JPH10304211A - Image processing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow the image processing unit to optionally select the presence of under-color elimination processing before error spread processing. SOLUTION: The processing unit is provided with black generating circuit 21 that generates black image data from color image data, an under-color elimination circuit 22 that corrects the color image data based on the black image data generated by the black generating circuit 21, and an error spread processing circuit 25 that applies error spread processing to the black image data generated by the black generating circuit 21 and the color image data corrected by the under-color elimination circuit 22 directly or after other processing, and also with a selector 23 that, based on the under-color elimination signal from the outside, selects a state that the color image data corrected by the under-color elimination circuit 22 is processed by the error spread processing circuit 25 or a state that the color image data not corrected by the under-color elimination circuit 22 are processed by the error spread processing circuit 25.

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 for performing black generation and under color removal processing and error diffusion processing on color image data.

[0002]

2. Description of the Related Art Color image data is subjected to processes such as black generation and undercolor removal to enhance the color reproducibility by vividly developing black color during printing. In addition, color reproducibility is improved by performing an error diffusion process on color image data to improve gradation at the time of printing.

However, if the error diffusion process is performed after the undercolor removal process, the error data is not accurately propagated, and the color reproducibility at the time of printing is rather lowered depending on the characteristics of the paint used for printing. Sometimes. In short, whether the undercolor removal process is performed before the error diffusion process is performed or the undercolor removal process is not performed before the error diffusion process is performed, it is determined which one of the color reproducibility during printing is better. Is determined by the properties of the paint used.

In a conventional image processing apparatus, it is determined at the design stage whether or not to perform undercolor removal processing before performing error diffusion processing in consideration of the characteristics of a paint used for a device such as a printer to be incorporated. The circuit was designed and manufactured based on it.

[0005]

However, the above-mentioned conventional image processing apparatus has a problem that it cannot cope with a change in paint used for printing.

For example, paints such as inks used in ink jet type printers have been actively developed with new products. Therefore, the inks are changed, and the presence or absence of undercolor removal processing before error diffusion processing is changed. As a result, it is easily presumed that an image having extremely excellent color reproducibility may be printed in some cases. However, the conventional image processing apparatus cannot cope with such a case.

The present invention has been proposed in view of the above points, and has as its object to provide an image processing apparatus capable of arbitrarily selecting the presence or absence of undercolor removal processing before error diffusion processing.

[0008]

According to an aspect of the present invention, there is provided an image processing apparatus comprising: a black generating unit configured to generate black image data from color image data; An under color removing unit that corrects color image data based on the generated black image data, and a black image data generated by the black generating unit and a color image data corrected by the under color removing unit. Alternatively, the image processing apparatus includes an error diffusion processing unit that performs an error diffusion process after performing another process, and based on an external undercolor removal control signal, the color of the color that has been corrected by the undercolor removal unit. The state is switched between a state in which the image data is processed by the error diffusion processing unit and a state in which the color image data not corrected by the under color removing unit is processed by the error diffusion processing unit. And a color removal control unit.

According to this image processing apparatus, the under-color removal control means sends the color image data corrected by the under-color removal means to the error diffusion processing means based on an external under-color removal control signal. Since the state to be processed and the state in which the color image data that has not been corrected by the undercolor removal unit are processed by the error diffusion processing unit are switched, the presence or absence of the undercolor removal process before the error diffusion process can be arbitrarily selected. Appropriate processing can be performed according to the characteristics of the paint used for printing, and a high-quality image excellent in color reproducibility and the like can be obtained at the time of printing.

[0010] Between the undercolor removal processing and the error diffusion processing,
Other processing such as the γ correction processing for recording adjustment may or may not be performed.

An undercolor removal control signal is written in an EEPROM by, for example, a predetermined key operation, and a CP is written in accordance with the contents of the undercolor removal control flag.
It suffices that U generates an undercolor removal control signal and writes it to a register or the like.

According to a second aspect of the present invention, in the image processing apparatus of the first aspect, the undercolor removal control means changes between a first level and a second level. A selector for selecting and outputting one of the two inputs according to the level of the undercolor removal control signal to be output. The color image data corrected by the above is processed by the error diffusion processing means, and the under color removal control signal
At the level, the color image data not corrected by the under color removing means is processed by the error diffusion processing means.

According to this image processing apparatus, in addition to the effect of the image processing apparatus according to the first aspect, the under-color removal control means can be constituted by a simple circuit including one selector.

According to a third aspect of the present invention, there is provided the image processing apparatus according to the first or second aspect, wherein the error diffusion processing means is configured to execute the image processing after the error diffusion processing is performed. A state in which image data of another color is processed and then binarized so that black and other colors are not mixed in the same pixel on the basis of only an external black signal with respect to the data. Is switched to a state where binarization is performed without performing the color processing.

