JPH09270930A - Method for generating print proof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate the print proof being a hard copy, in which even a sense of quality of paper for a color printed matter is expressed by using a color printer. SOLUTION: The sense of 'unevenness' and the sense of 'roughness' in the sense of quality of paper are expressed through the provision of a process of revising dot area rate data at expansion to bit map data for a color printer 3, based on a type of print paper P (high class paper or art paper or the like) and dot area rate data ap of a PS version 17 (process of dot area rate data aj into dot area rate data ak) (step S51), a density distribution is obtained by measuring the surface of a printed matter with 100% of the dot area rate data ap for each type of the paper P, and a process (step S52) correcting the density of photometry data is provided based on the measured density distribution to express a sense of 'texture' in a sense of quality of paper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color printing proof (color printing proof) in which a color image for proofing is formed before a color printed matter is formed by a dot image by a color printing machine using a rotary press or the like. (Also referred to as “printing”), the present invention relates to a method of creating a print proof by creating a color print proof with a color printer or the like that forms an image for each pixel on a sheet by a density gradation method.

[0002]

2. Description of the Related Art Conventionally, a color image based on a halftone dot image as a product is a main paper (a final product, for example, fine paper,
Before using a color printing machine to create a color print on official paper such as coated paper or art paper, which is used for final printing, make a color print proof for proofing colors etc. with a color printer. There is.

The use of color printers to create color printing proofs is relatively inexpensive and inexpensive, and, as is well known, color printers are commonly used in color printing machines. This is because it is not necessary to create such a plate-making film or a printing plate (PS plate), and a hard copy with an image formed on a sheet can be easily created a plurality of times in a short time.

FIG. 12 shows a flow of a conventional method for producing a color printing proof.

First, the color image on the image original 2 is a CCD.
R (red), G (green), B (blue) read by an image reading device such as a color scanner having an area sensor
The gradation image data Ia for each color is created (step S1: image reading process).

Next, the RGB gradation image data Ia is subjected to color conversion processing to obtain C (cyan), M (magenta), and Y.
It is converted into four dot halftone dot area ratio data (also called halftone dot% data) aj (j = 0 to 3) for each color (yellow) and K (black) (step S2). This conversion can be performed in various ways depending on the relationship with the color printing machine, and is usually the know-how of each printing company corresponding to the color printing machine.

The image on the color printed matter produced by this color printing machine is a halftone dot image. Therefore, when the color printed matter is actually produced, the halftone dot area ratio data aj after the color conversion processing is bitmapped. Although it is developed into data and a plate-making film or the like is created based on this, an automatic processor (automatic developing machine) or the like is required, and the steps after the plate-making film creating process are considerably complicated.

Therefore, in order to easily create a color printing proof, the color printer (hereinafter, also referred to as a color digital printer, also referred to as DP) 3 is used for the reason described above. The DP3 digitally controls the light emission intensity and time of an LED (light emitting diode) or laser corresponding to three primary colors for each pixel by a density gradation method to form an image on a donor film, and the image is formed on the image receiving sheet. The PS plate is formed on the image receiving sheet by transferring the image onto the image receiving sheet, and therefore, the PS plate is considerably inexpensive compared to a color printing machine which prints using the PS plate, and has a large volume. It is small and lightweight.

Therefore, in order to use DP3, the halftone dot area ratio data a of the four versions of CMYK created in step S2 is used.
j is a device (print, CRT, photo,
Image data (also referred to as common color space data) that does not depend on LEDs, for example, tristimulus value data X,
It is necessary to convert into Y and Z.

Therefore, image data processing for converting the halftone dot area ratio data aj of CMYK4 version into tristimulus value data X, Y, Z is performed (step S4). As this image data processing, processing using the Neugebauer equation has been conventionally used.

In this case, colorimetric value data Xi, Yi, Zi (i is 2 ⁴ colors = 16 colors in the case of the 4th edition of CMYK) for each color is previously measured by a colorimeter ( Step S
3). In this measurement, first, each color of 16 colors is printed in advance on a printing paper, which is a so-called main paper, for making a color printed matter by a color printing machine (usually called solid printing). The 16 colors are specifically C color, M color, and Y color.
Corresponding to the presence or absence of each color, K, 2 ^{4 in} total
Color = 16 colors.

That is, the ground color W (white) of the printing paper when nothing is printed, the primary colors C, M and Y only, the K color, and the mixed colors C + M, C + Y and C +.
K, M + Y, M + K, Y + K, C + M + Y, C + M +
There are a total of 16 colors of K, C + Y + K, M + Y + K, and C + M + Y + K. These reflected colors formed on the printing paper are measured by a colorimeter, for example, a spectrometer, and colorimetric value data X
Obtain i, Yi, and Zi in advance.

In the processing using the Neugebauer equation, the colorimetric value data Xi, Y are obtained as shown in the following equation (1).
halftone dot area ratio data hi as respective coefficients of i and Zi
Tristimulus value data X after being multiplied by and image data processed,
Y and Z are created (step S4).

X = Σhi · Xi Y = Σhi · Yi Z = Σhi · Zi (1) where i = 0 to 15 h0 = (1-c) · (1-m) · (1-y) · ( 1-k) h1 = c * (1-m) * (1-y) * (1-k) h2 = (1-c) * m * (1-y) * (1-k) h3 = c * m * (1-y) * (1-k) h4 = (1-c) * (1-m) * y * (1-k) h5 = c * (1-m) * y * (1-k) ) H6 = (1-c) * m * y * (1-k) h7 = c * m * y * (1-k) h8 = (1-c) * (1-m) * (1-y) * Kh9 = c * (1-m) * (1-y) * kh10 = (1-c) * m * (1-y) * kh11 = c * m * (1-y) * kh12 = (1-c) * (1-m) * y * kh13 = c * (1-m) * y kh14 = (1-c) * m * y * kh15 = c * m * y * k, where c, m, y, and k are halftone dot area ratio data for each color of C, M, Y, and K. It is a value obtained by converting aj (0 to 255) into (1/255) and converting the existence probability into 0 to 1.0.

