JP2004330563A - Color tone controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color tone controller for settling control operation of ink supply amount quickly by recognizing an actually printed matter again as a new reference sheet. <P>SOLUTION: A control section 20 comprises an ROM 21, an RAM 22, a CPU 23, and first and second image memories 24 and 25. Reference image data obtained from an imaging means 14 is stored in the image memory 24. Image data of a printed matter obtained from the imaging means 14 is stored in the image memory 25. When an operator judges that the color tone of a printed matter is sufficiently close to that of the reference sheet, a control panel 15 designates to replace the original reference image data stored in the image memory 24 through the CPU 23 by new reference image data, i.e. the image data of a printed matter stored in the image memory 25. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a color tone control device that adjusts the color tone of a printed matter by comparing a reference image and an image of the printed matter.
[0002]
[Prior art]
In order to properly adjust the color tone of the printed matter, it is necessary to appropriately control the ink supply amount. For this reason, Japanese Patent Application Laid-Open No. H11-163873 discloses a method in which the density of a printed matter output from a printing apparatus is measured on a color stand, compared with a reference sheet prepared in advance by a proof machine, etc., and based on the comparison result, ink supply to a printing plate is performed. An apparatus for generating a signal for controlling a quantity is described.
[0003]
[Patent Document 1]
JP-A-2001-353852
[0004]
[Problems to be solved by the invention]
However, when the printing machine and the type of ink are different, it is difficult to completely match the image of the reference paper with the image of the printed matter actually printed. For this reason, when the images cannot be completely matched, the above-described apparatus determines that the image of the reference paper and the image of the printed material do not match, and matches the color tone of the printed material with the color tone of the reference paper. Therefore, the ink supply amount is continuously changed. At this time, for example, there is a case where the control is not stabilized by repeating the contradictory control.
[0005]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and provides a color tone control device that re-recognizes a printed material that has been actually printed as a new reference paper and quickly stabilizes an operation of controlling an ink supply amount. The purpose is to do.
[0006]
[Means for Solving the Problems]
According to the first aspect of the present invention, a first storage unit that stores a reference image as reference image data, an imaging unit that captures an image of a print, and an image of the print obtained by the imaging unit as print image data A second storage unit for storing, an ink amount calculation unit for comparing a difference in color or density between the reference image data and the print image data to calculate an ink amount to be applied to a print, A reference image data changing unit that stores the print image data as new reference image data in a first storage unit.
[0007]
According to a second aspect of the present invention, in the color tone control device according to the first aspect, the reference image data includes position information of a representative point used as a reference for controlling the color tone, and the reference image data changing unit includes: Reference image data excluding the position information of the representative point is stored in the first storage means.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a color tone control device according to the present invention, and FIG. 2 is a side view thereof. 2, illustration of the light source 13 and the control panel 15 is omitted.
[0009]
This color tone control device is for creating control data for controlling the ink supply amount of a printing machine by comparing an image of a reference sheet with an image of a printed material actually printed.
[0010]
The color tone control device includes a table 12 disposed above a 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, an upper light shield 17 and a rear light shield 18 supported by a pair of columns 16, an auxiliary light source 19 attached to the rear light shield 18, and a control panel for controlling the entire apparatus. And a control unit 20 disposed inside the gantry 11.
[0011]
The table 12 has a planar shape on which printed matter can be placed. The surface of the table 12 is composed of a suction plate capable of holding a printed material by electrostatic or vacuum suction. 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 sucked and held on the surface of the inclined table 12 is irradiated from the side by a pair of light sources 13.
[0012]
The imaging means 14 disposed above the table 12 divides the reflected light emitted from the light source 13 and reflected on the surface of the printed matter into three primary color components of RGB by a dichroic mirror, and receives each of the three primary color components by a separate CCD array. Having a digital camera configured as described above. With this imaging means 14, RGB data can be obtained from the printed matter.
[0013]
The control panel 15 is of a touch panel type including a liquid crystal monitor having a pressure-sensitive input function, and has both functions of a display unit and an input unit. The control panel 15 is connected to the control unit 20.
