JP2018129652A - Image comparison device, image comparison method, and image comparison program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image comparison device capable of simply and surely performing a version checking work of a printed matter.SOLUTION: An image comparison device 1 comprises: a difference image formation part 111 that extracts a luminance difference in each pixel from a first image and a second image as a difference, and forms a difference image; a different point display image formation part 112 that extracts the pixel having the luminance difference which is equal to a first threshold value or more from the different image, and forms a difference point display image; a weighting image formation part 113 that forms at least one image of the image weighted at a connection point of each pixel arranged in a vertical direction from the different point display image, the image weighted at the connection position of each pixel arranged in the horizontal direction, and the image weighted by a number of connections of each pixel in the vertical direction a horizontal direction; a filtering image formation part 114 that extracts the pixel having a weighted value that is equal to a second threshold value or more from the weighted image, and forms a filtering image; and a display control part 3 that displays the filtering image onto a display screen.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image comparison device, an image comparison method, and an image comparison program.

  Conventionally, in order to improve the efficiency of plate inspection work for printed matter, the difference in luminance difference for each pixel is extracted from the pre-correction image and the post-correction image obtained in the plate making process, and the area where the difference exceeds the threshold is regarded as a difference. An apparatus for creating displayed image data has been proposed (see Patent Document 1). In addition, an apparatus has been proposed in which a plurality of threshold values are set for the difference in luminance difference extracted for each pixel, and image data in which differences at each threshold value are displayed (see Patent Document 2). .

JP2013-80524A WO 2015/114833 A1

  In the conventional apparatus, the difference extracted from the pre-correction image and the post-correction image occurs in a data conversion process called rasterization processing in addition to the correction result of characters, patterns, designs, etc., performed in the plate making operation. Quantum error may be included. Among these differences, the differences caused by the plate making work are corrected to confirm whether the location where correction is instructed is properly corrected and whether the location where correction is not instructed is corrected. It is necessary to leave as history. On the other hand, the difference caused by the rasterizing process occurs even though it has not been corrected in the plate making operation, so it must be removed as dust. This is to remove unnecessary dust from the image data on which the difference to be left is displayed, thereby improving the efficiency of the plate inspection work.

  In the plate making operation, a correction result added due to an operation error needs to be deleted from the image after correction after the plate inspection operation, and therefore needs to be left as a correction history. In the apparatus of Patent Document 1, a correction result added due to an operation mistake is removed as dust if the difference in luminance difference at the correction portion is smaller than a threshold value, so that the plate inspection operation is overlooked. In this case, if the threshold value is decreased, much of the dust to be removed remains in the image data as the correction history. On the other hand, if the threshold value is increased, most of the dust can be removed, but the correction result by the plate making operation may also be removed. In either case, the plate inspection work becomes complicated or oversight occurs.

  Further, in the apparatus of Patent Document 2, since the image data displaying the difference at each threshold value can be referred to, the operator discriminates the correction result that should be left as the correction history and the one that can be removed as dust. It becomes easy. However, if the variation in the luminance difference of the pixels to be removed as dust is large compared to the difference in the luminance difference at the correction location, the operator will repeatedly refer to a plurality of image data. Work becomes complicated and oversight occurs.

  An object of the present invention is to provide an image comparison apparatus, an image comparison method, and an image comparison program that can perform a plate inspection operation of a printed matter more easily and accurately.

The present invention solves the problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected and demonstrated, it is not limited to this. In addition, the configuration described with reference numerals may be improved as appropriate, or at least a part thereof may be replaced with another configuration.
The first invention extracts a luminance difference for each pixel as a difference from a first image that is an inspection reference and a second image that is an inspection target, and creates a difference image, and the difference A difference display image creation unit (112) for extracting a pixel having a luminance difference equal to or greater than a first threshold as a difference from the difference image created by the image creation unit, and creating a difference display image; and the difference From the difference display image created by the display image creation unit, an image weighted at the connection position of each pixel arranged in the vertical direction, an image weighted at the connection position of each pixel arranged in the horizontal direction, and the vertical direction and A weighted image creation unit (113) that creates at least one image as a weighted image among images weighted by the number of connected pixels in the horizontal direction, and the weighted image creation unit. A pixel having a weight value equal to or greater than a second threshold is extracted from the weighted image, and a filtering image creation unit (114) that creates a filtering image; and the filtering image created by the filtering image creation unit is displayed on a display screen. A display control unit (3) to be displayed on the image comparison apparatus (1).
2nd invention is the image comparison apparatus (1) of 1st invention, Comprising: The said display control part (3) is at least 2 when the said filtering image is produced in multiple numbers based on the said several weighted image. The two filtered images are displayed side by side on a display screen.
A third invention is the image comparison device (1) according to the first invention, wherein the display control unit (3) has at least 2 when the plurality of filtering images are created based on the plurality of weighted images. The two filtered images are alternately displayed at the same position on the display screen.
4th invention is the image comparison apparatus (1) of 1st or 2nd invention, Comprising: The said display control part (3) displays the said 1st image and the said 2nd image with the said filtering image. It is characterized by being displayed side by side.
5th invention is the image comparison apparatus (1) of 1st or 3rd invention, Comprising: The said display control part (3) is a display screen of the said 1st image and the said 2nd image with the said filtering image. Are alternately displayed at the same position.
A sixth aspect of the invention is the image comparison device (1) according to any one of the first to fifth aspects of the invention, wherein a threshold value changing unit that changes at least one of the first threshold value and the second threshold value ( 10).
According to a seventh aspect of the present invention, a difference image creation step of extracting a luminance difference for each pixel as a difference from a first image serving as an inspection reference and a second image serving as an inspection target, and creating the difference image, and the difference image creation step A pixel having a luminance difference equal to or greater than a first threshold is extracted as a difference from the difference image created by the steps, and a difference display image creation step for creating a difference display image and a difference display image creation step Further, from the difference display image, an image weighted at a connection position of each pixel arranged in the vertical direction, an image weighted at a connection position of each pixel arranged in the horizontal direction, and a connection of each pixel in the vertical direction and the horizontal direction A weighted image creating step for creating at least one image as a weighted image among the images weighted by the number, and the weighted image created by the weighted image creating step A filtering image creating step for extracting a pixel having a weighting value equal to or greater than the second threshold and creating a filtered image, and a display control step for displaying on the display screen at least one filtering image created by the filtering image creating step And an image comparison method.
An eighth invention is an image comparison program executed in a computer, wherein the computer extracts a luminance difference for each pixel as a difference from a first image as an inspection reference and a second image as an inspection target, A difference image creating unit that creates a difference image, and a difference in which a pixel having a luminance difference equal to or greater than a first threshold is extracted as a difference from the difference image created by the difference image creating unit, and a difference display image is created. A point display image creating means; an image weighted by a connecting position of pixels arranged in the vertical direction from the difference display image created by the difference display image creating means; a connecting position of each pixel arranged in the horizontal direction At least one image is created as a weighted image from among the images weighted by, and the images weighted by the number of connected pixels in the vertical and horizontal directions. A weighted image creating means, a filtering image creating means for creating a filtered image by extracting a pixel having a weight value greater than or equal to a second threshold from the weighted image created by the weighted image creating means, and the filtering image creating The present invention relates to an image comparison program that functions as display control means for displaying at least one filtered image generated by the means on a display screen.