The tristimulus value data X, Y, Z after the image data processing thus created are supplied to DP3, and D
In P3, the tristimulus value data X, Y, and Z are data for each of the three primary colors of the LEDs and the like based on a look-up table (LUT) (so-called device-dependent image data and also called unique color space data). ), A color printing proof CPa, which is a hard copy with an image formed on the sheet, is created.

By the way, as described above, by using the Neugebauer equation, the tristimulus value data X, Y, Z for DP3 are used.
When using the color copy on the hard copy, the colorimetric value obtained by measuring the color of the image formed on the color printout created by the color printing machine with a colorimeter is used. Although it can be reproduced faithfully to the image, the interference fringes (hereinafter also referred to as false patterns) such as moire and rosette appearing on the color printed matter, in other words, the periodic structure of halftone dots, which is a characteristic of printing, is the cause. There is a problem that the interference unevenness cannot be reproduced in the image on the hard copy.

If these spurious patterns actually appear on the color printed matter, there is a demand to faithfully reproduce the spurious patterns on the color printing proof Cpa as well. Color printing proof C
Pa, in this respect, is generally not the exact (fidelity) proof for color prints in terms of image structure.

It should be noted that the reason why the pseudo pattern does not appear in the image on the hard copy of DP3 is that the Neugebauer equation is an equation based on a kind of probability theory, and a microscopic image structure (micro) relating to the pseudo pattern ( It is considered that this is because the network structure) is not taken into consideration.

In order to reproduce the image structure without using this method, a mechanism (for example, a small printing machine for proofreading) having the same structure as the printed matter to be approximated is provided on the image output device for outputting the hard copy. It is difficult to handle all the various printing conditions with such a mechanism.
And it becomes a considerably expensive device.

As a technique for reproducing the image structure with a simple device such as a color printer, there is, for example, a printing proof making method described in Japanese Patent Application No. 7-273297 by the present applicant.

In this technique, halftone dot area ratio data for at least three plates including three primary colors is developed into bitmap data,
A print proof of a color printed matter created based on the bitmap data is created via a DP or the like, and the space peculiar to the DP is preserved while preserving the spatial frequency response peculiar to the printing net of the color printed matter. After the image structure simulation including the filtering process for blocking the frequency response is performed, the color misregistration amount when the image structure simulation is performed is corrected, and the color misregistration amount is corrected by using DP or the like after the correction. is there.

With the print proof created by this technique, it is possible to faithfully reproduce the color of the color print and the image structure {interference fringes (false patterns) such as moire and rosette}.

[0023]

The printing paper, which is the main paper, has a so-called paper texture. In this specification, the texture of paper means, firstly, that a uniform image on a printing plate is felt as a light and shade pattern that randomly changes in a print reproduced image on the main paper to which ink is transferred from the printing plate, So-called "unevenness", secondly, so-called "roughness", which is felt as a fine and randomly changing light and shade pattern that disturbs the edge portion of the reproduced image, third
In addition, it is defined as a so-called "texture feeling", which is a texture pattern unique to each paper type. The "unevenness" appears in a relatively long cycle compared to the "roughness".

The texture of this paper is not taken into consideration in the above-mentioned DP or the like, and is not reproduced at all in the print proof output via the DP or the like.

As a technique for expressing the texture of paper,
For example, there is a technique using a transfer film sold by the applicant as a product. This technology is a technology to transfer the halftone image formed on the transfer film to the main paper under pressure.
According to this technique, it is possible to reproduce only the above-mentioned “texture feeling” in the texture of paper, but the above-mentioned “unevenness caused by the transfer of ink to paper” found by the inventors of the present application. "Feeling" and "texture" cannot be reproduced.

The present invention is based on the above-mentioned Japanese Patent Application No. 7-27329.
The image output device such as a color printer having a relatively low price and a relatively low resolution reproduces the texture of the paper faithfully on the print proof. An object of the present invention is to provide a method of creating a print proof that enables the above.

[0027]

According to the present invention, an original image is converted into halftone dot area ratio data, this halftone dot area ratio data is expanded into bit map data, and this bit map data is converted into gradation data. , A process of changing the halftone dot area ratio data according to the type of the actual paper of the printed matter when creating a print proof of the printed matter through the image output device using the gradation data, and the changed halftone dot area ratio The process of developing the bitmap data based on the data, the resolution of the bitmap data is converted into the resolution of the image output device and the colorimetric data, and the halftone dot area ratio data is obtained for each type of the real paper. A density distribution in a two-dimensional space measured on the surface of the printed matter printed at 100%, and correcting the density of the colorimetric data based on the measured density distribution. Characterized in that it comprises.

According to the present invention, the process of changing the halftone dot area ratio data at the time of development into the bitmap data is provided based on the type of the real paper and the halftone dot area ratio data, whereby the paper texture Medium, "unevenness" and "roughness" can be expressed, and a density distribution measured on the surface of a printed matter printed with 100% halftone dot area data for each type of paper is obtained.
By providing a process of correcting the density of the colorimetric data based on the measured density distribution, "texture" can be expressed in the texture of the paper.

Further, according to the present invention, in the process of changing the halftone dot area ratio data according to the type of the actual printed matter, when the halftone dot area ratio data has a value in the vicinity of 50%, The amount of change is the maximum amount, and the dot area ratio data is 0%
It is characterized in that the amount of change in the halftone dot area ratio is set to the minimum amount in the vicinity value and the value near 100%.

According to the present invention, it is possible to more faithfully represent all the texture of paper at any value of the dot area ratio data.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. In the drawings referred to below, the same components as those shown in FIG. 12 are designated by the same reference numerals, and the description thereof will be appropriately omitted.

FIG. 1 shows a general color printing system 11
The process flow for creating the color print proof CPb according to the present embodiment by the color digital printer (DP) 3 for the color printed matter 12 created in (1) is shown.

First, the contents of the general color printing system 11 will be described.

In the general color printing system 11, the image on the image original 2 is read by an image reading device such as a color scanner having a CCD area sensor, and R
Gradation image data Ia for each color of (red), G (green), and B (blue) is created (step S1: image reading process). In this case, as the resolution of the CCD area sensor or the like, for example, about 400 DPI (dot per inch) is selected, and here, 1 dot (dot) corresponds to one pixel and has a density level of 256 or the like. It means a pixel according to a tone system (also called a continuous tone system).

