JP2007283750A - Device for generating banding correction information, method for generating banding correction information, program for generating banding correction information, printer, printing method, printing program and recording media on which program is recorded - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for generating banding correction information, which is suitable for obtaining proper correction information to correct the banding, and to provide a method for generating banding correction information, a program for generating banding correction information, a printer, and a recording media. <P>SOLUTION: The printer 1 comprises a density information extraction means 20 for extracting density information according to the banding, a density gradient calculation means 30 for calculating gradient of the change of the density information which is extracted by the density information extraction means 20, a density gradient correction means 40 for correcting gradient of the change of the density which is calculated by the density gradient calculation means 30, a banding correction information generating means 50 for generating the banding correction information for correcting the banding more properly from the density information having the gradient of the change of the density corrected by the density gradient correction means 40, and a banding correction information storing means 80 for executing the banding correction processing to an image data for printing using the banding correction information produced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a correction process for banding that occurs in a printed image or the like, and in particular, a banding correction information generation apparatus, a banding correction information generation method, and a banding correction information generation method for generating banding correction information that can correct banding that should be originally obtained. The present invention relates to a banding correction information generation program, a printing apparatus, a printing method, a printing program, and a recording medium on which the program is recorded.

Conventionally, as an apparatus for correcting banding, an apparatus as in Patent Document 1 has been proposed.
This device is an image forming device that can stably output an image having no density unevenness and density streaks in all gradations, and prints in a direction different from the direction of the print head in which a plurality of print elements are arranged. In an image forming apparatus that forms an image by moving relative to a medium, a first correction unit that selectively indicates a recording characteristic of each recording element of a recording head for each of a plurality of density regions; The second correction unit that corrects the density signal based on the recording characteristic instructed by the correction unit, and the recording characteristic instructed by the first correction unit according to the density region to which the density signal corresponding to each recording element belongs. It is an apparatus comprising selection means for selecting.

However, in this apparatus, there is a problem caused by a measurement system such as a scanner in which an end portion when a patch image (for example, a solid image of each gradation) for generating correction information is scanned cannot be used. The result of scanning to create correction information may be tilted as shown in FIG.
FIG. 13A shows a primary concentration gradient, and forms a steep slope from the upper left to the lower right. This slope is basically generated due to the measurement device and the periphery of the measurement device. For example, incident light from the outside is one of the causes. FIG. 13B shows a second-order density gradient, which draws a curve that suddenly descends from the upper left and rises again. This curve was taken with a lens like a camera. The image is basically generated due to the characteristic that the periphery of the lens becomes dark. That is, although it depends on which part of the lens the light is used, it is considered that the characteristic (for example, the amount of light) of the light passing through the peripheral part of the lens is different.
Japanese Patent Laid-Open No. 5-220977

  There is a problem that the method of “discarding the end” as described in Patent Document 1 cannot cope with the problem caused by the measurement system. This problem should originally improve the fundamental problem of the measurement system, but the situation that is unlikely to be possible due to problems such as cost, even if it was time-consuming, solved the fundamental problem of the measurement system However, the situation is not solved completely, and the situation as described above remains.

  The present invention has been made in view of the above-described circumstances, and corrects a density gradient to obtain accurate correction information for correcting banding, which should be originally obtained, An object of the present invention is to provide a banding correction information generation method, a banding correction information generation program, a printing apparatus, and a recording medium.

[Mode 1] In order to solve the above-described problem, the banding correction information generation device according to mode 1 includes:
Correction information generation image data acquisition means for acquiring correction information generation image data that is image data of an image for generation of banding correction information;
Density information extraction means for extracting density information of the image based on the correction information generation image data;
Density gradient calculating means for calculating a gradient of density change of the image based on the density information extracted by the density information extracting means;
Density gradient correction means for correcting the correction information generating image data based on the gradient of the density change calculated by the density gradient calculation means;
Banding correction information generation means for generating banding correction information for correcting banding based on the correction information generation image data corrected by the density gradient correction means.

  According to this configuration, it is possible to acquire correction information generation image data that is image data of an image for generation of banding correction information by the correction information generation image data acquisition unit, and by the density information extraction unit, It is possible to extract the density information of the image based on the correction information generation image data, and the gradient of the density change of the image based on the density information extracted by the density information extracting means by the density gradient calculating means. The image data for generating correction information can be corrected based on the gradient of the density change calculated by the density gradient calculating unit by the density gradient correcting unit, and banding correction can be performed. Banding is compensated by the information generation unit based on the correction information generation image data corrected by the density gradient correction unit. It is possible to generate a banding correction information for.

Therefore, by correcting (removing) the density gradient that is caused by a measurement system error that does not exist originally, banding correction information that can correct banding more accurately can be created. .
Note that the “density information” is information extracted based on, for example, image data generated from the measured density of the measurement system or image data captured by a digital camera, and the strength of banding generated in the image. Etc. are information expressed as density changes. For example, when the luminance value is used to express the density, the average luminance value for each line of the image is used. In general, banding is perceived as uneven brightness change (not color change), so the expression of density shows the same brightness, not just the luminance value. For the scale, a density value (OD value), a brightness value (Lab L value), or the like may be used. Hereinafter, a mode related to a banding correction information generation method, a mode related to a banding correction information generation program, a mode related to a printing apparatus, a mode related to a printing method, a mode related to a printing program, a mode related to a computer-readable recording medium storing the program, and an invention It is the same in the column of the best mode for doing.

  The “banding” is, for example, a so-called “flight bend phenomenon” caused by a nozzle whose dot formation position is deviated from an ideal formation position in a printing apparatus. “White streaks” and “Dense streaks” appear in the print result due to printing defects that cause “streaks” at the same time, ink ejection failure in the nozzles, and ink ejection volume that is greater or less than normal. Applicable to defective printing.

  In addition, the “flight bend phenomenon” is different from the non-ejection phenomenon of some nozzles, but ink is ejected, but the ejection direction of some of the nozzles is inclined and the dots are displaced from the ideal position. A phenomenon that is formed. Hereinafter, a mode related to a banding correction information generation method, a mode related to a banding correction information generation program, a mode related to a printing apparatus, a mode related to a printing method, a mode related to a printing program, a mode related to a computer-readable recording medium storing the program, and an invention It is the same in the column of the best mode for doing.

  In addition, the above-mentioned “white streaks” continuously cause a phenomenon in which the distance between adjacent dots becomes wider than a predetermined distance due to the “flying curve phenomenon”, and the background color of the print medium becomes noticeable in a streak shape. The above-mentioned “dark streaks” are the same as the “flight bend phenomenon”, and a phenomenon in which the distance between adjacent dots is continuously shorter than a predetermined distance due to the “flight bend phenomenon” occurs. The color disappears, or the distance between the dots becomes shorter, so it looks relatively darker. Furthermore, some of the dots that are off are overlapped with normal dots, and the overlapped part is conspicuous as a dark streak The part (area) that is In addition, white streaks may occur due to nozzles with a small amount of ink, while dark streaks may occur due to nozzles with a large amount of ink. Hereinafter, a mode related to a banding correction information generation method, a mode related to a banding correction information generation program, a mode related to a printing apparatus, a mode related to a printing method, a mode related to a printing program, a mode related to a computer-readable recording medium storing the program, and an invention will be implemented It is the same in the column of the best mode for doing.