According to this image processing apparatus, in addition to the effects of the image processing apparatus according to claim 1 or 2,
At the time of printing, it is possible to arbitrarily switch between a state where black and other colors are mixed and a state where they are not mixed in the same pixel,
Color reproducibility can be further improved according to the characteristics of the paint used for printing.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 is a circuit block diagram of a facsimile apparatus provided with an image processing apparatus according to the present invention. This facsimile apparatus has a CPU (central processing unit).
) 1, NCU (network control unit) 2, RAM (r
andom access memory) 3, modem 4, ROM (read on)
ly memory) 5, EEPROM (electrically erasable)
and programmable read only memory) 6, gate array 7, codec 8, DMAC (direct memory acce)
ss controller) 9, reading unit 11, recording unit 12, operation unit 1
3 and a display unit 14. CPU1, NCU
2, RAM 3, modem 4, ROM 5, EEPROM 6,
Gate array 7, codec 8, and DMAC 9
They are interconnected by bus lines. The bus lines include an address bus, a data bus, and a control signal line.
A reading unit 11, a recording unit 12, an operation unit 13, and a display unit 14 are connected to the gate array 7. A telephone line 15 is connected to the NCU 2 as an example of a communication line.

The CPU 1 controls the entire facsimile machine. The NCU 2 is connected to the telephone line 15 and performs network control. The RAM 3 stores various data. Modem 4
Performs modulation of transmission data and demodulation of reception data.
The ROM 5 stores various programs and data such as initial setting values. The EEPROM 6 stores various flags such as an undercolor removal control flag, registration data, and the like.
The gate array 7 functions as an input / output interface of the CPU 1 and performs various image processing such as black generation and undercolor removal processing and error diffusion processing on the image signal from the reading unit 11. The codec 8 encodes transmission facsimile data and decodes reception facsimile data. The DMAC 9 writes and reads data to and from the RAM 3. The reading unit 11 includes a light source and a color CCD.
An image sensor, a document feed motor, and the like are provided to read a document and output a color image signal. This image signal is an analog image signal of each color of red, green, and blue.
The recording unit 12 includes, for example, an inkjet printing unit, and records a received image, a read image at the time of copying, and the like on a recording sheet. The operation unit 13 includes a key switch group and the like, and outputs a signal according to a user operation. The display unit 14 includes an LCD or the like, and performs various displays under the control of the CPU 1.

FIG. 2 is a circuit block diagram of a black generation and under color removal section and an error diffusion processing section of the image processing apparatus constituted by the gate array 7. The processing unit includes a black generation circuit 21, an under color removal circuit 22, a selector 23, a register 2
4. Error diffusion processing circuit 25 and buffer memory 26
It has.

The black generation circuit 21 generates the so-called minimum K data by selecting the minimum data for each pixel from the image data of each color of cyan, magenta, and yellow, for example. Each of the multiplications is multiplied by a black generation parameter, and the multiplication result is output as black image data. Further, the generated minimum K data is supplied to the under color removing circuit 22.

The under color removal circuit 22 multiplies, for example, the so-called minimum K data generated by the black generation circuit 21 with the under color removal parameter from the register 24, and outputs the multiplication result as cyan, magenta, and yellow image data. , The image data of each of the cyan, magenta, and yellow colors from which the under color has been removed is output.

When the under color removal control signal from the register 24 is at a high level, the selector 23 supplies the output from the under color removal circuit 22 input to the input terminal A to the error diffusion processing circuit 25, When the under color removal control signal is low level, the input image data input to the input terminal B is supplied to the error diffusion processing circuit 25.

The register 24 holds the black generation parameter, the under color removal parameter, and the under color removal control signal from the CPU 1, and supplies the black generation parameter to the black generation circuit 21.
The under color removal parameter is supplied to the under color removal circuit 22, and the under color removal control signal is supplied to the control terminal of the selector 23. The black generation parameter and the under color removal parameter are digital data of a predetermined number of bits, and the under color removal control signal is a 1-bit signal of a high level or a low level.
The undercolor removal control signal is controlled to a high level or a low level by the CPU 1. For example, when the power is turned on, the CPU 1 reads the undercolor removal control flag stored in the EEPROM 6 and outputs the undercolor removal control flag. Is ON, that is, “1”, the CPU 1 writes “1” to a predetermined bit of the register 24 to set the undercolor removal control signal to a high level, and the undercolor removal control flag is OFF, that is, “0”. For example, the CPU 1 writes “0” to a predetermined bit of the register 24 in order to set the under color removal control signal to a low level. The undercolor removal control flag is written in the EEPROM 6 before the facsimile apparatus is shipped from the manufacturing factory. If the undercolor removal processing is performed before performing the error diffusion processing, the undercolor removal control flag is turned on. If the under color removal processing is not performed before the error diffusion processing is performed, the under color removal control flag is set to off.