  ADVANTAGE OF THE INVENTION According to this invention, the image comparison apparatus, the image comparison method, and image comparison program which can perform the plate inspection work of printed matter more simply and correctly can be provided.

It is a figure explaining the image comparison apparatus 1 of embodiment. It is a figure explaining the image 20 before correction, the image 30 after correction, and the difference image 40. FIG. It is a figure explaining the difference display image. It is a figure explaining the weighted image. It is a figure explaining the filtering image. It is a figure explaining the filtering image. It is a figure explaining the filtering image. 3 is a flowchart showing a processing procedure of an image comparison program executed by the image comparison device 1. It is a figure explaining the example which displayed the some image side by side on the display screen. It is a figure explaining the example which displayed the some image side by side on the display screen. FIG. 10 is a diagram illustrating an example in which a plurality of images are alternately displayed at the same position on the display screen S. FIG. 10 is a diagram illustrating an example in which a plurality of images are alternately displayed at the same position on the display screen S.

Hereinafter, embodiments of the present invention will be described. The drawings attached to the present specification are all schematic diagrams, and the shape, scale, vertical / horizontal dimensional ratio, etc. of each part are changed or exaggerated from the actual ones in consideration of ease of understanding.
FIG. 1 is a diagram illustrating an image comparison apparatus 1 according to the present embodiment.
The image comparison apparatus 1 according to the present embodiment is an apparatus for plate inspection work that detects and displays a corrected portion from a pre-correction image and a post-correction image obtained in a plate making process of a printed matter.
As shown in FIG. 1, an image comparison apparatus 1 according to this embodiment includes a display device 2, a display control unit 3, a data input unit 4, an operation input unit 5, an input control unit 6, a storage unit 7, and a DB (database) device. 8, a DB control unit 9, a control unit 10, and an image processing unit 11. Among these, the display control unit 3, the input control unit 6, the storage unit 7, the DB control unit 9, the control unit 10, and the image processing unit 11 constitute an apparatus main body 12.

The display device 2 is a display device having a display screen that can display various images such as a pre-correction image 20, a post-correction image 30, a difference display image 50, a filtering image 70, and the like, which will be described later.
The display control unit 3 controls display of various images on the display device 2. The display control unit 3 displays, for example, a filtered image read from the DB device 8 (described later) side by side on the display screen of the display device 2 in accordance with the operator's operation instruction acquired by the operation input unit 5. Or display alternately at the same position.

The data input unit 4 is an apparatus capable of inputting image data such as the pre-correction image 20 and the post-correction image 30 used for the plate making operation. The data input unit 4 includes, for example, one or more of a scanner, a PC (personal computer), a network communication terminal device, a reading device for a recording medium such as a CD-ROM, and the like.
The operation input unit 5 is a device that allows an operator to input various character information, numerical data, operation instructions, operation instructions, and the like. The operation input unit 5 includes, for example, a keyboard, a mouse, a touch panel, etc. (not shown).
The input control unit 6 acquires the image data input from the data input unit 4, the data input from the operation input unit 5, instructions, etc., and stores them in the storage unit 7 or via the DB control unit 9. 8 is memorized.

The storage unit 7 is a storage device that stores programs executed by the control unit 10 and the image processing unit 11, data, and the like. The storage unit 7 is configured by, for example, a semiconductor memory, a hard disk, or the like.
In addition to the image data such as the pre-correction image 20 and the post-correction image 30 input from the data input unit 4, the DB device 8 stores image data such as the difference image 40 and the difference display image 50 created by the image processing unit 11. Is an external storage device.
The DB control unit 9 stores image data and the like in the DB device 8 and sends image data and the like read from the DB device 8 to the display control unit 3.

  The control unit 10 is a unit that comprehensively controls the operation of the image comparison device 1 and is configured by a microprocessor including a CPU (Central Processing Unit), a memory, and the like. The control unit 10 reads out and executes an operating system, an application program, and the like from the storage unit 7, thereby realizing various functions in cooperation with each hardware.

