JP2005003482A - Printed matter measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed matter measuring method capable of accurately measuring a color. <P>SOLUTION: This printed matter measuring method measuring the color of a specified position in a printed matter based on an image data obtained by measuring the printed matter is provided with a control point designating process designating the position of a control point, an extraction process extracting the image data near the control point, a selection process selecting a related pixel relevant to the control point from the image data near the control point, and a decision process determining the color of the control point from the related pixel selected in the selection process. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a printed matter measuring method.
[0002]
[Prior art]
In order to perform proper printing in a printing machine, it is necessary to appropriately control the amount of ink supplied. At the time of controlling the ink supply amount, conventionally, the density of the control strip is measured by a densitometer, and the excess or deficiency of the ink is determined based on the density data. However, it is not always possible to obtain an appropriate color tone or the like in the pattern area only by the density data in the control strip.
[0003]
For this reason, a printed matter measuring apparatus is used that creates control data for controlling the ink supply amount of the printing press by comparing the image of the reference paper with the image of the printed matter that has actually been printed.
[0004]
Here, the reference paper is also called a calibration paper, and serves as a reference for an appropriate printed matter by instructing the color tone of the finished print. In addition, the printed paper on which printing has actually been performed is also referred to as a drawing paper, and is drawn by the operator at regular intervals from the paper discharge unit of the printing machine during printing. When the color tone of the extracted paper and the color tone of the reference paper are substantially the same, it is determined that proper printing is being performed.
[0005]
When such a printed matter measuring apparatus is used, it is difficult to make the color of the reference paper image and the printed image on which the printing has actually been performed match in all regions. For this reason, among these images, control points such as representative points representing colors characterizing the pattern of the printed matter are used. This control point is a point to be noted in order to control the ink supply amount, and is a point set by the operator from the image.
[0006]
This control point needs to be set so as to correspond to each other accurately in the image on the reference paper and the image of the printed matter on which printing has actually been performed. For this reason, in Patent Document 1, a pair of reference points for specifying the position of the image is specified in each of the reference paper image and the printed image actually printed, and these reference points and reference points are specified. There is disclosed a printed matter evaluation apparatus that uses control points in a paper image to calculate the positions of control points in an image of a printed matter that has actually been printed.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-305562
[Problems to be solved by the invention]
However, since the image part is usually composed of halftone dots, the color information of only one pixel may not match the color information of the image composed of a plurality of halftone dots, especially when a large halftone dot is used. Arise. Also, even when there is noise or scratches on the printed matter of the CCD camera as the image pickup means, accurate measurement cannot be performed if the measurement is performed based on the color information of only one pixel.
[0009]
The present invention has been made to solve the above-described problem, and an object of the present invention is to provide a printed matter measuring method capable of accurately performing color measurement.
[0010]
[Means for Solving the Problems]
The invention according to claim 1 is a printed matter measuring method for measuring a color at a predetermined position in a printed matter based on image data obtained by measuring the printed matter, and a control point designating step for designating a position of a control point; An extraction step for extracting image data in the vicinity of the control point, a selection step for selecting a related pixel related to the control point from the image data in the vicinity of the control point, and a control point from the related pixel selected in the selection step And a determining step for determining a color.
[0011]
According to a second aspect of the present invention, in the first aspect of the present invention, the selecting step includes a plurality of image data having a pixel arrangement different from that of the image data in the region including the control point in the image data in the vicinity of the control point. By comparing with the template, the template closest to the image of the region including the control point is selected, and the pixel at the same position as the pixel arranged in the selected template is selected as the related pixel.
[0012]
According to a third aspect of the present invention, in the second aspect of the invention, by calculating a variance of pixels located in the same position as the pixels arranged in the template in the image of the region including the control points, A template closest to the image of the region including the control points is selected.
[0013]
According to a fourth aspect of the present invention, in the second or third aspect of the present invention, in the determining step, an average value of the colors of the related pixels selected in the selecting step is determined as a control point color. .