[0014]
FIG. 3 is an electrical block diagram showing a main configuration of the color tone control device.
[0015]
The control unit 20 includes a ROM 21 in which an operation program necessary for controlling the apparatus is stored, a RAM 22 in which data and the like are temporarily stored at the time of control, a CPU 23 that executes a logical operation, and first and second image memories. 24 and 25. The control unit 20 is connected to the control panel 15, the light source 13, and the imaging unit 14 via the 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 device that stores data of an image to be printed.
[0016]
Referring again to FIG. 1 and FIG. 2, the upper light shielding plate 17 supported above the pair of columns 16 has a shape curved in the front-rear direction of the color tone control device. The upper light shielding plate 17 is provided to block light that is specularly reflected on the table 12, such as light from lighting installed indoors. On the other hand, the rear light blocking plate 18 supported between the pair of columns 16 is for blocking light from the rear of the color tone control device.
[0017]
The auxiliary light source 19 attached to the rear light-shielding plate 18 is for coping with darkening of the table 12 by the action of the upper light-shielding plate 17 and the rear light-shielding plate 18. The auxiliary light source 19 is configured by a fluorescent lamp or the like, and is configured to be turned off when a printed matter is photographed by the imaging unit 14.
[0018]
In the case where the ink supply amount of the printing press is controlled using the color tone control device having the above configuration, first, the image data of the image to be printed stored in the image data supply unit 27 is used. , A representative color determination step and the like which will be described in detail later are executed. Next, a photographing step of photographing the image of the reference paper and the image actually printed is executed.
[0019]
Then, control data for controlling the ink supply amount of the printing press is created by performing an arithmetic process described in detail later. The control data is transferred on-line or off-line to a printer (not shown) via the interface 26.
[0020]
Here, the reference paper is also referred to as a calibration paper or an OK sheet, and serves as a reference for an appropriate printed matter by instructing a color tone of a finished print. The printed matter actually printed is also referred to as a sampled sheet, and is a sheet that is extracted by the operator at regular intervals from a sheet discharge unit of the printing press during execution of printing. Then, when the color tone and the like of the sampled paper and the color tone and the like of the reference paper substantially match, it is determined that appropriate printing is being performed.
[0021]
Note that, in the present embodiment, an example has been described in which the reference paper is supplied by a paper medium on which the reference paper is actually printed. However, the present invention includes a case where the reference paper is supplied only by image data.
[0022]
Next, each step in the ink supply amount control operation using the above-described color tone control device will be described in more detail. FIG. 4 is a flowchart showing the print measurement operation.
[0023]
When measuring a printed material to create control data for controlling the ink supply amount of a printing press, first, a representative color that is a color characterizing an image of the printed material based on image data to be printed. Is determined (step S1). This image data is supplied from the image data supply unit 27 shown in FIG. In this representative point determination step, a desired part determined to be important by the operator may be designated as a representative point, or the representative point may be automatically determined from image data according to a desired condition.
[0024]
Hereinafter, an example of automatically determining a representative point from image data will be described with reference to a subroutine shown in FIG.
[0025]
First, image data of an image to be printed is fetched from the image data supply unit 27 (step S11). This image data is CMYK (cyan, magenta, yellow, black) plate making data of an image to be printed obtained when plate making is performed, or image data created based on this plate making data. This image data is supplied as, for example, PPF (Print Production Format) data in the International Cooperation for Integration (CIP3) or Pressand Postpress (CIP3) standard. In this specification, black is appropriately referred to as K and Bk.
[0026]
Next, the PPF data (CMYK data) is converted into data having RGB gradations (step S12). Here, assuming that CMYK data has an 8-bit value of 0 to 255, this conversion is performed by the following equations (1) to (3). If the RGB value is negative, it is determined to be 0.
