JP2000066364A - Plate inspection apparatus and plate inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plate inspection apparatus and plate inspection method capable of executing precise plate inspection by detecting the 'floating up' and 'sinking in' of partial images of characters, line drawings, etc. SOLUTION: Contour images G4 and G5 are extracted from the respective images G1 of a second revise and the images G2 of a third revise and are compared. The differential image G6 thereof is extracted. The character '7' existing in the first revise is erased thus far by forming the character to the same color as a ground surface color and the character is eventually floated up by changing the ground surface color in the third revise. The 'floating up' which is such a proof reading error may be detected in the differential image G6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate inspection apparatus and a plate inspection method for comparing and inspecting first and second images obtained in a plate making process.

[0002]

2. Description of the Related Art In the process of making a printed matter, it is checked whether or not a plate obtained by editing image parts such as characters, photographs, and line drawings conforms to the contents of the plate making instruction. Sometimes various corrections need to be made. Then, such inspection and correction are repeatedly performed in a number of stages, and after the first school, re-school, three schools, etc., a finally completed version is obtained.

[0003] As a device for comparing two editions (old edition and new edition) in different calibration stages in such a calibration stage and automatically detecting a difference between the two editions, there is a plate inspection apparatus. This plate inspection device prepares the digital image data of the old and new versions, and automatically extracts the differences between the images where the tone values of the image data of the corresponding pixels are different from each other, and automatically corrects the errors that occur during the calibration stage. Has been discovered.

[0004]

By the way, in the above-described conventional plate inspection method, in the following cases, a partial image such as an erased character or a line diagram emerges again (hereinafter, "emerging"). No mistakes can be detected.

FIG. 11 is a diagram showing an example in which "emerging" of an erased character occurs due to calibration. In the first school shown in FIG. 11A, black characters are arranged on a yellow base. On the other hand, in the second school shown in FIG. 11B, a part of the character (the character “7”) is changed to yellow, which is the same as the base color, and is hidden. This is in consideration of the fact that the character “7” is to be erased, but may be restored in a later calibration stage. In many cases, you will delete a bad image.

However, as shown in FIG.
In some cases, such as when the background color is changed to blue at school, only the background color is changed at the calibration stage after the partial image is erased by making the background color the same color. In such a case, "emerging" occurs in which a partial image that should have been erased appears again. In the third school in FIG. 11C, the correction is only the change of the base color, but the characters that should have been erased have appeared in yellow.

[0007] Such "emerging" should be originally detected as a calibration error. However, in the plate inspection apparatus shown in the prior art, the second school (old version) and the third school shown in FIG. Only the fact that the background color has been changed is detected, as in the result of plate inspection of (new edition). That is, as can be seen by comparing the image of the second school in FIG. 11B with the image of FIG. 11C, the character “7” that has emerged, that is, erased by making it the same as the background color. Since the partial image itself is not changed between the second school and the third school, it cannot be detected by the conventional device that detects the difference image.

On the other hand, in contrast to this, partial images such as characters and line diagrams which should be originally displayed in the new version are changed to the same color by changing the background color. A phenomenon that the data is erased (hereinafter referred to as “subduction”) also occurs. Also in this case, since the color of the partial image itself has not been changed, the conventional apparatus could not detect this.

SUMMARY OF THE INVENTION The present invention is intended to overcome the above-mentioned problems in the prior art, and a plate inspection apparatus and a plate inspection method capable of detecting "emerging" or "sinking" and performing precise plate inspection. The purpose is to provide.

[0010]

According to a first aspect of the present invention, there is provided a plate inspection apparatus for comparing and inspecting first and second images obtained in a plate making process. Contour extracting means for extracting a contour of an image element included in the first image to obtain a first contour image, and extracting a contour of an image element included in the second image to obtain a second contour image; And a contour difference specifying means for specifying a contour difference portion where the second contour image differs from each other, and an output means for visually expressing and outputting the contour difference portion.

[0011] An apparatus according to a second aspect of the present invention is the plate inspection apparatus according to the first aspect, further comprising:
And a gradation difference specifying means for specifying a gradation difference portion in which the gradation difference is equal to or more than a predetermined threshold value in the second image,
The output means is for visually expressing and outputting the gradation difference portion together with the contour difference portion.