[0014]
According to a fifth aspect of the present invention, in the first aspect of the invention, the selecting step uses, as related pixels, pixels that are within a predetermined color difference from the color of the control point in the image data in the vicinity of the control point. select.
[0015]
According to the sixth aspect of the present invention, the first image data serving as a reference is compared with the second image data obtained by photographing an image of the printed matter actually printed by the printing machine. In a printed matter measurement method for obtaining data for controlling an ink supply amount of a printing machine, a control point designation step for designating a position of a control point in the first image data, and a vicinity of the control point from the first image data By comparing the extraction step of extracting image data, the image data of the region including the control point among the image data in the vicinity of the control point in the first image data, and a plurality of templates each having a different pixel arrangement, A template closest to the image of the region including the control point is selected, and a pixel located at the same position as the pixel arranged in the selected template is set as a related pixel in the first image data. A selection step of selecting the image, a printed matter imaging step of obtaining the second image data by imaging a printed matter that has been actually printed, an average value of colors of related pixels in the first image data, A calculation step of calculating data for controlling the ink supply amount of the printing press by comparing the average value of the color of the related pixel corresponding to the related pixel in the first image data in the second image data. It is characterized by providing.
[0016]
The invention according to claim 7 is the invention according to claim 6, wherein by calculating a variance of pixels located in the same position as pixels arranged in the template in an image of an area including the control points, A template closest to the image of the region including the control points is selected.
[0017]
The invention according to claim 8 compares the control point data in the image data obtained by imaging the reference paper with the control point data in the image data obtained by imaging the printed matter actually printed. In the printed matter measurement method for obtaining data for controlling the ink supply amount of the printing press, the reference paper imaging step for obtaining the first image data by imaging the reference paper, and the printed matter in the first image data A designated control point designating step for designating designated control points to be used for measurement for each region corresponding to an ink key of a printing press; and a pair of first reference points for specifying an image position in the first image data A first reference point designating step for designating the image data, and, for each region corresponding to the ink key of the printing press, image data in a region including a control point among image data in the vicinity of the designated control point in the first image data; By comparing a plurality of templates each having a different pixel arrangement, a template closest to the image of the region including the designated control point is selected, and a pixel located at the same position as the pixel arranged in the selected template is selected. A selection step of selecting as a related pixel in one image data, a printed matter imaging step of obtaining a second image data by imaging a printed matter actually printed, and the first reference in the second image data. From the second reference point designating step of designating a pair of second reference points corresponding to the points, the first reference point and the second reference point, the designated control point in the first image data The calculation step of calculating the position of the corresponding control point in the corresponding second image data for each region corresponding to the ink key of the printing press, and the first image data from the corresponding control point. A selection step of selecting a position of the related pixel in the second image data corresponding to the related pixel corresponding to the area corresponding to the ink key of the printing press; and a step of selecting the first pixel for each area corresponding to the ink key of the printing press. A calculation step of calculating data for controlling the ink supply amount of the printing press by comparing the average value of the color of the related pixel in the image data and the average value of the color of the related pixel in the second image data. It is characterized by providing.
[0018]
The invention according to claim 9 is the invention according to claim 8, wherein the control is performed by calculating a variance of pixels corresponding to each pixel arranged in the template in an image of an area including the control point. Select the template closest to the image of the area containing the point.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a printed matter measuring apparatus according to the present invention, and FIG. 2 is a side view thereof. In FIG. 2, the light source 13 and the control panel 15 are not shown.
[0020]
This printed matter measuring apparatus is for creating control data for controlling the ink supply amount in the printing press by measuring reference paper or printed matter that has actually been printed. This printed matter measuring apparatus includes a table 12 disposed above the gantry 11, a pair of light sources 13 disposed on the left and right sides of the table 12, an imaging unit 14 disposed above the table 12, and one light source. 13 for controlling the control panel 15, the upper light shielding plate 17 and the rear light shielding plate 18 supported by the pair of support columns 16, the auxiliary light source 19 attached to the rear light shielding plate 18, and the entire apparatus. The control part 20 arrange | positioned inside the gantry 11 is provided.
