JP2006094104A - Color reproduction characteristic acquiring method and system thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently guarantee color reproduction for a specified original document. <P>SOLUTION: An original image inputted via a network is stored in an image storage unit 64. The original image is read by a scanner unit and this read image is converted into colorimetric values in a prestage color converting unit. A corresponding color extracting unit 68 extracts corresponding colors between the original image stored in the unit 64 and the color-converted read image. The unit 68 extracts the corresponding relation between the colors used for the original image and the colors read in the read image, and the color reproduction characteristics can be acquired. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and system for obtaining color reproduction characteristics using a color multifunction peripheral installed in a convenience store or the like.

  To understand the color reproduction characteristics of output devices (printers, printing machines, copiers, facsimiles, etc.), output a color chart that is calibrated with multiple color patches, measure the color chart, and measure the color chart Color conversion parameters and color correction parameters are calculated from the correspondence between signals and reproduced colors. For example, in the invention described in Patent Document 1, a color information conversion apparatus is realized by using a color chart in which color material amounts are combined so as to be widely and uniformly distributed in a color gamut. Japanese Patent Application Laid-Open No. 2004-228867 discloses a technique that can accurately evaluate skin color reproduction using a color chart of skin color that is particularly important for color reproduction of photographs. In the international standard ISO12642, a color patch set for grasping the color reproduction characteristics of printing is standardized.

JP-A-10-173940 JP 2001-74556 A

  Usually, for example, in order to guarantee color reproduction in a remote place, grasp the color reproduction characteristics of one image output device, and the other refers to the color reproduction characteristics in order to realize the same color reproduction as that image output device Color correction. In order to grasp the color reproduction characteristics, it is necessary to output a predetermined color chart and measure the color. This color chart is unnecessary for the user, and an expensive color measuring device is required for color measurement, and since the number of colors to be measured is large, a large number of man-hours are also required.

  An object of the present invention is to efficiently guarantee color reproduction for a specified document.

  The first feature of the present invention is that an image printing means outputs a document image based on the document electronic image data, the output document image is read by the image reading means, and the read document reading data and There is a color reproduction characteristic acquisition method for extracting a color corresponding to original electronic image data and acquiring a color reproduction characteristic. Therefore, color reproduction characteristics can be acquired without outputting a color patch, and color reproduction of an original image can be performed efficiently.

  When extracting the correspondence between the original electronic image data and the original reading data, if the pixel position of the image to be associated is shifted even a little, the color association may be greatly wrong. In particular, in the read image, pixel position deviation is likely to occur due to misalignment, enlargement / reduction error, skew, or the like during printing and scanning.

  Therefore, it is preferable that the corresponding color is extracted by extracting an area from the document image based on a predetermined determination condition and performing the extraction on the extracted area. As a determination condition for extracting a region, a standard deviation of pixel values belonging to a region can be determined by comparing with a predetermined value, or a difference between a maximum value and a minimum value of pixel values belonging to a region can be employed by comparing with a predetermined value You can decide whether or not. In this case, the extraction of the corresponding color is performed by associating the center value of the extracted document image area with the center value of the corresponding read image, or the center area having a size smaller than the extracted document image area. Are associated with the average value of the corresponding read image. Preferably, the corresponding color is extracted by comparing the color histogram generated from the original image with the color histogram generated from the read image and associating them in the frequency order. In this case, it is preferable to correct the frequency order error based on the color characteristics of the original image and the read image.

  Preferably, before extracting the corresponding color, the characteristics of the original image and the read image are compared to align the orientation of the original image and the read image, the magnification and skew of the original image and the read image are corrected, Remove screen from image.

  According to a second aspect of the present invention, an image printing unit, an image reading unit, and original reading data obtained by reading an original image printed by the image printing unit based on original electronic image data by the image reading unit, A color reproduction characteristic acquisition system having corresponding color extraction means for extracting a corresponding color with original electronic image data.

  The third feature of the present invention is that the image printing means, the image reading means, the storage means for storing the original electronic image data, and the original image printed by the image printing means are read by the image reading means. A color reproduction characteristic acquisition system having corresponding color extraction means for extracting corresponding colors between original reading data and original electronic image data stored in the storage means.