[Mode 2] Furthermore, the banding correction information generation device according to mode 2 is the banding correction information generation device according to mode 1,
The density information uses one of a luminance value, a density value (OD value), and a lightness value (L value).
According to this configuration, the gradient of the density change can be obtained from the change in any one of the luminance value, density value (OD value), and lightness value (L value). By appropriately correcting (removing) the density gradient generated by the above, more appropriate banding correction information can be generated.

[Mode 3] Furthermore, the banding correction information generation device according to mode 3 is the banding correction information generation device according to mode 1 or 2,
The density information includes a statistical value of density of at least one of a banding occurrence direction and a direction orthogonal to the banding occurrence direction in the image.
According to this configuration, it is possible to accurately grasp the banding occurrence direction and the gradient generated in the direction perpendicular thereto, and accordingly, the gradient that should be ignored is appropriately removed from the gradient of the image density change (density gradient). It becomes possible. In particular, by using both the banding occurrence direction and the density information in the direction perpendicular thereto, the gradient can be grasped two-dimensionally (planar), so that it is possible to remove unnecessary gradient portions more appropriately. Therefore, more appropriate banding information can be generated.

[Mode 4] Furthermore, the banding correction information generation device according to mode 4 is the banding correction information generation device according to mode 3,
The statistical value of density is one of a luminance average value, a density average value, and a lightness average value for each line of the image.
According to this configuration, since it is possible to represent the density change of the image using any one of the change of the luminance value of the image, the change of the density value, and the change of the brightness value, from these density changes, It is possible to appropriately discriminate the gradient of concentration change (concentration gradient) that occurs due to an error in the measurement system that does not originally exist. Therefore, since an appropriate density gradient can be corrected, more appropriate banding correction information can be generated.

[Mode 5] Furthermore, the banding correction information generation device according to mode 5 is the banding correction information generation device according to any one of modes 1 to 4,
The concentration gradient calculation means is means for calculating the gradient by linear approximation using a least square method.
According to this configuration, since the gradient is calculated using the slope of the regression line obtained by the least square method with respect to the concentration information, an effect that the concentration gradient can be easily removed is obtained.

[Mode 6] Furthermore, the banding correction information generation device according to mode 6 is the banding correction information generation device according to any one of modes 1 to 4,
The concentration gradient calculating means is a means for calculating the gradient by polynomial approximation.
According to this configuration, since the gradient is calculated by polynomial approximation for the density information, the density gradient can be removed by various methods, and appropriate banding correction information can be created.

[Mode 7] Furthermore, the banding correction information generation device according to mode 7 is the banding correction information generation device according to any one of modes 1 to 6,
The density gradient correction unit is a unit that corrects the correction information generation image data so that the gradient calculated by the density gradient calculation unit is removed from the density change of the image.

  Normally, if there is no influence by the measuring device or the like, the density change (for example, change in the average luminance value of each image line) of the patch image (solid image of each gradation) is orthogonal to the density axis when viewed macroscopically. The characteristic is parallel or substantially parallel to the direction of the axis (axis indicating the position of each image line of the image). That is, since the patch image is an image having a uniform density, even if there is a fine blur due to banding, the density change when viewed macroscopically becomes flat or substantially flat. However, due to the influence of the measuring device or the like, the density change of the patch image viewed macroscopically has a gradient with respect to the axial direction perpendicular to the density axis.

  According to the configuration of this embodiment, since the gradient of density change calculated by the density gradient calculating means is removed from the density change of the image, only unnecessary density components different from the original pure density components of the image are removed. Can be removed. Thereby, the effect that banding correction information can be created more appropriately is obtained.

[Mode 8] Further, the banding correction information generation device according to mode 8 is the banding correction information generation device according to mode 7,
The density gradient correction unit may remove at least one of a gradient with respect to a density change in the banding occurrence direction of the image and a gradient with respect to a density change in a direction orthogonal to the banding occurrence direction from the density change of the image. A means for correcting the correction information generating image data.

Here, as the gradient of the density change, for example, a gradient with respect to a change in the average luminance value of the image line in the banding occurrence direction and a gradient with respect to a change in the average luminance value of the image line in the direction orthogonal to the banding occurrence direction. Conceivable. That is, the influence by the measuring device appears roughly as these two types of gradients.
According to the configuration of the present embodiment, at least one of the gradient in the banding generation direction and the gradient in the direction orthogonal to the banding generation direction with respect to the density change of the image calculated by the density gradient calculation unit is set as the image density. Since it can be removed from the change, unnecessary concentration components can be removed more appropriately. Thereby, the effect that banding correction information can be created more appropriately is obtained.

[Mode 9] On the other hand, in order to solve the above problem, the banding correction information generation method of mode 9
Correction information generation image data acquisition step of acquiring correction information generation image data which is image data of an image for generation of banding correction information;
A density information extraction step for extracting density information of the image based on the correction information generation image data;
A density gradient calculating step for calculating a gradient of density change of the image based on the density information extracted in the density information extracting step;
A density gradient correction step for correcting the correction information generating image data based on the gradient of the density change calculated in the density gradient calculation step;
And a banding correction information generation step for generating banding correction information for correcting banding based on the correction information generation image data corrected in the density gradient correction step.
According to this configuration, an effect similar to that of the banding correction information generation device according to the first aspect can be obtained.

[Mode 10] Further, the banding correction information generation method according to mode 10 is the banding correction information generation method according to mode 9,
The density information uses one of a luminance value, a density value (OD value), and a lightness value (L value).
According to this configuration, the same effects as those of the banding correction information generation device according to the second aspect can be obtained.

[Mode 11] Furthermore, the banding correction information generation method according to mode 11 is the banding correction information generation method according to mode 9 or 11,
The density information includes a statistical value of density of at least one of a banding occurrence direction and a direction orthogonal to the banding occurrence direction in the image.
According to this configuration, the same effect as that of the banding correction information generation device according to the third aspect can be obtained.

[Mode 12] Furthermore, the banding correction information generation method according to mode 12 is the banding correction information generation method according to mode 11,
The statistical value of density is one of a luminance average value, a density average value, and a lightness average value for each line of the image.
According to this configuration, an effect similar to that of the banding correction information generation device according to the fourth aspect is obtained.

[Mode 13] Furthermore, the banding correction information generation method according to mode 13 is the banding correction information generation method according to any one of modes 9 to 12,
The concentration gradient calculating step calculates the gradient by linear approximation using a least square method.
According to this configuration, the same effects as those of the banding correction information generation device according to the fifth aspect can be obtained.

[Mode 14] Further, the banding correction information generation method according to mode 14 is the banding correction information generation method according to any one of modes 9 to 12,
The concentration gradient calculating step calculates the gradient by polynomial approximation.
According to this configuration, an effect similar to that of the banding correction information generation device according to the sixth aspect is obtained.

[Mode 15] Furthermore, the banding correction information generation method according to mode 15 is the banding correction information generation method according to any one of modes 9 to 14,
In the density gradient correction step, the correction information generation image data is corrected so that the gradient calculated in the density gradient calculation step is removed from the density change of the image.
According to this configuration, an effect similar to that of the banding correction information generation device according to the seventh aspect can be obtained.

[Mode 16] Further, the banding correction information generation method according to mode 16 is the banding correction information generation method according to mode 15,
In the density gradient correction step, at least one of a gradient with respect to a density change in the banding occurrence direction of the image and a gradient with respect to a density change in a direction orthogonal to the banding occurrence direction is removed from the density change of the image. The correction information generating image data is corrected.
According to this configuration, an effect similar to that of the banding correction information generation device according to the eighth aspect is obtained.

