JP2003338927A - Color image processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve printing quality in the character region of a manuscript where characters and photos are mixed in a color copying operation. <P>SOLUTION: A color image processing apparatus is made of an interface section for making connection to a scanner section, a printing section, and a computer. The apparatus outputs image data outputted from the scanner section to the printing section when a copying operation is performed in a photo mode. Image data outputted from the scanner section are sent to the computer via the interface section when the copying operation is performed in a character photo mode. The data are received via the interface section for outputting by the printing section after character region judgment processing is performed at a computer side, and then gray conversion processing is performed. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image processing apparatus which reads a document in color and prints out in color.

[0002]

2. Description of the Related Art FIG. 7 shows an example of a conventional color image processing apparatus, the operation of which will be described with reference to FIG. Reference numeral 101 is an image pickup device such as a CCD or a contact sensor that scans a document and outputs RGB analog signals, 102 is an A / D converter that converts the analog signals output from the image pickup device 101 into digital signals, Reference numeral 104 is a scaling processing unit that performs scaling processing on the image data output from the A / D converter 102, 801 is a brightness density conversion processing unit that performs brightness density conversion processing on the image data output from the scaling processing unit 104, 1
Reference numeral 03 denotes a masking processing unit for performing a masking process on the image data output from the brightness / density conversion processing unit 801;
Reference numeral 2 is a density correction processing unit that performs density correction processing on the image signal output from the masking processing unit 103, 106 is an inkjet printer that prints out the image data output from the density correction processing unit 802, and 107 is the main color A CPU 108 for controlling each unit of the image processing apparatus is a C
A RAM 109 connected to the PU 107 and used as a work area is connected to the CPU 107, and the CPU 1
This is a ROM that stores the instruction code executed in 07.

FIG. 8 is a flow chart showing the procedure of a color copying operation by this color image processing apparatus, and the operation will be described with reference to this figure.

First, the image pickup device 101 scans a document to output an analog signal (step S901). Then A
A / D converter 102 performs A / D conversion processing to convert the analog signal into a digital signal (step S902).

Next, a scaling process is performed. Scanner CCD
The pixel density of the printer unit is changed to the pixel density of the head of the printer unit. The scaling method is a linear interpolation method or an SPC method (step S903).

The image data subjected to the scaling processing is converted from RGB luminance signals into CMY density signals (step S).
904). The brightness density conversion is performed for each color by referring to a table. FIG. 5 shows an example of the characteristics stored in the table.
The horizontal axis represents the luminance level input, and the vertical axis represents the density level output.

Next, the image data in the characteristic color space of the image pickup device is converted into the characteristic color space of the ink jet printer by masking processing (step S905).

The calculation method of the masking process is as follows when CMY is an input image value and C'M'Y 'is an output image value.

[Outer 1]

[0009]

Further, in order to match the characteristics of the ink jet printer 106, density correction processing is performed for each color of CMY by referring to a table (step S906). FIG. 6 shows an example of characteristics stored in the table. The horizontal axis is the input level and the vertical axis is the output level.

Next, the CMY multivalued signal is converted into a binary signal by the error diffusion method in order to be output from the ink jet printer 106 (step S907).

Finally, the binarized CMY signal is output from the ink jet printer 106 (step S90).
8) The color copying operation by this color image processing apparatus is ended.

[0013]

However, in the conventional example, when a copy operation is performed in a photo mode on a document in which characters and photographs are mixed, color misregistration or dust is read during scanning by the scanner, and thus a gray area appears in the character area. There was a defect that colors other than the above were output.

[0014]

By connecting to a computer, a character area and a photograph area can be determined on the computer side, and gray conversion processing can be performed on the character area to remove colors other than gray in the character area. It will be possible.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a color image processing apparatus embodying the present invention, and its operation will be described with reference to this drawing. Reference numeral 101 is an image pickup device such as a CCD or a contact sensor that scans a document and outputs RGB analog signals, 102 is an A / D converter that converts the analog signals output from the image pickup device 101 into digital signals, 1
Reference numeral 03 denotes a masking processing unit for performing masking processing on the digital signal output from the A / D converter 102, 104
Is a scaling processing unit that performs scaling processing on the image data output from the masking processing unit 103, and 105 is the scaling processing unit 1.
Image memory for storing image data output from 04,
An inkjet printer 106 prints out the image data read from the image memory 105, and 107.
Is a CPU that controls each part of the color image processing apparatus,
Reference numeral 108 is a RAM that is connected to the CPU 107 and is used as a work area. Reference numeral 109 is an R that is connected to the CPU 107 and stores an instruction code executed by the CPU 107.
The OM 110 is an interface unit for connecting the color image processing apparatus to a computer or the like.