  The fourth feature of the present invention is that an image printing means, an image reading means, a device signal image generating means for generating a device signal image from original electronic image data, and an original image printed by the image printing means. The color reproduction characteristic acquisition system includes a corresponding color extracting unit that extracts a corresponding color between the document read data read by the image reading unit and the device signal image generated by the device signal image generating unit.

  The fifth feature of the present invention is that image input means for inputting original electronic image data, original reading data obtained by reading an original image printed by the image printing means based on the original electronic image data by the image reading means, and The color reproduction characteristic acquisition system extracts a color corresponding to the original electronic image data input by the image input means.

  The sixth feature of the present invention is that an image printing means, an image reading means, an image input means for inputting original electronic image data, and an original image printed by the image printing means based on the original electronic image data. Is a color reproduction characteristic acquisition system that extracts a corresponding color between the original read data read by the image reading means and the original electronic image data input by the image input means.

  According to the present invention, color reproduction can be efficiently guaranteed for a specific document.

Next, an embodiment of the present invention will be described.
FIG. 1 shows an outline of a color reproduction acquisition system 10 according to the first embodiment of the present invention. For example, a personal computer 14 is installed in the user environment 12. Further, for example, a color multifunction device 18 that is an image forming apparatus is installed in a store 16 such as a convenience store. The color multifunction device 18 is connected to a billing device 20 called a coin kit or the like. In this store 20, an unspecified number of people use the color multifunction device 18 by paying a fee through the charging device 20. The color multifunction device 18 includes a display unit 22 that also serves as an input instruction device, a scanner unit 24 that reads an image, and a printer unit 26 that outputs an image. The personal computer 14 described above is connected to the color MFP 18 via a communication means such as a LAN (Local Area Network) or the Internet. Similarly, a server 28 is connected to the color multifunction device 18 via communication means.

  In FIG. 2, the hardware configuration of the color multifunction device 18 is shown. In the color multifunction device 18, a central processing unit (CPU) 32, a program ROM 34 and a RAM 36 are connected to a bus 38. Also, a charging device interface 40, a display unit interface 42, a scanner unit interface 44, and a printer unit interface 46 are connected to the bus 38, the charging device 20 is connected to the charging device interface 40, and the display unit 42 is connected to a display unit. 22, the scanner unit 24 is connected to the scanner unit interface 44, and the printer unit 26 is connected to the printer unit interface 46. A network interface 48 is connected to the bus 38 to receive signals from the outside and send signals to the outside. Furthermore, an external media interface 50 for writing data to a storage medium such as a flexible disk, a compact disk, a DVD, or an MO, or reading image data or the like is connected to the bus 38.

FIG. 3 shows a first embodiment relating to the software configuration of the color multifunction peripheral 14 realized by a program stored in the program ROM.
The pre-stage color conversion unit 52 converts the RGB color signal input via the scanner unit interface into a CIELAB (L *, a *, b *) signal (or CIEXYZ) that is a colorimetric value according to the profile of the scanner unit. The post-stage color converter 54 converts the CIELAB (L *, a *, b *) signal (or CIEXYZ) converted by the pre-stage color converter 52 into a CMYK signal according to the profile of the printer unit. The CMYK signal converted by the post-stage color conversion unit 54 is sent to the printer unit 26 via the printer unit interface 46 and printed out by the printer unit 26. The profile of the scanner unit and the profile of the printer unit are stored in, for example, the RAM 36 described above.

  The image analysis unit 56 analyzes a page image expressed in, for example, PDL (page description language) input via the network interface. The first raster image generation unit 58 generates a raster image that is an RGB signal from the page image according to the analysis result of the image analysis unit 56. When the page image is converted into CMYK by the image analysis unit 56, the second raster image generation unit 60 converts the CMYK signal into an RGB signal and generates a raster image that is an RGB signal. The raster image color conversion unit 62 converts the RGB signal generated by the first raster image generation unit 58 or the second raster image generation unit 60 into a CIELAB signal. The CIELAB signal converted by the raster image color conversion unit 62 is converted into a CMYK signal by the subsequent color conversion unit 54, and the CMYK signal converted by the subsequent color conversion unit 54 is connected to the printer unit 26 via the printer unit interface 46. To be printed out by the printer unit 26.