[0027]
R = 255- (C + K) (1)
[0028]
G = 255- (M + K) (2)
[0029]
B = 255- (Y + K) (3)
[0030]
Next, edge components are extracted from the RGB image and removed (step S13). In other words, if the edge amount, which is the sum of the difference (absolute value) between the pixel of interest and the upper, lower, left, and right pixels adjacent to the pixel of interest, is greater than a certain value, the pixel of interest is determined to be an edge pixel. Then, this edge pixel is excluded from the subsequent processing targets.
[0031]
Then, the RGB image is divided into sections corresponding to the ink keys in the ink fountain of the printing press (step S14). In the subsequent steps (steps S15 and subsequent steps), each process is executed for each of the divided sections.
[0032]
First, a pixel to which the contribution of Bk (black) ink is large is extracted and removed (step S15). That is, among the CMYK data before the conversion into RGB, a pixel having the minimum value of CMY smaller than the value of K is determined to be a pixel having a large contribution of Bk, and this pixel is excluded from the subsequent processing. .
[0033]
Next, a three-dimensional histogram is created from the RGB values of the remaining pixels (step S16). That is, the three-dimensional area is divided into an appropriate range for each of the RGB color components, and one side is equally divided into a cube including a predetermined gradation range, and then the frequency distribution of each section is obtained. The process of creating the three-dimensional histogram is also described in detail in Japanese Patent Application Laid-Open No. 11-296672 by the present applicant.
[0034]
In this embodiment, a histogram is created by RGB values, but a frequency distribution may be created by three other color system components such as CMY values.
[0035]
Next, weighting is performed by multiplying the frequency by an appropriate coefficient according to the color represented by the section of the histogram (step S17). For example, when it is desired to prioritize a skin color in a picture as a representative color, the color gamut is multiplied by a large coefficient. Then, the section of the maximum frequency after multiplication by the coefficient is set as a color gamut as a representative color, and only the pixels included in the section will be noted below.
[0036]
In the above description, the color gamut to be the representative color is determined by creating a histogram, but the operator may specify a predetermined color gamut instead of the section of the maximum frequency. In this case, the above-described calculation of the frequency becomes unnecessary.
[0037]
Next, isolated points are removed from the pixels included in the section of the maximum frequency after the coefficient multiplication (step S18). That is, the operation of removing the outermost pixels of the region by the pixels included in the section of the maximum frequency after the coefficient multiplication as the isolated point is repeated until the total number of pixels of all the regions becomes 1 or 0 (step S19). ).
[0038]
When the number of remaining pixels becomes 1, the CMYK value of the pixel is set as a representative color, and the pixel is set as a representative point. On the other hand, when the remaining number is 0, the CMYK value of a pixel near the center of the section corresponding to the ink key is set as a representative color, and the pixel is set as the representative color. It will be a representative point. Thus, the representative color and the representative point are determined (Step S20).
[0039]
It should be noted that the position where the area where the pixels included in the section having the maximum frequency are aggregated (the area of the continuous pixel group) is largest as the representative point by the above-described isolated point removal is selected as the representative point because of the error due to the noise of the imaging unit 14. This is to prevent the influence of the positioning error when comparing the color data at the representative point of the image of the reference paper and the color data at the representative point of the image of the printed matter, which will be described later.
[0040]
In the above-described embodiment, one pixel remaining after removal of the isolated point is set as a representative point, and the CMYK value of the pixel is set as the representative color. However, the CMYK values of several adjacent pixels including the pixel are averaged or weighted and averaged. It may be a representative color. When such a configuration is employed, it is possible to reduce the influence of noise included in the pixel.
[0041]
Referring to FIG. 4 again, next, a gray control point having a gray control color that is a color expressed almost achromatic is determined (step S2).
[0042]
This gray control point determination step is executed based on the same flowchart as the representative point determination step shown in FIG. However, in this gray control point determination step, in step S17 of FIG. 5, the section of the histogram corresponding to gray is multiplied by one or more coefficients, so that the gray portion is preferentially selected in step S18. I do. Of course, a predetermined color gamut may be directly specified as a section to be a gray control color. If the selected gray area does not have a certain area or more, that is, if the number of repetitions in step S19 is equal to or less than a certain number, the area corresponding to the ink key does not have the predetermined gray area or more. And the gray control point is not determined.
