JP2001016453A - Picture processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reproduce a highly precise picture by executing an optimum picture processing on picture data to be compressed/expanded and picture data not to be compressed/expanded through switching a filter and the parameter of a color correction coefficient at the time of executing the picture processing. SOLUTION: The processor where an original is digitally read by a color scanner 1 and is digitally reproduced by a color printer, is provided with a data compression part 2 compressing picture data which is read by the color scanner 1, a picture memory 3 holding picture data compressed by the compression data compression part 2, a data expansion part 4 expanding picture data held by the picture memory 3 and a picture processing part 6 selecting picture data (A) which is read by the color scanner 1 or picture data (B) compressed/ expanded by the data compression part 2 and the data expansion part 4 by a prescribed method and processing the selected picture, a parameter used by the picture processing part 6 is switched by A and B.

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 image processing for reproducing a high-precision image, which is suitable for a color image processing apparatus such as a color copying machine or a color printer having a compression / expansion function. .

[0002]

2. Description of the Related Art In an image reproducing apparatus such as a color copying machine or a color printer, the cost of a memory portion for holding the image data is generally large. In particular, in a color image reproducing apparatus such as a color copying machine or a color printer described above, the amount of data is extremely large, and when continuously printing a plurality of originals, the number of images that can be stored in the memory is necessarily limited. Would be done. For this reason, data compression is used to hold a larger number of image data at a lower cost. Also, by storing the image data compressed by the data compression technology in the memory, when outputting a plurality of copies, the image data stored in the memory is read out, expanded and output for the second and subsequent copies. Reproduction is possible, and in the case of outputting in this manner, scanning is unnecessary, so that the time required for scanning can be greatly reduced.

As a prior art relating to such an apparatus, for example, there is a technique relating to a color image encoding apparatus disclosed in Japanese Patent Application Laid-Open No. 4-316279. This known technique divides an image into m × n (m, n is a natural number of 2 or more) pixel blocks, determines whether each block is an edge portion or a non-edge portion, and determines whether the block is an edge portion or not. For example, lossless coding such as modified Huffman coding is applied to the block, and irreversible coding such as discrete cosine transform is applied to a non-edge portion. The irreversible coding method is basically a method of reducing the image data by cutting the high frequency side while leaving the low frequency side of the image spatial frequency.
Off relationship. As described above, the irreversible compression method is widely used because an image having a large amount of low frequency components such as a photographic part can be expected to have a high compression ratio with little image deterioration.

[0004] On the other hand, there is an apparatus which holds two modes, a mode for outputting image data after compression / expansion and a mode for outputting image data without compression / expansion. As such an apparatus, the invention disclosed in JP-A-9-224106 is known. This known technique aims at shortening the time from when the start button is pressed until the first copy is discharged (first copy time) in a digital copying machine having a compression / expansion function. At the time of outputting a copy image, image data which is not subjected to compression / expansion is output. At the time of outputting a second or subsequent copy image,
It is configured to decompress and output the compressed image held in the memory.

[0005]

By the way, in the latter device disclosed in Japanese Patent Application Laid-Open No. 9-224106, image data to be compressed / expanded and image data not to be compressed / Color processing such as spatial filtering, color correction, and gamma conversion is performed using the same parameters. However, as described above, when the irreversible compression method is used, image deterioration occurs to a considerable extent. In general, it is conceivable that the cut of the high-frequency component causes blurring or deteriorates the color reproducibility (particularly, the subtle hue of the highlight portion).

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances of the prior art, and has as its object to perform image processing on image data to be compressed / expanded and image data not to be compressed / expanded. By switching parameters such as a filter and a color correction coefficient, optimal image processing is performed for each of them to reproduce a highly accurate image.

[0007]

According to an aspect of the present invention, there is provided an image processing apparatus for performing image processing for reproducing an image based on input image data.
Compression means for compressing the input image data, data holding means for holding the image data compressed by the compression means, data expansion means for expanding the image data held in the data holding means, Image data (input image data that is not compressed / expanded)
Selecting means for selecting any of the image data compressed / decompressed by the compression means and the data decompression means; and selecting the image data not subjected to compression / decompression or the compressed / decompressed image data selected by the selection means. Image processing means for performing image processing by the image processing means, and when performing image processing by the image processing means, parameters used by the image processing means in accordance with the image data not subjected to the compression / expansion and the compressed / expanded image data. A switching means for switching is provided.

