JP2000125132A - Picture processor and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the picture quality of picture data obtained by raster scanning by providing a picture continuity means for judging the continuity of a picture and a gamma transformation means for converting the gradation characteristic of picture data and controlling the characteristic of the gamma transformation means with the judgement output of the picture continuity means. SOLUTION: A gradation processing part 13 applies the prescribed gradation processing of a binarization processing and a dither processing to data D3 added from a gamma transformation part 12, for example. Output data D4 of one bit is outputted to a next stage device and data corresponding to data D3 is outputted to a continuity judgment part 14. The continuity judgment part 14 judges the cumulative continuous number (black continuity value) of black picture elements from an adjacent picture element on the respective picture elements of picture data obtained by reading. Black continuity value data R is added to a filter circuit 11 and the gamma transformation part 12. The filter circuit 11 and the gamma transformation part 12 change respective processing characteristics in accordance with the value of data R.

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 multi-value processing on image data obtained by raster-scanning an original image, and a control method therefor.

[0002]

2. Description of the Related Art Normally, in an image processing apparatus such as a copying machine that performs multi-value processing on image data obtained by raster-scanning a document image, an image filter such as an edge emphasis processing is applied to obtain the acquired image data. The image quality is improved.

[0003]

However, if the same image filter is applied in the same manner to the entire area of the image data, the image quality is not improved depending on the type of the image, and the image quality is rather deteriorated. I was

The present invention has been made in view of such circumstances, and has as its object to provide an image processing apparatus capable of improving the image quality of image data obtained by raster scanning and a control method thereof.

[0005]

According to the present invention, there is provided an image processing apparatus for performing multi-level processing on image data obtained by raster-scanning an original image, comprising the steps of: A determination unit; a gamma conversion unit configured to convert a gradation characteristic of the image data; and a control unit configured to control a characteristic of the gamma conversion unit based on a determination output of the image continuity determination unit.

In an image processing apparatus for performing multi-level processing on image data obtained by raster-scanning a document image, an image continuity determining means for determining continuity of an image with respect to the image data; The image processing apparatus further comprises image filter means for converting image characteristics, and control means for controlling the filter characteristics of the image filter means based on the judgment output of the image continuity judgment means.

In an image processing apparatus for performing multi-level processing on image data obtained by raster-scanning an original image, an image continuity determining means for determining continuity of black pixels for each pixel constituting the image data. And gamma conversion means for converting the gradation characteristics of the image data, and control means for controlling the characteristics of the gamma conversion means based on the judgment output of the image continuity judgment means.

In an image processing apparatus for performing multi-value processing on image data obtained by raster-scanning an original image, an image continuity determining means for determining continuity of black pixels for each pixel constituting the image data. And image control means for converting the image characteristics of the image data, and control means for controlling the filter characteristics of the image filter means based on the judgment output of the image continuity judgment means.

When the continuity data determined by the image continuity determining means is large, the control means controls the characteristics of the gamma conversion means to increase the density.

[0010] When the continuity data determined by the image continuity determining means is large, the control means controls the edge enhancement characteristic of the image filter means to be strong.

In a control method of an image processing apparatus for performing multi-value processing on image data obtained by raster-scanning an original image, a gamma conversion means for converting a gradation characteristic of the image data is provided. The continuity of black pixels is determined for each of the constituent pixels, and the characteristics of the gamma conversion means are controlled based on the determination result.

In a control method of an image processing apparatus for performing multi-value processing on image data obtained by raster-scanning an original image, the image processing apparatus includes image filter means for converting image characteristics of the image data. The continuity of black pixels is determined for each pixel to be processed, and the filter characteristics of the image filter unit are controlled based on the determination result.

When the continuity of the black pixels is large, the characteristics of the gamma conversion means are controlled so as to increase the density.

When the continuity of the black pixels is large, the image filter is controlled so that the edge enhancement characteristic of the image filter is enhanced.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of the present invention will be described in detail.

FIG. 1 shows the appearance of a digital copying machine according to an embodiment of the present invention.

In the digital copying machine CP, a scanning unit (not shown) for scanning an image in the main scanning direction RR in the sub scanning direction RQ is provided below the contact glass.

FIG. 2 schematically shows a control system of the digital copying machine CP.

Referring to FIG. 1, a reading unit 1 drives a scanning unit to raster-scan one page of image data and outputs image data obtained by the raster scanning. The image data is added to the image processing unit 2.

