JP2007059968A - Unit and method for processing image, image reader, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing unit for converting an optically read image to a high-quality image. <P>SOLUTION: The image processing unit 20 corrects irregularity in read related to a chromatic color component to image data read by an image reading unit 12. More concretely, the image processing unit 20 has a four-dimensional DLUT allowing color data whose irregularity is corrected to correspond to an input data set comprising a read position and a plurality of color data. By using the four-dimensional DLUT, correction processing (irregularity correction processing) according to the read position is performed to the image data read by the image reading unit 12. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image reading apparatus that suppresses color variation in an image.

For example, Patent Document 1 discloses a method of realizing in-plane unevenness correction of a scanner by shading correction and black correction using a white reference plate.
JP-A-11-252361

  The present invention has been made from the above-described background, and an object thereof is to provide an image processing apparatus that converts an optically read image into a higher quality image.

[Image processing device]
In order to achieve the above object, an image processing apparatus according to the present invention is an image processing apparatus that performs image processing on an input image read by an image reading apparatus, and a position that specifies a reading position of the input image And a color variation correcting unit that performs color variation correction processing for suppressing color variation of at least a chromatic color component on the image data of the input image in accordance with the reading position identified by the position identifying unit. .

  Preferably, the apparatus further includes a correction table for associating the input data set including the color data and the sample value of the reading position with the output color data in which the color fluctuation generated at the reading position is suppressed, The means uses the correction table to calculate the color data corresponding to the reading position specified by the position specifying means and the color data of the input image as color data subjected to the color variation correction processing.

  Preferably, the color data includes gradation values of a plurality of color components, and the correction table is an input data set including a plurality of color component sample values and a reading position sample value. On the other hand, the output gradation values of the respective color components are associated with each other, and the color variation correcting means corresponds to the reading position specified by the position specifying means and the gradation values of a plurality of color components of the input image. The gradation value of each color component is calculated.

  Preferably, the image processing apparatus further includes color conversion means for converting image data of the input image expressed in the first color space into image data expressed in the second color space, and the correction table includes The output color data expressed in the second color space is associated with the input data set including the sample value of the color data expressed in the color space, and the color variation correcting means is controlled by the color converting means. A color variation correction process is performed on the converted image data of the second color space using the correction table.

  Preferably, the apparatus further includes correction table correction means for correcting data associated with the correction table, and the color fluctuation correction means uses the correction table corrected by the correction table correction means to perform color fluctuation correction processing. I do.

  Preferably, the correction table stores color data generated based on image data read by an image reading device from a predetermined color sample as color data of the input data set, and performs colorimetry from the color sample. Color data generated based on colorimetric values measured by a measuring device is stored as the output color data, and the position specifying unit obtains a reading position of an input image from the image reading device, and the color variation The correction unit performs color variation correction processing according to the reading position acquired from the image reading apparatus, using the correction table.

[Image reading device]
The image reading apparatus according to the present invention includes at least an image reading unit that optically reads an image from a document and image data read from the document according to a reading position read by the image reading unit. Color variation correction means for performing color variation correction processing for suppressing color variation of the chromatic component.

[Image processing method]
An image processing method according to the present invention is an image processing method for performing image processing on an input image read by an image reading apparatus, and specifies a reading position of the input image and sets the specified reading position to the specified reading position. Accordingly, color variation correction processing that suppresses at least color variation of the chromatic color component is performed on the image data of the input image.

[program]
According to another aspect of the invention, there is provided a computer program for performing image processing on an input image read by an image reading device, the step of specifying a reading position of the input image, and an input according to the specified reading position. Causing the computer to execute a step of performing color variation correction processing for suppressing color variation of at least a chromatic color component on the image data of the image.

  According to the image processing apparatus of the present invention, an optically read image can have higher image quality.

[Hardware configuration]
First, the printer apparatus 10 to which the present invention is applied will be described.
FIG. 1 is a diagram illustrating a configuration of a tandem type printer apparatus 10.
As shown in FIG. 1, the printer device 10 includes an image reading unit 12, an image forming unit 14, an intermediate transfer belt 16, a paper tray 17, a paper conveyance path 18, a fixing device 19, and an image processing device 20. In addition to a printer function for printing image data received from a client PC, a scanner function for reading an image from a document and transmitting the image to the client PC, and a function as a full-color copying machine using the image reading apparatus 12. Alternatively, it may be a multifunction device having a function as a facsimile.