The control unit 10 also functions as a threshold value changing unit that changes a first threshold value and a second threshold value, which will be described later, based on numerical data input by the operator via the operation input unit 5. When the operator inputs numerical data of the first threshold value or the second threshold value via the operation input unit 5, the control unit 10 stores these numerical data in the DB device 8. In the image processing unit 11, the difference display image creation unit 112 (described later) refers to the first threshold when creating the difference display image. Further, the filtering image creation unit 114 (described later) refers to the second threshold value when creating the filtering image.
Note that some or all of the functions of the image processing unit 11 described later may be executed by the control unit 10.

The image processing unit 11 is configured by a microprocessor including a CPU, a memory, and the like. The image processing unit 11 reads out and executes an application program (image comparison program) for plate inspection work from the storage unit 7 to create and display various images described later in cooperation with each hardware. It is displayed on the device 2.
As shown in FIG. 1, the image processing unit 11 includes a difference image creation unit 111, a difference display image creation unit 112, a weighted image creation unit 113, and a filtering image creation unit 114.
Hereinafter, the function of each part which comprises the image process part 11 is demonstrated with the specific example (FIGS. 2-7) of an image.

FIG. 2 is a diagram for explaining the pre-correction image 20, the post-correction image 30, and the difference image 40. FIG. 2A is a diagram illustrating an example of the pre-correction image 20. FIG. 2B is a diagram illustrating an example of the corrected image 30. FIG. 2C is a diagram illustrating an example of the difference image 40.
FIG. 3 is a diagram for explaining the difference display image 50. FIG. 3A is a diagram illustrating an example of the difference display image 50. FIG. 3B is an enlarged view of the region a shown in FIG.

  FIG. 4 is a diagram for explaining the weighted image 60. FIG. 4A is a diagram illustrating an image weighted by the connection position of each pixel arranged in the vertical direction. FIG. 4B is a diagram illustrating an image weighted by the connection position of each pixel arranged in the horizontal direction. FIG. 4C is a diagram illustrating an image weighted by the number of connected pixels in the vertical direction and the horizontal direction.

  5 to 7 are diagrams for explaining the filtering image 70. FIG. 5 is a diagram illustrating a filtered image created from a weighted image in the vertical direction. FIG. 6 is a diagram illustrating a filtered image created from a weighted image in the horizontal direction. FIG. 7 is a diagram illustrating a filtering image created from weighted images in the vertical direction and the horizontal direction.

  The difference image creation unit 111 creates the difference image 40 based on the pre-correction image 20 (first image) serving as the inspection reference and the post-correction image 30 (second image) serving as the inspection target. The difference image creation unit 111 acquires the pre-correction image 20 and the post-correction image 30 from the DB device 8 (see FIG. 1). These images are expressed in gradations from white to black. For example, when one pixel is expressed by 8 bits, it is displayed as a grayscale image of 256 gradations (0 to 255). The same applies to a difference image 40, a difference display image 50, and the like, which will be described later.

In the pre-correction image 20 of the present embodiment, as shown in FIG. 2A, a character string 22 is described in a character frame 21, and a square figure 23 is drawn on the lower right.
In the corrected image 30, as shown in FIG. 2B, a character string 22 is described in a character frame 21, and a triangular figure is drawn on the lower right. The corrected image 30 is an image that has been corrected in the plate making process. In the corrected image 30 of the present embodiment, the square figure 23 is replaced with a triangular figure 31 by a normal correction operation. In the corrected image 30, the character frame 21 and the character string 22 are not corrected, but an unnecessary circle 32 is added to the upper left of the character frame 21 due to a work mistake.

  The difference image creation unit 111 superimposes the pre-correction image 20 and the post-correction image 30 and extracts a luminance difference for each pixel as a difference to create a difference image 40 as shown in FIG. For superimposing the uncorrected image 20 and the corrected image 30, for example, the upper left corner of both images is used as a reference point, and the reference point of the uncorrected image 20 and the reference point of the corrected image 30 on the bitmap data And the like are used. The difference image 40 created by the difference image creation unit 111 is stored in the DB device 8.

  When the pre-correction image 20 and the post-correction image 30 are compared, and there is no change, that is, in the part where the correction is not applied to the pre-correction image 20, when both images are superimposed, the difference in luminance difference for each pixel Becomes zero. For this reason, as shown in FIG. 2C, the portion without change is a white background where nothing is displayed in the difference image 40. On the other hand, in the portion where the correction is applied to the pre-correction image 20, when both images are overlapped, a difference occurs in the luminance difference for each pixel. Therefore, the portion is displayed in light and shade according to the difference in luminance difference. .

  In the difference image 40 shown in FIG. 2C, a difference is partially generated in the luminance difference for each pixel in the uncorrected graphic 23 and the corrected graphic 31, so that part is extracted as the differential image 41. ing. In this example, the difference image 41 has a shape obtained by subtracting a triangle from a quadrangle. In addition, since a difference is generated in the luminance difference for each pixel in the portion of the circle 32 added due to an operation error, the portion is extracted as the same circular-shaped difference image 42. The circle 32 shows an example of a pattern that is likely to occur due to a work mistake.

  On the other hand, the difference image 40 of the present embodiment includes not only the difference image generated in the plate making process but also the error image 43 generated by the rasterizing process described above. Unlike the difference image generated in the plate making process, the error image 43 generated by the rasterizing process is an image treated as dust. Although not shown in the figure, the difference image 40 also extracts a minute difference image generated by the difference in luminance difference for each pixel of both images. Since most of the luminance differences of these difference images are less than a first threshold value described later, they are removed as dust when the difference display image 50 is created. In the present embodiment, as the difference display image 50, the same image as the difference image 40 shown in FIG. 2C is illustrated, but pixels less than the first threshold are actually removed.

