JP2006005649A - Area gradation image forming method, area gradation image forming apparatus and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming an area gradation image capable of reproducing a special color with high brightness and high chroma, and to provide a device for forming the area gradation image and a program. <P>SOLUTION: In the image forming device 1 for forming a proof image expressed by a gradation by the aggregate of dots whose color is variable based on image data including at least cyan, magenta, yellow, black, and the special color; the color of at least one dot inside and/or outside the edge of dots made of the special color is changed to color, where the color difference from the special color is at least 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an area gradation image forming method, an area gradation image forming apparatus, and a program.

In recent years, an original image is subjected to area gradation, and dots (pixels) forming halftone dots constituting the acquired area gradation image are represented by Y (yellow), M (magenta), C (cyan), K (black ( After being separated into black), the silver halide photosensitive material is exposed with R (red), G (green), and B (blue) beams, and the color density of each pixel is reproduced to form an image. DCP (Digital Color Proof) is widely used. According to this method, a proof image can be easily obtained in a short time without creating a printing plate for each CMY (K), and the image quality is stable. It is used as.
According to this method, an arbitrary color tone can be created by changing the intensities of the R, G, and B light, so that various special color images can be easily output (see, for example, Patent Document 1).
JP-A-5-66557

  As described above, the greatest feature of the proof using the silver halide photosensitive material is that an arbitrary color density (color tone) can be created by adjusting the color development amount of each YMC dye. However, in the case of the invention described in Patent Document 1, since the spectral absorption of the coloring material is broader than that of the printing ink, it is large in reproducing high brightness, high saturation color, particularly a color having a metallic luster and a fluorescent color. There was a gap.

  An object of the present invention is to provide an area gradation image forming method, an area gradation image forming apparatus, and a program capable of realizing color reproduction of a special color with high brightness and high saturation.

  In order to solve the above problems, the invention described in claim 1 is expressed in gradation by a set of dots whose colors are variable based on image data including at least cyan, magenta, yellow, black, and special colors. In the area gradation image forming method for forming an area gradation image, the color of one or more dots inside and / or outside of the edge of the halftone dot composed of the special color is changed to a color having a color difference of 5 or more different from the special color. It is characterized by doing.

  According to a second aspect of the present invention, an area for forming an area gradation image expressed in gradation by an aggregate of dots whose colors are variable based on image data including at least cyan, magenta, yellow, black, and a special color. The gradation image forming method is characterized in that the color of one or more dots inside and / or outside the edge of the halftone dot comprising the special color is changed to a complementary color of the special color.

  According to a third aspect of the present invention, in the area gradation image forming method according to the first or second aspect, the width of the one or more dot regions inside and / or outside the halftone dot edge is 10 μm to 50 μm. It is characterized by being.

  According to a fourth aspect of the present invention, there is provided an area for forming an area gradation image expressed in gradation by an aggregate of dots whose colors are variable based on image data including at least cyan, magenta, yellow, black, and a special color. The gradation image forming apparatus includes a changing unit that changes the color of one or more dots inside and / or outside the edge of the halftone dot made of the special color to a color different in color difference by 5 or more from the special color. And

  According to a fifth aspect of the present invention, an area for forming an area gradation image expressed in gradation by an aggregate of dots whose colors are variable based on image data including at least cyan, magenta, yellow, black, and a special color. The gradation image forming apparatus includes a changing unit that changes the color of one or more dots inside and / or outside the edge of the halftone dot made of the special color to a complementary color of the special color.

  According to a sixth aspect of the present invention, there is provided a computer for forming an area gradation image expressed by gradation by an aggregate of dots whose colors are variable based on image data including at least cyan, magenta, yellow, black, and a special color. In addition, a function of changing the color of one or more dots inside and / or outside the edge of the halftone dot made of the special color to a color different in color difference by 5 or more from the special color is realized.

  According to a seventh aspect of the present invention, there is provided a computer that forms an area gradation image expressed by gradation by an aggregate of dots whose colors are variable based on image data including at least cyan, magenta, yellow, black, and a special color. In addition, a function of changing the color of one or more dots inside and / or outside the edge of the halftone dot made of the special color to the complementary color of the special color is realized.