First, the outline of the printer apparatus 10 will be described. An image reading apparatus 12 and an image processing apparatus 20 are disposed above the printer apparatus 10 and function as image data input means. The image reading device 12 reads an image displayed on the document and outputs it to the image processing device 20. The image processing apparatus 20 performs image processing such as color conversion, gradation correction, and resolution correction on the image data input from the image reading apparatus 12 and outputs the processed image data to the image forming unit 14.
Below the image reading device 12, a plurality of image forming units 14 are arranged corresponding to the colors constituting the color image. In this example, the first image forming unit 14K, the second image forming unit 14Y, and the third image forming corresponding to each color of black (K), yellow (Y), magenta (M), and cyan (C). The unit 14M and the fourth image forming unit 14C are arranged horizontally along the intermediate transfer belt 16 with a certain interval. The intermediate transfer belt 16 rotates as an intermediate transfer member in the direction of an arrow A in the figure, and these four image forming units 14K, 14Y, 14M, and 14C are configured based on the image data input from the image processing apparatus 20. The toner images are sequentially formed and transferred (primary transfer) to the intermediate transfer belt 16 at a timing at which the plurality of toner images are superimposed on each other. The order of the colors of the image forming units 14K, 14Y, 14M, and 14C is not limited to the order of black (K), yellow (Y), magenta (M), and cyan (C). ), Magenta (M), cyan (C), black (K), and the like.

  The sheet conveyance path 18 is disposed below the intermediate transfer belt 16. The recording paper 32 supplied from the paper tray 17 is transported on the paper transport path 18, and the toner images of each color transferred onto the intermediate transfer belt 16 are collectively transferred (secondary transfer). The transferred toner image is fixed by the fixing device 19 and discharged to the outside along the arrow B.

Next, each configuration of the printer device 10 will be described in more detail.
As shown in FIG. 1, the image reading unit 12 reads a platen glass 124 on which a document is placed, a platen cover 122 that presses the document onto the platen glass 124, and an image of the document placed on the platen glass 124. An image reading device 130 (image reading means).
The image reading apparatus 130 illuminates a document placed on the platen glass 124 with a light source 132, and reflects a reflected light image from the document into a full-rate mirror 134, a first half-rate mirror 135, and a second half-rate mirror. Scanning exposure is performed on an image reading element 138 made of a CCD or the like via a reduction optical system consisting of 136 and an imaging lens 137, and the color material reflected light image of the original 30 is given a predetermined dot density (by this image reading element 138. For example, it is configured to read at 16 dots / mm).

The image processing apparatus 20 performs predetermined image processing such as shading correction, document position shift correction, gamma correction, frame deletion, color / movement editing, and the like on the image data read by the image reading unit 12.
In this example, the color material reflected light image of the document read by the image reading unit 12 is, for example, the document reflectance of three colors of red (R), green (G), and blue (B) (each 8 bits). The original color material gradation data of four colors of yellow (Y), magenta (M), cyan (C), and black (K) (each 8 bits: 256 gradations) by image processing by the image processing apparatus 20 Is converted to

The first image forming unit 14K, the second image forming unit 14Y, the third image forming unit 14M, and the fourth image forming unit 14C are arranged and formed in parallel at a certain interval in the horizontal direction. The configuration is almost the same except that the color of the image is different. Accordingly, the first image forming unit 14K will be described below. The configuration of each image forming unit 14 is distinguished by adding K, Y, M, or C.
The image forming unit 14K forms an electrostatic latent image by an optical scanning device 140K that scans a laser beam in accordance with image data input from the image processing device 20, and a laser beam scanned by the optical scanning device 140K. And an image forming apparatus 150K.