According to a third aspect of the present invention, there is provided the plate inspection apparatus according to the second aspect, wherein the contour extracting means has a gradation difference portion between the first and second images. It is characterized in that the first and second contour images are respectively extracted from the area.

The apparatus according to a fourth aspect of the present invention is the plate inspection apparatus according to the third aspect, further comprising a rectangle specifying means for specifying a rectangular area including a gradation difference portion, The extracting means extracts the first and second contour images from the rectangular area of the first and second images, respectively.

According to a fifth aspect of the present invention, there is provided a plate inspection apparatus according to any one of the first to fourth aspects, wherein each of the first and second contour images includes: Normalizing means for normalizing the gradation value and width of the contour portion to a common gradation value and width, and the first and second contour images after the contour difference specifying means has been normalized by the normalizing means. Is characterized by specifying a contour difference portion.

Further, a method according to a sixth aspect of the present invention is a plate inspection method for comparing and inspecting first and second images obtained in a plate making process, wherein a contour of an image element included in the first image is determined. A contour extracting step of extracting the first contour image to obtain a first contour image and extracting a contour of an image element included in the second image to obtain a second contour image; and a contour different portion in which the first and second contour images are different from each other. And an output step of visually expressing and outputting the contour difference portion.

[0016]

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

<1. Apparatus Configuration of First Embodiment >><< 1-1. System Configuration >> FIG. 1 is a schematic block diagram of a plate making system 1 including a plate inspection device 100 according to a first embodiment of the present invention. In the plate making system 1,
Various image parts (characters, line drawings,
The input unit 2 includes, for example, an input scanner, a character input unit, and a line drawing creating unit.

The data of the image components input from the image component input device 2 is given to the image editing / conversion device 3 online or offline, and after being laid out on each page in the page description language according to the plate making instruction, The image data is developed (RIP developed) into image data in pixel units, and further converted into a multivalued image or a halftone image in an image output unit 4 including an output scanner and the like, and is exposed and recorded on a photosensitive material. Then, the photosensitive material on which the exposure recording has been performed is developed to obtain a printing original plate.

Once a portion to be corrected is found in the image of the created version (old version), the process returns to the image component input device 2 or the image editing / converting device 3 to re-input the old version image component and to re-input image data on the page. Make corrections to obtain a new version of the image data. The new version is compared with the old version by using the plate inspection apparatus 100 to check for corrections, and when leaks or new corrections are discovered, the version is repeatedly corrected. An original version (printed version) for printing plate production is obtained.

In the actual plate making process, plate correction is often repeated a plurality of times. In the following, attention will be paid to correction at an arbitrary stage. to continue. The old version is, for example, the first school, and the new version is, for example, a re-school.

The plate inspection apparatus 100 for performing the comparison inspection between the old version and the new version can take in images of these original versions in two types. First, color image data of the old edition and the new edition which are RIP-decompressed by the image editing / conversion device 3 are taken in the form of digital data and compared. The capture of the digital data may be performed online via a network, or may be performed offline using an information storage medium such as a magnetic disk or a magneto-optical disk. In the example of FIG. 1, the plate inspection apparatus 100 is network-connected to the image editing / conversion apparatus 3 and the like so that data can be taken online.

Another method of capturing the image data of the original is to convert the visible image of each YMCK original developed after exposure recording and the image of the proof printed by color printing on proof paper into a photoelectric image. This is a method of reading information. The plate inspection apparatus 100 shown in FIG. 1 includes an image reader 110 in order to realize this method. In the case of a color image, the original plate usually consists of four plates of Y, M, C and K,
When the original is read by the image reader 110, these 4
The image of the plate is read, and one set of color plate image data of each color component is used as one original plate image data. Note that it is also possible to read an image on a printing plate instead of the original plate.

In addition to the above two methods, one of the two images to be compared is used as it is as the RIP-developed digital image data, and the other is obtained by photoelectrically reading an image on a print medium. Things can also be used.

<< 1-2. Configuration of Plate Inspection Apparatus >> The plate inspection apparatus 100 includes an operation control unit 130 that controls various inputs and outputs in addition to a comparison operation of image data. The arithmetic control unit 130 can be constituted by a main body of a computer, and includes a CPU 131 and a memory 132. The media drive 120 is used not only when inputting image data offline, but also when reading in advance the arithmetic control program of the plate inspection apparatus 100 from an information storage medium MA provided in the form of a CD-ROM, MO, DVD or the like. used. This arithmetic control program is installed in the arithmetic control unit 130. Color display 1 as described below
Display control program on the color printer 150
An output control program to the plotter 160 is also included in the arithmetic control program provided in the form of the storage medium MA.