[Mode 17] On the other hand, in order to solve the above problem, the banding correction information generation program of mode 17
Correction information generation image data acquisition step of acquiring correction information generation image data which is image data of an image for generation of banding correction information;
A density information extraction step for extracting density information of the image based on the correction information generation image data;
A density gradient calculating step for calculating a gradient of density change of the image based on the density information extracted in the density information extracting step;
A density gradient correction step for correcting the correction information generating image data based on the gradient of the density change calculated in the density gradient calculation step;
A program used for causing a computer to execute processing including a banding correction information generation step for generating banding correction information for correcting banding based on the correction information generation image data corrected in the density gradient correction step. It is characterized by including.
With such a configuration, when the program is read by the computer and the computer executes processing according to the read program, the same operation and effect as those of the banding correction information generating device according to the first aspect can be obtained.

[Mode 18] Further, the banding correction information generation program according to mode 18 is the banding correction information generation program according to mode 17,
The density information uses one of a luminance value, a density value (OD value), and a lightness value (L value).
With such a configuration, when the program is read by the computer and the computer executes processing in accordance with the read program, the same operation and effect as those of the banding correction information generating device of the second aspect can be obtained.

[Form 19] Furthermore, the banding correction information generation program according to form 19 is the banding correction information generation program according to form 17 or 18,
The density information includes a statistical value of density of at least one of a banding occurrence direction and a direction orthogonal to the banding occurrence direction in the image.
With such a configuration, when the program is read by the computer and the computer executes processing according to the read program, the same operation and effect as those of the banding correction information generating apparatus according to the third aspect are obtained.

[Mode 20] Furthermore, the banding correction information generation program according to mode 20 is the banding correction information generation program according to mode 19,
The statistical value of density is one of a luminance average value, a density average value, and a lightness average value for each line of the image.
With such a configuration, when the program is read by the computer and the computer executes processing according to the read program, the same operation and effect as those of the banding correction information generating device according to the fourth aspect are obtained.

[Mode 21] Furthermore, the banding correction information generation program according to mode 21 is the banding correction information generation program according to any one of modes 17 to 20,
The concentration gradient calculating step calculates the gradient by linear approximation using a least square method.
With such a configuration, when the program is read by the computer and the computer executes processing in accordance with the read program, the same operations and effects as those of the banding correction information generating apparatus according to the fifth aspect are obtained.

[Mode 22] Furthermore, the banding correction information generation program according to mode 22 is the banding correction information generation program according to any one of modes 17 to 20,
The concentration gradient calculating step calculates the gradient by polynomial approximation.
With such a configuration, when the program is read by the computer and the computer executes the process according to the read program, the same operation and effect as those of the banding correction information generating device according to the sixth aspect are obtained.

[Mode 23] Further, the banding correction information generation program according to mode 23 is the banding correction information generation program according to any one of modes 17 to 22,
In the density gradient correction step, the correction information generation image data is corrected so that the gradient calculated in the density gradient calculation step is removed from the density change of the image.
With such a configuration, when the program is read by the computer and the computer executes processing in accordance with the read program, the same operation and effect as those of the banding correction information generating device according to the seventh aspect are obtained.

[Mode 24] Further, the banding correction information generation program according to mode 24 is the banding correction information generation program according to mode 23,
In the density gradient correction step, at least one of a gradient with respect to a density change in the banding occurrence direction of the image and a gradient with respect to a density change in a direction orthogonal to the banding occurrence direction is removed from the density change of the image. The correction information generating image data is corrected.
With such a configuration, when the program is read by the computer and the computer executes processing in accordance with the read program, the same operation and effect as those of the banding correction information generating device according to the eighth aspect are obtained.

[Mode 25] In order to solve the above problem, the recording medium of mode 25
25. A computer-readable recording medium on which the banding correction information generation program according to any one of forms 17 to 24 is recorded.
As a result, the banding correction information generation program according to any one of Embodiments 17 to 24 is transmitted to a user such as a user via a computer-readable recording medium such as a CD-ROM, DVD-ROM, FD, or semiconductor chip. Can be provided easily and reliably.

[Mode 26] On the other hand, in order to solve the above problem, a printing apparatus according to mode 26,
Correction information generation image data acquisition means for acquiring correction information generation image data that is image data of an image for generation of banding correction information;
Density information extraction means for extracting density information of the image based on the correction information generation image data;
Density gradient calculating means for calculating a gradient of density change of the image based on the density information extracted by the density information extracting means;
Density gradient correction means for correcting the correction information generating image data based on the gradient of the density change calculated by the density gradient calculation means;
Banding correction information generation means for generating banding correction information for correcting banding based on the correction information generation image data corrected by the density gradient correction means;
Printing image data acquisition means for acquiring printing image data which is image data of an image to be printed;
Banding correction means for performing processing for correcting banding on the image data for printing using the banding correction information generated by the banding correction information generation means;
Printing means for printing the image to be printed on a medium used for printing based on the printing image data.

  According to this configuration, it is possible to acquire correction information generation image data that is image data of an image for generation of banding correction information by the correction information generation image data acquisition unit, and by the density information extraction unit, It is possible to extract the density information of the image based on the correction information generation image data, and the gradient of the density change of the image based on the density information extracted by the density information extracting means by the density gradient calculating means. The image data for generating correction information can be corrected based on the gradient of the density change calculated by the density gradient calculating unit by the density gradient correcting unit, and banding correction can be performed. Banding is compensated by the information generation unit based on the correction information generation image data corrected by the density gradient correction unit. It is possible to generate a banding correction information for.

  The printing image data acquisition unit can acquire printing image data that is image data of an image to be printed. The banding correction unit generates the banding correction information generated by the banding correction information generation unit. It is possible to execute processing for correcting banding on the printing image data, and the printing unit prints the image to be printed on a medium used for printing based on the printing image data. It is possible.

  Therefore, like the banding correction information generation apparatus of the first aspect, banding that can correct banding more accurately by correcting (removing) a density gradient that is not present in the field and is caused by a measurement system error. The effect that correction information can be created is obtained. Further, since printing can be performed based on the printing image data corrected using the banding correction information, it is possible to obtain an effect that a print image with banding corrected more effectively can be obtained.

[Mode 27] Further, the printing apparatus according to mode 27 is the printing apparatus according to mode 26,
The density information uses one of a luminance value, a density value (OD value), and a lightness value (L value).
According to this configuration, the same operation and effect as those of the banding correction information generating apparatus according to the second aspect can be obtained, and an effect can be obtained in which a print image with banding corrected more effectively can be obtained.

[Mode 28] Furthermore, the printing apparatus according to mode 28 is the printing apparatus according to mode 26 or 27,
The density information includes a statistical value of density of at least one of a banding occurrence direction and a direction orthogonal to the banding occurrence direction in the image.
According to this configuration, the same operation and effect as those of the banding correction information generating apparatus according to the third aspect can be obtained, and an effect that a print image in which banding is corrected more effectively can be obtained.

[Mode 29] Further, the printing apparatus according to mode 29 is the printing apparatus according to mode 28,
The statistical value of density is one of a luminance average value, a density average value, and a lightness average value for each line of the image.
According to this configuration, the same operation and effect as those of the banding correction information generating device according to the fourth aspect can be obtained, and an effect can be obtained that a print image in which banding is corrected more effectively can be obtained.