There are three types of operation modes, a copy operation, a scanner operation, and a printer operation. The copy operation includes a mode in which image data is directly input from the scanner section of the apparatus to the printer section and a copy operation. There is a mode in which after the data is passed to the computer, the image is processed by the computer and the data is returned to the printer section for printing.The scanner operation is to output the image data from the scanner section of this equipment to the computer and The printer operation is a mode in which the RGB image data stored in the hard disk of the computer is output to this apparatus and is printed out by the inkjet printer.

The respective operations will be described below in order using a flow chart.

The color copying operation will be described.

The color copying operation has a photo mode and a character photo mode.

FIG. 2 is a flow chart showing the procedure of the color copying operation, and the operation will be described with reference to this figure. First, the operation mode set on the operation panel (not shown) is determined (step S200).

In the case of the photograph mode, the processing is performed in the following procedure.

The image pickup device 101 scans the original and outputs an analog signal (step S201). Then A / D
The converter 102 performs A / D conversion processing to convert an analog signal into a digital signal (step S202). In the masking processing section of the scanner section, the image data of the color space having the characteristic of the image pickup device is converted into the NTSC standard RGB color space by masking processing (step S203).

The calculation method of the masking process is as follows, where RGB is the input image value and R'G'B 'is the output image value.

[Outside 2]

[0024]

Next, a scaling process is performed. Scanner CCD
The pixel density of is changed to the pixel density of the head of the printer unit (step S204).

The scaled image data is converted from RGB luminance signals into CMY density signals (step S).
205). The brightness density conversion is performed for each color by referring to a table. FIG. 5 shows an example of the characteristics stored in the table.
The horizontal axis represents the luminance level input, and the vertical axis represents the density level output.

Next, the masking process of the printer unit is performed,
The image signal in the standard color space is transferred to the inkjet printer 106.
Masking processing is performed in order to match the color characteristics of (step S206).

The calculation method of the masking process is as follows when CMY is an input image value and C'M'Y 'is an output image value.

[Outside 3]

[0029]

Further, in order to match the characteristics of the ink jet printer 106, density correction processing is performed for each CMY color by referring to a table (step S207). FIG. 6 shows an example of characteristics stored in the table. The horizontal axis is the input level and the vertical axis is the output level.

Next, the CMY multivalued signal is converted into a binary signal by the error diffusion method in order to be output from the ink jet printer 106 (step S208).

Finally, the binarized CMY signal is output from the ink jet printer 106, and the color copying operation by the present color image processing apparatus is completed.

When the character photograph mode is selected in step S200, the following processing is performed.

First, the image pickup device 101 scans a document to output an analog signal (step S210). Then A
The A / D conversion process is performed by the / D converter 102 to convert the analog signal into a digital signal (step S211). In the masking processing unit of the scanner unit, the image data in the color space having the characteristics of the image pickup device is masked to NTS.
Conversion to the RGB standard color space of C (step S21)
2).

The calculation method of the masking process is as follows, where RGB is the input image value and R'G'B 'is the output image value.

[Outside 4]

[0036]

Next, a scaling process is performed. Scanner CCD
The pixel density of the printer unit is changed to the pixel density of the head of the printer unit. The scaling method is the linear interpolation method, the SPC method, or the like (step S213).

Next, the data is transferred to the computer (step S214).

The computer first performs a character area determination process (step S215).

The determination is performed by dividing the image into blocks each having 256 pixels in the main scanning direction and 256 pixels in the sub scanning direction.

Equation 1 is calculated for all the pixels in the block.

(R−G) ² + (G−B) ² + (B−R) ² <k (Formula 1) R is the red value of the target pixel, G is the green value of the target pixel, and B is the target. The blue value of the pixel. k is a constant.