The optical scanning device 140K modulates the semiconductor laser 142K according to the black (K) image data, and emits the laser light LB (K) from the semiconductor laser 142K according to the image data. The laser beam LB (K) emitted from the semiconductor laser 142K is applied to the rotary polygon mirror 146K via the first reflection mirror 143K and the second reflection mirror 144K, and is deflected and scanned by the rotation polygon mirror 146K. The light is irradiated onto the photosensitive drum 152K of the image forming apparatus 150K through the second reflecting mirror 144K, the third reflecting mirror 148K, and the fourth reflecting mirror 149K.
The image forming apparatus 150K includes a photosensitive drum 152K as an image carrier that rotates at a predetermined rotational speed in the direction of arrow A, and primary charging as a charging unit that uniformly charges the surface of the photosensitive drum 152K. And a developing device 156K for developing the electrostatic latent image formed on the photosensitive drum 154K, and a cleaning device 158K. The photosensitive drum 152K is uniformly charged by the scorotron 154K, and an electrostatic latent image is formed by the laser beam LB (K) irradiated by the optical scanning device 140K. The electrostatic latent image formed on the photosensitive drum 152K is developed with black (K) toner by the developing device 156K and transferred to the intermediate transfer belt 16. Residual toner, paper dust, and the like adhering to the photosensitive drum 152K after the toner image transfer process are removed by the cleaning device 158K.
The other image forming units 14Y, 14M, and 14C also form yellow (Y), magenta (M), and cyan (C) toner images in the same manner as described above, and intermediately transfer the formed toner images of the respective colors. Transfer to belt 16.

The intermediate transfer belt 16 has a constant tension between the drive roll 164, the first idle roll 165, the steering roll 166, the second idle roll 167, the backup roll 168, and the third idle roll 169. The drive roll 164 is rotationally driven by a drive motor (not shown), and is circulated at a predetermined speed in the direction of arrow A. The intermediate transfer belt 16 is formed into an endless belt by, for example, forming a flexible synthetic resin film such as polyimide in a belt shape and connecting both ends of the synthetic resin film formed in a belt shape by welding or the like. It has been done.
Further, the intermediate transfer belt 16 includes a first primary transfer roll 162K, a second primary transfer roll 162Y, a third primary transfer roll 162M, and a position facing the image forming units 14K, 14Y, 14M, and 14C, respectively. A fourth primary transfer roll 162C is provided, and the toner images of the respective colors formed on the photosensitive drums 152K, 152Y, 152M, and 152C are transferred onto the intermediate transfer belt 16 in a multiple manner by these primary transfer rolls 162. The The residual toner adhering to the intermediate transfer belt 16 is removed by a cleaning blade or brush of a belt cleaning device 189 provided downstream of the secondary transfer position.

In the paper transport path 18, a paper feed roller 181 for taking out the recording paper 32 from the paper tray 17, a first roller pair 182, a second roller pair 183 and a third roller pair 184 for paper transport, and a recording paper A registration roll 185 is provided which conveys 32 to the secondary transfer position at a predetermined timing.
In addition, a secondary transfer roll 185 that is in pressure contact with the backup roll 168 is disposed at the secondary transfer position on the paper transport path 18, and each color toner image transferred onto the intermediate transfer belt 16 is Secondary transfer is performed on the recording paper 32 by the pressing force and electrostatic force of the secondary transfer roll 185. The recording paper 32 onto which the toner image of each color is transferred is conveyed to the fixing device 19 by the first conveyance belt 186 and the second conveyance belt 187.
The fixing device 19 melts and fixes the toner to the recording paper 32 by performing heat treatment and pressure treatment on the recording paper 32 to which the toner images of the respective colors are transferred.

[background]
As a problem of the image reading unit 12 illustrated in FIG. 1, in-plane reading unevenness may occur due to variations in light receiving sensitivity when a certain amount of light is applied to the image reading element 138 made of a CCD or the like.
As means for solving this, shading correction (for example, Patent Document 1) for correcting variations in light receiving sensitivity based on reading data of a white reference plate is widely used.
However, since there is a variation in spectral sensitivity depending on the reading position of the optical system provided in the image reading unit 12, in the shading correction by the normal white reference plate, the reading unevenness in the plane of the image reading unit 12 is completely corrected. There is a problem that it is not done.