[Mode 30] Furthermore, the printing apparatus according to mode 30 is the printing apparatus according to any one of modes 26 to 29,
The concentration gradient calculation means is means for calculating the gradient by linear approximation using a least square method.
According to this configuration, the same operation and effect as those of the banding correction information generation apparatus according to the fifth aspect can be obtained, and an effect that a print image in which banding is corrected more effectively can be obtained.

[Mode 31] Furthermore, the printing apparatus according to mode 31 is the printing apparatus according to any one of modes 26 to 29,
The concentration gradient calculating means is a means for calculating the gradient by polynomial approximation.
According to this configuration, the same operation and effect as those of the banding correction information generating apparatus according to the sixth aspect can be obtained, and an effect can be obtained that a print image in which banding is corrected more effectively can be obtained.

[Mode 32] Furthermore, the printing apparatus according to mode 32 is the printing apparatus according to any one of modes 26 to 31,
The density gradient correction unit is a unit that corrects the correction information generation image data so that the gradient calculated by the density gradient calculation unit is removed from the density change of the image.
According to this configuration, the same operation and effect as those of the banding correction information generation apparatus according to the seventh aspect can be obtained, and an effect that a print image in which banding is corrected more effectively can be obtained.

[Mode 33] Furthermore, the printing apparatus according to mode 33 is the printing apparatus according to mode 32,
The density gradient correction unit may remove at least one of a gradient with respect to a density change in the banding occurrence direction of the image and a gradient with respect to a density change in a direction orthogonal to the banding occurrence direction from the density change of the image. A means for correcting the correction information generating image data.
According to this configuration, the same operation and effect as those of the banding correction information generating apparatus according to the eighth aspect can be obtained, and an effect that a print image in which banding is corrected more effectively can be obtained.

[Form 34] On the other hand, in order to solve the above-mentioned problem, the printing method of form 34
Correction information generation image data acquisition step of acquiring correction information generation image data which is image data of an image for generation of banding correction information;
A density information extraction step for extracting density information of the image based on the correction information generation image data;
A density gradient calculating step for calculating a gradient of density change of the image based on the density information extracted in the density information extracting step;
A density gradient correction step for correcting the correction information generating image data based on the gradient of the density change calculated in the density gradient calculation step;
A banding correction information generation step for generating banding correction information for correcting banding based on the correction information generation image data corrected in the density gradient correction step;
A printing image data acquisition step of acquiring printing image data which is image data of an image to be printed;
Using the banding correction information generated in the banding correction information generation step, a banding correction step for executing processing for correcting banding on the print image data;
And a printing step of printing the image to be printed on a medium used for printing based on the printing image data.
According to this configuration, the same effect as that of the printing apparatus of the twenty-sixth aspect can be obtained.

[Form 35] Furthermore, the printing method of form 35 is the printing method according to form 34,
The density information uses one of a luminance value, a density value (OD value), and a lightness value (L value).
According to this configuration, the same effects as those of the printing device of aspect 27 can be obtained.

[Form 36] Furthermore, the printing method of form 36 is the printing method according to form 34 or 35,
The density information includes a statistical value of density of at least one of a banding occurrence direction and a direction orthogonal to the banding occurrence direction in the image.
According to this configuration, an effect similar to that of the printing apparatus according to the twenty-eighth aspect can be obtained.

[Form 37] Furthermore, the printing method according to form 37 is the printing method according to form 36,
The statistical value of density is one of a luminance average value, a density average value, and a lightness average value for each line of the image.
According to this configuration, the same effect as that of the printing apparatus according to the twenty-ninth aspect can be obtained.

[Form 38] Furthermore, the printing method of form 38 is the printing method according to any one of forms 34 to 37,
The concentration gradient calculating step calculates the gradient by linear approximation using a least square method.
According to this configuration, the same effect as that of the printing apparatus according to the thirtieth aspect can be obtained.

[Form 39] Furthermore, the printing method of form 39 is the printing method according to any one of forms 34 to 37,
The concentration gradient calculating step calculates the gradient by polynomial approximation.
According to this configuration, the same effect as that of the printing apparatus according to the thirty-first aspect can be obtained.

[Form 40] Furthermore, the printing method of form 40 is the printing method according to any one of forms 34 to 39,
In the density gradient correction step, the correction information generation image data is corrected so that the gradient calculated in the density gradient calculation step is removed from the density change of the image.
According to this configuration, an effect similar to that of the printing apparatus according to the thirty-second aspect is obtained.

[Form 41] Furthermore, the printing method according to Form 41 is the printing method according to Form 40,
In the density gradient correction step, at least one of a gradient with respect to a density change in the banding occurrence direction of the image and a gradient with respect to a density change in a direction orthogonal to the banding occurrence direction is removed from the density change of the image. The correction information generating image data is corrected.
According to this configuration, the same effect as that of the printing apparatus according to the thirty-third aspect can be obtained.

[Form 42] On the other hand, in order to solve the above problem, the printing program of form 42
Correction information generation image data acquisition step of acquiring correction information generation image data which is image data of an image for generation of banding correction information;
A density information extraction step for extracting density information of the image based on the correction information generation image data;
A density gradient calculating step for calculating a gradient of density change of the image based on the density information extracted in the density information extracting step;
A density gradient correction step for correcting the correction information generating image data based on the gradient of the density change calculated in the density gradient calculation step;
A banding correction information generation step for generating banding correction information for correcting banding based on the correction information generation image data corrected in the density gradient correction step;
A printing image data acquisition step of acquiring printing image data which is image data of an image to be printed;
Using the banding correction information generated in the banding correction information generation step, a banding correction step for executing processing for correcting banding on the print image data;
And a program used for causing a computer to execute a process including a printing step of printing the image to be printed on a medium used for printing based on the printing image data.

  With such a configuration, when the program is read by the computer and the computer executes processing in accordance with the read program, the same operations and effects as those of the printing apparatus of the twenty-sixth aspect are obtained.

[Form 43] Further, the print program of form 43 is the print program of form 42,
The density information uses one of a luminance value, a density value (OD value), and a lightness value (L value).
With such a configuration, when the program is read by the computer and the computer executes processing in accordance with the read program, the same operation and effect as those of the printing apparatus of the twenty-seventh aspect are obtained.

[Form 44] Furthermore, the print program of form 44 is the print program according to form 42 or 43,
The density information includes a statistical value of density of at least one of a banding occurrence direction and a direction orthogonal to the banding occurrence direction in the image.
With such a configuration, when the program is read by the computer and the computer executes processing according to the read program, the same operation and effect as those of the printing apparatus of the above-described form 28 are obtained.

[Mode 45] Furthermore, the printing program of mode 45 is the printing program according to mode 44,
The statistical value of density is one of a luminance average value, a density average value, and a lightness average value for each line of the image.
With such a configuration, when the program is read by the computer and the computer executes processing according to the read program, the same operation and effect as those of the printing apparatus of the above-described form 29 can be obtained.

[Form 46] Furthermore, the print program according to form 46 is the print program according to any one of forms 42 to 45.
The concentration gradient calculating step calculates the gradient by linear approximation using a least square method.
With such a configuration, when the program is read by the computer and the computer executes processing in accordance with the read program, the same operation and effect as those of the printing apparatus according to the thirtieth aspect are obtained.