The image processing unit 2 applies a filtering process and a gamma process for improving image quality to the image data added from the reading unit 1, and writes a bit width according to the writing characteristics of the writing unit 3. The image data is formed, and the write image data output from the image processing unit 2 is applied to the write unit 3.

The writing section 3 executes a predetermined writing operation based on the writing image data added from the image processing section 2, and outputs the image to a transfer section for transferring the image to copy paper. .

Further, the control unit 4 controls the digital copying machine C
The controller 4 controls the internal operation of the P. The control unit 4 controls the reading unit 1, the image processing unit 2, and the writing unit 3
Is controlled.

The operation unit 5 is provided with the digital copier C
It is used to operate P, and is composed of operation keys and various displays, and its operation input information and the like are output to the control unit 4.

FIG. 3 shows an example of the image processing section 2.

In FIG. 1, 8 is added from the reading unit 1.
The bit image data D1 is applied to the filter circuit 11. The filter circuit 11 applies any one of the filters F1, F2, and F3 having the convolution coefficient characteristics shown in FIGS. 4A, 4B, and 4C to the input image data D1. The 8-bit output data D2 is applied to the gamma converter 12. Here, the filters F1 and F2 are edge enhancement filters, respectively, and the filter F1 has stronger edge enhancement than the filter F2. Further, the filter F3 has a filter characteristic of performing through output of input data without performing any edge enhancement.

The gamma conversion section 12 applies any one of the gamma conversion processes of the characteristics A, B and C shown in FIG. 5 to the data D2 output from the filter circuit 11, Is output to the gradation processing unit 13. Here, the characteristic A is a gamma characteristic that greatly changes the density of output data with respect to input data, and the characteristic B is a gamma characteristic in which the rate of change in the density of input data and output data is smaller than that of characteristic A. The characteristic C is a gamma characteristic that keeps the density of the input data and the output data the same.

The gradation processing section 13 performs predetermined gradation processing, for example, binarization processing or pseudo-multi-tone binarization processing (dither processing) on the data D3 added from the gamma conversion section 12. The 1-bit output data D4 is output to the next-stage device.
Further, data corresponding to the data D3 is output from the gradation processing unit 13 to the continuity determination unit 14.

The continuity determining unit 14 determines, for each pixel of the image data obtained by reading, the cumulative number of black pixels from adjacent pixels (hereinafter, referred to as "black continuity value"). , The data R representing the black continuity value is
They are added to the filter circuit 11 and the gamma converter 12, respectively.

Then, according to the value of the data R, the filter circuit 11 and the gamma converter 12 change their processing characteristics in the manner shown in FIG. 6, respectively.

That is, when the value of the data R is smaller than 7, the filter circuit 11 selects the filter F3,
The gamma converter 12 selects the characteristic C. Thus, in this case, the input image data D1 is added to the gradation processing unit 13 as it is as data D3.

When the value of the data R is not less than 8 and less than 15, the filter circuit 11 selects the filter F2, and the gamma converter 12 selects the characteristic B. Accordingly, in this case, the input image data D1 is added to the gradation processing unit 13 as data D3 in a state where the edge enhancement processing is performed a little and the density is converted to a slightly higher density.

When the value of the data R is 16 or more, the filter circuit 11 selects the filter F1 and the gamma converter 12 selects the characteristic A. Accordingly, in this case, the input image data D1 is added to the gradation processing unit 13 as data D3 in a state where the edge enhancement processing is performed strongly and the density is considerably increased.

As described above, when the target pixel to be subjected to the gradation processing is not a continuous image such as an isolated point, the edge emphasis and the density emphasis are not performed. Can be avoided.

For the target pixel to be subjected to gradation processing,
If the pixel of interest is not an isolated point, but is not part of a continuous image, for example, if it is a part of a photographic image, edge enhancement and density enhancement are performed slightly, so that the image quality of the photographic image is reduced. Can be improved.

For the target pixel to be subjected to gradation processing,
When the pixel of interest is a part of a continuous image, for example, a part of a character image, the edge enhancement and the density enhancement are sufficiently performed, so that the image quality of the character image can be improved. .

FIG. 7 shows a specific configuration example of the filter circuit 11 and the gamma converter 12.

The filter circuit 11 performs a filter F1 process on the input image data D1, a filter circuit 11b performs a filter F2 process on the input image data D1, and
Output data of filter circuit 11a, filter circuit 11b
And the selector circuit 11c for selecting any one of the output data and the image data D1.