  The difference display image creation unit 112 extracts pixels having a luminance difference equal to or greater than the first threshold from the difference image 40 as differences, and creates the difference display image 50 shown in FIG. That is, the difference display image creation unit 112 creates an image obtained by selecting the difference image 40 with the first threshold as the difference display image 50. The difference display image 50 created by the difference display image creation unit 112 is stored in the DB device 8.

  As shown in the enlarged view of FIG. 3B, the image included in the difference display image 50 is formed by a plurality of pixels having a luminance difference equal to or greater than the first threshold value. In the difference display image 50, the area shown in the enlarged view of FIG. 3B includes a difference image 42 caused by a work mistake and a part of an error image 43 caused by the rasterizing process. Although not shown, the difference image 41 shown in FIG. 3A is also formed by a plurality of pixels having a luminance difference equal to or greater than the first threshold, as in the difference image 42 shown in FIG.

  The first threshold is a value set for removing dust from the difference image 40. As the first threshold value, a value capable of selecting a difference image that can be removed as dust among the difference images extracted as the difference in luminance difference for each pixel is set. If the luminance difference of the difference image is less than the first threshold, the difference image is removed as dust. If the first threshold value is reduced, much of the dust to be removed remains in the difference display image 50. On the other hand, if the first threshold value is increased, most of the dust can be removed, but the difference images 41 and 42 generated by the plate making operation may also be removed. For this reason, it is desirable to set the first threshold value to a value that can leave a differential image necessary for plate inspection work while eliminating a differential image that can be removed as dust. The operator can appropriately change the first threshold while comparing the difference image 40 displayed on the display device 2 with the difference display image 50.

  Next, an example in which the weighted image 60 and the filtering image 70 are created from the difference display image 50 will be described. The weighted image 60 shown in FIG. 4 and the filtering image 70 shown in FIGS. 5 to 7 are created from FIG. 3B, which is a partially enlarged view of the difference display image 50. The actual weighted image 60 and the filtered image 70 are created for all areas of the difference display image 50 shown in FIG.

  The weighted image creating unit 113 uses the difference display image 50 created by the difference display image creating unit 112 to weight the image at the connection position of each pixel arranged in the vertical direction, and the connection position of each pixel arranged in the horizontal direction. At least one image is created as a weighted image among the image weighted in step 1 and the image weighted by the number of connected pixels in the vertical and horizontal directions. The weighted image created by the weighted image creating unit 113 is stored in the DB device 8.

Here, an example of the weighted image created by the weighted image creating unit 113 will be described with reference to FIG.
As shown in FIG. 4A, the image weighted by the connection positions of the pixels arranged in the vertical direction is an image in which the pixels are weighted by the position from the end among the connection points in the vertical direction. That is, in the connection position of the pixels arranged in the vertical direction, the pixel located at the extreme end has a weight value of “1”, and the weight value increases by 1 as it is located on the inner side. In the image weighted at the connection position of the pixels arranged in the vertical direction, the weight values of the pixels arranged in the horizontal direction are all “1”. Hereinafter, the image weighted at the connection position of the pixels arranged in the vertical direction is also referred to as “weighted image 60a” or “vertical weighted image 60a”.

  As shown in FIG. 4B, the image weighted by the connection position of the pixels arranged in the horizontal direction is an image in which the pixel is weighted by the position from the end among the connection points in the horizontal direction. That is, in the connection position of each pixel arranged in the horizontal direction, the pixel located at the end has a weight value of “1”, and the weight value increases by 1 as it is located on the inner side. In the image weighted at the connection position of the pixels arranged in the horizontal direction, the weight values of the pixels arranged in the vertical direction are all “1”. Hereinafter, the image weighted at the connection position of each pixel arranged in the horizontal direction is also referred to as “weighted image 60b” or “horizontal weighted image 60b”.

  As shown in FIG. 4C, the image weighted by the number of connected pixels in the vertical and horizontal directions is an image weighted by the number of pixels connected in all directions in the vertical and horizontal directions. For example, if the number of connected pixels arranged linearly in the vertical direction is 11, the weight values of the pixels are all “11”. Further, if the number of connected pixels arranged in a line in the horizontal direction is 10, the weight value of each pixel is all “10”. Further, if the number of connected pixels arranged in a plane in the vertical direction and the horizontal direction is 21 as in the difference image 42, the weight value of each pixel is all “21”. Hereinafter, an image weighted by the number of connected pixels in the vertical and horizontal directions is also referred to as “weighted image 60c” or “weighted image 60c in all directions”.

In this embodiment, an example in which the weighted image creating unit 113 creates all the weighted images 60a to 60c will be described. However, at least one of the weighted images may be created. Hereinafter, the weighted images 60a to 60c are collectively referred to as a “weighted image 60”.
4 is not displayed on the display device 2 in the plate inspection operation, but is stored in the DB device 8 as image data, so that it is displayed on the display device 2 as necessary. You can also.

The filtering image creation unit 114 extracts pixels having a weighting value equal to or greater than the second threshold from the weighting image created by the weighting image creation unit 113, and creates a filtering image. The filtering image created by the filtering image creation unit 114 is stored in the DB device 8.
The second threshold value is a value set for selecting the pixel to be displayed in the weighted image 60. In the filtering image creation unit 114, pixels having a weight value that is less than the second threshold value are removed from the weighted image 60 as dust, so that pixels that are equal to or greater than the second threshold value can be extracted as pixels to be displayed.