According to the first, fourth, and sixth aspects of the invention, since the color of the edge of the halftone dot made up of the special color is changed to a color having a color difference of 5 or more different from the color of the special color, As the visual effect changes, the color reproduction of the special color can be realized with high brightness and high saturation.
The method of changing the color difference can be selected according to the type of the special color, and the color difference here means a color difference in the CIELAB color space.
When the spot color is a color having a metric chroma of 5 or less, it is preferable that the color difference is mainly changed by a brightness difference. In this way, a visual effect that enhances the brightness of the spot color can be obtained.

According to the invention described in claims 2, 5 and 7, since the color of the edge of the halftone dot comprising the special color is changed to the complementary color of the special color, the visual effect of the color of the halftone dot portion is changed. , Special color reproduction can be realized with high brightness and high saturation. In particular, when the spot color is a color having a metric chroma of 10 or more, the vividness of the spot color can be emphasized.
The complementary color here is synonymous with what is generally said, but the absolute value of the difference in metric hue angle with respect to the spot color is preferably 130 to 230 °, more preferably 150 to 210 °. . When the brightness of the spot color is high, it is preferable to give a difference in metric brightness, and in other cases, it is preferable to give a difference in metric chroma.

According to the third aspect of the present invention, the width of the region formed by the color different from the halftone dot, that is, the border region is 10 μm to 50 μm, so that the color tone of the whole halftone dot is greatly affected. And different visual effects can be obtained.
Here, the color change of the dot at the edge of the halftone dot of the present invention may be performed over the entire circumference of the halftone dot or at an appropriate ratio. Moreover, it may be performed in all the areas where the mesh% is 0 to 100%, or may be performed in a part of the areas.
In areas where the halftone percentage is 10% or less, the ratio of the edge area is relatively high, so the deviation from the original spot color is large, and the effect of the spot color is also small. It is preferable to change only the color of some of the dots existing in. In these regions, it is not necessary to change the color of dots existing at the edge. When halftone dot size increases, adjacent halftone dots stick together and the boundary area with the missing part becomes smaller, but the edge here refers to the edge of the halftone dot as a pixel, meaning only the boundary with the missing part. It is not a thing.

<Embodiment 1>
Embodiment 1 of the present invention will be described below in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated example.
FIG. 1 is a block diagram showing the main configuration of an image forming apparatus exemplified as a preferred embodiment to which the present invention is applied.

The image forming apparatus 1 according to the present embodiment uses a dot whose color is variable based on image data including C (cyan), M (magenta), Y (yellow), K (black (black)), and a special color. A proof image forming apparatus for forming a proof image (area gradation image) for forming an area gradation image expressed in gradation by an aggregate is configured, as shown in FIG. Area gradation image data is created from an image input unit 2 for inputting an image, a central processing unit (CPU) 3, a random access memory (RAM) 4, a read only memory (ROM) 5, and input original image data. An RIP (Raster Image Processor) 6, an image output unit 7 for outputting a proof image, and the like.
The image input unit 2, the CPU 3, the RAM 4, the ROM 5, the RIP 6, and the image output unit 7 are connected by a bus 10.

The image input unit 2 includes an image reading unit 21 for reading an image from the outside. The image reading unit 21 includes, for example, a so-called scanner as information reading means for reading original image data from an original image. That is, the image input unit 2 includes, for example, a light source (not shown), a lens, a CCD (Charge Coupled Device), an A / D conversion unit, etc., scans the original image from the light source and scans this reflected light with the CCD. The original image data is acquired by reading and converting it into an analog signal, and converting this analog signal into a digital signal by an A / D converter.
The original image data may not be read by a scanner like a color photograph, but may be image data stored on a hard disk or image data on a memory device of a digital camera.
Here, the image input unit 2 inputs original image data to the image forming apparatus 1, and includes various interfaces according to the form of the original image data. For example, an interface such as a USB (Universal Serial Bus) or a wireless LAN for receiving original image data transmitted from a predetermined external device may be provided.