The selector circuit 11c outputs the output data of the filter circuit 11a applied to the input terminal A, the output data of the filter circuit 11b applied to the input terminal B according to the values of the signals r1 and r2 representing the contents of the data R, Alternatively, any one of the image data D1 is selected, and the output data is applied as data D2 to a ROM (read only memory) 12a constituting the gamma conversion unit 12.

A ROM constituting the gamma converter 12
12a stores a table representing the relationship between input data and output data when characteristics A, B, and C are selected.

In the ROM 12a, a table corresponding to the values of the signals r1 and r2 representing the contents of the data R is selected as a table for processing the input data D2. The output data formed by the arithmetic processing is output as data D3 of the target pixel at that time.

Here, when the data R is 7 or less, the signals r1 and r2 take a value of "0, 0", and when the data R is 8 or more and less than 15, the signals r1 and r2 become "0". 1,0 "
When the data R is 16 or more and less than 63, the signals r1 and r2 take the values of “0, 1” and the data R
Is greater than or equal to 64, the signals r1 and r2 take the value of "1,1".

Therefore, the signals r1 and r2 are "0,0".
In this case, the selector circuit 11c selects through data corresponding to the input terminal C, and the ROM 12a outputs data D3 corresponding to the characteristic C.

When the signals r1 and r2 are "1, 0", the selector circuit 11c selects the operation data of the filter F2 corresponding to the input terminal B and outputs the data to the ROM 12a.
Outputs data D3 corresponding to the characteristic B.

When the signals r1, r2 are "0, 1" and "1, 1", the selector circuit 11c selects the operation data of the filter F1 corresponding to the input terminal A, and the ROM 12a , Data D3 corresponding to characteristic A
Is output.

Next, the processing of the continuity determining section 14 will be described.

First, the continuity judging section 14 applies a template as shown in FIG. 8 to extract the target pixel R0 and the adjacent pixels R1 to R4 of the target pixel R0.
Is a black pixel, a value obtained by adding 1 to the maximum value of the black continuity values of the adjacent pixels R1 to R4 is determined as the black continuity value for the target pixel R0. In the case of a pixel, a value corresponding to 1/2 of the maximum value among the black continuity values of the adjacent pixels R1 to R4 is determined as the black continuity value for the target pixel R0.

Thus, for example, as shown in FIG.
When there is a black pixel at the position indicated by “○”, the black continuity value for each pixel is the value displayed in each cell.

FIG. 10 shows an example of the configuration of the continuity determining unit 14. FIG. 11 shows the relationship between input and output data of each circuit element in FIG.

In the same figure, FIFO buffer 14a
Stores the black continuity value of the adjacent pixel R4.
The output of the FIFO buffer 14a is added to the register 14b as data of the pixel Rn.

The register 14b includes adjacent pixels R1, R2,
The black continuity value of R3 is stored, and its output is
It is added to the maximum value calculation circuit 14c.

The maximum value calculation circuit 14c calculates the maximum value from the black continuity values of the adjacent pixels R1, R2, and R3 to be added. The calculation result is added to the addition circuit 14d as the maximum value R5. ing.

The adding circuit 14d calculates the maximum value R5 to be added.
The output is applied as data R6 to the input terminal A of the comparator 14e and the input terminal B of the selector 14f.

The input terminal B of the comparator 14e has an adjacent pixel R
When the data R6 is larger than the black continuity value of the adjacent pixel R4, the comparator 14e raises the output signal h to a logic H level and outputs the data R6. Is less than or equal to the black continuity value of the adjacent pixel R4, the output signal h falls to the logical L level.
This output signal h is applied to the control input terminal S of the selector 14f.

The selector 14f selects the value of the input terminal B when the value of the control input terminal S is at the logical H level, and selects the value of the input terminal B when the value of the control input terminal S is at the logical L level. A value is selected, and the selected signal is applied as data R8 to the input terminal B of the next-stage selector 14g and the input terminal D of the decoder circuit 14h. The data R8
(= “1 bit left shifted value”) is applied to the input terminal A of the selector 14g.

The data D5 representing the pixel value of the pixel of interest R0 is added to the control input terminal S of the selector 14g. When the data D5 represents a black pixel,
The selector 14g outputs the data (R8) of the input terminal B as the black continuity value of the pixel of interest R0, and when the data D5 represents a white pixel, the selector 14g outputs the data (R8 / R8) of the input terminal B. 2) is output as the black continuity value of the pixel of interest R0. The output of the selector 14g is applied to a buffer circuit 14i.