The image disk 170 is constituted by a magnetic disk such as a large-capacity hard disk, and stores image data before and after plate inspection, and stores a plate inspection result image obtained as a result of plate inspection.

A color display 140 is connected to the arithmetic and control unit 130.
Operation input and menu selection in accordance with the display on 0 can be executed using a keyboard 181 and a mouse 182 included in the operation input unit 180. Although the screen of the color display 140 is referred to in every scene of the operation input, the essential purpose of the plate inspection is to display the inspection result images of the old and new versions so that the operator can visually recognize the contents. Especially important in relationships.

A color printer 150 and a plotter (monochrome plotter) 160 are also used to output the inspection result images of the old version and the new version. As the color printer 150, for example, an ink jet printer can be used. The output medium of the color printer 150 and the plotter 160 is a fixed image recording medium (image recording sheet) such as plain paper, translucent paper, or transparent film.

<2. Plate inspection process according to first embodiment >><< 2-1. Outline of Plate Inspection Process >> Next, an outline of the plate inspection process will be described. FIG. 2 is a diagram illustrating an example of an old image P1 and a new image P2 that are compared and inspected by the plate inspection apparatus 100. In the example of FIG. 2, in the process of correcting the old version images P1 such as the first school, the second school, etc. into the new version images P2 such as the second school, the third school,.
The image components are corrected in the regions CR1 to CR4 corresponding to each other. The plate inspection apparatus 100 is configured to use these images P
1. Compare and inspect P2. The old version image P1 and the new version image P2 in FIG. 2 correspond to the images of the second and third schools shown in FIG.

FIG. 3 is a diagram for explaining the outline of the plate inspection process in the first embodiment. In FIG. 3, the image P of FIG.
The plate inspection process is illustrated using the region CR4 of 1 and P2 as an example.

First, a pixel inspection process (hereinafter referred to as a "tone comparison process") for comparing pixels corresponding to the old and new versions of the image and detecting a difference image in which a portion where the tone of the two is different by a predetermined amount or more is extracted. .)I do. The details of the gradation comparison process will be described later.

In FIG. 3, an image G1 in the area CR4 of the image P1 of the old version (second school) and an image G2 in the area CR4 of the image P2 of the new version (third school) (gradation difference portion).
Is an example in which an image G3 is obtained. Here, FIG.
Similar to 1, the character "7" displayed in the first school was changed to yellow, which is the same color as the background color (background color) in the second school, and erased. Has been changed to blue, so that "emerging" occurs in which the character "7" appears again. That is, in the image G3 of FIG. 3, a different portion determined to have a difference between the second school and the third school is indicated by hatching, but the character “7” is not detected as a different portion. .

Therefore, in the present invention, the old version image P1
In addition to the gradation comparison processing between the image G1 and the new image P2, the old image P1 and the new image P2 (in FIG.
The outline is extracted for each image element of the school image G2, and two outline images (images G4 and G in FIG. 3) are extracted.
Find 5). By performing a contour comparison process for obtaining a difference between these contour images, it is possible to detect "emerging" or "sinking" of a partial image such as a character or a diagram. Here, the “image element” refers to each of the closed regions where there is a relatively clear gradation difference between the surrounding regions. Such an “image element” appears particularly clearly in a character part, a line drawing part, and the like. However, even in an image part of a natural image such as a photograph, a subject portion with respect to a background or the like may correspond to this. In some cases, the entire section of an image becomes an “image element” in relation to other image components. This contour extraction processing will be described later in detail.

Here, a description will be given using a specific example. In FIG. 3, in the image G1 of the second school, the character “7” is deleted as described above. An image obtained by extracting the outline of the image is an image G4. "7" deleted in image G4
No outline is generated in the character of. On the other hand, in the image G2 of the third school, “7”, which should have been deleted as described above,
Is emerging. Naturally, in the image G5, a contour is generated in the characters that appear.
Therefore, the image G which is the outline image of the second school from which the outline is extracted
When the difference between the image 4 and the image G5, which is the outline image of the third school, is obtained, in the image G6, which is the difference image, the outline of the character “7” (the outline difference portion) that has emerged is extracted.