  In the present embodiment, two second thresholds having different numerical values are set. That is, the threshold value set for the weighted image 60a in the vertical direction and the weighted image 60b in the horizontal direction, and the threshold value set for the weighted image 60c in all directions. In the present embodiment, the second threshold value set for the weighted image 60a in the vertical direction and the weighted image 60b in the horizontal direction is “1”. Further, the second threshold value set for the omnidirectional weighted image 60c is “20”. When creating a plurality of weighted images 60 as in the present embodiment, a plurality of second threshold values may be set. On the other hand, when the weighted image 60 to be created sets a common threshold value for one or a plurality of weighted images 60, the second threshold value may be one. The operator can appropriately change the second threshold value while comparing the difference display image 50 displayed on the display device 2 with the filtering image or the plurality of filtering images. In addition, the numerical value of the 2nd threshold value mentioned above is an example, and is not limited to this.

Here, an example of the filtering image created by the filtering image creation unit 114 will be described with reference to FIGS.
As shown in FIG. 5, by extracting pixels whose weighting value is less than “1” (pixels whose weighting value is “2” or more) in the weighting image 60a in the vertical direction, from the weighting image 60a in the vertical direction, A vertical filtered image 70a is created. As shown in FIG. 5, in the filtered image 70a in the vertical direction, the pixels arranged in the horizontal direction and the oblique direction are removed from the error image 43. Further, the difference image 42 is displayed as a horizontally long aggregate in which pixels having a weight value of “2” or more are connected in the vertical and horizontal directions.
In FIG. 5 to FIG. 7, pixels whose weighting value is less than the second threshold are shown in light gray for easy understanding. Pixels shown in light gray are pixels that are removed as dust and are not displayed in the filtered image.

  As illustrated in FIG. 6, by extracting pixels whose weighting value is less than “1” (pixels whose weighting value is “2” or more) in the horizontal weighting image 60 b, A horizontal filtered image 70b is created. As shown in FIG. 6, in the horizontal filtered image 70b, all the pixels arranged in the vertical direction and the oblique direction are removed from the error image 43. The difference image 42 is displayed as a vertically long aggregate in which pixels having a weight value of “2” or more are connected in the vertical and horizontal directions.

  As illustrated in FIG. 7, by extracting pixels whose weighting value is less than “1” (pixels whose weighting value is “2” or more) in the omnidirectional weighted image 60 c, An omnidirectional filtered image 70c is created. As shown in FIG. 7, in the omnidirectional filtering image 70c, all the pixels arranged in the vertical direction, the horizontal direction, and the diagonal direction are removed from the error image 43. The difference image 42 is displayed as a substantially square aggregate in which pixels having a weight value of “2” or more are connected in the vertical and horizontal directions.

  As described above, in the filtered images 70a to 70c, the error caused by the rasterizing process is removed as dust. Errors due to the rasterization process are likely to occur in the gradation portions such as symbols and patterns in addition to the boundary portions such as characters and graphics in the images before and after correction. Curve and oblique line errors caused by rasterization processing tend to be low in the vertical and horizontal connectivity of the pixels, so these errors remain in the difference display image 50 as pixels with large differences in luminance differences. However, as shown in FIG. 5 or FIG. 6, most of them can be removed as dust by filtering based on the vertical or horizontal weighting values.

  Further, when the connectivity of the pixels in the vertical direction or the horizontal direction is low, the weighting value based on the number of connections in the vertical direction and the horizontal direction is also small. Therefore, as shown in FIG. 7, by filtering based on the weighting values of the number of connections in the vertical direction and the horizontal direction, it is possible to remove errors of curves and diagonal lines generated by the rasterizing process as dust.

  On the other hand, errors in the straight lines extending in the vertical direction and the horizontal direction caused by the rasterizing process tend to be low in connectivity in directions orthogonal to each other (for example, the horizontal direction in the vertical direction). Therefore, even if these errors remain in the difference display image 50 as pixels having a large difference in luminance difference, the error of the straight line extending in the horizontal direction is based on the weighting value in the vertical direction as shown in FIG. Most of them can be removed as dust by filtering. Further, as shown in FIG. 6, most of the errors in the straight line extending in the vertical direction can be removed as dust by filtering based on the weighting value in the horizontal direction.

  Further, when the connectivity of the pixels in the vertical direction and the horizontal direction is low, the weighting value based on the number of connections in the vertical direction and the horizontal direction is also small. Therefore, as shown in FIG. 7, by filtering based on the weighting values of the number of connections in the vertical direction and the horizontal direction, most of errors in the straight lines extending in the vertical direction and the horizontal direction caused by the rasterizing process can be removed as dust. .

  On the other hand, in the present embodiment, the difference image 41 generated by the normal correction work and the round-shaped difference image 42 generated by the work mistake are aggregates of pixels connected in the vertical direction and the horizontal direction. The connectivity in the vertical and horizontal directions is increased. Therefore, as shown in FIGS. 5 and 6, when filtering is performed based on the weighting value in the vertical direction or horizontal direction, some pixels in the peripheral portion of the aggregate are removed, but the pixels in the central portion remain. become. Therefore, even if the difference image is filtered based on the weighting value in the vertical direction or the horizontal direction, the difference image is not removed as dust and can be left as a correction history.

  In addition, in the aggregate of pixels connected in the vertical direction and the horizontal direction, the weighting value based on the number of connections in the vertical direction and the horizontal direction also increases. Therefore, as shown in FIG. 7, when filtering is performed based on the weighting value of the number of connections in the vertical and horizontal directions, some pixels in the peripheral portion of the aggregate are removed, but many pixels in the central portion are Will remain. Therefore, even if the difference image is filtered based on the weighting values of the number of connections in the vertical direction and the horizontal direction, it is not removed as dust and can be left as a correction history.