2A illustrates an example of uneven reading when a yellow color sample is read, and FIG. 2B illustrates an example of uneven reading when a red color sample is read. It is. In this figure, the horizontal axis indicates the position of the image reading unit 12 in the main scanning direction (that is, the position of the image reading element 138), and the vertical axis indicates the color reading value by the image reading unit 12 and the colorimeter. Represents the color difference from the colorimetric value. 2A shows an evaluation result when a uniform yellow color sample is read by the image reading unit 12, and FIG. 2B shows a uniform red color sample read by the image reading unit 12. It is an evaluation result in the case of.
As illustrated in FIG. 2, in yellow (Yellow), there is almost no in-plane reading unevenness even with normal shading correction, but in red (Red), there is one or more reading unevenness due to color difference. I understand.

It should be noted that reading unevenness with a color difference of about 1 has not been a problem because it is not a concern when visually recognized by humans, but it becomes a problem when the image reading unit 12 is used like a colorimeter.
For example, it is considered that a test chart formed on the recording paper 32 by the image forming unit 14 is read by the image reading unit 12 to correct in-plane unevenness (image forming unevenness) caused by the image forming unit 14. In such a case, the reading unevenness of the image reading unit 12 becomes a problem because it adversely affects the correction accuracy of the image forming unevenness.

  Therefore, the printer device 10 according to the first embodiment corrects the reading unevenness related to the chromatic color component with respect to the image data read by the image reading unit 12. Since uneven reading occurs according to the reading position of the image reading unit 12, the printer apparatus 10 performs correction related to a plurality of color components according to the reading position.

[First Embodiment]
First, a first embodiment of the present invention will be described.
FIG. 3 is a diagram illustrating a functional configuration of the image processing program 5 which is executed by the image processing apparatus 20 (FIG. 1) and implements the image processing method according to the present invention.
As illustrated in FIG. 3, the image processing program 5 includes a color conversion unit 510, a reading position specifying unit 520, a parameter correcting unit 530, and an unevenness correcting unit 540.

In the image processing program 5, the color conversion unit 510 converts the input image data (RGB in this example) into image data (Lab) in the Lab color space, and outputs the image data to the unevenness correction unit 540.
As a color conversion method of the color conversion unit 510, known matrix conversion, DLUT conversion, or the like can be used. As a method for determining the color conversion parameter, it is proposed in Japanese Patent Application Laid-Open No. Sho 62-101181, or ANSI IT8.7 / 1 1993 and ANSI IT8.7 / 2 1993 Graphics Technology Color Transmission Target / Color Reflection Target for Input Scanner Calibration. As shown, the color sample with known color characteristics (L * a * b *, etc.) is scanned by the image reading unit 12 (FIG. 1), and the correspondence between the RGB values obtained here and the color characteristics of the color sample is obtained. From the relationship, it is possible to determine the color conversion parameters.
In this example, a case where the conversion destination is the Lab color space will be described as a specific example, but another device-independent color space such as an L * a * b * color space may be used.

The reading position specifying unit 520 specifies an image reading position.
The reading position specifying unit 520 of this example applies the position data input from the image reading unit 12 as it is. The position data in this example is a coordinate X indicating the position of the image reading unit 12 in the main scanning direction (that is, the direction in which a plurality of image reading elements are arranged).
Note that the reading position specifying unit 520 may specify the reading position in the sub-scanning direction in addition to the main scanning direction. The reading position specifying unit 520 may specify the reading position based on the reading start position in the image and the relative position in the image.

  The parameter correction unit 530 corrects the correction parameter applied by the unevenness correction unit 540 when a change in characteristics of the image reading unit 12 (FIG. 1) with time occurs. The correction parameter is a parameter for correcting color variation (that is, reading unevenness) that occurs in the read image.

The unevenness correction unit 540 uses the correction parameter provided from the parameter correction unit 530 to respond to the image data (Lab) input from the color conversion unit 510 according to the reading position specified by the reading position specifying unit 520. Correction processing is performed. This correction process converts the pixel value so as to suppress color variation that occurs in the plane of the image read by the image reading unit 12.
The unevenness correction unit 540 in this example uses color data (in-plane uniformity in the main scanning direction corrected) based on the input color data (Lab) of each pixel and the position data (coordinate X) of each pixel. L′ a′b ′) is calculated.