The error diffusion processing circuit 25 has a built-in register, in which a binary condition flag, threshold data, and a black only signal are written by the CPU 1. The threshold data is digital data of a predetermined number of bits, and the binarization condition flag and the black-only signal are 1-bit signals of a high level or a low level, respectively. The black-only signal is controlled to a high level or a low level by the CPU 1. For example, when the power is turned on, the CPU 1 reads the black control flag stored in the EEPROM 6 and turns on the black control flag, that is, when the black control flag is "1". If so, the CPU 1 writes "1" to a predetermined bit of the register to make the black-only signal high, and if the black control flag is off, that is, "0", the CPU 1 makes the black-only signal low. For this purpose, "0" is written to a predetermined bit of the register. This black control flag is written in the EEPROM 6 before the facsimile apparatus is shipped from the manufacturing factory. To prevent black from mixing with other colors in the same pixel, set the black control flag to ON. However, when black and other colors are mixed in the same pixel, the black control flag is set to off.

Based on the binarization condition flag and the threshold data held in the register and the error data from the buffer memory 26, the error diffusion processing circuit 25 outputs the image data of each color of cyan, magenta and yellow from the selector 23. The error diffusion processing is performed on the black image data from the black generation circuit 21 to binarize the image data. At this time, if only the black signal held in the register is at a high level, the image data of the other colors is set to 0 for the pixel where the black image data is not 0. If the black only signal held in the register is at a low level, such processing is not performed.

The buffer memory 26 stores error data generated by the error diffusion processing circuit 25.

That is, the black generation circuit 21 constitutes black generation means for generating black image data from color image data. The under color removing circuit 22 constitutes under color removing means for correcting color image data based on black image data generated by the black generating means. The error diffusion processing circuit 25 and the buffer memory 26 perform an error diffusion process on the black image data generated by the black generation unit and the color image data corrected by the under color removal unit, directly or after other processing. It constitutes error diffusion processing means. The selector 23 causes the error diffusion processing unit to process the color image data corrected by the undercolor removal unit based on an external undercolor removal control signal, and the selector 23 does not correct the image data. The lower color removal control means switches to a state where the color image data is processed by the error diffusion processing means. When the under color removal control signal is at the first level, the selector 23 causes the error diffusion processing unit to process the color image data corrected by the under color removal unit, and the under color removal control signal
At this level, a selector is configured to cause the error diffusion processing unit to process color image data that has not been corrected by the under color removal unit.

Next, the essential points of the operation of the facsimile apparatus thus configured will be described. For example, in the copy mode, when reading of a read document is started by the reading unit 11, analog image signals of red, green, and blue corresponding to the image of the read document are serially output from the reading unit 11 and gated. Input to array 7. This image signal is
Red by the A / D converter built in the gate array 7,
The data is converted into, for example, 8-bit image data of each color of green and blue, subjected to various corrections such as shading correction and γ correction by the gate array 7, and then converted into image data of each of cyan, magenta and yellow. Generation circuit 21
And input to the under color removal circuit 22.

On the other hand, when the power is turned on, for example, the CPU 1 reads the under color removal control flag stored in the EEPROM 6 and sets a predetermined bit of the register 24 in accordance with the contents of the under color removal control flag. Write "1" or "0". Further, for example, when the power is turned on, the CPU 1 reads the black control flag stored in the EEPROM 6, and according to the content of the black control flag, a predetermined bit of a register built in the error diffusion processing circuit 25. "1" or "0" is written in.
Further, at a predetermined time, the CPU 1 reads out the black generation parameter, the under color removal parameter, the binarization condition flag, and the threshold data stored in the ROM 5 and writes the black generation parameter and the under color removal parameter into the register 24. Then, the binarization condition flag and the threshold data are written into a register built in the error diffusion processing circuit 25.

Assuming that the under color removal control flag is set to ON, since "1" is written in a predetermined bit of the register 24 by the CPU 1, the under color removal supplied to the selector 23 is performed. The control signal is at a high level. Accordingly, the image data of each color of cyan, magenta, and yellow, which are input to the input terminal A of the selector 23 and are subjected to the undercolor removal processing by the undercolor removal circuit 22, are supplied to the error diffusion processing circuit 25, and the error diffusion processing is performed. Will be applied. The image data after the error diffusion processing is stored in the RAM 3 by the DMAC 9 and then supplied to the recording unit 12.
An image corresponding to the image data is printed on recording paper.