[0043]
Next, a Bk control point having a Bk control color that is a color expressed in black is determined (step S3).
[0044]
This Bk control point determination step is executed based on the same flowchart as the representative point determination step shown in FIG. However, in the Bk control point determination step, in step S15 in FIG. 5, pixels in which the contribution of Bk (black) ink is small are extracted and removed. That is, of the CMYK data, a pixel having the maximum value of CMY larger than the value of K is determined as a pixel having a small contribution of Bk, and this pixel is excluded from the subsequent processing. If the area of Bk does not have a certain area or more, that is, if the number of repetitions in step S19 is equal to or less than a certain value, it is determined that the area corresponding to the ink key does not have a predetermined area of Bk or more. No control point is determined.
[0045]
FIG. 6 is an explanatory diagram showing the above-described representative points, gray control points, and Bk control points. Here, D1 to D7 shown in FIG. 6A represent the representative points determined in the above-described representative point determination step (step S1), and G1 to G7 shown in FIG. The gray control points determined in the step (step S2), and B2 and B6 shown in FIG. 6C indicate the Bk control points obtained in the above-described Bk point determination step (step S3).
[0046]
These representative points (hereinafter, representative points, gray control points, and Bk control points are collectively referred to as representative points) are displayed on the control panel 15 shown in FIG. 1 together with an image to be printed. The operator may check the position and color tone of the representative point displayed on the control panel 15 and change the position of the representative point as shown in FIG.
[0047]
The embodiment shown in FIG. 6 shows a case where the image area is divided into seven sections corresponding to the ink keys in the ink fountain of the printing press. Further, in this embodiment, a case is shown where the Bk control point exists only in the second area from the right and the second area from the left.
[0048]
Referring again to FIG. 4, an image of the reference paper is photographed next (step S4). In this case, the reference paper is placed on the table 12 and held there by suction. Then, the reference paper is illuminated by the light source 13, and an image of the reference paper is captured by the imaging unit 14. The data of the image of the reference paper obtained in this way is stored in the first image memory 24 of the control unit 20.
[0049]
When the image data itself is supplied as the reference paper as described above, this photographing step is not performed, and the image data serving as the reference is stored in the first image memory 24 as an alternative.
[0050]
Next, an image of the printed matter is photographed (step S5). In this case, the printed matter extracted by the operator from the paper discharge unit of the printing press during the execution of the printing is placed on the table 12 and held there by suction. Then, the printed matter is illuminated by the light source 13, and an image of the printed matter is photographed by the imaging unit 14. The data of the image of the printed matter obtained in this way is stored in the second image memory 25 of the control unit 20. This printed matter is a printed matter on which a desired image to be actually printed is printed.
[0051]
The image data of the reference paper includes the position information of each representative point and the RGB values at each representative point.
[0052]
FIG. 7 is an explanatory diagram showing an image 30 of a printed matter displayed on the control panel 15 and an image 40 displaying CMYK values at respective representative points thereof.
[0053]
As shown in FIG. 7, the control panel 15 displays an image 30 representing the representative points D1 to D7 selected in the section corresponding to each ink key and the printed matter. As shown in FIG. 7, the control panel 15 displays an image 40 in which each of the CMYK values at the representative points D1 to D7 of the displayed printed matter is represented as a bar graph.
[0054]
Further, the image 30 and the image 40 displayed on the control panel 15 can be switched to an image based on reference paper.
[0055]
Referring again to FIG. 4, data obtained by photographing the image of the reference paper and the image of the printed matter actually printed are compared, and the color difference between the image data of the reference printed matter and the image data of the printed matter is calculated. (Step S6). More specifically, after converting the pixel values of all the pixels of the image data of the reference paper and the image data of the printed matter into color values corresponding to the L * a * b * color space, the color difference ΔE of each corresponding pixel is calculated. Calculate.