If Expression 1 is true, the target pixel is judged to be gray because the R, G, and B values are close to each other. k is a constant determined by the accuracy of the CCD of the scanner, the contact sensor, the feed motor, or the like, and is a value of 50, for example. Further, the method of determining whether or not the color is gray may be based on another calculation.

According to equation 4, for example.

[0045]   | R-G | + | GB- | + | BR- <k (Equation 4) An example value for k is 15.

Next, the result of judging the pixels in the block is counted to obtain the number of true pixels Ngray.

Ngray> d (Equation 2) d is a constant.

If Expression 2 is true, it is determined that the block is a character area.

An example of the value of d is 256 ² × 0.9.

The entire image area is divided into blocks and the determination is performed as described above. If the image size is not a multiple of 256 pixels, the size of the last block is a fraction, but in this case, the determination is performed using Equation 3.

Ngray> d × (number of existing pixels) / 256 ² (Equation 3) d is a constant.

To perform the above processing, at least 25
It is necessary to store the image data for 6 lines in the memory.
The size of the block to be determined is not limited to this description.

Next, gray conversion processing is performed on the character area determined in step S215 (step S21).
6).

In the conversion method, the minimum value of R, G, and B values is obtained for the pixels in the block determined to be gray, and the value is used to replace all R, G, and B values.

As another method, all of R, G and B may be replaced by (R + G + B) / 3. It is also possible to use another calculation method.

The image data processed by the computer is transferred from the computer to the main body (step S2).
17).

The image data received from the computer is converted from RGB luminance signals into CMY density signals (step S205). The brightness density conversion is performed for each color by referring to a table. FIG. 5 shows an example of the characteristics stored in the table. The horizontal axis represents the luminance level input, and the vertical axis represents the density level output.

Next, masking processing of the printer unit is performed,
The image signal in the standard color space is transferred to the inkjet printer
Masking processing is performed in order to match the color characteristics of (step S206).

The calculation method of the masking process is as follows when CMY is an input image value and C'M'Y 'is an output image value.

[Outside 5]

Is performed by

Further, in order to match the characteristics of the ink jet printer 106, density correction processing is performed for each color of CMY by referring to a table (step S207). FIG. 6 shows an example of characteristics stored in the table. The horizontal axis is the input level and the vertical axis is the output level.

Next, the CMY multivalued signal is converted into a binary signal by the error diffusion method in order to be output from the ink jet printer 106 (step S208).

Finally, the binarized CMY signal is output from the ink jet printer 106, and the color copying operation by the present color image processing apparatus is completed.

The scanner operation will be described.

FIG. 3 is a flow chart showing the procedure of the scanner operation.

First, the image pickup device 101 scans a document to output an analog signal (step S301). Then A
The A / D conversion process is performed by the / D converter 102 to convert the analog signal into a digital signal (step S302). In the masking processing unit of the scanner unit, the image data in the color space having the characteristics of the image pickup device is masked to NTS.
Conversion to the standard color space of C (step S303). The masking method is the same as in the copying operation.

A scaling process is performed from the resolution of the scanner to the resolution designated by the computer (step S30).
4). The method of scaling processing is the same as in the copying operation.

Finally, the image data is output to the computer through the interface section 110 and the scanner operation is completed. Interface is Bi-Centro, RS
An interface such as 232C or SCSI is used,
It goes without saying that the present invention can be applied to other interfaces.

The printer operation will be described.

FIG. 4 is a flow chart showing the procedure of the printer operation.

First, RGB input from the computer
The image data in the format is received via the interface unit 110 and stored in the image memory 105 (step S40).
1). Next, the RG stored in the image memory by the CPU 107
Luminance density conversion processing is performed on the B image data (step S402). The brightness density conversion method is the same as in the copying operation. Next, masking processing is performed to match the image data in the standard color space with the characteristics of the inkjet printer 106 (step S403). The masking method is the same as in the copying operation. Further, in order to match the characteristics of the inkjet printer 106, density correction processing is performed for each CMY color by referring to a table (step S404). The method of density correction processing is the same as in the copying operation. Next, a scaling process is performed so that the resolution of the image data input from the computer matches the resolution of the printer (step S405). The scaling method uses a linear interpolation method as in the copying operation. Next, the CMY multi-level signal is converted into a binary signal by the error diffusion method in order to be output from the inkjet printer 106 (step S40).
6). Finally, the image data is printed out from the inkjet printer 106, and the printer operation is completed.