The selection means selects image data which is not compressed / expanded until the number of reproductions specified by the user exceeds a predetermined number, and when the number exceeds the predetermined number, the compressed / expanded image data is selected. This is done by selecting the data. The parameters used in the image processing means include a weighting coefficient of a spatial filter, a color correction coefficient set in advance by a predetermined method, and a gamma table coefficient for performing gamma conversion according to the characteristics of the image reproducing apparatus.

The color correction coefficient is set based on data obtained by reading a plurality of color patches as RGB digital signals, and the compression / expansion color correction coefficient is set based on data read out as RGB digital signals. A color correction coefficient for the expanded image data is set based on data obtained by reading a plurality of color patches as RGB digital signals based on data compressed / expanded by the compression unit and the data expansion unit.

[0010]

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

<First Embodiment> First, FIGS.
The first embodiment of the present invention will be described with reference to FIG.

The color image processing apparatus according to the present embodiment comprises:
As shown in the block diagram of FIG. 1, a color scanner 1, a data compression unit 2, an image memory 3, a data decompression unit 4, a transmission line switching unit 5, an image processing unit 6, a color printer 7, an operation panel 8, and a data transmission control unit 9. With this configuration, the color scanner 1 uses the RGB
The signal is read, and the image data is compressed by the data compression unit 2 and stored in the image memory 3. The image memory 3 reads out image data in response to a signal from the data transmission control unit 9. The data decompression unit 4 decompresses the image data output from the image memory 3. The transmission path switching unit 5 receives the signal from the data transmission control unit 9 and switches the transmission path.
Either output data from the data decompression unit 4 or image data read from the color scanner 1 is output. The image processing unit 6 receives the signal from the data transmission control unit 9 and performs image processing on the image data output from the transmission line switching unit 5. Then, the image subjected to the image processing is output by the color printer 7.

When outputting in this manner, the user can specify the number of reproductions from the operation panel 8. The data transmission control unit 9 controls the image memory 3 and the transmission path switching unit to switch the processing as described below when a predetermined number (K) or more is specified according to the specified reproduction number. 5. Send a signal to the image processing unit 6.

(1) When outputting the L-th (L <K) -th image data, the transmission line switching section 5 outputs the image data read from the color scanner 1. In the image processing unit 6,
Performs image processing for image data that is not subjected to compression / decompression processing.

(2) When outputting the L-th (L ≧ K) image data, the image memory 3 reads out the compressed image data. The transmission line switching unit 5 outputs the output data from the data decompression unit 4. The image processing unit 6 performs image processing for image data that has been subjected to compression / expansion processing.

An image processing unit 6 for performing such image processing
Is a smoothing filter 601, as shown in detail in FIG.
Edge enhancement filter 602, color correction unit 603, UCR unit 604, gamma conversion unit 605, and filter determination unit 606
It is composed of The following describes (1) image processing for image data not subjected to the compression / expansion processing and (2) image processing for image data subjected to the compression / expansion processing, which are executed by the image processing unit 6. I do. In the image processing unit 6, the smoothing filter processing unit 601 and the edge enhancement filter processing unit 602 perform spatial filtering on the image data output from the transmission line switching unit 5. Then, color processing is performed by the color correction unit 603, UCR (under color removal) unit 604, and gamma conversion unit 605.

The filters used in the smoothing filter processing unit 601 and the edge enhancement filter processing unit 602 are loaded from the filter determination unit 606. The filter determining unit 606 includes a coefficient storage table memory and a product-sum operation unit. This filtering is a spatial filter that determines the value of the target pixel by performing a product-sum operation on the target pixel and its surrounding pixels. For example, a smoothing filter as shown in FIG. 3 or an edge enhancement filter as shown in FIG. Is used. In the first embodiment, image processing for image data not subjected to the compression / expansion processing of (1) and image processing for image data subjected to the compression / expansion processing of (2) are respectively performed. The optimal filter coefficients are stored in a memory, and the filter determining unit 606 receives the signal from the data transmission control unit 9 and switches the filter coefficient to be loaded, thereby performing an optimal spatial filtering process on each image.

FIG. 3 shows an example of two smoothing filters having different smoothing degrees. In this case, (b) rather than (a)
The use of the above filter results in more smoothing. Thus, the degree of smoothing can be adjusted by switching the filter coefficients.

FIG. 4 shows an example of two edge enhancement filters having different degrees of edge enhancement. In this case, the edge is more emphasized by using the filter of (b) than by (a). As described above, similarly to the smoothing, the degree of edge enhancement can be adjusted by switching the filter coefficient.