[Form 47] Furthermore, the print program according to form 47 is the print program according to any one of forms 42 to 45.
The concentration gradient calculating step calculates the gradient by polynomial approximation.
With such a configuration, when the program is read by the computer and the computer executes processing in accordance with the read program, the same operations and effects as those of the printing apparatus according to the thirty-first aspect are obtained.

[Form 48] Further, the print program according to form 48 is the print program according to any one of forms 42 to 47,
In the density gradient correction step, the correction information generation image data is corrected so that the gradient calculated in the density gradient calculation step is removed from the density change of the image.
With such a configuration, when the program is read by the computer and the computer executes processing in accordance with the read program, the same operation and effect as those of the printing apparatus according to the thirty-second aspect are obtained.

[Form 49] Further, the print program of the form 49 is the print program according to the form 48,
In the density gradient correction step, at least one of a gradient with respect to a density change in the banding occurrence direction of the image and a gradient with respect to a density change in a direction orthogonal to the banding occurrence direction is removed from the density change of the image. The correction information generating image data is corrected.
With such a configuration, when the program is read by the computer and the computer executes processing in accordance with the read program, the same operation and effect as those of the printing apparatus according to the thirty-third aspect are obtained.

[Mode 50] In order to solve the above problem, a recording medium of mode 50
A computer-readable recording medium on which the printing program according to any one of forms 42 to 49 is recorded.
As a result, the printing program according to any one of the forms 42 to 49 can be easily and easily transmitted to a user such as a user via a computer-readable recording medium such as a CD-ROM, DVD-ROM, FD, or semiconductor chip. It can be reliably provided.

Hereinafter, a printing apparatus according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating a configuration of a banding correction information generation apparatus in a printing apparatus according to an embodiment of the present invention.
As shown in FIG. 1, the banding correction information generation device 2 of the printing apparatus 1 includes a correction information generation image data acquisition unit 10, a density information extraction unit 20, a density gradient calculation unit 30, and a density gradient correction unit 40. And a banding correction information generation means 50 and a banding correction information storage means 60.

The correction information generation image data acquisition unit 10 acquires correction information generation image data, which is patch image data for generating correction information, from the outside or the inside of the apparatus.
The density information extraction unit 20 extracts density information of the patch image based on the correction information generation image data in order to generate banding correction information for correcting banding, which is a kind of factor that degrades the image quality. .

The density gradient calculating means 30 calculates the density change gradient of the patch image based on the density information extracted by the density information extracting means 20.
The density gradient correcting unit 40 corrects the density change gradient of the patch image calculated by the density gradient calculating unit 30.
The banding correction information generation unit 50 generates banding correction information based on the density information in which the density gradient correction unit 40 corrects the gradient of density change.

The banding correction information storage unit 60 stores the banding correction information generated by the banding correction information generation unit 50.
FIG. 2 is a block diagram showing the configuration of the printing apparatus 1 according to the embodiment of the present invention.
As shown in FIG. 2, the printing apparatus 1 includes a banding correction information generation apparatus 2, a printing image data acquisition unit 70, a banding correction unit 80, and a printing unit 90.

The printing image data acquisition unit 70 acquires printing image data that is image data for printing from the outside of the apparatus or the inside of the apparatus.
The banding correction unit 80 performs banding correction processing on the print image data acquired by the print image data acquisition unit 70 based on the banding correction information stored in the banding correction information storage unit 60 described in FIG. Execute.

The printing unit 90 prints an image on a medium (for example, printing paper) used for printing based on the printing image data corrected by the banding correction unit 80.
Hereinafter, detailed functions of each unit will be described with reference to the drawings.
[Correction Information Generation Image Data Acquisition Unit 10]
3 to 6 are diagrams showing examples of images of correction information generation image data acquired by the correction information generation image data acquisition means 10 of the printing apparatus 1 of the present invention.

3 and 4 are diagrams showing actual images of the correction information generation image data acquired by the correction information generation image data acquisition means 10.
These images show examples of images for generating banding correction information according to the present invention. The print image is a two-dimensional image represented by ink dots on the print paper, and can be formed by moving the nozzles of the printing unit 90 that eject ink and the print paper relative to each other. In the printing means 90, nozzles capable of ejecting ink are formed on the print head provided on the lower surface of the carriage that accommodates the ink cartridges for each color, and the carriage is shifted in the same direction by reciprocating in a certain direction. A plurality of ink dots can be formed. A clearance of a predetermined distance is formed between the print head and the printing paper, and the ink particles ejected through the clearance fly and ink dots are formed at the landing positions. The carriage operation is referred to as main scanning, and the moving direction is referred to as main scanning direction.

  Further, the printing unit 90 is provided with a paper feeding mechanism for moving the printing paper, so that the printing paper can be fed in a certain direction every time the carriage performs main scanning a predetermined number of times. The operation of the printing paper is referred to as sub-scanning, and the movement direction is referred to as sub-scanning direction. The main scanning direction and the sub-scanning direction are generally orthogonal to each other. By combining these, ink dots can be formed at an arbitrary position on the printing paper. Therefore, it is possible to reproduce a two-dimensional image on the printing paper. Further, the paper feed mechanism does not perform sub-scanning while the print head performs main scanning.

  According to this configuration, the ink dots formed by the same nozzle are arranged in the main scanning direction on the printing paper. Therefore, when there is a defective nozzle that causes a deviation in the flying direction of the ink particles of black (K) ink, when a print image is formed with dots of only K ink, the ink dots formed at the shifted positions are continuous, A streak noise (banding) along the scanning direction is formed.

Further, banding in the printing apparatus 1 having the above configuration appears in the sub-scanning direction of the image (here, the vertical direction of the image).
For example, in the example shown in FIG. 3, there is almost no difference in the vertical stripes or the density, so that the density change when viewed macroscopically is flat (for example, the density change has no gradient). It is a real sample of the acquired image. Further, in the example shown in FIG. 4, since the lower side is brighter when the vertical stripes are slightly or shaded, the density change when viewed macroscopically is not flat (the density change has a gradient). It is a real sample of the acquired image of a state.

  5 and 6 are schematic diagrams of acquired images. The example shown in FIG. 5 is a schematic diagram of an acquired image in a state where the density change has no gradient when viewed macroscopically, and is a schematic diagram corresponding to FIG. The example shown in FIG. 6 is a schematic diagram of an acquired image in a state where the density change has a gradient when viewed macroscopically, and is a schematic diagram corresponding to FIG. The schematic diagrams of FIGS. 5 and 6 are images with clearer image characteristics. In an extreme example, the schematic diagram of the acquired image in FIG. 6 has a step in the vertical direction and the lower side becomes brighter. I understand that

  In addition, factors that reduce the image quality of a printed image include banding (striped noise) and granular noise. In order to correct banding appropriately, it is necessary to extract density information that understands the banding state. . For example, when ink dots formed at shifted positions are arranged in the main scanning direction, a blank area continuous in the main scanning direction is formed and banding occurs. In actual printing, it is rare to perform printing using only a single ink, and banding is rarely continued in the main scanning direction in a strict sense. However, since the shifted ink dots are formed periodically, streaking banding is felt when the printed image is viewed as a whole. Such banding is a factor that degrades the image quality of the printed image. Therefore, in order to reduce or remove banding from a printed image, it is necessary to adjust nozzles that cause banding or to correct image data to be printed. However, the error caused by the nozzle is often caused by a manufacturing error that occurs in the manufacturing stage, and is extremely difficult to remove.