FIG. 4 is a diagram for explaining the unevenness correction unit 540 shown in FIG. 3 in more detail.
As illustrated in FIG. 4, the unevenness correction unit 540 includes a four-dimensional lookup table (four-dimensional LUT) 542, a lookup table reference unit (LUT reference unit) 544, and an interpolation processing unit 546.
The four-dimensional LUT 542 holds the correction parameter for unevenness correction provided from the parameter correction unit 530 (FIG. 3) as a lookup table.
The four-dimensional LUT 542 of the present example uses an image reading unit 12 for an input data set consisting of three color data (L value, a value, b value) and reading position data (coordinate X) in the main scanning direction. A four-dimensional table for associating output color data (L value, a value, and b value) in which in-plane unevenness occurring in an image to be read is corrected is held.
Note that the four-dimensional LUT 542 of this example does not store output color data corresponding to all the input data sets that may exist in order to reduce the data size of the table, but instead of input consisting of grid points at predetermined intervals. Only the output color data corresponding to the data set is stored. That is, the four-dimensional LUT 542 of this example holds an input data set and output color data thinned out at a predetermined interval as a look-up table. Hereinafter, the input data set existing in the lookup table is referred to as a grid point.

The LUT reference unit 544 reads output color data corresponding to the image data (color data and position data) input from the color conversion unit 510 (FIG. 3) with reference to the four-dimensional LUT 542, and the read output color Data is output to the interpolation processing unit 546.
The LUT reference unit 544 of this example, when the input image data matches the lattice point held in the four-dimensional LUT 542, output color data (L value, a value, and b value) corresponding to this lattice point. Is output to the interpolation processing unit 546. When the input image data does not match the grid points held in the four-dimensional LUT 542, output color data corresponding to a plurality of grid points in the vicinity of the image data is output. The values of these grid points are output to the interpolation processing unit 540.

  The interpolation processing unit 546 performs an interpolation process and calculates output color data corresponding to the input image data. More specifically, the interpolation processing unit 546 applies a predetermined interpolation method, the image data input from the color conversion unit 510, the output color data input from the LUT reference unit 544, and the values of the grid points. Based on the above, image data subjected to unevenness correction is calculated. The interpolation method is, for example, an n-dimensional (four-dimensional in this example) linear interpolation method, a cube interpolation method for calculating an interpolation value based on the volume of an n-dimensional cube, or an interpolation value based on the volume of an n-dimensional tetrahedron. The interpolation processing unit 546 of this example uses a hypercube interpolation method or a hypertetrahedral interpolation method.

FIG. 5 is a diagram for explaining a parameter creation method by the parameter correction unit 530 (FIG. 3). FIG. 5A illustrates a color sample 900 used for creating a correction parameter, and FIG. The correction parameters created by the parameter correction unit 530 are exemplified. In the drawing, the left-right direction corresponds to the main scanning direction of the image reading unit 12, and the up-down direction corresponds to the sub-scanning direction of the image reading unit 12.
As illustrated in FIG. 5A, the color sample 900 includes a plurality of color patches 902 having major axes in the main scanning direction. The plurality of color patches 902 </ b> A to 902 </ b> G are substantially uniformly coated with different colors and are arranged in the sub-scanning direction. The length of each color patch 902 in the major axis (main scanning direction) corresponds to the image reading element 138 (FIG. 1) of the image reading unit 12.
The color sample 900 uses, for example, an image output device (printer device 10 or the like) such as a printing press or electrophotography, and the YMC area ratio is 20% increments (0, 20, 40, 60, 80, 100%). This is created by forming a color patch 902 of 6 × 6 × 6 = 216 colors by all the combinations. The correction accuracy may be further improved by making the area ratio interval finer.
The color sample 900 can obtain a high correction accuracy by using an image output device having a spectral characteristic close to that of a reflection object to be read by the image reading unit 12.