  The image storage unit 64 stores the raster image generated by the first raster image generation unit 58 or the second raster image generation unit 60 in the form of RGB signals. As will be described later, the preprocessing unit 66 processes the CIELAB signal converted by the previous color conversion unit 52 so that the corresponding color can be easily extracted. The corresponding color extracting unit 68 is read by the scanner unit 24 output from the printer unit 26 based on the original electronic image data, and extracts the corresponding colors between the read original reading data and the original electronic image data.

  In the above configuration, when normal copying is performed, the RGB signal read by the scanner unit 24 is converted into the CIELAB signal by the front color conversion unit 52, and the CIELAB signal is converted from the CIELAB signal to the CMYK signal by the rear color conversion unit 54. The converted CMYK signal is sent to the printer unit 26 via the printer unit interface 44 and printed out by the printer unit 26. When performing normal printing, the PDL input via the network interface 48 is analyzed by the image analysis unit 56 and a raster image is generated by the first raster image generation unit 58. This raster image is converted into a raster image. The color conversion unit 62 converts the CIELAB signal into a CIELAB signal, and the converted CMYK signal is sent to the printer unit 26 via the printer unit interface 44 and printed out by the printer unit 26, or the image analysis unit 56 uses the CMYK signal. The converted CMYK signal is sent to the printer unit 26 via the printer unit interface 44, and is printed out by the printer unit 26.

FIG. 4 shows a control flow for obtaining color reproduction characteristics using the system of the first embodiment.
First, in step 10 (S10), the input PDL document image is analyzed by the image analysis unit 56. In the next step 12 (S12), the first raster image generation unit 58 or the second raster image generation unit 60 generates a raster image that is an RGB signal. In the next step 14 (S14), the raster image generated in step 12 is stored in the image storage unit 64. In the next step 16 (S16), the raster image generated in step 12 is converted into a CIELAB signal by the raster image color conversion unit 62. In the next step 18 (S18), the subsequent color conversion unit 54 converts the CIELAB signal from the CIELAB signal. The data is converted into a CMYK signal and printed out by the printer unit 26 via the printer unit interface 46. In step 20 (S20), the original image output in step 18 is scanned and read by the scanner unit 24. In the next step 22 (S22), the read RGB read image is converted from the RGB signal to the CIELAB signal by the pre-stage color conversion unit 52, and in the next step 24 (S24), the read image converted to CIELAB is the preprocessing unit. 66. Preprocess. In the next step 26 (S26), the corresponding colors of the RGB original image stored in the image storage unit 64 in step 14 and the CIELAB read image preprocessed in step 24 are extracted.

FIG. 5 shows a second embodiment relating to the software configuration of the color multifunction peripheral 14 realized by a program stored in the program ROM.
In the second embodiment, a first color conversion unit 70 is provided instead of the preceding color conversion unit 52 and the subsequent color conversion unit 54 of the first embodiment. The first color conversion unit 70 converts the RGB signal from the scanner unit interface and the RGB signal from the raster image color conversion unit 62 into a YMCK signal. Further, the corresponding color extraction unit 68 extracts the corresponding color between the RGB original image stored in the image storage unit 64 and the RGB read image read by the scanner unit 24. The second color conversion unit 72 converts the RGB read compatible color extracted by the corresponding color extraction unit 68 into a CIELAB read compatible color (or CIEXYZ), and the correspondence between the RGB original color and the CIELAB read color (or CIEXYZ). obtain.

FIG. 6 shows a control flow for obtaining color reproduction characteristics using the system of the second embodiment.
The processing from step 30 (S30), step 32 (S32), step 34 (S34), step 36 (S36) and step 38 (S38) is from step 10 to step 18 shown in the first embodiment. This is the same as the process. In step 40 (S40), preprocessing is performed on the RGB read image read by the scanner unit 24. In the next step 42 (S42), the corresponding colors of the RGB read image and the RGB original image are extracted. In the next step 44 (S44), the RGB read corresponding color extracted by the corresponding color extracting unit 68 is converted into a CIELAB read compatible color (or CIEXYZ), and the correspondence between the RGB original color and the CIELAB read color (or CIEXYZ). Get a relationship.