The CPU 3 controls and controls each part constituting the image forming apparatus 1, reads a predetermined program stored in the ROM 5, develops it in the work area of the RAM 4, and executes various processes according to the program. . Specifically, the CPU 3 executes a predetermined control program and performs image output processing for outputting a proof image from the image output unit 7 based on the image data input via the image input unit 2.
The RAM 4 forms a storage area for temporarily storing programs, data, and the like, a work area for executing the programs, and the like in various processes executed by the CPU 3.
The ROM 5 stores various application software and programs necessary for executing the operation of the present invention. Specifically, for example, as shown in FIG. 1, a spot color tone acquisition program 51, an edging method determination program 52, Color determination program 53, spot color halftone edge detection program 54, pixel-specific image data correction program 55, color characteristic information acquisition program 56, color discrimination table (hereinafter referred to as “color discrimination TBL”) 57, color collection table (hereinafter referred to as “color discrimination table”). “Color collection TBL”) 58, material property table (hereinafter referred to as “material property TBL”) 59, and the like are stored.

The special color tone acquisition program 51 is a program for reading out information on the color tone of the special color from the color collection TBL 58 (for example, see FIG. 5), and the CPU 3 executes the special color tone acquisition program 51 as a special color tone acquisition unit. Function. Information relating to the color tone of the special color is stored in the RAM 4 as information necessary for correcting the image data for each pixel.
Information on the color tone of the special color may be specified by an input device (not shown) such as a keyboard or a touch panel.

  The edging method determination program 52 performs the edging on the inner edge of the halftone dot, or the outer edge, changes all the colors of the dots existing on the edge, or determines a predetermined predetermined value. A program for determining an edging method such as whether to change according to the probability, and the CPU 3 functions as an edging method determining means by executing an edging method determining program 52. Specifically, for example, it is determined by selecting an arbitrary method in advance from the bordering method described above. When the border method is determined, it is stored in the RAM 4 as information necessary for correcting the image data for each pixel.

The color determination program 53 determines the color of a pixel after correction for the purpose of bordering (hereinafter referred to as “corrected pixel color”) based on information relating to the color tone of the special color stored in the RAM 4. The CPU 3 functions as a color determination unit by executing the color determination program 53.
At this time, the color to be corrected may be designated by an input device (not shown) such as a keyboard or a touch panel, or may be calculated based on a preset condition.
The preset conditions are, for example, 1) a color having a color difference of 5 or more with respect to a special color, and 2) a special color having a metric chroma of 5 or less and a metric brightness of 50 or more. Colors with a metric lightness of 10 low, 3) When the special color is a color with a metric chroma of 20 or more, the metric hue angle difference is 150 to 210 ° and the metric chroma is 20 colors. Can be used.
The corrected pixel color is stored in the RAM 4 as information necessary for correcting the pixel-specific image data. Based on this information, the color collection TBL58 may be rewritten.

The spot color halftone edge detection program 54 is a program for determining whether or not the read pixel corresponds to the edge of the halftone dot based on the pixel-specific image data (for example, see FIG. 4). By executing the spot color halftone edge detection program 54, the spot color halftone edge detection means functions.
In the case where the read pixel itself hits the halftone dot edge and the pixel itself is in the halftone dot portion, it is the inner edge of the halftone dot, and in the case of the missing portion, it is the outer edge.

The pixel-by-pixel image data correction program 55 is a program for changing the color of one or more dots inside and / or outside the edge of the special color halftone dot, and the CPU 3 executes the pixel-by-pixel image data correction program 55. Thus, it functions as a pixel-by-pixel image data correction means.
In this embodiment, the color of one dot inside the edge of the special color halftone dot is changed. Specifically, the CPU 3 obtains information obtained by the edging method determination program 52 (information on the edging method). ) To determine whether or not the corresponding pixel is a pixel whose color tone is to be changed. When the color tone is to be changed, the border is obtained from the information obtained by the color determination program 53 (information relating to the color of the corrected pixel). Is replaced with the corrected pixel color to create new pixel-specific image data, and the target dot color is changed.
The changing means is formed by the special color tone acquisition means, bordering method determination means, color determination means, special color halftone edge detection means, and pixel-by-pixel image data correction means described above.

Here, the visual effect by changing the color of the dot near the edge of the spot color halftone dot will be described.
It is known that the density difference is recognized to be enlarged by slightly increasing the density on the high density side and slightly decreasing the low density side at the edge portion of the image. It is known that the brightness is enhanced by emphasizing the color or by framing a bright color with black.
Unlike printing, unlike the proof system using silver halide light-sensitive material, the color of the dot at the edge of the spot color dot is appropriately changed even in a system that cannot accurately reproduce the fluorescent color as a spectral absorption characteristic. By doing so, a visual effect similar to these can be obtained in a pseudo manner, and it is considered that high brightness and high saturation color can be reproduced.

