-valued color data.
The color difference correction data is obtained, and based on the obtained color difference correction data, binary data of a color that can be represented by the output device and that corresponds to the color indicated by the color difference correction data is output using a table, and is output. The color difference between multi-valued color point data corresponding to the binary data and the color difference correction data relating to the output of the binary data is calculated, and the calculated color difference is stored as the color difference data used in the step of adding the color difference data. A storage medium characterized by storing a program having steps.