Next, the above-described preprocessing method will be described.
As shown in FIG. 7, first, in step 50 (S50), direction alignment processing is performed. This orientation adjustment processing is performed because there is a possibility that the orientation of the original placed on the platen is incorrect when the scanner unit 24 scans. For example, the read image is divided into a plurality of areas, the color distribution (lightness distribution, hue distribution, etc.) between the areas is compared with the distribution of the original image, the correlation is extracted, and the read image orientation is incorrect. In this case, the read image is rotated to match the orientation of the original image. In the next step 52 (S52), magnification and skew correction are performed. For example, an edge image is generated for each of the original image and the read image using a differential filter or the like, and magnification correction and skew correction are performed so that both edge images overlap as much as possible. When the document image is continuously input, the magnification correction and skew correction parameters may be calculated and sent to the scanner unit 24 so that the scanner unit 24 performs the magnification correction and the skew correction. In the next step 54 (S54), the original image printed out by the printer unit 26 is screened. Therefore, when the original image is read by the scanner unit 24, a filter process is performed so that no screen remains. .

Next, the corresponding color extraction method will be described.
As shown in FIGS. 8 and 9, first, in step 60 (S60), the document image is divided into blocks so as to extract pixel values of, for example, 5 × 5 blocks. The document image is first blocked from, for example, the upper left corner of the document image. In the next step 62 (S62), it is determined whether or not pixel values (eg, RGB values) of the document image belonging to the block meet a predetermined determination condition. Whether the determination condition is determined by comparing the standard deviation or average value of the pixel values belonging to the block with a predetermined value, or comparing the difference between the maximum value and the minimum value of the pixel value belonging to the block with a predetermined value. You can decide whether or not. As shown in FIGS. 10 and 11, for example, if the determination condition is determined to be an area where the standard deviations σ of the RGB channels are all 16 or less, R is 0 and G is 13.84 in the block shown in FIG. 10. , B is adopted because it is 13.84, but in the block shown in FIG. 11, it is not adopted because R is 99.44, G is 102.12, and B is 0. Also, as shown in FIG. 12 and FIG. 13, if Δ (maximum value−minimum value) of each channel of RGB values is determined as an area of 64 or less as a determination condition, R is 0 and G is set in the block shown in FIG. 51 and R are adopted because 51, but in the block shown in FIG. 13, R is 255, G is 255, and B is 0.

  If it is determined in step 62 that the block matches the determination condition, the process proceeds to step 64 (S64), the block is set as a corresponding color extraction block, and the process proceeds to the next step 66 (S66). If it is determined in step 62 that the block does not meet the determination condition, the process proceeds to step 66, and the block is moved, for example, by one pixel in the column direction. In the next step 68 (S68), it is determined whether or not the corresponding color extraction block has been determined for the blocks up to the lower right corner of the original image. If it is determined in step 68 that all the corresponding color extraction blocks have not been determined, the process returns to step 62. If it is determined in step 68 that all the corresponding color extraction blocks have been determined, the corresponding color is determined in the next step 70 (S70).

  As shown in FIG. 14, the corresponding color is determined by each block belonging to a block smaller than the corresponding color extracting block 74 of the original image (in this example, a 4 × 4 block excluding the periphery of the corresponding color extracting block 74). The average value of the pixel values and the average of each pixel value belonging to a block smaller than the corresponding color extraction block 76 of the corresponding read image (in this example, a 4 × 4 block excluding the periphery of the corresponding color extraction block 76) Associate a value. Further, as shown in FIG. 15, each pixel value of the center pixel of the corresponding color extraction block 74 of the original image is associated with each pixel value of the center pixel of the corresponding color extraction block 76 of the corresponding read image. Also good. Further, the median of the pixel values in the corresponding color extraction block 74 of the original image may be associated with the median of the pixel values in the corresponding color extraction block 76 of the corresponding read image.

  16 and 17 show another embodiment related to the corresponding color extraction method. In the above-described embodiment, an area is extracted from an original image based on a predetermined determination condition, and a corresponding color is extracted from the extracted area. In this embodiment, a histogram is used. It is intended to be used.