As described above, according to the present invention, as to a method of ignoring color information while paying attention to the shape of the image, the outline of the image is extracted from the images at various calibration stages in the plate making process. By making the difference of the object an inspection, it is possible to detect "emerging" or "sinking" of a partial image such as a character or a figure.

<< 2-2. Details of Plate Inspection Process >> FIG. 4 is a functional block diagram of the plate inspection device according to the first embodiment. FIGS. 5 and 6 are diagrams for explaining the details of the outline comparison processing in the first embodiment. Hereinafter, FIG.
The details of the plate inspection process performed by the apparatus according to the present embodiment will be described with reference to FIG. Although this apparatus targets a color image, a two-color plate image, a monochrome image, and the like, the following description will be directed to a color image. Therefore, the images for each color plate are compared for each image. Specifically, Y
(Yellow) · M (magenta) · C (cyan) · K
(Sumi), R (Red), G (Green), B (Blue)
The following comparative inspection is performed on each color plate that has been decomposed into color, brightness, saturation, hue, etc. Therefore, the image G1 appearing below
G6 have a plurality of color plate components.

First, as a pre-process, an old image P1 (FIG. 3)
5 and an image G1 in FIG. 5 and a new version image P2 (image G2 in FIGS. 3 and 5). This means that even if input from multi-value image input means such as image reader 110,
Multi-valued digital data resulting from output calculation (RIP processing) from a page description language or the like may be used. The old version image P1
The image data of the new version image P2 (images G1 and G2 in FIGS. 3 and 5) is stored in the image disk 17 for each color plate.
0 is stored. FIGS. 5A and 5B show a part of the images G1 and G2, respectively. The images G1 and G2 have been subjected to preprocessing such as correction of misalignment, distortion, color tone, etc., reduction of noise, and smoothing of halftone dots as preparation for comparison processing (step S).
1).

The CPU 131 of the arithmetic control unit 130
In step S2, the above-described gradation comparison process is performed on the old image P1 and the new image P2 for each color plate (step S2), and a difference image (the image G3 in FIG. 3) between the two images is stored in the memory 132.

The details are as follows. First, the old image P1 and the new image P2 are read from the image disk 170.
Are read out, and the parts of these images are compared with each other. FIG. 7 shows the old version image P1 and the new version image P.
FIG. 3 is a diagram showing a situation in which each matrix is divided into matrices (tile division or block division) into a set {Bij} of small rectangular blocks. As shown in the drawing, in this comparison, the images P1 and P2 are each divided into a matrix of small rectangular blocks {Bij}, and the image of the old image P1 and the image of the new image P2 corresponding to each block are divided into blocks. Compare.

In the first embodiment, when the old version image P1 and the new version image P2 are color images, the comparison is made by YM
This is performed for each color component of CK. If the old image P1 and the new image P2 are obtained by photoelectrically reading a plate, an error occurs in the spatial positional relationship between the old image P1 and the new image P2. A data shift is performed such that the relative position between the old image P1 and the new image P2 is sequentially shifted by a small amount for each block Bij, and the mutual matching between the images is determined based on the positional relationship having the highest degree of correlation between the images. . For this portion, the technique disclosed in Japanese Patent Application Laid-Open No. 9-211836 disclosed by the applicant of the present invention can be used.

In such an image comparison, the old image P1 and the new image P1 in the block Bij for one or more color plates
If the difference between the image levels of the blocks Bij is equal to or greater than a predetermined threshold value, the block is determined to be a "mismatched block". If the value is equal to or smaller than the threshold value, the block is determined to be a “matching block”. Each block B
With respect to the difference between the image levels in ij, for example, a method of projecting the distribution of the image levels in the block Bij onto a predetermined spatial axis and comparing the projected waveforms with each other can be adopted. A method of comparing the average values of the image levels in the block Bij may be adopted.

As described in the outline of the plate inspection process, in the first embodiment, together with the gradation comparison process, the CPU 131 of the arithmetic control unit 130 extracts the outline images of the old plate image P1 and the new plate image P2. Then, a contour comparison process for comparing them is performed (step S
3). Therefore, first, the old version image P1 and the new version image P
2 to extract an outline image. FIGS. 5C and 5D show the gradation distributions of the scanning line SL of the image G1 as the old image and the image G2 as the new image. As shown in the drawing, among the character images, those having a color different from the background color have at least one of the gradations of each color plate different from the background gradation. There is a gradation gap at the boundary between the image of the base and the image of the character or the like, and a contour image as an image representing such a boundary is extracted.