  On the other hand, since the print image is formed of a plurality of ink dots, even if the ink dots are properly arranged, granular noise of the ink dots occurs. For example, granular noise can be grasped as light and dark undulations such that the lightness is low at a part formed by overlapping a plurality of ink dots, and the lightness is high at a part not covered with ink dots. However, the granular noise is uniformly distributed over the entire printed image unlike the banding, and has no directivity.

  As described above, the printed image includes both the granular noise and the banding having different properties, but in the present invention, attention is paid to the banding. Then, correction information appropriate for correcting the banding is generated, and the image data is corrected using the correction information, thereby reducing or removing the banding from the print image.

[Density information extraction means 20]
7 and 8 are graphs in which banding is extracted as a change in density information by the density information extraction means 20.

FIG. 7 is a graph showing the result of density information extraction by the density information extraction means 20 for two types of model A and model B from the actual images, that is, the images described above with reference to FIGS. It is.
7, the horizontal axis is the X axis, the vertical axis is the Y axis, and 0, 89, 178, 267. ... 2581 and the line number of the image, the luminance value in the range of 120 to 160 is taken on the Y axis, and the average luminance value for each line is obtained in the vertical direction of the images in FIGS. 3 and 4, and this average luminance value It is the graph which used the change of as a signal sequence. Line A shows the result for model A, that is, the image of FIG. 3, and line B shows the result for model B, that is, the image of FIG.

  As a result, the model A has a small concentration gradient in the horizontal direction, and no significant difference was observed between the line numbers 0 to 2581, but the model B had a concentration gradient in the horizontal direction of the line numbers 0 to 0. It can be seen that the luminance value 155 to 135 and the concentration gradient in the horizontal direction are intense during 2581. As described above, the actual image is an image as shown in FIG. 2 or FIG. 3 described above. As a result of obtaining the average luminance for each line in the vertical direction of the image, a horizontal density gradient is generated. From this, it can be visually understood that the model B has a factor that generates a large concentration gradient that should not exist.

  The primary density gradient as shown by the line B in FIG. 7 may occur, for example, when a scanner is used when generating patch image data for generating banding correction information. For example, the scanner scans the print image with a line sensor while irradiating the print image with light, and photoelectrically converts the reflected light to obtain density information. When there is an abnormality in the scanner due to manufacturing defects or the like, for example, a primary density gradient shown in FIG. 13A is generated in the density information of the patch image generated by the scanner.

From this, it can be predicted that the density gradient as shown by the line B in FIG.
The banding correction is generally performed by inverting the sign of the average luminance value of each image line and adding it to the value of each pixel of each image line. Therefore, if banding is corrected by the above correction method based on density information having a density gradient that should not exist (hereinafter referred to as an inappropriate density gradient), the density gradient changes due to the inappropriate density gradient. Since up to a luminance value of one minute is added to the value of each pixel, there is a possibility that the print image quality is deteriorated by performing banding correction.

In addition, although the luminance value was used as a physical quantity here, generally, banding is perceived as unevenness in brightness change (not color change) and shows the same brightness. For the scale, a density value (OD value), a brightness value (Lab L value), or the like may be used.
Actually, from the signal sequence shown in FIG. 7, a wave having a cycle that is desired to be used for generating banding correction information is a high-cycle wave whose luminance is increased or decreased in units of several lines. In model B, a high-frequency wave is extracted as a signal, but at present, the influence of an inappropriate concentration gradient is large, and appropriate concentration information for generating banding correction information cannot be obtained. However, if only the improper density gradient that appears in the density change of the image can be removed and only the high-frequency wave can be left, only the pure banding component will remain, so an appropriate signal (density for correcting banding) Information).

FIG. 8 shows the change in the average luminance value for each vertical line, that is, the density gradient in the vertical direction, with the horizontal axis representing the image line number and the vertical axis representing the luminance value, as in FIG. As shown in FIG. 8, the concentration gradient also occurs in the vertical direction.
Also in this example, the density information extraction means 20 is a graph in which the average luminance value for each line is obtained in the horizontal direction for the two types of models, model A and model B, in the actual image.

[Concentration gradient calculating means 30]
For the calculation of the concentration gradient by the concentration gradient calculating means 30, the slope of the regression line obtained by the least square method is used for each signal sequence. Since the least squares method is a known method, description thereof is omitted here.

With reference to FIGS. 7 and 8, the concentration gradient is calculated for each signal as follows.
Concentration gradient in the horizontal direction of model A = −0.0007
Concentration gradient in the horizontal direction of model B = −0.0076
Concentration gradient in the vertical direction of model A = −0.0060
Concentration gradient in the vertical direction of model B = −0.0283
As a result, the concentration gradient in the horizontal direction is | −0.0007 | <| −0.0076 |, and the concentration gradient in the vertical direction is | −0.0060 | <| −0.0283 | As a result, the concentration gradient of model B was worse than that of model A. Also, since the X-axis range is different, the density gradient is numerically worse for both models A / B by an order of magnitude, but as a drop in density due to joining as an absolute value, It can be said that the vertical direction is relatively good.

[Density gradient correction means 40]
FIG. 9 is a flowchart illustrating an example of the density gradient correction process.
A method of density gradient correction processing will be described with reference to this flowchart.
First, after starting in step S101, in step S102, the density gradient correction unit 40 acquires the gradient of the density change of the image calculated by the density gradient calculation unit 30 as the gradient in the X-axis direction and the gradient in the Y-axis direction. To do. Next, in step S103, the density gradient correction unit 40 obtains coordinates (hereinafter referred to as center coordinates) corresponding to the pixels including the center pixel of the image in the density change of the image. Next, in step S104, the density gradient correction unit 40 obtains an X coordinate and a Y coordinate corresponding to the target pixel in the density change of the image. Next, in step S105, the density gradient correcting unit 40 determines the pixel of interest whose inclination with respect to the center coordinate of the coordinate corresponding to the pixel of interest becomes 0 based on the distance between the coordinate corresponding to the pixel of interest and the center coordinate. A correction amount is calculated. Next, in step S106, the density gradient correction unit 40 corrects the luminance value of the target pixel using the correction amount calculated in step S105. Next, in step S107, the density gradient correction unit 40 determines whether or not all the target pixels have been corrected. If correction has not been performed for all the pixels, the process returns to step S104 to return to the next target pixel. The same processing is performed for. On the other hand, when the correction process is completed for all the target pixels, the density gradient correction process is ended in step S108.

FIG. 10 is a graph showing the concept of density gradient correction. This figure assumes that the straight line having the density gradient obtained in FIGS. 7 and 8 is assumed based on the central coordinates in the density change of the image in the flowchart of FIG. It is the figure which showed the concept in that case.
10A shows the center coordinates (points on the density gradient straight line), and B shows the moving direction for making the inclination zero. Specifically, when the inclination in the X-axis direction is corrected, the distance between the Y coordinate in the center coordinate and the Y coordinate in the coordinate corresponding to the target pixel is 0 (the Y coordinate of the target pixel is A correction amount of the target pixel (moving up to the X axis in the middle B direction) is determined, and the pixel value (in this case, the luminance value) of the target pixel is corrected using the determined correction amount.