  That is, as shown in FIG. 16, first, in step 80 (S80), the neighboring colors of the read image are collected. In the next step 82 (S82), a histogram for the original image use color is generated, and a read image use color histogram in which the neighboring colors are collected in step 80 is generated. In the next step 84 (S84), the histogram of the document image and the histogram of the read image are associated in descending order of frequency. In the next step 86 (S86), the frequency error is corrected. Since there is a possibility that there is an error in the frequency order due to an error, for example, referring to the color characteristics (hue, saturation, brightness) of the original image and the read image, if there is an error in the frequency order, the error is corrected (the order is changed, etc.) )I do.

As described above, the color reproduction characteristics can be acquired using the color multifunction peripheral 26, but the server 28 can also be used as another method.
That is, as shown in FIG. 18, the server 28 includes a read image input unit 78, a raster image input unit 80, a color conversion unit 82, and a corresponding color extraction unit 84. An RGB read image obtained by reading an original image by the scanner unit 24 of the color multifunction machine 18 is input to the read image input unit 78 via a network. A raster image input unit 80 receives a color raster format original image from the color multifunction peripheral 18 via a network. The color conversion unit 82 converts the RGB read image into colorimetric values such as CIELAB. The corresponding color extracting unit 84 corresponds to the color of the original image device signal (RGB or the like) input via the raster image input unit 80 and the reproduced color (CIELAB or the like) of the read image color-converted by the color converting unit 82. And the corresponding data can be obtained. As shown in FIG. 19, the server 28 is provided with a PDL image input unit 86 and a raster image generation unit 88. The PDL image input unit 86 inputs a document image in PDL format from the color multifunction device 26 or the personal computer 14 described above. Then, the corresponding color between the device signal (RGB, etc.) of the original image generated by the raster image generation unit 88 in the corresponding color extraction unit 84 and the reproduced color (CIELAB, etc.) of the read image color-converted by the color conversion unit 82 is obtained. It is possible to extract and obtain corresponding data.
When the read image is sent to an output device such as a print center, the original image can be garbled or the layout can be confirmed in addition to the color calibration of the read image.

  As described above, the present invention can be used in a system for efficiently performing color reproduction on a specified document. The printed sample can be used as it is as a color proof sample (color sample) after scanning, and can accurately convey the color reproduction state of the printer unit without performing unnecessary printing such as color patches.

It is a block diagram which shows the color reproduction characteristic acquisition system which concerns on embodiment of this invention. FIG. 2 is a block diagram showing a hardware configuration of a color multifunction peripheral used in an embodiment of the present invention. It is a block diagram which shows 1st Embodiment regarding the software configuration of this invention. 3 is a flowchart illustrating a first embodiment relating to acquisition of color reproduction characteristics according to the present invention. It is a block diagram which shows 2nd Embodiment regarding the software configuration of this invention. It is a flowchart which shows 2nd Embodiment regarding the color reproduction characteristic acquisition of this invention. It is a flowchart which shows embodiment regarding the pre-processing of this invention. It is a flowchart which shows 1st Embodiment regarding the corresponding color extraction of this invention. It is a figure which shows the 1st determination state at the time of using a standard deviation for the determination conditions regarding the block extraction of this invention. It is a figure which shows the 2nd determination state at the time of using a standard deviation for the determination conditions regarding block extraction of this invention. It is a figure which shows the 1st determination state at the time of using the difference of the maximum value and the minimum value for the determination conditions regarding block extraction of this invention. It is a figure which shows the 2nd determination state at the time of using the difference of the maximum value and the minimum value for the determination conditions regarding block extraction of this invention. It is a figure which shows the 1st determination state at the time of using a standard deviation for the determination conditions regarding the block extraction of this invention. It is explanatory drawing at the time of using the inner average value regarding the corresponding color determination of this invention. It is explanatory drawing at the time of using a center value regarding the corresponding color determination of this invention. It is a flowchart which shows 2nd Embodiment regarding the corresponding color extraction of this invention. It is explanatory drawing at the time of using a histogram for the corresponding color extraction of this invention. It is a block diagram which shows 1st Embodiment which performed the corresponding color extraction of this invention with the server. It is a block diagram which shows 2nd Embodiment which performed the corresponding color extraction of this invention with the server.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Color reproduction characteristic acquisition system 18 Color compound machine 20 Charging apparatus 22 Display part 24 Scanner part 26 Printer part 28 Server 52 Pre-stage color conversion part 54 Post-stage color conversion part 56 Image analysis part 58 1st raster image generation part 60 2nd Raster image generation unit 64 Image storage unit 66 Preprocessing unit 68 Corresponding color extraction unit 70 First color conversion unit 72 Second color conversion unit 73 Color space 74 Original image block 76 Read image block 78 Read image input unit 80 Raster image input unit 82 Color conversion unit 84 Corresponding color extraction unit 86 PDL image input unit 88 Raster image generation unit