[0021]
The table 12 has a planar shape on which a printed material can be placed. The surface of the table 12 is composed of a suction plate capable of sucking and holding printed matter by static electricity or vacuum suction. Further, the surface of the table 12 is inclined by about 10 degrees in order to facilitate the operation by the operator. Then, the printed matter attracted and held on the surface of the inclined table 12 is irradiated from the side by a pair of light sources 13.
[0022]
The imaging means 14 disposed above the table 12 divides the reflected light emitted from the light source 13 and reflected by the surface of the printed material into RGB three primary color components by a dichroic mirror, and each of them is received by an individual CCD array. A digital camera configured as described above. With this imaging means 14, RGB data can be obtained from the printed matter.
[0023]
The control panel 15 is a touch panel type composed of a liquid crystal monitor having a pressure-sensitive input function, and has both functions of display means and input means. The control panel 15 is connected to a control unit 20 described later.
[0024]
FIG. 3 is a block diagram illustrating a main configuration of the control unit 20.
[0025]
The control unit 20 includes a ROM 21 that stores an operation program necessary for controlling the apparatus, a RAM 22 that temporarily stores data and the like during control, a CPU 23 that executes a logical operation, and first and second images. And memories 24 and 25. The control unit 20 is connected to the control panel 15, the light source 13, and the imaging unit 14 described above via an interface 26. The control unit 20 is also connected to an image data supply unit 27 such as a hard disk or an image processing apparatus that stores image data to be printed.
[0026]
Referring to FIGS. 1 and 2 again, the upper light shielding plate 17 supported above the pair of support columns 16 has a shape curved in the front-rear direction of the printed matter measuring apparatus. The upper light shielding plate 17 is installed to block light that is regularly reflected on the table 12, for example, light from illumination installed indoors. On the other hand, the rear light shielding plate 18 supported between the pair of support columns 16 is for shielding light from the rear part of the printed matter measuring apparatus.
[0027]
The auxiliary light source 19 attached to the rear light shielding plate 18 is for responding to the darkness on the table 12 due to the action of the upper light shielding plate 17 and the rear light shielding plate 18. The auxiliary light source 19 is composed of a fluorescent lamp or the like, and is configured to be turned off when the printed material is imaged by the imaging means 14.
[0028]
Next, a printed matter measurement operation for obtaining data for controlling the ink supply amount of the printing press using the above-described printed matter measuring apparatus will be described. FIG. 4 is a flowchart showing the printed matter measurement operation.
[0029]
In order to obtain data for controlling the ink supply amount of the printing press using the above-described printed matter measuring apparatus, first, the reference paper is imaged. That is, the reference paper is placed on the table 12 and sucked and held there. Then, the reference paper is illuminated by the light source 13 and the reference paper is imaged by the imaging means 14. The reference sheet image data is stored as first image data in the first image memory 24 of the control unit 20 (step S2).
[0030]
The image data of the reference paper stored in the first image memory 24 is displayed on the control panel 15. FIG. 5 is an explanatory diagram showing an image of the reference sheet displayed on the control panel 15. In this embodiment, the case where the ink key of the printing press is divided into seven regions is shown. For this reason, seven areas corresponding to the ink keys are set in the image of the reference paper.
[0031]
Next, a control point that is a point to be noted in order to control the ink supply amount is designated. That is, the operator designates control points P1 to P7 (referred to as “designated control point P” when these are collectively referred to) for each region corresponding to each ink key from the image of the reference paper displayed on the control panel 15. . As this control point, for example, a representative point representing a color characterizing the pattern of the printed material is used. This control point may be set automatically. In this specification, the control points set by the operator in this way are called designated control points. Information on these designated control points P1 to P7 is stored in the first image memory 24 or the RAM 22 in the control unit 20.
[0032]
Next, a pair of first reference points T1 and T2 for specifying the position of the image in the first image data is designated (step S4). As the first reference points T1 and T2, it is preferable to select a point located on a diagonal line in the image as shown in FIG. Information on the first reference points T1 and T2 is stored in the first image memory 24 or the RAM 22 in the control unit 20.