Specifically, as the contour extraction processing, there are known methods such as a method of performing first-order differentiation on an image and a method of obtaining a difference between an original image and an image obtained by expanding (or contracting) the image. Although a method can be used, this embodiment employs a method using a neighborhood operator, particularly a Laplacian operator, for a predetermined local region (3 pixels × 3 pixels) of an image. That is, a Laplacian operator is applied to an image, and an absolute value is obtained for each pixel with respect to the obtained result. Note that the Laplacian operator is a spatial filter that performs isotropic and second-order differential image processing. By using this method, a contour line having a relatively uniform width can be extracted. Can be easier.

Examples of the outline images of the old image P1 and the new image P2 obtained by such outline extraction are shown in the image G4 (FIG. 5 (e)) and the image G5 (FIG. 5).
(F)), and FIGS. 5 (g) and 5 (h) show the distribution of the gradation for those scanning lines SL. FIG.
As shown in (g) and (h), the outline of an image such as a character in the outline image has different gradations and line widths in pixel units.

The old image P1 and the new image P
In order to eliminate the image of the same shape extracted from the contour image 2 in the difference extraction process described below (an image common to both contour images is not extracted as a differential image), the It is necessary to accurately select (binarize) the contour line and the other image, and to determine the gradation (gradation dn1, dn2 in FIGS. 5G and 5H) and the line width (FIG. 5).
In (g) and (h), the line widths px1 and px2) need to be common, that is, normalized. for that reason,
In the first embodiment, a normalization process (including a binarization process) is performed on the contour images extracted from each of the images G1 and G2 together with the contour extraction process (step S3).

Hereinafter, the normalization processing will be described in more detail. The image after contour extraction (before normalization) is an old version image P1 (image G1 in FIG. 5) as shown in FIGS. 5 (g) and 5 (h).
And the new image P2 (image G2 in FIG. 5) have different gradation values of the outline image due to the difference in the gradation values of the background (dn1 ≠ d
n2). The differential value obtained by the Laplacian operator is “0” when there is no change in gradation in the area, and if it has a value, it can be determined that there is a change. Therefore, the differentiation result is converted into a binary image using a value near “0” as a threshold. FIGS. 6A and 6B show images obtained by normalizing FIGS. 5G and 5H. The gradation values of both contour images are equal (dn3 = dn4) by this normalization processing.

In the case where the image to be compared is digital data after RIP expansion, adjacent pixels in the outline portion of an image such as a character have the gradation value of the background and the gradation value of the image of the character, respectively. If the conditions such as the size of the neighborhood operator and whether the range of the neighborhood of interest is 4 neighborhoods or 8 neighborhoods are common to both images, the line width of the generated contour image is common. Since the contour image is extracted in common, the line width can be made common (px1 = px2).

However, when the image to be compared is data captured from the image reader 110, the outline of the image is slightly blurred and the line width is different (px1
≠ px2) is also conceivable. In this case, line width correction such as adjustment of a threshold value for binarization is performed to make the line width of the contour common (px3 = px4).

In FIGS. 3 and 5, the contour images extracted from the images G1 and G2 of the second and third schools are images G4 and G5.

Next, a comparison process for detecting a difference in pixel units is performed for both contour images (images G4 and G5 in FIGS. 3 and 5) (step S4). More specifically, the comparison and the extraction of the difference image, which are almost the same as the above-described gradation comparison processing, are performed on both contour images (the images G4 and G5 in FIGS. 3 and 5). However, since the outline image has already been binarized and normalized at this stage, the outlines of both images have the same gradation and line width where the outline is common to both images. Therefore, when the two images are compared in a state where they correspond to each other, only the difference in the presence or absence of the outline can be detected. Therefore, the difference is that the threshold value of the tone difference for determining whether there is a difference between the two images is set to a value close to “0”. The comparison of the outline images is also performed for each color plate, whereby a difference image (image G6 in FIGS. 3 and 6) is obtained for each color plate. 6A and FIG.
FIG. 6C shows a difference image from FIG.
6 has a gradation distribution on the scanning line SL.