Next, each pixel data forming the RGB gradation image data Ia is subjected to color conversion processing to obtain four plates for each color of C (cyan), M (magenta), Y (yellow) and K (black). Halftone dot area ratio data (also referred to as halftone dot data or simply halftone dot area ratio) aj (step S
2: color conversion process). This conversion is a phototyper, an automatic processor,
Since various conversions are possible depending on the relationship with the color printing machine, it is usually the know-how of each printing company corresponding to the color printing machine.

For example, (value of) halftone dot area ratio data (value of halftone dot data or simply halftone dot area ratio) ap on a PS plate 17 as a printing plate mounted on a color printing machine and the halftone dots described above. The area ratio data (value thereof) aj usually do not match. However, when considering mainly a color printing machine, the halftone dot area ratio data ap on the PS plate 17 is important, and in this embodiment, the halftone dot area ratio data aj is taken into consideration in consideration of easy understanding. And the halftone dot area ratio data ap on the PS plate 17 are assumed to be equal (aj = ap).

Actually, the halftone dot area ratio data aj and the halftone dot area ratio data ap on the PS plate 17 (for example, C, M, Y,
The average value of the halftone dot area ratio data for the 4th edition of K) is measured in advance, and the measurement results are stored in a lookup table or the like or stored as an arithmetic expression. PS version 1 using up-table or arithmetic expression
The halftone dot area ratio data aj for obtaining the desired halftone dot area ratio data ap on 7 may be determined.

After the processing of step S2, the resolution is about 2000 DPI with respect to the CMYK4 version halftone dot area ratio data aj created in pixel units (here, it is set to 1600 DPI for easy understanding). At CMYK4
With reference to four threshold matrixes (also referred to as threshold templates) 14 having desired halftone angles and screen rulings for each plate, each threshold in each element of the threshold matrix 14 and halftone dot area ratio data aj The value is compared and converted into binary data having a value "0" or a value "1", that is, bitmap data bj (step S5: comparison process). Note that the halftone angle is usually 45 for the Y-version threshold matrix 14 and the M-version threshold matrix 14, for example.
There is an angle difference such as °, and the net angle is, for example, in the 4th edition of CMYK, the 45th edition of the M edition, the 75th edition of the C edition, and the 15th edition of the K edition with the Y edition as the reference (0 °). It has an angle difference such as °. The screen frequency is 17 in this embodiment.
There are 5 lines.

FIG. 2 is a diagrammatic drawing in which the threshold matrix 14 and the like are schematically drawn in order to explain the comparison process (bitmap expansion process) in step S5 in detail.

In FIG. 2, the two diagrams drawn at the top show that one dot of the dot area ratio data aj of 400 DPI is converted into 16 dots of the bitmap data bj of 1600 DPI.

One dot of the halftone dot area ratio data aj is, for example, a C plate, and the value of the halftone dot area ratio data aj is aj =
If it is 30% (77 in 0-255 expression), this and the threshold matrix 14 for C version are referred to. In the threshold matrix 14, for example, thresholds T as shown in FIG. 2 are spirally arranged in the elements of the threshold matrix 14. The threshold value T in this case is 0 to 100% as the quantization number (8
In the case of a bit, an example in which the values assigned in 0 to 255) are arranged in a spiral shape is shown.

As is well known, the expansion into the bitmap data bj, that is, the conversion into binary data, is performed by the following equation (2),
This is performed as shown in equation (3).

Aj> T → 1 (2) aj ≦ T → 0 (3) In this way, one pixel of the C plate shown at the bottom of FIG. 2 (halftone dot area ratio data aj = 30%) The bitmap data bj for the pixel) is created. Note that, as described above, Y, M, and
The threshold matrix 14 for the K plane has a predetermined selectable screen angle.

Next, based on the bitmap data bj created in this way, as shown in FIG. 1, processing by a typesetting machine, an automatic developing machine, etc. is performed (step S6: plate making process), and as a block copy. A plate making film 16 of four plates having a halftone image and a PS plate 17 as a printing plate are prepared.

Finally, the PS plate 17 is used to prepare a color printed matter 12 by a color printing machine having a rotary press or the like (step S7: printing process). In this case, the color printed matter 12 has a halftone dot image CI formed by transferring the ink from the PS plate 17 with the ink on the actual paper P which is the actual printing paper.

The halftone dot image CI on the color print 12 has an image structure such as interference fringes such as moire and rosette which does not exist in the image original 2 and is generated by using the threshold matrix 14 having different halftone angles. As it appears, this paper P
Texture (as described above, a so-called “unevenness”, which appears as a periodic light and shade pattern with a relatively long period, and a light and shade pattern with a relatively short random period, which appears on a reproduced image, resulting in a fine random pattern. Various light and shade patterns appear based on a so-called “roughness” in which the light and shade pattern disturbs the edge of the reproduced image and a so-called “texture” that appears as a light and shade pattern unique to each paper type of the actual paper P).

The above is the general color printing system 11.
Is a description of the contents of.

In this embodiment, the color, the image structure and the texture (shading pattern) of the color printed matter 12 created by the color printing system 11 are faithfully reproduced on the color printing proof CPb created by DP3. To do so.

In this case, a paper texture first correction process (step S51) and a paper texture second correction process (step S52 or step S52 '), which will be described in detail later, are performed to convert the paper texture into a real color printed matter 12. It becomes possible to express (reproduce) almost in the same manner as described above, and the image structure of the color printed matter 12 can be accurately obtained by performing the image structure simulation process (step S8) described in Japanese Patent Application No. 7-273297. Can be reproduced. The image structure simulation process (step S
Since color misregistration occurs by performing step 8), a color misregistration amount correction lookup table (hereinafter referred to as LUT) 21 for correcting the color misregistration is required, and DP3
Misregistration amount correction L for correcting color misregistration that occurs due to the difference between the color reproduction range of the image and the color reproduction range of printing
UT22 is required.