For example, in general, image data after compression / expansion tends to be blurred from image data that has not been subjected to compression / expansion processing because high-frequency components are deteriorated.
In this case, as for the filter for image data that has been subjected to the compression / expansion processing of (2), the smoothing is weaker than the filter for image data that has not been subjected to the compression / expansion processing of (1). What is necessary is just to prepare a filter coefficient.

As described above, according to the first embodiment, since the smoothing filter and the edge enhancement filter are switched between (1) and (2), the compression / expansion of the output image of (2) is performed. This has the effect of making deterioration less noticeable.

<Second Embodiment> FIG. 5 is a block diagram showing a detailed configuration of an image processing unit according to a second embodiment. The configuration of the entire color image processing apparatus according to the second embodiment is the same as the configuration of FIG. 1 according to the first embodiment, but the specific configuration and operation of the image processing unit 6 are different. Therefore, a specific configuration of the image processing unit 6 in the second embodiment is described in (1) of the compression /
Image processing for image data that is not subjected to decompression processing; (2)
The image processing for the image data subjected to the compression / expansion processing will be described. The overall processing flow of spatial filtering and color processing in FIG. 5 is the same as that in FIG.

In the second embodiment, the color correction unit 60
3. The parameters used in the gamma correction unit 605 are loaded from the parameter selection unit 607. The parameter selection unit 607 has a memory for storing parameters, and includes (1) a color processing parameter for image data not subjected to the compression / expansion processing and (2) a color processing parameter for image data subjected to the compression / expansion processing. Are stored. Then, by receiving the signal from the data transmission control unit 9 and switching the color processing parameters to be loaded, optimal color processing is performed on each image.

Hereinafter, each color processing parameter stored in the memory of the parameter selection unit 607 will be described.

In the color correction processing in the color correction unit 603, in the second embodiment, it is assumed that the color correction is performed by a linear linear expression for simplicity of description, and the RGB signal of the input image,
CMY signal which is a printer drive signal, color correction coefficient group a0
Ａa3, b0 to b3, and c0 to c3 are represented by the following equation 1.

C = a0 + a1 × R + a2 × G + a3 × B M = b0 + b1 × R + b2 × G + b3 × B Y = c0 + c1 × R + c2 × G + c3 × B (1) Correction coefficient groups a0 to a3, b0 to b3, c0 to c3 Is set by the following method. First, for the color correction coefficient group for image data not subjected to the compression / expansion processing of (1), a method described in JP-A-6-197218, in which patches are generated based on data input by a color scanner, is used. Used.

The method described in JP-A-6-197218 is performed by the following steps (a) to (c).

(A) A printer approximation formula (L *, a *, b * -C, M, Y) is created for setting a color correction coefficient group. That is, the C, M, and Y signals are selected at appropriate sampling intervals, and the mixed color patches are output by the color printer 8.
Then, this mixed color patch is measured by an appropriate colorimeter. Here, the measured colorimetric values are represented by L *, a *, b *. Thus, C, M, Y-L *, a *, b * 0 0 0 88.5 -2.5 0.8 0 0 8 ・ ・ ・ ・ ・ ・ ・ ・ ・ 0 0 16 ・ ・ ・ ・ ・ ・ ・ ・ ・・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 255, 255,255 ・ ・ ・ ・... A data group such as Therefore, based on the above data group, for example, the coefficients (α0 to
α9, β0 to β9, γ0 to γ9) are determined by the least squares method.

C = α0 + α1L * + α2a * + α3b * + α4L * L * + α5a * a * + α6b * b * + α7L * a * + α8a * b * + α9b * L * M = β0 + β1L * + β2a * + β3b * + β4L * L * + β5a * a * + β6b * b * + β7L * a * + β8a * b * + β9b * L * Y = γ0 + γ1L * + γ2a * + γ3b * + .gamma.4L * L * +. gamma.5a * a * +. gamma.6b * b * +. gamma.7L * a * +. gamma.8a * b * +. gamma.9b * L * (2) (b) Subsequently, a color patch composed of a silver halide photograph (for example, 5
FIG. 6 shows an example of a color patch of about 12 colors, which is an example of a patch of 64 colors when the dot ratios of C and M are changed between 8 steps, respectively, from the color scanner 1 and after log conversion. R, G, and B signals of each patch are obtained. Actually, in order to reduce noise, copy pixels near the center of each patch are averaged (averaging process).