First, the color patch 902 included in the color sample 900 is measured by a colorimeter at predetermined intervals of the reading position (coordinate X) in the main scanning direction, and the measured color characteristics L, a, and b are shown in FIG. As illustrated in (B), the color correction value L′ a′b ′ is input to the parameter correction unit 530 in association with the reading position.
In this example, the color characteristic Lab is measured at intervals of 10 mm with respect to the main scanning direction reading width (300 mm) of the image reading unit 12.
Note that the correction accuracy may be improved by reducing the interval between the read coordinate positions.

Next, the color sample 900 is scanned by the image reading unit 12, and the RGB value read here is color-converted into a Lab value, and the color-converted Lab is associated with a reading position as a reading value (Lab). Input to the parameter correction unit 530.
As described above, as illustrated in FIG. 5B, the reading value (Lab) read by the image reading unit 12 and the measurement value measured by the colorimeter are associated with each reading position (coordinate X). The color value (L′ a′b ′) is input to the parameter correction unit 530.
The parameter correction unit 530 uses the reading position (coordinate X) and the reading value (Lab value) illustrated in FIG. 5B as lattice points of the input data set, and the colorimetric values (corresponding to these reading position and reading value ( A lookup table is created using L′ a′b ′) as grid points of the output color data, and the created lookup table is provided to the unevenness correction unit 540. Each value stored in the lookup table is an example of a correction parameter.

[Operation]
Next, the operation of the image processing program 5 will be described.
FIG. 6 is a flowchart for explaining the image reading operation (S10) of the printer apparatus 10 (image processing program 5).

As shown in FIG. 6, in step 100 (S100), when the user places an original 30 on the platen glass 124 (FIG. 1) and instructs to read an image, the printer 10 sends the image reading unit 12 to the image reading unit 12 from the original 30. The image is read optically.
In the present example, the read image data is image data (R value, G value, and B value) in the RGB color space, and is input to the image processing apparatus 20.

  In step 110 (S110), the color conversion unit 510 (FIG. 3) of the image processing apparatus 20 (image processing program 5) converts the image data (RGB) read by the image reading unit 12 into image data (Lab color space). Lab).

In step 120 (S120), the image processing program 5 sets the pixel of interest in the scanning order from the input image data.
In this example, scanning is performed downstream one pixel at a time from the upstream end in the main scanning direction, and when scanning to the downstream end of this line, the next line is moved in the sub-scanning direction and the next line is moved in the main scanning direction. A case where scanning is similarly performed from the upstream end will be described as a specific example.

  In step 130 (S130), the reading position specifying unit 520 (FIG. 3) specifies the reading position (coordinate X) of the target pixel in the main scanning direction based on the reading position data input from the image reading unit 12. The identified reading position (coordinate X) is output to the unevenness correction unit 540.

  In step 140 (S140), the LUT reference unit 544 (FIG. 4) of the unevenness correction unit 540 refers to the four-dimensional LUT 542 (FIG. 5B), the color data (Lab) of the target pixel, and the reading position. Output color data (L′ a′b ′) corresponding to the position data (coordinate X in the main scanning direction) input from the specifying unit 520 is read, and the read output color data is output to the interpolation processing unit 546. The output color data to be read out includes at least one set of L ′ value, a ′ value, and b ′ value.

  In step 150 (S150), the interpolation processing unit 546 calculates an interpolation value based on the color data (L′ a′b ′) read out by the LUT reference unit 544, and uses the calculated interpolation value as the target pixel. Is output as color data. Note that when the output color data to be read is one (that is, when the input color data and position data coincide with the grid points), the output color data is output as it is.

  In step 160 (S160), the image processing program 5 determines whether or not the processing has been completed for all the pixels, and if there is an unprocessed pixel, the process returns to the processing of S120 and the next pixel of interest. Is set, and when the process is completed for all pixels, the process (S10) is terminated.