[0033]
Next, image data near each designated control point P is extracted (step S5). Image data near the designated control point P is displayed on the control panel 15.
[0034]
FIG. 6 is an explanatory diagram showing an image in the vicinity of the designated control point P displayed on the control panel 15. FIG. 6 shows a state in which the linear figure I is arranged in the horizontal direction.
[0035]
Next, a related pixel associated with each designated control point P is selected (step S6). More specifically, the image data including the designated control point P among the previously extracted image data near the designated control point P is compared with a plurality of templates having different pixel arrangements, and the designated control point P is determined. Select the template closest to the image of the area to be included. Then, a pixel at the same position as the pixel arranged in the selected template is selected as a related pixel.
[0036]
FIG. 7 is a schematic diagram showing eight templates having different pixel arrangements.
[0037]
This template has an area of 5 rows and 5 columns. In this figure, areas where pixels are arranged are hatched.
[0038]
When selecting a related pixel, first, as shown in FIG. 6, the center of one of the templates L of the eight templates shown in FIG. Then, how much the position of the pixel in the template L matches the figure I is determined by calculating the variance of the pixel.
[0039]
That is, for example, as shown in FIGS. 7E to 7H, when using a template L having five pixels, the dispersion Mr of R color is obtained using the following equation.
[0040]
Mr = [(AF) ² + (BF) ² + (C−F) ² + (D−F) ² + (E−F) ² ] / 5
[0041]
Here, A, B, C, D, and E are pixel values of each of the five pixels, and F is an average value of the pixel values A, B, C, D, and E.
[0042]
Then, using the same formula, the dispersions Mg and Mb of G color and B color are obtained. When a template L having seven pixels as shown in FIGS. 7A to 7D is used, the same seven-term expression is used for these seven pixels. The RGB color dispersion Mr, Mg, and Mb may be obtained.
[0043]
Next, the final variance M is obtained using the following equation.
[0044]
M = (Mr + Mg + Mb) / 3
[0045]
While sequentially exchanging the eight templates L shown in FIGS. 7A to 7H, the variance M is obtained for all the eight templates L shown in FIGS. 7A to 7H. Then, the template L corresponding to the minimum variance M among those variances M is determined to be the shape most similar to the previously extracted figure near the designated control point P, and this is selected. In the case of the graphic I shown in FIG. 6, the template L shown in FIG. 7 (f) is selected. Then, each pixel arranged in the selected template L is selected as a related pixel related to the designated control point P.
[0046]
Referring to FIG. 4 again, next, a printed matter that has been actually printed is imaged (step S7). That is, the printed material extracted by the operator from the paper discharge unit of the printing press during printing is placed on the table 12 and sucked and held there. Then, the reference paper is illuminated by the light source 13 and the printed matter is imaged by the imaging means 14. The image data of the printed matter is stored as the second image data in the second image memory 25 in the control unit 20 (step S8).
[0047]
The printed image data stored in the second image memory 24 is displayed on the control panel 15 as in the case of the reference sheet image data. Then, a pair of second reference points T3 and T4 corresponding to the pair of first reference points T1 and T2 specified in the first image data is specified (step S9). Information on the second reference points T3 and T4 is stored in the second image memory 25 or the RAM 22 in the control unit 20.
[0048]
Then, the position of the corresponding control point, which is a control point corresponding to the designated control points P1 to P7, in the image of the printed matter actually printed is calculated (step S10). That is, the position of the corresponding control point is calculated by geometric calculation from the position data of the first reference points T1 and T2, the second reference points T3 and T4, and the designated control points P1 to P7 obtained previously. . As with the designated control points P1 to P7 shown in FIG. 5, seven corresponding control points are set for each region corresponding to the ink key of the printing press. Information on these corresponding control points is stored in the second image memory 25 or the RAM 22 in the control unit 20.
[0049]
Next, image data near each corresponding control point is extracted (step S11). Image data near the corresponding control point is displayed on the control panel 15.