The color shift amount correction LUTs 21 and 22 are
You may combine in one LUT. Also, the color shift amount correction L
Instead of the UTs 21 and 22, a correction function that approximates these may be used.

The data corrected by the color shift amount correction LUTs 21 and 22 are the common color space data (that is, also referred to as device-independent image data or colorimetric data) described in the section of the prior art. This common color space data is converted into the unique color space data of the DP3 (image data depending on the device) as described in the section of the related art (in FIG. 1, represented by the LUT indicated by reference numeral 23). The color printing proof CPb that can faithfully reproduce the image structure, the color, and the texture of the paper by being supplied to the DP3.
Can be created. The LUT 23 may be incorporated in DP3.

Next, the first correction processing (step S51) of the texture of paper will be described.

The first correction processing of the texture of the paper is such that, among the textures of the paper described above, a uniform image on the printing plate is randomly generated on the printing reproduction image on the main paper to which the ink is transferred from the printing plate. Colors output from the DP3 are so-called "unevenness", which is felt as a changing light and shade pattern, and secondly, so-called "roughness", which is felt as a fine and randomly changing light and shade pattern that disturbs the edge portion of the reproduced image. This is a process for reproducing on the print proof CPb.

In order to find out how to carry out this first correction process, the inventors of the present application have found that the halftone dot image CI formed on the main paper P of the color printed matter 12 is used.
Was observed by a micrograph. As a result, in comparison with the halftone dots formed on the PS plate 17, it was found that the halftone dots on the color printed matter 12 as ink had a random change in the area, so-called ink size. It was The shape of the ink transferred on the color printed matter 12 was also found to be different from the shape of the halftone dots on the PS plate 17, but it is microscopic and cannot be discerned by the human eye. I understood.

Further, as compared with the individual halftone dot areas on the PS plate 17 described above, the phenomenon that the corresponding individual halftone dot areas in the halftone dot image CI on the real paper P change randomly is a PS plate 17
The halftone dot image CI on the paper P is printed for each of the above halftone dot areas.
Rather than the corresponding individual halftone dot areas changing in a uniform proportion, the amount of change was found to be random for each individual halftone dot.

Further, even when the same PS plate 17 is used for printing, the type of the real paper P, for example, high-quality paper, art paper,
It was found that the rate of change in the dot area varies depending on the coated paper.

Furthermore, the halftone dot area ratio of the PS plate 17 is set to 0.
It was found that when the percentage was changed from 100% to 100%, the change rate of the halftone dot area on the color printed matter 12 was different depending on the halftone dot area ratio.

FIG. 3 shows the characteristic of the average random change rate Hr of the dot area ratio obtained from the experimental result by the microscopic observation. The symbol Pw represents the characteristic of high-quality paper, and the symbol Pa represents the characteristic of art paper. Further, the symbol Pc represents the characteristics of coated paper. As the actual paper P, there is matte coated paper or the like.

The average random change rate Hr of the halftone dot area ratio is explained by taking the characteristic Pw of the fine paper in FIG. 3 as an example. For example, when the halftone dot area ratio of the PS plate 17 is about 55%, The value of the characteristic Pw of high-quality paper is Pw = 10%,
From now on, the halftone dot area ratio on the main paper P which is a high quality paper is ± 10.
%, Which means that the value 55% of the individual dot area ratio on the PS plate 17 is the area ratio of the corresponding individual dot in the dot image CI on the paper P. In other words, 45%
, 56%, 63%, and so on.

Therefore, the process corresponding to the average random change rate Hr of the halftone dot area ratio may be performed in the paper texture first correction process.

Therefore, the halftone dot area ratio before the first correction processing step S51 of the paper texture is aj (in this embodiment, since it is complicated, the halftone dot area ratio of the PS plate 17 is as described above. If the halftone dot area ratio after the first correction processing is ak, the halftone dot area ratio ak is given by the following equation (4).

Ak = ap + Hr (P, ap) × R (4) Assuming ap = aj, the following equation (5) is obtained.

Ak = aj + Hr (P, aj) × R (5) Hr (P, ap) is the characteristic Pw (high-quality paper in FIG. 3 depending on the type of the main paper P and the dot area ratio ap on the PS plate 17. ), Pa
It is the value of the average random change rate of the dot area ratio uniquely obtained from (art paper) and Pc (coated paper).

In the equations (4) and (5), R is a standardized normal random number, which has a value of 0 on average, and -1 to +
Takes a value of 1. For example, values such as R = -0.5 and R = 0.8 are taken.

Print proof Cp by DP3 using the halftone dot area ratio ak after the paper texture first correction processing shown in equation (4).
By creating b, a uniform image on the PS plate 17 as a printing plate is a halftone image C which is a print reproduced image on the real paper P.
On I, it is perceived as a light and shade pattern that randomly changes, so-called “unevenness”, and as a light and shade pattern that changes randomly at random so as to disturb the edge portion of a halftone dot image (also referred to as a reproduced image) CI. ,
It is possible to reproduce the so-called "roughness".

Next, FIG. 4 includes the configuration of the image structure simulation process (step S8) and the configuration for creating the color shift amount correction LUT 21 for correcting the color shift amount generated by the image structure simulation process. Shows.

When the color shift amount correction LUT 21 is created, first, a color reproduction prediction process (step S21) and an image structure simulation process (step S8) are performed.

As the color reproduction prediction processing in step S21, for example, the processing using the above-mentioned Neugebauer equation or when each of the CMYK4 version halftone dot area ratio data aj is changed by a predetermined% (predetermined amount) A plurality of color samples on the color printed matter 12 printed corresponding to the above are measured with a colorimeter, and colorimetric data (colorimetric data or colorimetric data or colorimetric data or (Also referred to as colorimetric value data), for example, tristimulus value data Xi, Yi, and Zi are obtained, and colorimetric data between color samples when the predetermined% is changed are obtained by an interpolation process to obtain the colorimetric system. The process of holding the colorimetric value measured in step 1 and the colorimetric data obtained by the interpolation process as a lookup table or correction function using the halftone dot area ratio data ak as input data is superior. It is. In either case, at least the colorimetric value data X for each color is measured by the colorimeter.
i, Yi, Zi (i is 2 in case of CMYK 4th edition)
It is necessary to measure ⁴ colors = 16 colors) (Fig. 1
Step 3 in 2).