Conversely, if the under color removal control flag is set to off, the CPU 1 writes "0" in a predetermined bit of the register 24, and the under color removal control flag is supplied to the selector 23. The removal control signal is at low level. Therefore, the image data of each color of cyan, magenta, and yellow, which has not been subjected to the under color removal processing and is input to the input terminal B of the selector 23, is transferred to the error diffusion processing circuit
And subjected to error diffusion processing. The image data after the error diffusion processing is stored in the RAM 3 by the DMAC 9 and then supplied to the recording unit 12, where an image corresponding to the image data is printed on recording paper.

The undercolor removal control flag set in the EEPROM 6 is changed, for example, by operating a predetermined key of the operation unit 13 so that the CPU 1 executes a predetermined program to change the undercolor removal control flag. It is configured to be. Of course, by operating a switch provided inside the housing of the facsimile apparatus, the CPU 1 may execute a predetermined program to change the under color removal control flag. This is the same for the black control flag.

To set the under color removal control flag, the black control flag is set to on, the image is printed on the recording unit 12 when the under color removal control flag is on and off, and the image is printed. It is determined by comparing the color reproducibility of the images.

As described above, by setting the undercolor removal control flag in the EEPROM 6, the error diffusion can be performed simply by switching the undercolor removal control signal supplied to the selector 23 from high level to low level or from low level to high level. Presence / absence of undercolor removal processing before the processing can be selected.

In the above-described embodiment, the image processing apparatus of the present invention is incorporated in a facsimile apparatus. However, the image processing apparatus of the present invention is not limited to a facsimile apparatus, but may be a printing function such as a printer, a copier, or a multifunction machine thereof. Can be adopted for all electronic devices having

[0036]

As described above, according to the image processing apparatus of the first aspect of the present invention, the undercolor removal control means corrects the undercolor removal means based on an external undercolor removal control signal. The state is switched between the state in which the color image data after the processing is processed by the error diffusion processing means and the state in which the color image data not corrected by the under color removing means is processed by the error diffusion processing means. Can be arbitrarily selected as to whether or not to perform under color removal processing, so that appropriate processing can be performed in accordance with the characteristics of the paint used for printing, and a high-quality image with excellent color reproducibility can be obtained during printing. .

According to the image processing apparatus of the second aspect of the present invention, in addition to the effect of the image processing apparatus of the first aspect, undercolor removal control means is provided by a simple circuit including one selector. Can be configured.

Further, according to the image processing apparatus of the present invention, in addition to the effects of the image processing apparatus of the first or second aspect, at the time of printing, black and other colors in the same pixel. Can be arbitrarily switched between a state in which is mixed and a state in which they are not mixed, and the color reproducibility can be further improved in accordance with the characteristics of the paint used for printing.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of a facsimile apparatus including an image processing device according to the present invention.

FIG. 2 is a circuit block diagram of a black generation / under color removal processing unit and an error diffusion processing unit of the image processing apparatus provided in the facsimile apparatus shown in FIG.

[Explanation of symbols]

 1 CPU 3 RAM 5 ROM 6 EEPROM 11 Reading Unit 12 Recording Unit 21 Black Generation Circuit 22 Under Color Removal Circuit 23 Selector 24 Register 25 Error Diffusion Processing Circuit 26 Buffer Memory

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI H04N 1/46 H04N 1/46 Z

Claims (3)

[Claims] A black generation unit configured to generate black image data from color image data; and a lower color removal unit configured to correct the color image data based on the black image data generated by the black generation unit. An error diffusion processing means for performing error diffusion processing after directly or other processing on the black image data generated by the black generation means and the color image data corrected by the under color removal means; A processing device for processing the color image data corrected by the undercolor removal unit on the error diffusion processing unit based on an undercolor removal control signal from the outside; An image processing unit that switches between a state in which color error image data not corrected by the error diffusion processing unit is processed by the under color removal control unit. Equipment. 2. The undercolor removal control means selects and outputs one of two inputs according to a level of an undercolor removal control signal that changes between a first level and a second level. A selector configured to cause the error diffusion processing unit to process the color image data corrected by the undercolor removal unit when the undercolor removal control signal is at a first level; 2. The image processing apparatus according to claim 1, wherein when the control signal is at the second level, the error diffusion processing unit processes color image data that has not been corrected by the under color removal unit. 3. The image processing apparatus according to claim 1, wherein the error diffusion processing means performs processing on the image data after the error diffusion processing based on an external black only signal so that black and other colors are not mixed in the same pixel. 3. The image processing according to claim 1, wherein the image processing is switched between a state of binarizing after processing image data of another color and a state of binarizing without performing processing of such another color. 4. apparatus.