FIG. 7 is a diagram for explaining the effect of the present embodiment. FIG. 7A illustrates reading unevenness when a yellow color sample is read (corresponding to FIG. 2A). FIG. 7B is a diagram illustrating reading unevenness when a red color sample is read (corresponding to FIG. 2B).
As illustrated in FIGS. 7A and 7B, it can be seen that the reading unevenness seen in FIGS. 2A and 2B is completely corrected. 2A and 2B, an error over the entire reading position between the color reading value read by the image reading unit 12 and the color measurement value measured by the colorimeter (FIG. 2 ( In FIG. 7A and FIG. 7B, this error is almost zero, although a color difference of about 1 in A) and a color difference of about 2 in FIG.
This error is caused by a color conversion error of the color conversion unit 510 and becomes a problem when a color conversion method with low conversion accuracy such as matrix conversion is adopted. However, as another effect of the present embodiment, image reading is performed. It can be seen that the absolute value of the color conversion accuracy in the image processing apparatus 20 is improved in addition to the suppression of the reading unevenness of the unit 12.

As described above, the printer device 10 according to the present embodiment can correct reading unevenness due to the reading position of the image reading unit 12. As another effect, the color conversion by the color conversion unit 510 is complemented, and the absolute value of the color conversion accuracy is also improved.
In addition, by correcting the correction parameter using the parameter correction unit 530, the printer device 10 can realize high-precision color reading even if the characteristics of the image reading unit 12 change.

[Modification]
Next, a modification of the above embodiment will be described.
FIG. 8 is a diagram for explaining a modification. FIG. 8A illustrates the functional configuration of the second image processing program 52, and FIG. 8B is created by the second parameter correction unit 532. The look-up table (correction parameter) to be performed is illustrated. It should be noted that among the components shown in the figure, the same reference numerals are given to the components that are substantially the same as those shown in FIG.
As illustrated in FIG. 8A, the second image processing program 52 includes a parameter correction unit 530 and an unevenness correction unit 540 of the image processing program 5 illustrated in FIG. The configuration replaced by the conversion unit 550 is adopted.
The second parameter correction unit 532 generates a synthesis parameter that realizes the color conversion process performed by the color conversion unit 510 (FIG. 3) and the correction process performed by the unevenness correction unit 540 (FIG. 3). The combined parameters are provided to the composite conversion unit 550550.
For example, the second parameter correction unit 532 combines the color conversion parameter used for the color conversion process and the correction parameter used for the unevenness correction process, and generates a combined parameter that realizes the color conversion process and the unevenness correction process. To do.
The parameter correction unit 532 of this example inputs the reading position (coordinate X) and reading value (RGB value) when the color sample is read by the image reading unit 12 as input data, as illustrated in FIG. 8B. A lookup table is created by using the set of grid points and the colorimetric values (L'a'b ') measured by the colorimeter at these reading positions as grid points of the output color data. Is provided to the composite correction unit 550 as a synthesis parameter.
The composite correction unit 550 has substantially the same configuration as the unevenness correction unit 540 illustrated in FIG. 4, and the color input using the look-up table (synthesis parameter) illustrated in FIG. 8B. Color data corresponding to the data and reading position is calculated. Thereby, color conversion processing (in this example, conversion from RGB to Lab) and unevenness correction processing are realized.

  As described above, the image processing program 52 according to the present modification has a high accuracy because the number of conversion means connected in series is reduced and the amount of calculation is reduced as compared with the first image program 5 (FIG. 3). In addition, the correction process can be realized at high speed.

In the above embodiment, each color component that has been subjected to unevenness correction based on a plurality of color component values (L value, a value, and b value) and a reading position (X coordinate) using a four-dimensional DLUT. Although the values are calculated, the present invention is not limited to this. For example, an LUT that performs unevenness correction may be provided for each color component, and each color component value may be corrected independently.
For example, the unevenness correction unit 540 (FIG. 3) is input using an L value two-dimensional DLUT that associates an L ′ value that has been subjected to unevenness correction with respect to an input data set composed of an L value and a reading position X. For the L value, the unevenness correction corresponding to the reading position is performed, and similarly, using the two-dimensional DLUT for the a value and the two-dimensional DLUT for the b value, respectively, the a value and the b value are independent. The unevenness correction may be performed.