Further, the OR of each pixel of the difference image of each color plane is calculated. Thereby, even if there is a difference in the outline image of any one color plate, it can be detected.

Finally, as post-processing, the difference image (image G3 in FIGS. 3 and 5) obtained by the gradation comparison processing in the CPU 131 and the difference image obtained by the contour comparison processing (the image G3 in FIGS. 3 and 6). G6) is synthesized to obtain an inspection result image (image G7 in FIG. 3), and further, the comparison result is highlighted to make it easy for the user to understand, the display is switched by an instruction of the user, and the like. And output means such as a color printer 150 and a plotter 160 (step S5).

Although "emerging" has been described as an example in the above description, "sinking" of an image described above can also be detected through the above processing.

As described above, according to the first embodiment, each of the old version image P1 and the new version image P2
It extracts contour images that are the contours of the image elements contained in them, and further extracts and displays the difference images of those contour images, so that "emerging" and "sinking" of partial images such as characters and diagrams are performed. Inconsistency "can be detected, thereby enabling precise plate inspection.

Further, a gradation comparison process is also performed on the old image P1 and the new image P2, and a difference image obtained by the gradation comparison process and a difference image of the outline image are displayed together. It can be carried out.

Since the difference images are obtained by normalizing the outline images of the old image P1 and the new image P2 and comparing them, the coincidence and non-coincidence of the outline images can be accurately determined.
"Elevation" and "subduction" can be detected more accurately.

Further, as described above, in the first embodiment, after extracting outline images from the old image P1 and the new image P2, respectively, the outline images are binarized and normalized.
Then the difference is taken. This is the old version image P1
And an image different from the new version image P2 is extracted (image G in FIG. 3).
3) When the outline of the difference image is extracted, even if the image exists in common between the old version image P1 and the new version image P2 of the target color plate, a slight difference in gradation is obtained when the image is read by an image reader or the like. In the case where the difference has occurred, the difference image includes the image that exists in common, and extracting the outline of such an image results in extraction of an extra image that does not originally need to be extracted. . Therefore, the difference is obtained after binarizing and normalizing the contour image so as to prevent such a situation. By doing this,
According to the first embodiment, “emerging” and “sinking” are efficiently detected.

<3. Second Embodiment> The configuration of the plate making system 1 and the plate inspection apparatus 100 of the second embodiment is the first
This is the same as the embodiment. However, in the second embodiment, a gradation comparison process is performed first, and a rectangular region including a different portion, which is a portion where the image has been corrected, is extracted. The contour extraction and normalization process are performed on only the rectangular region. The difference is that the contour comparison process is performed on the obtained contour image.

FIGS. 8 and 9 are block charts showing the procedure of the plate inspection process in the second embodiment. Less than,
The plate inspection process according to the second embodiment will be described in detail with reference to FIGS.

First, image reading and gradation comparison processing are performed (steps S11 and S12), but since these are exactly the same as in the first embodiment, description thereof will be omitted.

Next, a minimum rectangular area including the different portions obtained by the gradation comparison process is set (step S13). Regions CR1 to CR4 in the new edition image P2 in FIG. 2B represent the smallest rectangular regions including the different portions.

FIG. 10 conceptually shows the result of the above-described matching judgment for each block Bij, in which non-matching blocks indicated by oblique lines are distributed in the image plane.
Here, since the new version image P2 is obtained by partial modification of the old version image P1, the unmatched blocks of those images are not randomly distributed, but the unmatched blocks are present in one or more places. .
Each block of the unmatched blocks represents a different image. For example, in the example of FIG.
A set of unmatched blocks exists.

Therefore, as shown in FIG. 10, a rectangular area R having a minimum size including a range in which unmatched blocks are continuous is set as a portion where the old image P1 and the new image P2 have a difference. That is, in the case of the example of FIG. 2B, the rectangular areas R1 to R4 correspond to the correction areas CR1 to CR1 of FIG.
Coordinate values specified corresponding to CR4 and specifying these areas are stored in the memory 132.