In this way, in the color reproduction prediction processing of step S21, the resolution 400 supplied from the input terminal 51 is set.
For example, the colorimetric data Xi, Yi, and Zi are applied to the DPI halftone dot area ratio data ak to obtain colorimetric data α.

Next, in the image structure simulation process of step S8, first, a bitmap expansion process peculiar to this image structure simulation process is performed (step S2).
2).

In this case, the threshold matrix 24 is selected according to the screen ruling and the halftone angle under the same conditions as the printing supplied from the input terminal 52, but various moire, for example, primary moire and secondary moire are selected. In order to respond to moiré and also to reproduce moiré in response to various net generation conditions,
A threshold matrix 24 having a higher resolution than that of the threshold matrix 14 shown in FIG. 2 is selected. This is to increase the resolution of the bitmap data b'j. The screen ruling and the halftone angle according to the threshold matrix 24 are the same as those in the case of printing in order to reproduce moire and the like, so the screen ruling is set to 175. As described above, the mesh angle is C with reference to the Y plate.
Each of the MYK plates is selected to have an angle of 45 ° for M plate, 75 ° for C plate, and 15 ° for K plate.

On the other hand, in order to increase the resolution, the number of elements is 256 × 256 as a threshold matrix for creating halftone dots.
= 65536 threshold matrix 24 is used. As the threshold value in each element, for example, values 0, 1, 2, ..., 255 are set. The threshold value matrix 24 and the halftone dot area ratio data aj are compared and the bitmap data b ′ is obtained.
j is created (step S10).

The resolution of the bitmap data b'j for the four CMYK versions created in this way is 44800 (25
6 × 175) DPI. This resolution is 2000D
Although it is necessary to have PI or more, the case of 44800 DPI will be described here as a desirable example corresponding to various conditions.

Then, next, the bitmap data b'j of 44800 DPI is converted into the data of resolution 1600 DPI. To this end, the bitmap data b'j
28 × 28 (784) dots of the above are counted, and the counting process for converting into 1 dot of the counting data p may be performed (step S12).

In order to explain the counting process of step S12 in an easy-to-understand manner, an example of 28 × 28 dots of the C version bitmap data b′j is shown in FIG. 5A, and the M version bitmap data b′j 28 is shown. An example of x 28 dots is shown in FIG. 5B.
Shown in In FIG. 5A and FIG. 5B, the values of the elements not shown are all “0”. Further, it is assumed that all the elements of the remaining Y and K versions of the bitmap data b′j also have the value “0”.

Therefore, for 28 × 28 dots, CM
Bit map data b′j for YK4 version (here, C
It goes without saying that the bitmap data b′j for two editions, the edition and the M edition, may be sufficient. ) To see simultaneously performs a process of enumerating area ratio ci of each color (because the version number is four plates 2 ^4-color colors every).

In the pixels (corresponding to 28 × 28 dots) in the examples of FIGS. 5A and 5B, the area ratio ci for each color is calculated as follows.

C color: ci = c _C = 3/784 (Area ratio c _C indicates a portion where only C color exists when transparently seen by overlapping the C plate and the M plate. The area where C and M colors overlap with each other is C + M = area ratio C _{C + M of} B color.) C + M color: c _{C + M} = 2/784 W color: c _W = 779/784 (area ratio c _W Represents a portion where neither C nor M exists when transparently viewed by overlapping the C and M plates.) Remaining colors (for 13 colors such as Y color and K color) The area ratio ci of is a zero value. By creating the area ratio ci for every 28 × 28 dots in this manner, the enumerated data p of 1600 DPI (each element value is represented by the area ratio ci).
Is created.

Next, 1 printed on the color printed matter 12
Processing for measuring 6 solid colors with a colorimeter (step S
3) Colorimetric value data X for each color that has been measured in advance
i, Yi, Zi (i is 2 in case of CMYK 4th edition)
^The colorimetric data q (tristimulus value data X, Y, Z) is obtained as shown in equation (6) using the area ratio ci for each color counted in step S12 for ⁴ colors = 16 colors) as a weighting coefficient. (Step S13). In other words, the colorimetric value data X
i, Yi, Zi are weighted and averaged by the area ratio ci for each color to obtain tristimulus value data X, Y, Z (colorimetric data q).

X = Σci · Xi = (3/784) X _C + (2/784) X _{C + M} + (779/784) X _W Y = Σci · Yi = (3/784) Y _C + (2 / 784) Y _{C + M} + (779/784) Y _W Z = Σci · Zi = (3/784) Z _C + (2/784) Z _{C + M} + (779/784) Z _W (6) In this way, the counting process (step S12) and the weighted average process (step S1) for each 784 (28 × 28) dots are performed.
By performing 3) in the entire range of 44800 DPI bitmap data b′j, 1600 DPI colorimetric data q is obtained.

Next, the obtained 1600 DPI colorimetric data q is subjected to anti-aliasing filter processing using the anti-aliasing filter AF shown in FIG. 6, and 400 DPI equal to the resolution of DP3 after the anti-aliasing filter processing. Colorimetric data β (tristimulus value data X,
Y, Z) are created (step S14).

The anti-aliasing filter process in step S14 is performed in the DP3 resolution (400 DPI in this embodiment and the resolution 1 of the color printed matter 12).
This is a low value compared to 600 DPI. ) When creating a color print proof CPb, aliasing noise (folding noise) caused by the resolution of DP3
Is a process of inserting in order to avoid the occurrence of. In order to effectively perform the anti-aliasing filter processing, the resolution of the image data (in this case, colorimetric data q) which is the original signal to which the anti-aliasing filter AF is applied becomes higher than the resolution of DP3 (400 DPI). It is necessary to be. In this embodiment, the resolution is selected as 1600 DPI.

Consider the structure of the matrix of the anti-aliasing filter AF shown in FIG. 5 (here, a square matrix having n × n elements).