On the other hand, a color patch composed of a silver halide photograph is measured (L *, a *, b *) with a colorimeter. Thereby, the relationship between (R, G, B) and (L *, a *, b *) of each patch is obtained.

(C) As in (a) above, a color patch of a halftone dot photograph is input and (R, G, B) and (L)
*, A *, b *).

And, these (a), (b), (c)
From the result of (1), the color correction coefficient group (a0 to a3, b0
To b3, c0 to c3) are determined. That is, a group of color correction coefficients for silver halide photography (a0 to a3, b0 to b3, c0 to c
3), (R, G, B) and (L *, a *,
b *), and further using equation (2), a data group of (R, G, B) and (C, M, Y) can be obtained. A color correction coefficient group (a0-a3, b0-b3, b0-b3,...) For the silver halide photograph is applied to this data group so that the original color of the silver halide photograph matches the color printed using the least squares method.
c0 to c3) are determined.

Color correction coefficient group (a0-a3,
b0 to b3, c0 to c3) are obtained by using the relationship between (R, G, B) and (L *, a *, b *) of the patch obtained in (c), and further using equation (2). Obtains (R, G, B) and (C, M, Y) data groups. A color correction coefficient group (a0
To a3, b0 to b3, c0 to c3).

Color correction coefficient group (a0 to
a3, b0 to b3, c0 to c3) represent an appropriate ratio of the data groups of (R, G, B) and (C, M, Y) obtained in (b) and (c), for example, 1 [512 patches ]: Select with [512 patches]. Then, a color correction coefficient group (a
0-a3, b0-b3, c0-c3).

The group of color correction coefficients for halftone photographs, the group of color correction coefficients for silver halide photography, and the group of color correction coefficients for silver halide / halftone photography determined in this way are each composed of ROM or RAM. Is written to the stored color correction coefficient storage unit 5.

Next, regarding the group of color correction coefficients for image data subjected to the compression / expansion processing of (2), the data obtained by inputting the patches by the color scanner 1 is compressed by the data compression section 2 and 4, based on the data decompressed in the same manner as in the method described in JP-A-6-197218. In the second embodiment, the color correction based on the linear linear equation has been described. However, the CMY of the representative point in the RGB space calculated in advance by using the nonlinear color correction method or the result of the nonlinear color correction is used. The present invention can also be applied to a memory interpolation method for performing color correction by interpolating values.

The gamma conversion unit 605 performs gamma conversion processing in accordance with the characteristics of the color printer 7 that outputs.
Optimum processing is performed for each of the coefficients γ1 to γ4 in Expression 3 below as gamma table coefficients by switching the coefficients between (1) and (2).

C ′ = γ1 × C M ′ = γ2 × M Y ′ = γ3 × Y Bk ′ = γ4 × Bk (3) In the second embodiment, color is used as a color processing parameter for switching. Although the correction coefficient and the gamma table coefficient have been described, parameter switching in the UCR unit 604 and the like may be considered. The UCR unit 604 reduces the amount of CMY, and generates a corresponding amount of Bk (black). For example, in the UCR equation of the following equation 4, the amount of Bk to be generated is adjusted by the coefficient d, but (1) and (2)
By switching the coefficient d with
Perform CR processing.

[0039] As described above, according to the second embodiment,
The color correction coefficient and the gamma conversion table coefficient are switched between (1) and (2).
This has the effect of making color deterioration due to elongation less noticeable.

[0040]

As described above, according to the first aspect of the present invention, the image data which is not subjected to the compression / expansion or the image which is subjected to the image processing to the compressed / expanded image data selected by the selection means. Processing means; and switching means for switching parameters used in the image processing means according to the image data not subjected to the compression / expansion and the compressed / expanded image data when performing image processing by the image processing means. Therefore, by switching the parameters used for image processing between the mode of outputting image data without compression / expansion and the mode of outputting image data with compression / expansion, the optimum mode is selected for each mode. Processing can be performed. By doing this,
Image deterioration due to compression / decompression is made inconspicuous, and the degree of deterioration can be made substantially uniform in output images in either mode.

According to the second aspect of the present invention, image data for which compression / expansion is not performed is selected until the number of reproductions specified by the user exceeds a predetermined number, and when the number exceeds the predetermined number, compression / expansion is performed. Since image data is selected, 1
The first copy time is shortened by outputting an image that is not subjected to compression / expansion when outputting the first to predetermined number of images, and the image is subjected to compression / expansion from the first to the predetermined number and thereafter. By switching parameters used for image processing at the time of output, it is possible to perform optimal processing for each of them, thereby making image deterioration due to compression / decompression inconspicuous and reducing any of the first to the specified number of reproductions. Also in the output image, the degree of deterioration can be made substantially uniform.