1 is a diagram illustrating a configuration of a tandem type printer device 10. FIG. (A) illustrates reading unevenness when a yellow color sample is read, and (B) illustrates reading unevenness when a red (Red) color sample is read. It is a figure which illustrates the functional structure of the image processing program 5 which is performed by the image processing apparatus 20 (FIG. 1) and implement | achieves the image processing method concerning this invention. It is a figure explaining the uneven | corrugated correction | amendment part 540 shown by FIG. 3 in detail. 3A and 3B are diagrams illustrating a parameter creation method by the parameter correction unit 530 (FIG. 3), in which FIG. 3A illustrates a color sample 900 used for creating correction parameters, and FIG. 3B is created by the parameter correction unit 530. The correction parameters are exemplified. 6 is a flowchart illustrating an image reading operation (S10) of the printer device 10 (image processing program 5). It is a figure explaining the effect of this embodiment, (A) illustrates the reading nonuniformity when yellow (Yellow) color sample is read (equivalent to FIG. 2 (A)), (B) is red It is a figure which illustrates the reading nonuniformity at the time of reading the color sample of (Red) (equivalent to FIG. 2 (B)). FIG. 10 is a diagram illustrating a modification example, where (A) illustrates the functional configuration of the second image processing program 52, and (B) is a lookup table (correction parameter) created by the second parameter correction unit 532. ).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Printer apparatus 12 ... Image reading unit 5, 52 ... Image processing program 510 ... Color conversion part 520 ... Reading position specific | specification part 530, 532 ... Parameter correction part 540 ... Unevenness correction unit 542 ... 4D LUT
544 ... LUT reference unit 546 ... interpolation processing unit 550 ... composite conversion unit

Claims (9)

An image processing apparatus that performs image processing on an input image read by an image reading apparatus,
Position specifying means for specifying the reading position of the input image;
An image processing apparatus comprising: color variation correction means for performing color variation correction processing for suppressing color variation of at least a chromatic color component on the image data of the input image according to the reading position identified by the position identifying unit. A correction table for associating the input data set including the color data and the sample value of the reading position with the output color data in which the color variation generated at the reading position is suppressed;
The color variation correction unit uses the correction table to convert color data corresponding to the color data of the reading position specified by the position specifying unit and the input image to the color data subjected to the color variation correction process. The image processing apparatus according to claim 1, wherein: The color data includes gradation values of a plurality of color components,
The correction table associates an output gradation value of each color component with an input data set including a plurality of color component sample values and reading position sample values,
3. The image according to claim 2, wherein the color variation correction unit calculates the gradation value of each color component corresponding to the reading position specified by the position specifying unit and the gradation values of a plurality of color components of the input image. Processing equipment. Color conversion means for converting image data of the input image expressed in the first color space into image data expressed in the second color space;
The correction table associates output color data expressed in the second color space with an input data set including sample values of color data expressed in the second color space,
4. The image processing according to claim 2, wherein the color variation correction unit performs a color variation correction process on the image data of the second color space converted by the color conversion unit, using the correction table. 5. apparatus. Correction table correction means for correcting data associated with the correction table;
The image processing apparatus according to claim 2, wherein the color fluctuation correction unit performs a color fluctuation correction process using the correction table corrected by the correction table correction unit. The correction table stores color data generated based on image data read by an image reading device from a predetermined color sample as color data of the input data set, and is measured by the colorimeter from the color sample. Color data generated based on the measured color values is stored as the output color data,
The position specifying unit acquires a reading position of the input image from the image reading device,
The image processing apparatus according to claim 2, wherein the color fluctuation correction unit performs color fluctuation correction processing according to a reading position acquired from the image reading apparatus, using the correction table. Image reading means for optically reading an image from a document;
An image reading apparatus comprising: a color variation correction unit that performs color variation correction processing that suppresses color variation of at least a chromatic color component on image data read from a document according to a reading position read by the image reading unit. . An image processing method for performing image processing on an input image read by an image reading device,
Specify the reading position of the input image,
An image processing method for performing color variation correction processing for suppressing color variation of at least a chromatic component on image data of an input image according to a specified reading position. In a computer that performs image processing on an input image read by an image reading device,
Identifying a reading position of the input image;
A program for causing the computer to execute a step of performing color variation correction processing for suppressing color variation of at least a chromatic component on image data of an input image according to an identified reading position.

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