In order to convert the colorimetric data q which is the image data of resolution 1600 DPI into the colorimetric data β which is the image data of resolution 400 DPI, one dot of 400 DPI corresponds to 16 dots of 1600 DPI. The minimum number of elements of the filter when the effect of aliasing is not considered is 4 × 4.

In order to reduce the aliasing noise as much as possible, the larger the number of elements of the anti-aliasing filter AF is, the more preferable it is.
Limited by the relationship with hardware etc.

On the other hand, as can be inferred from the fact that the color information can be reproduced by the Neugebauer equation, it is necessary to pass a relatively low frequency component including a DC component, so that an insertion loss does not occur in the vicinity of the DC component as much as possible. It is necessary to have such frequency characteristics. Therefore, it is ideal that the response at the center of the matrix is 0 dB.

Further, it is desired that all the interference fringe components such as moire {components equal to or less than halftone frequency (screen frequency) component} be left after the anti-aliasing filter process (step S14).

Further, the anti-aliasing filter AF
It must be taken into consideration that if the attenuation characteristic of is steep, a new false pattern appears due to the antialiasing filter processing.

FIG. 6 shows an anti-aliasing filter AF having a number of elements of 9 × 9, which is created by integrating such viewpoints.
The example of composition of is shown. When each element is represented by dij, it is necessary to add all the values of each element dij (also referred to as filter coefficients) to 1.0.
The actual value of ij is divided by the total sum (Σdij) of each element dij.

As can be seen from FIG. 6, the arrangement of the filter coefficients of the anti-aliasing filter AF thus configured has a frequency characteristic in which it is monotonically decreasing like a bell as it goes outward from the central portion. ing.

FIG. 7 shows the frequency characteristic of the anti-aliasing filter AF. In FIG. 7, the horizontal axis represents the resolution, and the DP Ra resolution Ra = 400 DPI is standardized to a value of 1.0. Therefore, the screen frequency of 175 lines, which is the halftone frequency, is standardized to a value of 0.44. The vertical axis represents the response, and the center element d ₅₅ = 121 in the anti-aliasing filter AF shown in FIG. 6 is standardized to a value of 1.0.

In the example of FIG. 6, as can be seen from FIG. 7, at the resolution of 1.0, the response is about 0.23, and at the resolution of 0.44, the response is about 0.77.

As a result of examining various examples, when the resolution is a halftone frequency (corresponding to the number of screen lines), the response is 0.5.
(50%) or higher, the response is 0.3 when the resolution of the color digital printer DP3 is 1.0.
It was found that if it is (30%) or less, interference fringes such as moire appearing on the color printed matter 12 can be reproduced by the color printing proof CPb, and the aliasing noise can be made invisible.

The above description is the matrix of the anti-aliasing filter AF (here, the number of elements is n × n (9 ×
9) is a description of the configuration of the square matrix}.

FIG. 8 shows this anti-aliasing filter.
FIG. 7 is a diagram provided for explaining processing. As shown in Figure 8A
And the upper left 9 × 9 dot of the colorimetric data q of 1600 DPI
The elements shown in FIG. 6 are represented by dij for the
Corresponding to the antialiasing filter AF of × 9,
Multiply each corresponding element to find the sum of them
Performs aliasing filter processing. That is, colorimetric
When each element of the data q is represented by eij, Σ (dij × e
ij) (for 9 × 9 elements) is calculated and the resolution is 400D.
Let PI be colorimetric data β. As mentioned above,
The sum of the antialiasing filters AF is Σdij = 1
Standardized, but multiplication involving decimals takes time
So, the value of each element of the anti-aliasing filter AF is
When the value shown in 6 is used as it is as d'ij,
Σ (d′ ij × eij) / Σd′ij
The value after the aging filter processing may be obtained. This place
In the case of anti-aliasing filter processing, the resolution is 16
The colorimetric data q of 00 DPI is measured at the resolution of 400 DPI.
Since it is converted to the color data β, the colorimetric data q
The second antialiasing filtering process for
As shown in FIG. 8B, the anti-aliasing filter AF
Shift 4 dots of colorimetric data q, for example to the right
You can do it. Similarly, shift 4 dots each
Antialiasing filter processing
The right edge of the aging filter AF is at the right edge of the colorimetric data q
Antialiasing filtering was done at the same position
After that, the element e on the fifth surface from the top shown in FIG. 8B₅₁To Ann
Element d of the aliasing filter AF₁₁Corresponding line
I, element e_16001600And element d ₉₉And correspond
Anti-aliasing file by shifting by 4 dots until
Color measurement data of 1600 DPI
The colorimetric data β of 400 DPI by reducing the resolution of q
Can be obtained. Anti-aliasing filtering
Is the spatial frequency response peculiar to the printing mesh of the color printed matter 12.
The spatial frequency response peculiar to DP3 is cut off while keeping
It can be said that this is a filtering process that

Next, the second correction processing (step S52) for the texture of paper will be described.

The second correction processing of the texture of the paper is performed on the color printing proof CPb output from the DP3, which is a so-called texture pattern that is perceived as a light and shade pattern peculiar to each paper type of the actual paper P among the above-described paper texture. It is a process that enables reproduction.

The second correction processing of the texture of the paper may be performed in the preceding step of the anti-aliasing filter processing of step S14 described above, like the processing of step S52 'shown by the dotted line in FIG. When the second texture correction process is performed on the colorimetric data q (resolution 1600 DPI: also referred to as intermediate resolution) before the anti-aliasing filter process, the colorimetric data is obtained after the anti-aliasing filter process. Compared to the case where the second texture correction processing is performed on β (resolution 400 DPI: printer resolution), the resolution is higher, so it takes more calculation time, but a structure with a smaller texture feeling can be taken into consideration. Accuracy is improved.