The output data of the buffer circuit 14i is used as the black continuity value of the pixel of interest R4 as the FIFO buffer 14a.
, An input terminal B of a comparator 14e, and an input terminal A of an addition circuit 14j.

The adder circuit 14j adds 1 to the black continuity value of the target pixel R4, and its output data is applied to the input terminal A of the selector 14f.

The decoder 14h outputs the values of the signals r1 and r2 corresponding to the data R in the relationship described above.

Accordingly, a value obtained by adding 1 to the maximum value of the black continuity value of the adjacent pixels R1 to R3 (ie, data R6)
Is greater than the black continuity value of the adjacent pixel R4,
If the data R6 is selected as the black continuity value of the target pixel R0, and if the black continuity value of the adjacent pixel R4 is larger than the data R6, a value obtained by adding 1 to the black continuity value of the adjacent pixel R4 ( That is, the data R7) is selected as the black continuity value of the target pixel R0.

The black continuity value of the target pixel R0 is 1
After the clock, it is used as the value of the adjacent pixel R4 of the next pixel. Further, since the FIFO buffer 14a has a data capacity of one line, the value of the black continuity value of the pixel on the previous line is stored in the register 14b as the black continuity value of the adjacent pixels R1 to R3.

In this way, the calculation for calculating the black continuity value as described above is executed. The calculation of the black continuity value can also be executed by software, and FIG. 12 is a flowchart showing an algorithm applicable in that case.

First, the black continuity values of the adjacent pixels R1 to R3 are read (process 101), and the maximum value of the black continuity values of the adjacent pixels R1 to R3 is calculated and substituted into a variable R5 (process 102). Then, a value obtained by adding 1 to the value of the variable R5 is substituted for the variable R6 (process 103).

Then, it is checked whether or not the value of the variable R6 is larger than the black continuity value of the adjacent pixel R4 (decision 104).
When the result of determination 104 is YES, the value of variable R6 is substituted for variable R8, and the value of variable R8 is output as data R of target pixel R0 (process 105).

When the result of determination 104 is NO, the value of variable R7 (described later) is substituted for variable R8, and the value of variable R8 is output as data R of target pixel R0 (process 106).

Next, it is checked whether or not the target pixel R0 is a black pixel (decision 107). The result of judgment 107 is YES
, The value of the variable R8 is substituted into the black continuity value of the target pixel R0 (processing 108), and the result of the judgment 107 is NO
, The value obtained by multiplying the value of the variable R8 by (1/2) is assigned to the black continuity value of the target pixel R0 (Process 10).
9).

Next, the value of the black continuity value of the adjacent pixel R4 is written into the address of the adjacent pixel R1 (process 110), and the value of the black continuity value of the target pixel R0 is written into the black continuity value of the next adjacent pixel R4. (Process 111), and a value obtained by adding 1 to the value of the black continuity value of the adjacent pixel R4 is substituted for a variable R7 applied to the process of the next pixel (process 112), and this process ends. .

In the above-described embodiment, the filter processing is set to three steps, the gamma conversion processing is set to three steps, and the case classification for the black continuity value is set to three steps. There is no.

In the above-described embodiment, two types of image processing, edge enhancement processing and gamma conversion processing, are applied. However, other image processing, such as smoothing processing and contour extraction processing, may be applied. Can also.

In the above-described embodiment, the present invention is applied to a digital copying machine. However, the present invention is similarly applied to other apparatuses for processing image data by raster scanning, such as a facsimile apparatus. Can be applied.

[0070]

As described above, according to the present invention,
If the target pixel to be subjected to the gradation processing is not a continuous image such as an isolated point, the edge emphasis and the density emphasis are not performed, so that it is possible to avoid a situation in which the background stain of the read data is emphasized. The effect is obtained.

For the target pixel to be subjected to gradation processing,
If the pixel of interest is not an isolated point, but is not part of a continuous image, for example, if it is a part of a photographic image, edge enhancement and density enhancement are performed slightly, so that the image quality of the photographic image is reduced. There is also obtained an effect that it can be improved.