  In this embodiment, an example in which the filtering images 70a to 70c are created in the filtering image creation unit 114 based on the weighted images 60a to 60c created in the weighting image creation unit 113 will be described. Created based on images. Therefore, for example, if there is one weighted image created by the weighted image creation unit 113, the filtering image created by the filtering image creation unit 114 is one. In the following description, the filtering images 70a to 70c are collectively referred to as a “filtering image 70”.

  The pre-correction image 20, the post-correction image 30, the difference display image 50, and the filtering image 70 described above are displayed side by side on the display device 2 or alternately at the same position by the display control unit 3 (see FIG. 1). The display form of each image by the display control unit 3 will be described later.

Next, processing contents of the image comparison program executed in the image comparison apparatus 1 described above will be described with reference to FIG.
FIG. 8 is a flowchart showing the processing procedure of the image comparison program executed by the image comparison apparatus 1.

  In step S <b> 1 illustrated in FIG. 8, the difference image creation unit 111 acquires from the DB device 8 a pre-correction image that is an inspection reference and a post-correction image that is an inspection target. Then, the difference image creation unit 111 extracts a difference in luminance for each pixel from the pre-correction image and the post-correction image as a difference, and creates a difference image (difference image creation step). In step S <b> 1, the difference image creation unit 111 performs, for example, a difference as illustrated in FIG. 2C based on the uncorrected image 20 illustrated in FIG. 2A and the corrected image 30 illustrated in FIG. An image 40 is created.

  In step S2, the difference display image creating unit 112 extracts pixels having a luminance difference equal to or greater than the first threshold from the difference image 40 created in step S1, and creates a difference display image (difference). Point display image creation process). The difference display image creation unit 112 creates a difference display image 50 as shown in FIG. 3A from the difference image 40, for example.

  In step S2, a pixel having a luminance difference equal to or greater than the first threshold may not be extracted from the difference image 40. For example, there is a case where there is an error in the content of the correction instruction or the correction is canceled. In this case, all pixels having a luminance difference in the difference image 40 are pixels that can be determined as dust, so that plate inspection for comparing the images and confirming the correction contents is not necessary. Thus, in step S2, if a pixel having a luminance difference equal to or greater than the first threshold cannot be extracted from the difference image 40, for example, a message for ending the image comparison program may be displayed on the display device 2. A message that prompts the operator to input an instruction as to whether or not to continue work may be displayed on the display device 2.

  In step S3, the weighted image creation unit 113 uses the difference display image 50 created in step S2 as an image weighted at the connection position of each pixel arranged in the vertical direction and the connection position of each pixel arranged in the horizontal direction. Of the weighted image and the image weighted by the number of connected pixels in the vertical and horizontal directions, at least one image is created as a weighted image (weighted image creation step). For example, the weighted image creating unit 113 creates at least one of the weighted images 60a to 60c as shown in FIGS.

In step S4, the filtering image creation unit 114 extracts pixels having a weighting value equal to or greater than the second threshold from the weighting image created in step S3, and creates a filtering image (filtering image creation step). When the weighted images 60a to 60c are created in step S3, the filtering image creation unit 114 creates filtering images 70a to 70c as shown in FIGS.
In step S5, the display control unit 3 displays the image designated by the operator among the corrected image 30, the difference display image 50, and the filtering image 70 side by side on the display device 2 or alternately at the same position (display). Control process).

Next, the display form of each image will be described. The display of each image on the display device 2 is executed by the display control unit 3 in the display control process described above.
9 and 10 are diagrams illustrating an example in which a plurality of images are displayed side by side on the display screen S. FIG. Each image is displayed in full size on the display screen S, but partially enlarged images of the images may be displayed side by side.

FIG. 11A shows an example in which a vertical filtering image and a horizontal filtering image are displayed side by side on the display screen S. FIG. FIG. 11B shows an example in which a vertical filtering image 70a, a horizontal filtering image 70b, and an omnidirectional filtering image 70c are displayed side by side on the display screen S.
FIG. 12A shows an example in which the difference display image 50 and the omnidirectional filtering image 70 c are displayed side by side on the display screen S. FIG. 12B shows an example in which the pre-correction image 20, the post-correction image 30, and the omnidirectional filtering image 70c are displayed side by side on the display screen S.

  In the plate inspection operation, as shown in FIG. 9, the operator causes a plurality of filtered images to be displayed side by side on the display screen S of the display device 2, and these images are compared with each other. The difference image 41, the difference image 42 generated due to a work error, the error image 43 generated by the rasterizing process, and the like can be discriminated. For example, since most of the error image generated in the rasterization process is removed from the filtered image, an image that is not displayed in the plurality of filtered images can be determined as dust. Further, since the difference image generated by the normal correction work and the work mistake remains in the filtered image even if the contour shape changes, it can be determined that the part has been corrected.

  In the plate inspection work, as shown in FIG. 11B, the vertical, horizontal, and omnidirectional filtering images can be compared with each other to further improve the dust discrimination accuracy, but this is the inspection target. Depending on the image, it may be desirable to compare the filtered images in the vertical and horizontal directions as shown in FIG.

  What is displayed on the display screen S of the display device 2 is not limited to the filtering image 70. For example, as shown in FIG. 12A, the difference display image 50 and the omnidirectional filtering image 70c are displayed side by side. Also good. Further, as shown in FIG. 12B, the pre-correction image 20, the post-correction image 30, and the omnidirectional filtering image 70c may be displayed side by side.