Next, only the old image P1 and the rectangular areas R1 to R4 obtained by the outline extraction and normalization processing are performed (step S14). By the way, phenomena such as “emerging” and “sinking” are phenomena that occur only when the background color surrounding a partial image is changed. And a non-difference portion surrounded by the difference portion). Therefore, these phenomena can be detected by comparing the contour images only for such different portions. However, since the actual difference can have an arbitrary outer shape, when the plate inspection device automatically performs plate inspection, it is better to perform the comparison processing on the rectangular area and to improve the control efficiency of the processing and the difference. It is convenient for preventing omission of detection.
Therefore, in the second embodiment, the minimum rectangular area including the different part is extracted, the outline image in the rectangular area is extracted, and the outline comparison processing is performed only on them (step S15). It should be noted that the outline comparison process is performed only within the rectangular area, except that the old version image P1 and the new version image P2
The comparison of the outline image with the image and the generation of the difference image are the same as those in the first embodiment.

Further, post-processing of the comparison processing (step S1)
6) and the output of the comparison result are the same as in the first embodiment.
In this manner, the second embodiment can also perform plate inspection involving detection of "emerging" or "subsidence".

As described above, according to the second embodiment, the same effects as those of the first embodiment can be obtained.
Since the comparison of the outline images only needs to be performed within the rectangular area, efficient plate inspection can be performed, and the outline comparison processing only needs to be performed within the rectangular areas of the old image P1 and the new image P2. Therefore, image data is read out in consideration of the outer shape (arbitrary shape) of the different portion, such as when comparing different portions (lumps of unmatched blocks) when comparing two outline images in the outline comparison process described later. Since there is no need to perform this, the processing and control for comparison can be performed easily and efficiently. In addition, they can improve the processing speed.

<4. Modifications> In the first and second embodiments, examples of the plate making system, the plate checking device, and the plate checking process by the plate making device have been described, but the present invention is not limited thereto.

For example, in the first embodiment, the contour image is extracted, normalized, and contour-comparison processing is performed for all the images in the second embodiment, and for the rectangular area in the second embodiment. A contour image is extracted and normalized for an area (more precisely, an area composed of the different part itself and a part surrounded by the different part) where the different part (lump of unmatched blocks) detected by A comparison process may be performed. This is because, as described in the second embodiment, “emerging” and “sinking” always occur in a region where a different portion exists. More specifically, the tone comparison processing is performed in the same manner as in the second embodiment, and the old version is used not in the rectangular area R in FIG. 10 but in a block of unmatched blocks Bij (a group of hatched blocks). The contour images of the image P1 and the new version image P2 are extracted, and the two contour images are compared for each block Bij to generate a difference image. Then, the obtained difference image is combined with the image G3 obtained by the gradation comparison process, post-processed, and output to the output unit.

Although the above-described processing slightly complicates the control when comparing the old version with the new version, the number of pixels in the different portions is smaller than when the image in the rectangular area is to be compared. Therefore, the storage capacity of the difference image between the two contour images can be reduced.

In the first and second embodiments, the contour images are respectively extracted from the old version image P1 and the new version image P2, and then the contour images are binarized and normalized, and then the difference is calculated. However, the difference image between the old version image P1 and the new version image P2 may be extracted first, and the outline of the difference image may be extracted.

In the first and second embodiments, the inspection of a color image is described as an example. However, the inspection of a two-color image, a monochrome image, and the like is performed by the same method. You can also.

Further, in the first and second embodiments, comparison of outline images has been described using character images as an example. However, similar processing is performed on other general images such as diagrams, and the like. It is also possible to detect "lift" and "subduction" of the image.

[0072]

As described above, according to the first to sixth aspects of the present invention, the outline of the image element included in the first image is extracted to obtain the first outline image, and the second image is extracted. A second contour image is obtained by extracting the contours of the included image elements, a contour difference portion in which the first and second contour images are different from each other is specified, and the contour difference portion is visually expressed and output. Therefore, it is possible to detect "emerging" or "sinking" of a partial image such as a character or a line diagram, and thereby to perform a precise plate inspection.

According to the second aspect of the present invention, a gradation difference portion in which the gradation difference is equal to or more than a predetermined threshold value in the first and second images is specified, and is visually expressed together with the outline difference portion. Output, the difference between the two images due to the gradation difference can be detected, and more precise plate inspection can be performed.

According to the third aspect of the present invention, since the first and second contour images are respectively extracted from the areas where the tone difference portions exist in the first and second images, the portions other than the tone difference portions are extracted. Since it is not necessary to extract the contour image and specify the contour difference part, it is possible to perform efficient plate inspection and improve the plate inspection processing speed.