According to the knowledge of the inventor of the present application, the minimum size capable of expressing the texture of the paper, that is, the change in shading (change in lightness) of the paper is 5 mm square. Therefore,
A 5 mm square template (called a paper texture template) for correcting the texture of paper is created. The number of elements of the paper texture template is (1600 DPI / 5 mm) ² when the process is performed before the anti-aliasing filter processing step S14, and when the process is performed after the anti-aliasing filter processing step S14, (400DPI / 5mm)
²

Specifically, for each paper type of the main paper P, for example, high-quality paper, art paper, and coated paper, the C color printed with the halftone dot area ratio data ap of the PS plate 17, which is the printing plate, is 100%. M
The lightness of each element constituting the paper texture template is determined by microscopic photography of a so-called solid color surface of colors Y, K, or using a densitometer capable of measuring minute area density. The brightness of each element is standardized by the average brightness of the entire paper texture template so that the brightness does not change when the paper texture template is applied to the colorimetric data q or β, and the average value is “1. The brightness ratio (brightness ratio) is set to be "0.00". That is, lightness ratio data is stored in each element of the paper texture template. In this way, a paper texture template having a colorimetric lightness ratio as an element is created for each paper type of the real paper P, for example, high-quality paper, art paper, and coated paper.

When these 5 mm square paper texture templates are applied in parallel to colorimetric data,
Due to the action of the paper texture template, there arises a problem that a seam based on the brightness difference is visible at the edge portion of the size of the paper texture template.

The reason why the seam is visible will be explained visually with reference to FIG.

FIG. 9 schematically shows how a 5 mm square schematic paper texture template PT is applied to a 5 mm square area (colorimetric data) β1 of the colorimetric data β. By this action, each element of the colorimetric data β1 is multiplied by each corresponding element (lightness ratio) of the paper texture template PT to obtain colorimetric data β1 ′ in which each element is corrected. Next, when the paper texture template PT is made to act on the area (colorimetric data) β2 next to the area (colorimetric data) β1, among the elements on the left side (edge) of the paper texture template PT Since the value and the value in the element on the right side (edge) are not the same value, a seam based on the difference in brightness will be visible at the edge portion indicated by the arrow in the figure.

In order to avoid this, when the paper texture template PT is made to act on the area β2, the left and right elements of the paper texture template PT may be exchanged and made to work, but the paper texture template PT is made to act on the area β3. When operating the paper texture template PT on the region β4, it is necessary to exchange the elements on the upper left and the lower right, and thus it is necessary to exchange the upper and lower elements. (In practice, it takes a long time to calculate and the program becomes complicated.)

As another method for avoiding the seam, a local averaging process with a proper number of pixels, so-called unsharp processing, can be performed on the seam portion, but this method still requires a long time.

Therefore, in this embodiment, as shown in FIG. 10, when the paper texture template PT of 5 mm square having the minimum size capable of expressing the paper texture feeling is created, the values of the elements are schematically shown. Also, the representatively drawn letter "R" is replaced so that it looks as shown in FIG. 10 (values "1", "2", "3" and "4" of the schematic elements at the four corners of the paper texture template PT are changed. See also)
The other three paper texture templates PTa, PT
b, PTc is created. These four 5 mm square paper texture templates PT, PTa, PTb, and PTc are spliced together to create a larger 10 mm square paper texture template PTB.

The 10 mm square paper texture template PTB (see the thick frame in FIG. 9) thus created is sequentially acted on the colorimetric data β so that they do not overlap in parallel vertically and horizontally, The seam is not visible at the edge portion in the colorimetric data β ′ that is caused by the action of the paper texture template PTB.

Paper texture using a 10 mm square paper texture template PTB By creating a print proof CPb by DP3 using the colorimetric data β ′ after the second correction processing, the paper texture P It is possible to reproduce a so-called texture feeling that is perceived as a light and shade pattern unique to each paper type.

It should be noted that the action of the paper texture template PTB on the colorimetric data β means that the value X, the value Y, and the tristimulus value data X, Y, and Z constituting the colorimetric data β are applied. The value Z is the value X x the lightness ratio (the value of each element of the paper texture template PTB),
The value Y is the lightness ratio, and the value Z is the lightness ratio. Further, as the paper texture template PT, the same tristimulus value data X, Y, and Z are used in this embodiment, but individually created ones may be used.

Next, from the colorimetric data β'created in step S52 and the colorimetric data α created in step S21, the color shift amount due to the image structure simulation process in step S8 is calculated. Color shift amount correction data γ for correction is created (step S25). The color shift amount correction data γ appearing at the output terminal 53 is a simple difference β′−α (= γ) and a ratio (α / β ′) (=
It is obtained by a mathematical operation such as γ).

The color shift amount correction LUT 21 can be created by supplying the color shift amount correction data γ from the input end 54 shown in FIG.

The above is the description of the creation of the color shift amount correction LUT 21 for correcting the color shift amount generated by executing the image structure simulation process (step S8).

FIG. 11 is a diagram which is used to create the color shift amount correction LUT 22 which occurs when the DP3 having a color reproduction range narrower than the color reproduction range of the color printed matter 12 is used.

In this case, the halftone dot area ratio data ak supplied to the input terminal 51 is converted into colorimetric data β ′ by the image structure simulation processing (step S8) and the paper texture second correction processing step S52 ′. The color shift amount due to this image structure simulation processing is the color shift amount correction LU.
Colorimetric correction data δ corrected in T21 (for example, δ =
β′−γ = α, δ = β ′ × γ = α) is obtained.

This colorimetric correction data δ is common color space data, and is, for example, tristimulus value data X, Y, Z. Therefore, this is color space data unique to DP3 in the LUT 23, in this case RGB data. Is converted to. A preliminary color printing proof CPa, which is a hard copy, is created by DP3 based on the RGB data created in this way.

Next, this preliminary color printing proof CP
A is measured by a colorimeter to obtain colorimetric data ζ (step S26). Next, the color shift amount correction data η for correcting the color shift amount by using DP3 is created from the color measurement data ζ and the color measurement correction data δ (step S27). Color shift amount correction data η appearing at the output end 55
Similarly to the color shift amount correction data γ, the data difference δ−ζ
(= Η) or ratio of each colorimetric data (ζ / δ) (= η)
It can be obtained by a simple mathematical operation.

By supplying the color shift amount correction data η from the input end 56 shown in FIG. 1, the color shift amount correction LUT 22 can be created.