  Thus, the pre-correction image 20, the post-correction image 30, the difference display image 50, the filtering image 70, and the like can be displayed in an appropriate combination on the display screen S of the display device 2. The operator can instruct the image comparison device 1 via the operation input unit 5 about the type, arrangement, display magnification, and the like of the image to be displayed on the display screen S of the display device 2.

  11 and 12 are diagrams illustrating an example in which a plurality of images are alternately displayed at the same position on the display screen S. FIG. Each image is displayed in full size on the display screen S, but a partially enlarged image of each image may be displayed alternately.

FIG. 11A shows an example in which the vertical filtered image 70a is displayed on the display screen S. FIG. FIG. 11B shows an example in which the horizontal filtered image 70b is displayed on the display screen S. FIG. 11C illustrates an example in which the omnidirectional filtering image 70 c is displayed on the display screen S. Each image shown in FIGS. 11A to 11C is displayed at the same position on the display screen S.
FIG. 12A shows an example in which the pre-correction image 20 is displayed on the display screen S. FIG. 12B shows an example in which the corrected image 30 is displayed on the display screen S. FIG. 12C illustrates an example in which the omnidirectional filtering image 70 c is displayed on the display screen S. Each image shown in FIGS. 12A to 12C is displayed at the same position on the display screen S.

  In the present display form, the display control unit 3 performs so-called “tilting display” in which images to be displayed are alternately displayed at the same position on the display screen S of the display device 2. Here, `` Aori '' means using the afterimages of both printed materials by overlaying the printed materials of the original before and after correction, turning the upper printed material quickly manually, and repeating the operation of overlaying again on the lower printed material, This is a technique for inspecting errors such as characters and designs by visual inspection. The operator visually inspects for errors such as characters and designs by using the afterimage of the displayed image by electronically displaying a plurality of images on the display screen S, as in the case of printed matter. it can.

  In the present display mode, an example in which three images are alternately displayed on the display screen S of the display device 2 has been described, but two images may be alternately displayed. Also in this display mode, the pre-correction image 20, the post-correction image 30, the difference display image 50, the filtering image 70, and the like can be displayed in appropriate combination on the display screen S of the display device 2. The operator can instruct the image comparison device 1 via the operation input unit 5 such as the type of image to be displayed on the display screen S of the display device 2, the display order, and the display magnification. The switching of the image displayed on the display screen S may be instructed by the operator via the operation input unit 5, or a plurality of images may be sequentially and repeatedly displayed at regular time intervals.

  In this display form (tilting display), as in the form in which a plurality of images are displayed side by side on the display screen S, an error image generated by the rasterization process, a difference image generated by a normal correction operation, and a difference generated by an operation error Images can be discriminated more appropriately. In particular, in this display mode, a plurality of images can be compared at the same position on the display screen S, so that the visibility when a difference between the images is detected visually can be improved. Therefore, in this display form, the difference between images can be visually recognized more accurately and easily than the form in which a plurality of images are displayed side by side on the display screen S.

According to the image comparison apparatus 1 of the present embodiment described above, for example, the following effects can be obtained.
The error image generated by the literizing process in the plate-making process tends to be low in the vertical and horizontal connectivity of the pixels, and therefore depends on the vertical weighting value, the horizontal weighting value, or the number of vertical and horizontal connections. By filtering based on the weighting values, most of them can be removed as dust. On the other hand, in the plate making process, many of the difference images generated by normal correction work or work mistakes have high pixel vertical and horizontal connectivity, so the vertical weighting value, horizontal weighting value, or vertical Even if filtering is performed on the basis of the weighting value based on the number of connections in the direction and the horizontal direction, it is not removed as dust and can be left as a correction history.

  In the difference display image creation process described above, when pixels having a luminance difference equal to or greater than the first threshold value are extracted from the difference image 40 as differences, if the first threshold value is decreased, many dust pixels to be removed remain. End up. On the other hand, when the first threshold value is increased, the pixels of the difference image generated by the normal correction work or work mistake are also removed as dust. However, in the image comparison apparatus 1 of the present embodiment, even if many pixels that become dust remain in the difference display image 50 in the difference display image creation step, the weighting value in the vertical direction and the horizontal By filtering based on the weighting value of the direction or the weighting value based on the number of connections in the vertical and horizontal directions, most of the pixels that become dust can be removed. As described above, in the image comparison apparatus 1 of the present embodiment, even when the first threshold value is reduced and the pixels of the difference image generated due to the normal correction work or work mistake are left, the pixel that becomes dust is left. Most can be removed. Therefore, in the image comparison apparatus 1 of the present embodiment, the complexity of the plate inspection work is alleviated and the occurrence of oversight can be reduced.

Further, as in Patent Document 2 described above, in the difference display image creation step, a plurality of first threshold values can be set, and a difference display image at each threshold value can be created. However, when there is a large variation in the luminance difference of pixels to be removed as dust compared to the difference in luminance difference at the correction location, the operator needs to repeatedly refer to a plurality of difference display images. In particular, when the difference display image includes an error image generated by the rasterizing process, it takes time and effort for the operator to determine the error image as dust. On the other hand, in the image comparison device 1 of the present embodiment, the filtering images displayed on the display device 2 or the difference display image may be compared with the filtering image, so that the operator repeats a plurality of difference display images. Save time and effort to refer to. Even when the difference display image includes an error image generated by the rasterization process, the operator can easily determine this error image as dust by referring to the filtering image. Therefore, in the image comparison apparatus 1 of the present embodiment, the complexity of the plate inspection work is alleviated and the occurrence of oversight can be reduced.
Therefore, by using the image comparison apparatus 1 of the present embodiment, the plate inspection work can be performed more easily and accurately.