[0050]
Then, a related pixel related to the corresponding control point is selected from the image data near the corresponding control point (step S12). More specifically, the center of the template L shown in FIG. 7 (f) selected previously can be matched with the corresponding control point. In this state, a pixel at the same position as the pixel arranged in the selected template L shown in FIG. 7F is selected as a related pixel.
[0051]
Next, using the color data of the designated control point and the color data of the corresponding control point, control data for controlling the ink supply amount of the printing press for each area corresponding to each ink key in the printing press. Calculate (step S13). At this time, the average value of the colors of the related pixels associated with each designated control point P is determined as the color of each designated control point. In addition, the average value of the related pixels associated with each corresponding control point is determined as the color of each corresponding control point. That is, the average value of the color of the related pixel related to each specified control point P is used as the color data of the specified control point, and the average value of the related pixel related to each corresponding control point is used as the data of the corresponding control point. The For this reason, even when a large halftone dot is used, noise is generated in the CCD camera, or dust or scratches are generated on the printed matter, it is possible to accurately measure the color.
[0052]
This control data is transferred to a printing press (not shown) online or offline via the interface 26 shown in FIG.
[0053]
Then, it is determined whether or not the necessary number of sheets have been printed (step S14). If the required number of prints has not been completed, the operations in steps S7 to S13 are repeated. At this time, for example, every time printing is performed on 100 sheets of printing paper, the operator pulls out the printed matter from the paper discharge unit of the printing press and images it. Then, when the necessary number of prints are finished, the process is finished.
[0054]
Next explained is the second embodiment of the invention.
[0055]
In the first embodiment described above, in step S4 shown in FIG. 4, the image data in the region including the designated control point among the image data in the vicinity of the designated control point is compared with a plurality of templates having different pixel arrangements. Thus, the template closest to the image of the region including the designated control point is selected, and each pixel arranged in the selected template is selected as a related pixel. However, in the second embodiment, in step S4, a pixel within a predetermined color difference from the color of the designated control point is selected as the related pixel from the image data near the designated control point.
[0056]
In this case, in step S12 shown in FIG. 4, a pixel at a position corresponding to the related pixel selected in step S4 may be selected as the related pixel of the corresponding control point.
[0057]
In the above-described embodiment, image data obtained by imaging a reference sheet is used as the reference image data. However, the image data supplied from the image data supply unit 27 is used for plate making. Image data may be used as reference image data. Further, the imaging order of the reference paper and the printed material may be reversed.
[0058]
In the above-described embodiment, the designated control point is designated in the reference sheet image, and the coordinates of the corresponding control point in the printed image that is actually printed are corrected. However, the printing is actually performed. The designated control points may be designated in the printed image, and the coordinates of the corresponding control points in the reference paper image may be corrected.
[0059]
【The invention's effect】
According to the first to eighth aspects of the invention, color measurement is performed even when a large halftone dot is used, noise is generated in the CCD camera, or dust or scratches are generated on the printed matter. It becomes possible to execute accurately.
[Brief description of the drawings]
FIG. 1 is a perspective view of a printed matter measuring apparatus according to the present invention.
FIG. 2 is a side view of the printed matter measuring apparatus according to the present invention.
3 is a block diagram showing a main configuration of a control unit 20. FIG.
FIG. 4 is a flowchart showing a printed matter measurement operation.
FIG. 5 is an explanatory diagram showing an image of a reference sheet displayed on the control panel 15;
6 is an explanatory diagram showing an image in the vicinity of a designated control point P displayed on the control panel 15. FIG.
FIG. 7 is a schematic diagram showing eight templates having different pixel arrangements.