In the above description, the masking process is 1
Although an example has been described in which the masking calculation is performed in two dimensions, the masking calculation in two dimensions or higher order enables more accurate processing. Further, although the linear interpolation method is described as the scaling method, it can be simplified by the SPC method, or another scaling method can be used.

[0073]

As described above, when a copy operation is performed in the photo mode on a document in which characters and photographs are mixed, colors other than gray are not output in the character area, so that there is an effect of improving print quality.

By performing the character region determination process on the computer side, there is an effect that a large capacity memory for determining the character region is not required in the color image processing apparatus.

By performing the character area determination processing on the computer side, there is an effect that the load on the CPU in the color image processing apparatus is not increased.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a color image processing apparatus embodying the present invention.

FIG. 2 is a flowchart showing the procedure of a color copying operation by the color image processing apparatus embodying the present invention.

FIG. 3 is a flowchart showing the procedure of a scanner operation by the color image processing apparatus embodying the present invention.

FIG. 4 is a flowchart showing a procedure of printer operation by the color image processing apparatus embodying the present invention.

FIG. 5 is a diagram showing an example of characteristics of a table of luminance density conversion.

FIG. 6 is a diagram showing an example of characteristics of a table of density correction processing.

FIG. 7 is a diagram showing an example of a conventional color image processing device.

FIG. 8 is a flowchart showing a procedure of a color copying operation by the conventional color image processing apparatus.

[Explanation of symbols]

101 image pickup device 102 A / D converter 103 Masking processing unit 104 Magnification processing unit 105 image memory 106 inkjet printer 107 CPU 108 RAM 109 ROM 110 Interface section

Continued front page    F-term (reference) 2C262 AB13 BA01 BA09 BA10 BA19                       BA20 BB03 BB15 DA02 EA06                       EA07 GA52 GA57                 5B057 AA11 BA02 CA01 CA08 CA12                       CA16 CB01 CB08 CB12 CB16                       CC01 CE17 CE18 CH07 CH08                 5C077 LL19 MP08 PP27 PP28 PP32                       PP33 PP37 PP38 PP68 PQ12                       PQ23 TT02                 5C079 HB01 HB02 HB12 LA03 LA06                       LB01 MA04 MA11 NA03 NA06                       PA02 PA03

Claims (6)

[Claims] 1. A scanner unit, a printer unit, and an interface unit for connecting to a computer. When performing a copying operation in the photo mode, the image data output from the scanner unit is output to the printer unit, and the character photo mode is set. When performing a copy operation with, the image data output from the scanner section is sent to the computer through the interface section, the character area determination processing is performed on the computer side, the gray conversion processing is performed, and then the data is transferred through the interface section. A color image processing apparatus, which receives the image and outputs it in a printer unit. 2. The unit for determining the character area is n pixels × m pixels (n and m are integers).
The described color image processing device. 3. A method of determining a character area is performed for each pixel by (R−G) ² + (G−B) ² + (B−R) ² <k, and the above formula is true in a block. 3. The color image processing apparatus according to claim 2, wherein the color image processing apparatus determines that the area is a character area when it is larger than a constant d. 4. When the main scanning direction is not a multiple of n or the sub scanning direction is not a multiple of m, the value of k in claim 3 is set to (the number of existing pixels) / (n × m). The color image processing apparatus according to claim 3, wherein the determination is made by multiplying. 5. A method for determining a character area is performed by determining | R−G | + | GB− | + | B−R | <k for each pixel and counting pixels for which the above expression is true in a block. The color image processing apparatus according to claim 2, wherein the color image processing apparatus determines that the area is a character area when it is larger than a constant d. 6. When the main scanning direction is not a multiple of n, or when the sub scanning direction is not a multiple of m, the value of k in claim 5 is (the number of existing pixels) / (n × m). The color image processing apparatus according to claim 5, wherein the determination is made by multiplying.