According to the fourth aspect of the present invention, a rectangular area including a gradation difference part is specified, and the first and second contour images are respectively extracted from the rectangular area of the first and second images. Therefore, it is not necessary to extract the contour image and specify the contour difference portion except for the rectangular area, so that efficient plate inspection can be performed. Further, since the rectangular areas need only be compared, the processing for comparison is performed. And control can be performed easily and efficiently. In addition, they can improve the processing speed.

Furthermore, according to the invention of claim 5,
In each of the first and second contour images, the gradation value and width of the contour portion are normalized to a common gradation value and width, and the contour difference portions of the normalized first and second contour images are determined. Since the identification is performed, it is possible to accurately determine whether the contour images match or not, and to more accurately detect “emerging” or “sinking”.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a plate making system including a plate inspection device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of an old image and a new image that are compared and inspected by the plate inspection apparatus according to the first embodiment.

FIG. 3 is a diagram for explaining an outline of a plate inspection process according to the first embodiment.

FIG. 4 is a block chart illustrating a procedure of a plate inspection process according to the first embodiment.

FIG. 5 is a diagram illustrating details of a contour comparison process according to the first embodiment;

FIG. 6 is a diagram illustrating details of a contour comparison process according to the first embodiment.

FIG. 7 is a diagram illustrating a situation where an old version image and a new version image are each divided into a set of rectangular blocks by matrix.

FIG. 8 is a block chart illustrating a procedure of a plate inspection process according to the second embodiment.

FIG. 9 is a block diagram illustrating a procedure of a plate inspection process according to the second embodiment.

FIG. 10 is a diagram for explaining extraction of a rectangular area.

FIG. 11 is a diagram illustrating an example in which an erased character appears by proofreading.

[Explanation of symbols]

100 plate inspection device 130 arithmetic control unit (contour extraction means, contour difference identification means, gradation difference identification means, rectangle extraction means, normalization means) CR1 to CR4 correction area G3 image (tone difference part) G4, G5 image ( Contour image) G6 image (contour difference part) P1, G1 Old version image (first or second image) P2, G2 New version image (first or second image) R, R1 to R4 Rectangular area

Claims (6)

[Claims] 1. A plate inspection apparatus for comparing and inspecting a first image and a second image obtained in a plate making process, wherein a contour of an image element included in the first image is extracted to obtain a first image.
A contour extracting means for obtaining a contour image and extracting a contour of an image element included in the second image to obtain a second contour image; and specifying a contour difference portion where the first and second contour images are different from each other. A plate inspection device, comprising: a contour difference specifying unit that performs the contour difference output unit; and an output unit that visually expresses and outputs the contour difference portion. 2. The plate inspection apparatus according to claim 1, further comprising: a gradation specifying a gradation difference portion in the first and second images, wherein the gradation difference is equal to or greater than a predetermined threshold. A plate inspection apparatus, comprising: a difference specifying unit, wherein the output unit visually represents and outputs the gradation difference portion together with the contour difference portion. 3. The plate inspection apparatus according to claim 2, wherein the contour extracting unit is configured to determine the first and second images from a region where the gradation difference portion exists in the first and second images. A plate inspection device for extracting two contour images, respectively. 4. The plate inspection apparatus according to claim 3, further comprising: a rectangle specifying unit that specifies a rectangular area including the gradation difference portion, wherein the contour extracting unit includes the first and second outline extracting units. A plate inspection apparatus for extracting each of the first and second contour images from within the rectangular area of an image. 5. The plate inspection device according to claim 1, wherein each of the first and second contour images includes:
A normalization unit for normalizing the gradation value and the width of the contour portion to a common gradation value and a common width, wherein the first and the second after the contour difference specifying unit has been normalized by the normalization unit A plate inspection device for specifying the outline difference portion in a second outline image. 6. A plate inspection method for comparing and inspecting first and second images obtained in a plate making process, wherein a contour of an image element included in the first image is extracted to obtain a first image.
A contour extraction step of obtaining a contour image and extracting a contour of an image element included in the second image to obtain a second contour image; and specifying a contour difference portion where the first and second contour images are different from each other. A plate inspection method, comprising: a step of specifying a contour difference; and an output step of visually expressing and outputting the contour difference portion.