Note that the target pixel in the present embodiment is a pixel constituting each image line used for calculating the average luminance value. For example, if the number of pixels in one line is 512, all 512 pixels correspond to the target pixel. The correction process is performed on all image lines (all pixels of interest) of the image.
11 and 12 are diagrams showing the luminance change for each line after correction. FIG. 11 is a correction for the average luminance value (horizontal density gradient) for each vertical line shown in FIG. FIG. 12 shows the luminance change of the average luminance value for each subsequent vertical line. FIG. 12 shows the average luminance value (vertical density gradient) for each horizontal line shown in FIG. It is a graph which shows the luminance change of average luminance.

As shown in FIGS. 11 and 12, it can be seen that only an inappropriate density gradient can be removed from the luminance change for each line after correction. Also, numerically, the corrected concentration gradient is as follows, and it can be seen that only the inappropriate concentration gradient is removed.
First, referring to the figure of the corrected average luminance for each vertical line shown in FIG. 11, that is, the horizontal density gradient, the horizontal density gradient of model A = 0.000 and the horizontal density gradient of model B = 0.0000. Further, referring to the figure of the corrected average luminance for each horizontal line shown in FIG. 12, that is, the vertical density gradient, the vertical density gradient of model A = 0.0002 and the vertical density of model B. The gradient was 0.0000, and only the vertical concentration gradient of model A had a negative value.

[Banding correction information generating means 50]
The banding correction information generation unit 50 obtains an average luminance value for each line from the image corrected by the density gradient correction unit 40, and generates banding correction information representing the density shading of each line using the average luminance value. Is. Since the banding correction information is shading information for some input value, it can be easily generated by calculating which line is how dark or how thin.

[Banding correction information storage means 60]
The banding correction information storage means 60 stores and stores the banding correction information generated by the banding correction information generation means 50 in a predetermined place so that it can be used as necessary.

[Printing Image Data Acquisition Unit 70]
In response to the print instruction, image data to be printed corresponding to the print instruction is acquired from the external apparatus or the internal apparatus.

[Banding correction means 80]
The banding correction unit 80 acquires the print image data by the print image data acquisition unit 70 and then converts the acquired print image data to the acquired print image data based on the banding correction information stored in the banding correction information storage unit 60 described above. On the other hand, banding correction processing is executed.

  Here, in the banding correction process, since the density of each image line with respect to each gradation value can be determined from the banding correction information, for example, the density is insufficient with respect to the average gradation value of an image line with image data for printing. If the density is excessive, correction is performed to reduce the excess density. Specifically, if the pixel value is a luminance value, if the density is insufficient, the luminance value corresponding to the insufficient density is subtracted, while if the density is excessive, the excess density The luminance value corresponding to is added.

[Printing means 90]
The printing unit 90 prints an image on a medium such as printing paper based on the printing image data that has been subjected to the banding correction process by the banding correction unit 80.

As described above, the printing apparatus 1 according to the present invention can remove a density gradient that should not exist from the density change of the patch image, and thereby, banding correction information including only a pure banding component can be obtained. It is possible to generate.
As mentioned above, although embodiment of this invention was described, this invention is not limited to this embodiment, A various change is possible without deviating from the meaning of this invention.

  For example, in the above-described embodiment, the primary concentration gradient as shown in FIG. 13A is removed by the least square method, but the concentration gradient to be removed is not always primary. For example, when the measurement system has a lens such as a microscope or a camera, the characteristics of the lens are different between the central part and the peripheral part, so that a secondary curve (concentration gradient) is obtained as shown in FIG. ) Occurs. Such a secondary concentration gradient should be present because it should not exist.

In order to remove the second-order concentration gradient, second-order polynomial approximation may be used. In addition, if you know how to find an approximate expression such as exponential function or logarithmic function, and it is a concentration gradient within the expected range for removal, the same effect can be obtained by removing the concentration gradient. Is obtained.
Hereinafter, based on FIG. 14 to FIG. 20, the effect on banding correction when a secondary inappropriate density gradient occurs in the density change of the patch image will be specifically described.

  Here, FIG. 14 is a diagram illustrating an example of a density change generated only by lens characteristics. FIG. 15 is a diagram illustrating an example of a density change in which the density change due to the lens characteristics and the density change of the patch image are combined. FIG. 16 is a diagram showing banding correction information generated from the density information having the density change of FIG. FIG. 17 is a diagram illustrating a density change as a result of correcting the banding using the banding correction information of FIG. FIG. 18 is a diagram illustrating an example of a pure density change of a patch image. FIG. 19 is a diagram showing banding correction information generated from the density information having the density change of FIG. FIG. 20 is a diagram showing a change in density as a result of correcting the banding using the banding correction information of FIG.

  In general, when the density information of a patch image is acquired using an area sensor that captures an image two-dimensionally by combining a lens such as a microscope, it is known that the periphery of the acquired patch image of the density information is dark. ing. As shown in FIG. 14, when the difference from the target density is taken on the vertical axis and the nozzle number (corresponding to the line number of the image) is taken on the horizontal axis, the density difference is zero at both ends of the image. The density difference increases toward the center.

As shown in FIG. 15, the density information (average luminance value of each image line) of the patch image obtained through the lens having such characteristics takes the difference from the target density on the vertical axis, and the nozzle number (image If the horizontal axis represents the line number (corresponding to the line number), a second-order large inappropriate concentration gradient is generated with respect to the concentration change seen macroscopically.
On the other hand, when banding correction information is generated in a state where there is an inappropriate density gradient as described above, the correction amount is obtained by taking the density correction amount on the vertical axis and nozzle numbers (corresponding to image line numbers) as shown in FIG. When the horizontal axis is taken, the density change in FIG. 15 is just inverted upside down. That is, the banding correction information reflects the secondary density gradient as it is.

  When correction is performed with banding correction information reflecting the secondary inappropriate density gradient, the correction amount of the special component of the lens is added to the value of each pixel, so the density change of the correction result is As shown in FIG. 17, if the difference from the target density is taken on the vertical axis and the nozzle number (corresponding to the line number of the image) is taken on the horizontal axis, the density change due to the lens characteristics shown in FIG. It will be reversed.

In other words, since the original image data used when printing the patch image does not include any influence due to the lens characteristics, the density change corresponding to the correction amount obtained by inverting the density change due to the lens characteristics is directly applied. It will be mixed.
Therefore, by using the method of the present invention described above, the secondary density gradient due to the lens characteristics is removed from the density change shown in FIG. In this case, a quadratic curve representing the lens characteristic is approximated using a quadratic polynomial, and correction is performed so that the gradient becomes zero. By this correction, density information of only pure banding components as shown in FIG. 18 is obtained. In FIG. 18, the vertical axis represents the difference from the target density, and the horizontal axis represents the nozzle number (corresponding to the line number of the image).

  Then, the banding correction information is generated by vertically inverting the pure banding component shown in FIG. 18, and the change in the correction amount is as shown in FIG. In FIG. 19, the vertical axis represents the density correction amount, and the horizontal axis represents the nozzle number (corresponding to the line number of the image). By correcting the banding of the original image data using the density correction amount shown in FIG. 19, the correction result shows that the density difference in all the image lines becomes 0 and flat characteristics are obtained as shown in FIG. . In FIG. 20, the vertical axis represents the difference from the target density, and the horizontal axis represents the nozzle number (corresponding to the line number of the image).

  Regarding the density gradient correction, in the above-described embodiment, the primary concentration gradient is removed using the least square method, but the present invention is not limited to this, and the concentration gradient can be removed using various methods.