According to the third aspect of the present invention, in image processing on image data that has been subjected to compression / expansion and image data that has not been subjected to compression, weighting coefficients of a spatial filter are switched to optimize smoothing and edge enhancement for each. To reduce the blurring of images due to compression / decompression,
In any of the output images, the degree of smoothing and edge enhancement can be made substantially uniform.

According to the fourth and sixth aspects of the present invention, in the image processing for the image data which has been subjected to the compression / expansion and the image data which has not been subjected to the compression, the optimum color correction processing is performed by switching the color correction coefficients. In addition, the change in the color tone of the image due to compression / expansion is made inconspicuous, and the color accuracy after color correction can be made substantially uniform in any output image.

According to the fifth aspect of the present invention, in image processing of image data that has been subjected to compression / expansion and image data that has not been subjected to compression, gamma table coefficients for gamma conversion are switched in accordance with the characteristics of the output device. By performing an optimal gamma conversion process, the change in the color tone of the image due to compression / expansion is made inconspicuous, and the color accuracy after the gamma conversion can be made substantially uniform in any output image.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an entire color image processing apparatus according to a first embodiment of the present invention.

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

FIG. 3 is an explanatory diagram showing a configuration of a smoothing filter of FIG. 2;
(A) shows a filter with a small degree of smoothing, and (b) shows a filter with a large degree of smoothing.

4A and 4B are explanatory diagrams showing the configuration of the edge enhancement filter of FIG. 2, wherein FIG. 4A shows a filter with a small edge enhancement and FIG. 4B shows a filter with a large edge enhancement.

FIG. 5 is a block diagram illustrating a detailed configuration of an image processing unit of a color image processing device according to a second embodiment of the present invention.

FIG. 6 is an example of a color patch of 64 colors when the dot ratios of C and M are respectively changed to eight levels.

[Explanation of symbols]

 Reference Signs List 1 color scanner 2 data compression unit 3 image memory 4 data decompression unit 5 transmission path switching unit 6 image processing unit 7 color printer 7 8 operation panel 9 data transmission control unit 601 smoothing filter processing unit 602 edge enhancement filter processing unit 603 color correction Unit 604 UCR (under color removal) unit 605 gamma conversion unit 606 filter determination unit 607 parameter selection unit

 ──────────────────────────────────────────────────続 き Continued from the front page F term (reference) 5B057 BA23 CA01 CA08 CA12 CA16 CB01 CB06 CB08 CB12 CB16 CC01 CE05 CE06 CE11 CE17 CG01 CH07 CH11 CH18 5C077 LL17 MM27 MP08 PP02 PP15 PP32 PP33 PP38 PP63 PQ08 PQ22 TT23

Claims (6)

[Claims] An image processing apparatus for performing image processing for reproducing an image based on input image data, comprising: a compression unit for compressing the input image data; Data holding means for holding, data expanding means for expanding image data held in the data holding means, image data which is the input image data which is not compressed / expanded, the compressing means and the data Selecting means for selecting any of the image data compressed / decompressed by the decompressing means; and performing image processing on the image data not subjected to the compression / decompression or the compressed / decompressed image data selected by the selecting means. Image processing means; and performing image processing by the image processing means.
An image processing apparatus, comprising: switching means for switching parameters used in the image processing means according to image data not to be expanded and the compressed / expanded image data. 2. The method according to claim 1, wherein the selecting means selects image data which is not subjected to compression / expansion until the number of reproductions specified by the user exceeds a predetermined number. The image processing apparatus according to claim 1, wherein data is selected. 3. The image processing apparatus according to claim 1, wherein the parameter used in the image processing means is a weight coefficient of a spatial filter. 4. The image processing apparatus according to claim 1, wherein the parameter used in the image processing means is a color correction coefficient preset by a predetermined method. 5. The image processing apparatus according to claim 1, wherein the parameter used in the image processing means is a gamma table coefficient for performing gamma conversion according to characteristics of the image reproducing apparatus. 6. The setting of the color correction coefficient is such that the color correction coefficient for image data not subjected to compression / expansion is set based on data obtained by reading a plurality of color patches as RGB digital signals. A color correction coefficient for expanded image data is set to data obtained by reading a plurality of color patches as RGB digital signals based on data compressed / expanded by the compression unit and the data expansion unit. Item 5. The image processing device according to Item 4.