[0056]
On the other hand, in the next step S7, a difference ΔD1 based on the CMYK values is calculated from the image data of the reference sheet at the representative point and the image data of the printed matter.
[0057]
Then, the difference value ΔD1 and the color difference ΔE are displayed on the control panel 15 (step S8).
[0058]
As described above, in the present embodiment, the color difference ΔE is obtained for all the pixels of the image data, and the difference value ΔD1 is obtained for the representative point. The color difference ΔE is used as a reference display to the operator, The value ΔD1 is used for controlling the ink supply amount.
[0059]
FIG. 8 shows an image 50 displaying the color difference ΔE at each pixel corresponding to the reference paper and the printed matter displayed on the control panel 15 and a difference value ΔD1 of the CMYK values between the reference paper and the printed matter at the representative point. FIG. 9 is an explanatory diagram showing an image.
[0060]
As schematically shown in FIG. 8, the color difference ΔE calculated in step S6 is displayed as a change in brightness at a position corresponding to each pixel of the image 50 displayed on the control panel 15. For example, the change in brightness is represented in a stepwise manner such that the larger the color difference ΔE is, the brighter the color difference ΔE becomes, and the smaller the color difference ΔE becomes, the darker the color difference ΔE becomes. A hatched portion 51 schematically represented in FIG. 8 indicates a particularly bright portion in the image 50 displayed on the control panel 15. For this reason, the operator can determine at a glance that the color difference ΔE between the reference paper and the printed matter is larger in the portion represented by the hatched portion 51 than in the other portions.
[0061]
As shown in FIG. 8, the control panel 15 displays an image 60 representing a difference value ΔD1 between the reference paper and the printed material at the representative point for each CMYK as a bar graph. The difference value ΔD1 at the representative points D1 to D7 selected in the section corresponding to each ink key is shown at 61 to 67 for each CMYK. Specifically, the difference value ΔD1 (C) of the C value is shown at 61a to 67a, the difference value ΔD1 (M) of the M value is shown at 61b to 67b, and the difference value ΔD1 (Y) of the Y value is 61c. To 67c, and the difference value ΔD1 (K) of the K value is indicated by 61d to 67d. Therefore, for example, in the case of the image 60 shown in FIG. 8, at each representative point of the reference paper and the printed matter, the C value at D1, D2, D3, D5, and D6, the M value at D1, the D1, D2, The operator can easily determine that the Y value at D3, D4 and D5 and the K value at D1 deviate.
[0062]
Note that the color difference calculation may be performed by converting into a value corresponding to a color space such as L * u * v * or XYZ.
[0063]
From the image displayed in step S8, if the operator finds that the color difference is large near the other important colors even if the difference is small near the representative point, the representative point designating means is used as necessary. To change the representative point (step S9).
[0064]
If the representative point has been changed in step S9, the process returns to step S7, and steps S7 to S8 are performed.
[0065]
If the representative point is not changed or the change of the representative point is completed, the ink supply amount by the ink supply device of the printing press is adjusted based on the result of the representative point difference in S7 (step S10).
[0066]
Next, the operator visually checks the extracted printed matter and determines that the quality is sufficiently satisfactory, and sets the printed matter as a new reference sheet.
[0067]
That is, when the operator determines in step S11 that the reference image data may be changed, the reference image data is changed as necessary (step S12).
[0068]
Specifically, when the operator gives an instruction on the control panel 15, the print image data stored in the image memory 25 is replaced with the original reference image data stored in the image memory 24 as new reference image data. Is done.
[0069]
At this time, the position of the representative point determined on the original reference paper can be used without change as the position of the representative point on the printed material used as the reference paper. For this reason, it is possible to control the color tone of the printed matter without interrupting the printing.
[0070]
When the operator determines in step 11 that the reference image data is not to be changed, it is not necessary to change the reference image data in step 12, and printing is continued.
[0071]
Then, it is determined whether or not to end the printing (step S13). That is, when printing is completed, all the printed matter measurement operations of the color tone control device are completed.