[Explanation of symbols]
12 Table 13 Light source 14 Imaging means 15 Control panel 20 Control unit 24 First image memory 25 Second image memory 27 Image data supply unit I Graphic L Templates P1 to P7 Designated control points T1, T2 First reference point

Claims (9)

In a printed matter measurement method for measuring a color at a predetermined position in a printed matter based on image data obtained by measuring the printed matter,
A control point specifying step for specifying the position of the control point;
An extraction step of extracting image data in the vicinity of the control point;
A selection step of selecting a related pixel associated with the control point from image data in the vicinity of the control point;
A determination step of determining a color of the control point from the related pixels selected in the selection step;
A printed matter measuring method comprising: In the printed matter measuring method according to claim 1,
The selection step includes
A template closest to the image of the region including the control point is selected by comparing the image data of the region including the control point with the plurality of templates having different pixel arrangements among the image data in the vicinity of the control point. A printed matter measurement method for selecting a pixel at the same position as a pixel arranged in a selected template as a related pixel. In the printed matter measuring method according to claim 2,
A printed matter measurement method for selecting a template closest to an image in an area including the control point by calculating a variance of pixels located at the same position as the pixels arranged in the template among the image in the area including the control point. In the printed matter measuring method according to claim 2 or claim 3,
In the determining step, the printed matter measuring apparatus that determines an average value of the colors of the related pixels selected in the selecting step as a control point color. In the printed matter measuring method according to claim 1,
The selection step includes
A printed matter measuring apparatus that selects, as related pixels, pixels that are within a predetermined color difference from the color of the control point in the image data in the vicinity of the control point. In order to control the ink supply amount of the printing press by comparing the first image data serving as a reference with the second image data obtained by photographing an image of a printed matter actually printed by the printing press. In the printed matter measurement method for obtaining the data of
A control point designating step of designating a position of a control point in the first image data;
An extraction step of extracting image data in the vicinity of the control point from the first image data;
By comparing the image data of the region including the control point in the image data near the control point in the first image data with a plurality of templates having different pixel arrangements, the image of the region including the control point is obtained. A selection step of selecting the closest template and selecting a pixel at the same position as the pixel arranged in the selected template as a related pixel in the first image data;
A printed matter photographing step of obtaining the second image data by imaging a printed matter that has been actually printed;
By comparing the average value of the color of the related pixel in the first image data with the average value of the color of the related pixel corresponding to the related pixel in the first image data in the second image data. A calculation process for calculating data for controlling the ink supply amount of the machine;
A printed matter measuring method comprising: In the printed matter measuring method according to claim 6,
A printed matter measurement method for selecting a template closest to an image in an area including the control point by calculating a variance of pixels located at the same position as the pixels arranged in the template among the image in the area including the control point. By comparing the control point data in the image data obtained by imaging the reference paper with the control point data in the image data obtained by imaging the printed material actually printed, the ink supply amount of the printing press In a printed matter measurement method for obtaining data for controlling
A reference paper imaging step of capturing the reference paper and obtaining first image data;
A designated control point designating step for designating a designated control point used for measurement of a printed matter in the first image data for each region corresponding to an ink key of a printing press;
A first reference point designating step of designating a pair of first reference points for specifying the position of an image in the first image data;
For each region corresponding to the ink key of the printing press, image data in a region including the control point in the image data in the vicinity of the designated control point in the first image data is compared with a plurality of templates having different pixel arrangements. A selection step of selecting a template closest to the image of the region including the designated control point, and selecting a pixel at the same position as the pixel arranged in the selected template as a related pixel in the first image data; ,
A printed matter imaging step of capturing a second printed image by imaging a printed matter that has been actually printed;
A second reference point designating step of designating a pair of second reference points corresponding to the first reference point in the second image data;
The position of the corresponding control point in the second image data corresponding to the designated control point in the first image data from the first reference point and the second reference point corresponds to the ink key of the printing press. A calculation process to calculate for each area;
A selection step of selecting, from the corresponding control point, the position of the related pixel in the second image data corresponding to the related pixel in the first image data for each region corresponding to an ink key of a printing press;
By comparing the average value of the color of the related pixel in the first image data with the average value of the color of the related pixel in the second image data for each region corresponding to the ink key of the printing machine. A calculation process for calculating data for controlling the ink supply amount of
A printed matter measuring method comprising: In the printed matter measuring method according to claim 8,
A printed matter measurement method for selecting a template closest to an image in an area including the control point by calculating a variance of pixels corresponding to each pixel arranged in the template among images in the area including the control point.

Images