It is a block diagram which shows the structure of the banding information creation apparatus of the printing apparatus which concerns on embodiment of this invention. 1 is a block diagram illustrating a configuration of a printing apparatus main body according to an embodiment of the present invention. It is a real sample which shows the input image in case boundary conditions are favorable. It is a real sample which shows the input image in case of boundary condition failure. It is a schematic diagram which shows the input image in case boundary conditions are favorable. It is a schematic diagram which shows a boundary condition defect input image. It is a graph which shows the fluctuation | variation of the average brightness | luminance for every vertical direction line. It is a graph which shows the fluctuation | variation of the average brightness | luminance for every horizontal direction line. It is a flowchart which shows an example of a density gradient correction process. It is a conceptual diagram of density gradient correction. It is a figure which shows the fluctuation | variation after correction | amendment of the average luminance for every horizontal line. It is a figure which shows the fluctuation | variation after correction | amendment of the average luminance for every horizontal line. It is a figure which points out the problem of a prior art example, and is a schematic diagram which shows the result scanned for making correction information, and when (a) forms a steep slope, (b) falls rapidly Then, it shows the case of rising again. It is a figure which shows an example of the density | concentration change generate | occur | produced only by the characteristic of a lens. It is a figure which shows an example of the density change which combined the density change by the characteristic of a lens, and the density change of a patch image. It is a figure which shows the banding correction information produced | generated from the density information which has a density change of FIG. It is a figure which shows the density | concentration change of the result of having corrected the banding using the banding correction information of FIG. It is a figure which shows an example of the pure density change of a patch image. It is a figure which shows the banding correction information produced | generated from the density information which has a density change of FIG. It is a figure which shows the density | concentration change of the result of having corrected the banding using the banding correction information of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Printing apparatus, 2 ... Banding correction information generation apparatus, 10 ... Image data acquisition means for correction information generation, 20 ... Density information extraction means, 30 ... Density gradient calculation means, 40 ... Density gradient correction means, 50 ... Banding correction information Generation means 60 ... Banding correction information storage means 70 ... Printing image data acquisition means 80 ... Banding correction means 80 ... Printing means

Claims (15)

Correction information generation image data acquisition means for acquiring correction information generation image data that is image data of an image for generation of banding correction information;
Density information extraction means for extracting density information of the image based on the correction information generation image data;
Density gradient calculating means for calculating a gradient of density change of the image based on the density information extracted by the density information extracting means;
Density gradient correction means for correcting the correction information generating image data based on the gradient of the density change calculated by the density gradient calculation means;
Banding correction information generation means comprising: banding correction information generation means for generating banding correction information for correcting banding based on the correction information generation image data corrected by the density gradient correction means. apparatus.   The banding correction information generating apparatus according to claim 1, wherein the density information uses any one of a luminance value, a density value (OD value), and a lightness value (L value).   3. The banding correction information according to claim 1, wherein the density information includes a statistical value of density of at least one of a banding occurrence direction and a direction orthogonal to the banding occurrence direction in the image. Generator.   4. The banding correction information generation apparatus according to claim 3, wherein the density statistical value is one of a luminance average value, a density average value, and a lightness average value for each line of the image.   5. The banding correction information generation apparatus according to claim 1, wherein the concentration gradient calculation unit is a unit that calculates the gradient by linear approximation using a least square method. 6.   The banding correction information generating apparatus according to any one of claims 1 to 4, wherein the density gradient calculating unit is a unit that calculates the gradient by polynomial approximation.   The density gradient correction unit is a unit that corrects the correction information generation image data so that the gradient calculated by the density gradient calculation unit is removed from the density change of the image. The banding correction information generation device according to any one of claims 1 to 6.   The density gradient correction unit may remove at least one of a gradient with respect to a density change in the banding generation direction of the image and a gradient with respect to a density change in a direction orthogonal to the banding generation direction from the density change of the image. The banding correction information generation apparatus according to claim 7, wherein the correction information generation image data is means for correcting the correction information generation image data. Correction information generation image data acquisition step of acquiring correction information generation image data which is image data of an image for generation of banding correction information;
A density information extraction step for extracting density information of the image based on the correction information generation image data;
A density gradient calculating step for calculating a gradient of density change of the image based on the density information extracted in the density information extracting step;
A density gradient correction step for correcting the correction information generating image data based on the gradient of the density change calculated in the density gradient calculation step;
A banding correction information generation step for generating banding correction information for correcting banding based on the correction information generation image data corrected in the density gradient correction step. . Correction information generation image data acquisition step of acquiring correction information generation image data which is image data of an image for generation of banding correction information;
A density information extraction step for extracting density information of the image based on the correction information generation image data;
A density gradient calculating step for calculating a gradient of density change of the image based on the density information extracted in the density information extracting step;
A density gradient correction step for correcting the correction information generating image data based on the gradient of the density change calculated in the density gradient calculation step;
A program used for causing a computer to execute processing including a banding correction information generation step for generating banding correction information for correcting banding based on the correction information generation image data corrected in the density gradient correction step. A banding correction information generation program characterized by comprising:   The computer-readable recording medium which recorded the banding correction information generation program of Claim 10. Correction information generation image data acquisition means for acquiring correction information generation image data that is image data of an image for generation of banding correction information;
Density information extraction means for extracting density information of the image based on the correction information generation image data;
Density gradient calculating means for calculating a gradient of density change of the image based on the density information extracted by the density information extracting means;
Density gradient correction means for correcting the correction information generating image data based on the gradient of the density change calculated by the density gradient calculation means;
Banding correction information generation means for generating banding correction information for correcting banding based on the correction information generation image data corrected by the density gradient correction means;
Printing image data acquisition means for acquiring printing image data which is image data of an image to be printed;
Banding correction means for performing processing for correcting banding on the image data for printing using the banding correction information generated by the banding correction information generation means;
A printing apparatus comprising: a printing unit configured to print the image to be printed on a medium used for printing based on the printing image data. Correction information generation image data acquisition step of acquiring correction information generation image data which is image data of an image for generation of banding correction information;
A density information extraction step for extracting density information of the image based on the correction information generation image data;
A density gradient calculating step for calculating a gradient of density change of the image based on the density information extracted in the density information extracting step;
A density gradient correction step for correcting the correction information generating image data based on the gradient of the density change calculated in the density gradient calculation step;
A banding correction information generation step for generating banding correction information for correcting banding based on the correction information generation image data corrected in the density gradient correction step;
A printing image data acquisition step of acquiring printing image data which is image data of an image to be printed;
Using the banding correction information generated in the banding correction information generation step, a banding correction step for executing processing for correcting banding on the print image data;
And a printing step of printing the image to be printed on a medium used for printing based on the printing image data. Correction information generation image data acquisition step of acquiring correction information generation image data which is image data of an image for generation of banding correction information;
A density information extraction step for extracting density information of the image based on the correction information generation image data;
A density gradient calculating step for calculating a gradient of density change of the image based on the density information extracted in the density information extracting step;
A density gradient correction step for correcting the correction information generating image data based on the gradient of the density change calculated in the density gradient calculation step;
A banding correction information generation step for generating banding correction information for correcting banding based on the correction information generation image data corrected in the density gradient correction step;
A printing image data acquisition step of acquiring printing image data which is image data of an image to be printed;
Using the banding correction information generated in the banding correction information generation step, a banding correction step for executing processing for correcting banding on the print image data;
A printing program comprising: a program used for causing a computer to execute a process including a printing step of printing the image to be printed on a medium used for printing based on the printing image data.   The computer-readable recording medium which recorded the printing program of Claim 14.

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