[0072]
On the other hand, when the printing is continued, the process returns to step S5, and by the same operation as the above-described operation, the printed matter extracted by the operator from the paper discharge unit of the printing press at an appropriate interval during the printing is photographed. Thereafter, the processes from step S6 to step S12 are performed.
[0073]
In the above-described embodiment, the color difference between the image data of the reference paper and the image data of the printed matter is displayed as a change in brightness, but may be displayed based on a change in color. This change in color is expressed stepwise such that, for example, the larger the color difference ΔE is, the redder the color difference ΔE is, the bluer the smaller the color difference ΔE is, and yellow in the middle.
[0074]
Further, in the above-described embodiment, the reference printed matter or the printed matter is conveyed to the dedicated color tone control device shown in FIGS. 1 and 2 and its color data is measured. May be provided, and the image of the reference printed matter or the printed matter may be measured using the imaging mechanism.
[0075]
Such an imaging mechanism is disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-253054 by the present applicant, and a detailed description thereof will be omitted.
[0076]
Further, in the above-described embodiment, the difference value of each corresponding pixel is calculated based on the value corresponding to the color space. However, the calculation may be performed using the value of the density difference in the YMCK density space. .
[0077]
【The invention's effect】
According to the first aspect of the present invention, since there is provided a reference image data changing means for storing the printed matter image data as new reference image data in the first storage means in accordance with an instruction of an operator, the reference paper and the printed matter are compared. It is an object of the present invention to provide a color tone control device for quickly stabilizing the control operation of the ink supply amount even if the printing machine and the type of ink are different.
[0078]
According to the second aspect of the present invention, the reference image data changing means stores the reference image data excluding the position information of the representative point in the first storage means. Can be controlled.
[Brief description of the drawings]
FIG. 1 is a perspective view of a color tone control device according to the present invention.
FIG. 2 is a side view of the color tone control device according to the present invention.
FIG. 3 is a block diagram showing a main electrical configuration of a color tone control device according to the present invention.
FIG. 4 is a flowchart showing an ink supply amount control operation in the color tone control device according to the present invention.
FIG. 5 is a flowchart illustrating a representative color determination step.
FIG. 6 is an explanatory diagram showing representative points, gray control points, and Bk control points.
FIG. 7 is an explanatory diagram showing an image 30 of a captured printed matter displayed on the control panel 15 and an image 40 displaying CMYK values at respective representative points thereof.
FIG. 8 shows an image 50 displaying the color difference ΔE at each pixel corresponding to the image data of the reference paper and the image data of the printed matter displayed on the control panel 15, and the image data of the reference paper and the image of the printed matter at a representative point. FIG. 9 is an explanatory diagram showing an image 60 displaying a difference between CMYK values and data.
[Explanation of symbols]
11 Stand
12 tables
13 Light source
14 Imaging means
15 Control Panel
16 props
17 Upper light shield
18 Rear light shield
19 Auxiliary light source
20 control unit
21 ROM
22 RAM
23 CPU
24 Image memory
25 Image memory
26 Interface
27 Image data supply unit
30 images
40 images
41 Difference
42 Difference
43 Difference
44 Difference
45 Difference
46 Difference
47 Difference
50 images
51 Shaded area
60 images
61 Difference
62 Difference
63 Difference
64 differences
65 Difference
66 Difference
67 Difference
D Representative point
G Gray control point
B Bk control point

Claims (2)

First storage means for storing a reference image as reference image data;
Imaging means for imaging a printed matter;
A second storage unit that stores an image of the printed matter obtained by the imaging unit as printed image data,
An ink amount calculation unit that calculates the amount of ink to be applied to the print by comparing the difference in color or density between the reference image data and the print image data;
A reference image data changing unit that stores the print image data as new reference image data in a first storage unit according to an instruction of an operator;
A color tone control device comprising: The color tone control device according to claim 1,
The reference image data includes position information of a representative point serving as a reference for controlling a color tone,
The color tone control device, wherein the reference image data changing unit stores the reference image data excluding the position information of the representative point in the first storage unit as new reference image data.

Images