Claims (16)

  Based on the original electronic image data, the original image is output by the image printing means, the output original image is read by the image reading means, and the corresponding color between the read original reading data and the original electronic image data is extracted. Color reproduction characteristic acquisition method for acquiring color reproduction characteristics.   The color reproduction characteristic acquisition method according to claim 1, wherein the extraction of the corresponding color is performed by extracting an area from the original image based on a predetermined determination criterion and performing the extraction on the extracted area.   The color reproduction characteristic acquisition method according to claim 2, wherein the extraction of the corresponding color is performed by associating the center value of the extracted area of the original image with the center value of the corresponding read image.   The color reproduction characteristic acquisition method according to claim 2, wherein the extraction of the corresponding color is performed by associating the average value of the central area having a size smaller than the extracted original image area with the average value of the corresponding read image.   The color reproduction characteristic acquisition method according to claim 2, wherein the corresponding color is extracted by associating the pixel value at the center in the region of the extracted document image with the pixel value at the center in the region of the corresponding read image.   The color reproduction characteristic acquisition method according to claim 2, wherein the extraction of the corresponding color is performed by comparing the color histogram generated from the original image with the color histogram generated from the read image and associating them in a frequency order.   The color reproduction acquisition method according to claim 6, wherein an error in the frequency order is corrected based on the color characteristics of the original image and the read image.   The color reproduction characteristic acquisition method according to claim 1, wherein the characteristics of the original image and the read image are compared to align the directions of the original image and the read image, and then the corresponding color is extracted.   9. The color reproduction characteristic acquisition method according to claim 1, wherein the characteristics of the original image and the read image are compared to correct the magnification of the original image and the read image, and then the corresponding color is extracted.   The color reproduction characteristic acquisition method according to claim 1, wherein the skew between the original image and the read image is corrected by comparing the characteristics of the original image and the read image, and then the corresponding color is extracted.   The color reproduction characteristic acquisition method according to claim 1, wherein the screen is removed from the read image.   Image printing means, image reading means, and correspondence for extracting the corresponding colors of the original reading data obtained by reading the original image printed by the image printing means by the image reading means and the original electronic image data based on the original electronic image data A color reproduction characteristic acquisition system having color extraction means.   Image printing means, image reading means, storage means for storing original electronic image data, original reading data obtained by reading an original image printed by the image printing means by the image reading means, and originals stored in the storage means A color reproduction characteristic acquisition system comprising: a corresponding color extraction unit that extracts a corresponding color with electronic image data.   Image printing means; image reading means; device signal image generating means for generating a device signal image from original electronic image data; original reading data obtained by reading an original image printed by the image printing means by the image reading means; A color reproduction characteristic acquisition system comprising: a corresponding color extracting unit that extracts a corresponding color with the device signal image generated by the device signal image generating unit.   Image input means for inputting original electronic image data, original read data obtained by reading an original image printed by image printing means based on the original electronic image data by image reading means, and original electronic image data input by the image input means Color reproduction characteristic acquisition system that extracts the corresponding color.   Image printing means, image reading means, image input means for inputting original electronic image data, and original reading data obtained by reading an original image printed by the image printing means based on the original electronic image data by the image reading means A color reproduction characteristic acquisition system for extracting a color corresponding to original electronic image data input by the image input means.

Images