  In the image comparison device 1 of the present embodiment, the operator can appropriately change the first threshold while comparing the difference image displayed on the display device 2 with the difference display image. According to this, by changing the first threshold according to the change of display / non-display of the difference image and error image at each threshold, while leaving the pixels of the difference image caused by normal correction work or work mistake, It is possible to create a difference display image from which more dust pixels are removed.

  In the image comparison device 1 of the present embodiment, the operator can appropriately change the second threshold while comparing the difference display image displayed on the display device 2 with the filtering image or the plurality of filtering images. According to this, by changing the second threshold value according to the change in the display shape of the filtering image at each threshold value, the operator can more appropriately discriminate the error image generated by the rasterizing process in the filtering image.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above, Various deformation | transformation and a change are possible like the deformation | transformation form mentioned later, These are also this invention. Within the technical scope of The effects described in the embodiments are merely a list of the most preferable effects resulting from the present invention, and are not limited to those described in the embodiments. In addition, although the above-mentioned embodiment and the deformation | transformation form mentioned later can also be used combining suitably, detailed description is abbreviate | omitted.

(Deformation)
In the present embodiment, the example in which the same threshold (second threshold) is set for the weighted image in the vertical direction and the weighted image in the horizontal direction in the filtering image creation process has been described. However, the present invention is not limited to this. Different threshold values may be set for the weighted image in the vertical direction and the weighted image in the horizontal direction.
In the present embodiment, as illustrated in FIGS. 7 and 8, the example in which a plurality of images are displayed side by side on the display screen S of the display device 2 has been described, but the present invention is not limited to this. For example, from the state where two images are displayed side by side, one image instructed by the operator may be displayed superimposed on the other image. Further, after a predetermined time elapses after one image is superimposed on the other image, the one image may be displayed so as to return to the original position again.

DESCRIPTION OF SYMBOLS 1 Image comparison apparatus 3 Display control part 111 Difference image creation part 112 Difference display image creation part 113 Weighted image creation part 114 Filtering image creation part

Claims (8)

A difference image creating unit that extracts a luminance difference for each pixel as a difference from the first image to be inspected and the second image to be inspected, and creates a difference image;
From the difference image created by the difference image creation unit, a pixel having a luminance difference equal to or greater than a first threshold is extracted as a difference, and a difference display image creation unit that creates a difference display image;
From the difference display image created by the difference display image creation unit, an image weighted at the connection position of each pixel arranged in the vertical direction, an image weighted at the connection position of each pixel arranged in the horizontal direction, and A weighted image creation unit that creates at least one image as a weighted image among images weighted by the number of connected pixels in the vertical direction and the horizontal direction;
From the weighted image created by the weighted image creating unit, a pixel having a weight value equal to or greater than a second threshold is extracted, and a filtering image creating unit that creates a filtered image;
A display control unit for displaying the filtering image created by the filtering image creation unit on a display screen;
An image comparison apparatus comprising: The image comparison device according to claim 1,
The display control unit, when a plurality of the filtering images are created based on a plurality of the weighted images, displaying at least two of the filtering images side by side on a display screen;
An image comparison apparatus. The image comparison device according to claim 1,
The display control unit, when a plurality of the filtering images are created based on the plurality of the weighted images, to alternately display at least two of the filtering images at the same position on the display screen;
An image comparison apparatus. The image comparison apparatus according to claim 1 or 2,
The display control unit displays the first image and the second image side by side on a display screen together with the filtering image;
An image comparison apparatus. The image comparison apparatus according to claim 1 or 3, wherein
The display control unit alternately displaying the first image and the second image together with the filtering image at the same position on a display screen;
An image comparison apparatus. An image comparison apparatus according to any one of claims 1 to 5,
A threshold changing unit that changes at least one of the first threshold and the second threshold;
An image comparison apparatus. A difference image creation step of extracting a luminance difference for each pixel as a difference from the first image as the inspection reference and the second image as the inspection target, and creating a difference image;
From the difference image created by the difference image creation step, a pixel having a luminance difference equal to or greater than a first threshold is extracted as a difference, and a difference display image creation step of creating a difference display image;
From the difference display image created by the difference display image creation step, an image weighted at the connection position of each pixel arranged in the vertical direction, an image weighted at the connection position of each pixel arranged in the horizontal direction, and a vertical A weighted image creating step of creating at least one image as a weighted image among images weighted by the number of connected pixels in each direction and the horizontal direction;
From the weighted image created by the weighted image creating step, a pixel having a weight value greater than or equal to a second threshold is extracted, and a filtering image creating step for creating a filtered image;
A display control step of displaying at least one filtering image created by the filtering image creation step on a display screen;
An image comparison method comprising: An image comparison program executed on a computer,
The computer,
A difference image creating means for extracting a luminance difference for each pixel as a difference from the first image to be inspected and the second image to be inspected, and creating a difference image;
From the difference image created by the difference image creating means, a pixel having a luminance difference equal to or greater than a first threshold is extracted as a difference, and a difference display image creating means for creating a difference display image;
From the difference display image created by the difference display image creation means, an image weighted at the connection position of each pixel arranged in the vertical direction, an image weighted at the connection position of each pixel arranged in the horizontal direction, and Weighted image creating means for creating at least one image as a weighted image among images weighted by the number of connected pixels in the vertical and horizontal directions;
Filtering image creating means for extracting a pixel having a weighting value equal to or greater than a second threshold from the weighted image created by the weighted image creating means, and creating a filtered image;
Display control means for displaying on the display screen at least one filtering image created by the filtering image creation means;
Image comparison program to make it work.