Under such preparation, in FIG.
When creating the color printing proof CPb, first, the color shift amount generated in the image structure simulation process (step S8) is corrected by the color shift amount correction LUT 21 to obtain colorimetric correction data δ, and then DP3 Is used to correct the color shift amount generated by using the color shift amount correction LUT 22 to obtain colorimetric data θ. The obtained colorimetric data θ is L
UT23 converts into RGB data. The image on the hard copy created by DP3 by this RGB data, that is, the color print proof CPb, is the color print 12
, And the image structure of the halftone dot image can be reproduced.
That is, on the color printing proof CPb, interference fringes such as moire and rosette, which are almost the same as those appearing on the color printed matter 12, that is, the image structure is faithfully reproduced.

In this case, the resolution of DP3 is 400 DPI.
2000DP despite its relatively low value
Interference fringes such as moire and rosette that are almost the same as appearing on the color printed matter 12 created by a color printing machine having a resolution of I (1600 DPI in this embodiment) can be reproduced on the color printing proof CPb. Since the color can be faithfully reproduced by the color reproduction prediction process and the color misregistration amount correction process, the color printing proof CPb can be easily and inexpensively created.

Further, since anti-aliasing filter processing is applied, aliasing noise (also referred to as a false pattern due to a beat on the image) caused by the resolution of DP3, in other words, a network obtained by using DP3. False image structures due to interference between period and printer resolution (DP3 resolution) can also be eliminated.

Further, based on the type of the main paper P and the halftone dot area ratio data ap of the PS plate 17, the texture of the paper which is a process of changing the halftone dot area ratio data at the time of developing to the bitmap data b'j. Since the first correction processing step S51 is provided, “unevenness” and “roughness” can be expressed in the texture of the paper, and the PS plate 17 is provided for each type of the real paper P that is paper.
Process of obtaining the density distribution measured on the surface of the printed matter printed with the halftone dot area ratio data ap of 100% and correcting the density of the colorimetric data based on the measured density distribution (paper texture second Correction step S52 or step S5
2 ') is provided, it is possible to express a "texture feeling" in the texture of paper.

In the above embodiment, the DP3 is used as the image output device, but the present invention is not limited to this, and a color monitor having a bit map memory and a bit map display can be used instead of the DP3. Of course.

The present invention is not limited to the above-mentioned embodiments, and it goes without saying that various configurations can be adopted without departing from the gist of the present invention.

[0124]

As described above, according to the present invention, when the image data for the image output device for creating the print proof is created, based on the type of the actual paper used as the printing paper, A process to change the dot area ratio data when expanding to bitmap data is provided, and the density distribution measured for the surface of the printed matter printed with 100% dot area ratio data for each type of this paper is obtained. A process of correcting the density of the colorimetric data based on the measured density distribution is provided.

As a result, "unevenness", which is the texture of the paper, is obtained.
The effect of being able to express the "roughness" and "texture" on the print proof is achieved.

[Brief description of drawings]

FIG. 1 includes a processing flow according to an embodiment of the present invention,
FIG. 1 is a flow diagram provided for explaining a process of creating a color printing proof corresponding to a color printed matter as a whole.

FIG. 2 is a diagram used for explaining general bitmap data for creating a color print in the process flow of FIG.

FIG. 3 is a diagram showing the characteristics of the average random change rate of the dot area ratio obtained from the experimental results by microscopic observation.

FIG. 4 is a diagram used for explaining when creating color misregistration correction data by image structure simulation.

FIG. 5 is a diagram provided for explanation when creating average colorimetric value data from relatively high-resolution bitmap data when creating a color print proof in the processing flow of FIG. 1; 5A is a diagram showing bitmap data of C plane for 28 × 28 dots, and FIG. 5B is a diagram showing bitmap data of M plane for 28 × 28 dots.

FIG. 6 is a diagram showing a configuration of an anti-aliasing filter.

FIG. 7 is a diagram showing a frequency response of an anti-aliasing filter.

FIG. 8A is a diagram used for explaining an anti-aliasing filter applied to colorimetric data, and FIG.
Is a diagram relating to the first process, and FIG. 8B is a diagram relating to the next process.

FIG. 9 is a diagram used for explaining a case where a paper texture template is applied to colorimetric data.

FIG. 10 is a diagram used for explaining a method of creating a paper texture template that is inconspicuous at a joint portion.

FIG. 11 is a diagram provided for explaining when creating color shift amount correction data associated with the use of a color printer.

FIG. 12 is a flowchart for explaining the conventional technique.

[Explanation of symbols]

2 ... Image original 3 ... Color digital printer 11 ... Color printing system 12 ... Color printed matter aj, ak, ap, ki ... Halftone dot area ratio data bi, bj, b'j ... Bit map data ci ... Area ratio CPa, CPb ...
Color printing proof Hr ... Average random change rate PT, PTB, PTa to PTc ... Paper texture template Step S7 ... Processing by printing machine Step S8 ... Image structure simulation processing Step S51 ... Paper texture first correction processing Step S52, Step S52 ′ ... Paper texture second correction processing

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H04N 1/46 H04N 1/46 Z

Claims (2)

[Claims] 1. An original image is converted into halftone dot area ratio data, this halftone dot area ratio data is expanded into bit map data, this bit map data is converted into gradation data, and an image is output by this gradation data. When creating a print proof of a printed matter through a device, a process of changing the halftone dot area ratio data according to the type of the real paper of the printed matter, and a bitmap data based on the changed halftone dot area ratio data. The process of developing, the resolution of the bitmap data is converted into the resolution of the image output device and the colorimetric data, and the halftone dot area data is printed at 100% for each type of the real paper. A step of obtaining a density distribution in a two-dimensional space measured on the surface of the sheet and correcting the density of the colorimetric data based on the measured density distribution. Proof of how to create. 2. The process of changing the halftone dot area ratio data according to the type of the printed matter of the printed sheet, the change amount of the halftone dot area ratio data when the halftone dot area ratio data is a value in the vicinity of 50%. 2. The printing proof according to claim 1, wherein the maximum amount is set, and the change amount of the dot area ratio is set to the minimum amount when the dot area ratio data is a value near 0% and a value near 100%. How to make.