For the target pixel to be subjected to gradation processing,
When the pixel of interest is a part of a continuous image, for example, a part of a character image, the edge enhancement and the density enhancement are sufficiently performed, so that the image quality of the character image can be improved. The effect is also obtained.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing the appearance of a digital copying machine according to one embodiment of the present invention.

FIG. 2 is a block diagram schematically showing a control system of the digital copying machine CP.

FIG. 3 is a block diagram showing an example of an image processing unit 2.

FIG. 4 is a schematic diagram illustrating an example of a convolution coefficient of a filter circuit.

FIG. 5 is a graph illustrating an example of characteristics of a gamma conversion process.

FIG. 6 is a schematic diagram showing an example of a characteristic switching mode of the filter circuit 11 and the gamma converter 12.

FIG. 7 shows a filter circuit 11 and a gamma converter 12
FIG. 2 is a block diagram showing a specific configuration example of FIG.

FIG. 8 is a schematic diagram showing an example of a template applied by the continuity determination unit 14;

FIG. 9 is a schematic diagram showing an example of a black continuity value.

FIG. 10 is a block diagram showing a configuration example of a continuity determination unit 14;

11 is a timing chart showing an example of a change in data of each circuit element in FIG.

FIG. 12 is a flowchart illustrating an example of an algorithm for calculating a black continuity value.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Filter circuit 12 Gamma conversion part 13 Gradation processing part 14 Continuity judgment part

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 5B057 CA08 CA12 CA16 CB07 CB12 CB16 CE03 CE06 CE13 CH07 CH09 CH11 DB02 DC03 5C021 PA17 PA58 PA62 PA80 RB08 XA13 XA34 XB03 YC07 ZA00 5C077 LL19 MM02 MP01 NN08 PP03 PP03 PP03 PP03

Claims (10)

[Claims] An image processing apparatus for performing multi-value processing on image data obtained by raster-scanning a document image, comprising: an image continuity determination unit configured to determine continuity of an image with respect to the image data; An image processing apparatus comprising: gamma conversion means for converting gradation characteristics; and control means for controlling characteristics of the gamma conversion means based on a judgment output of the image continuity judgment means. 2. An image processing apparatus for performing multi-value processing on image data obtained by raster-scanning a document image, comprising: an image continuity determining unit for determining continuity of an image with respect to the image data; An image processing apparatus comprising: image filter means for converting image characteristics; and control means for controlling a filter characteristic of the image filter means based on a determination output of the image continuity determination means. 3. An image processing apparatus for performing multi-value processing on image data obtained by raster-scanning a document image, wherein image continuity determining means for determining continuity of black pixels for each pixel constituting the image data. An image processing apparatus, comprising: gamma conversion means for converting gradation characteristics of the image data; and control means for controlling characteristics of the gamma conversion means based on a judgment output of the image continuity judgment means. . 4. An image processing apparatus for performing multi-value processing on image data obtained by raster-scanning a document image, wherein image continuity determining means for determining continuity of black pixels for each pixel constituting the image data. An image processing apparatus, comprising: image filter means for converting image characteristics of the image data; and control means for controlling filter characteristics of the image filter means based on a judgment output of the image continuity judgment means. . 5. The control means controls the characteristic of the gamma conversion means to increase the density when the continuity data determined by the image continuity determination means is large. The image processing apparatus according to claim 1. 6. The image processing apparatus according to claim 1, wherein when the continuity data determined by the image continuity determining unit is large, the control unit controls the edge enhancement characteristic of the image filtering unit to be strong. The image processing apparatus according to claim 2 or 4. 7. A control method for an image processing apparatus for performing multi-value processing on image data obtained by raster-scanning a document image, comprising: gamma conversion means for converting gradation characteristics of the image data; A control method for an image processing apparatus, comprising: determining the continuity of black pixels for each of the constituent pixels; and controlling the characteristics of the gamma conversion unit based on the determination result. 8. A control method for an image processing apparatus for performing multi-value processing on image data obtained by raster-scanning a document image, comprising: image filter means for converting image characteristics of the image data; A control method for an image processing apparatus, comprising: determining continuity of black pixels for each pixel to be processed; and controlling a filter characteristic of the image filter means based on a result of the determination. 9. When the continuity of the black pixels is large,
8. The method according to claim 7, wherein the characteristic of the gamma conversion unit is controlled to increase the density. 10. The method according to claim 8, wherein when the continuity of the black pixels is large, control is performed so that the edge enhancement characteristic of the image filter unit is enhanced.