  Here, as the area | region of the dot which changes a color, it is preferable that the width shall be 10 micrometers-100 micrometers, and it is more preferable that it shall be 10 micrometers-50 micrometers. This is because if the area of the dots for changing the color is too wide, the influence cannot be ignored, and the deviation as the colorimetric value becomes large, which is not preferable.

  The color characteristic information acquisition program 56 uses the changed pixel-by-pixel image data and the color density data (for example, see FIG. 6) of each pixel according to the color of the pixel specified in the pixel-by-pixel image data from the color collection TBL58. The CPU 3 functions as a color characteristic information acquisition unit by executing the color characteristic information acquisition program 56. The acquired color density data is stored in the RAM 4.

  The color discrimination TBL 57 (see, for example, FIG. 3) includes Y (yellow), M (magenta), C (cyan), K (black), and special colors of image data in pixels (dots) constituting a halftone dot. The color development state for each component is associated with the color of the pixel in the color development state. The CPU 3 acquires image data for each pixel, which is the color of each pixel, from the image data (see, for example, FIG. 2) and the color determination TBL57. The acquired image data for each pixel is stored in the RAM 4.

  In the color collection TBL58, the color of the pixel is associated with color density data relating to the analytical density of the Y component, M component, and C component relating to the image forming conditions corresponding to the silver halide photosensitive material. Each numerical value in the color collection TBL58 is coded and defined according to the density.

  In the material characteristic TBL59 (see, for example, FIG. 7), the analytical density of the Y, M, and C color components constituting each pixel and the exposure amount are associated as color density data. The CPU 3 obtains exposure amount data (for example, see FIG. 8) for each photosensitive layer in each pixel from the material characteristic TBL59 and the color density data.

  The RIP 6 performs raster conversion by screening the original image data input to the image forming apparatus 1 to create area gradation image data (image data). That is, the RIP 6 functions as area gradation image data creation means.

  The image output unit 7 includes an exposure unit 71. The exposure part 71 exposes the silver halide photosensitive material to form a latent image related to the proof image on the silver halide photosensitive material. The exposure unit 71 is controlled by the CPU 3.

  Next, an example of the area gradation image creation operation by the image forming apparatus 1 will be described with reference to the flowchart shown in FIG.

  First, the original image is read by the image reading unit 21 provided in the image input unit 2 (step S1). Next, the read original image data is output to the RIP 6 and subjected to area gradation processing, whereby area gradation image data (image data) is acquired (step S2).

Next, the CPU 3 reads the color collection TBL 58 in accordance with the special color tone acquisition program 51, and acquires information on the color tone of the special color from the color collection TBL 58 (step S3; special color tone acquisition step). The CPU 3 stores information on the acquired color tone of the special color in the RAM 4.
Further, the CPU 3 determines the method of bordering by executing the bordering method determination program 52 (step S4; bordering method determination step). The CPU 3 stores information on the acquired border method in the RAM 4.
And CPU3 determines the color of the pixel after correction by executing the color determination program 54 based on the information regarding the color tone of the special color memorize | stored in RAM4 (step S5; color determination process). The CPU 3 stores information on the pixel color after correction in the RAM 4.

  In step S2, the CPU 3 reads out the color discrimination TBL 57 from the ROM 4 by using the area gradation image data generated by decomposing the image data into Y image data, M image data, C image data, K image data, and spot color image data. The color of the pixel corresponding to the image data decomposed into the color components is determined by referring to the expanded color discrimination TBL57. Then, by performing color discrimination for all pixels, pixel-specific image data in which each pixel is associated with that color is generated (step S6). The CPU 3 stores the acquired pixel-specific image data in the RAM 4.

  In step S7, the CPU 3 executes the spot color halftone edge detection program 54 based on the pixel-specific image data, thereby determining whether the pixel of the pixel-specific image data read for each pixel corresponds to the edge of the spot color halftone dot. (Step S7; spot color halftone edge detection step). When the CPU 3 determines that the dot is the edge of the halftone dot of the special color (step S7; Yes), the range for changing the dot color tone is determined based on the information regarding the border method acquired in step S4 and stored in the RAM 4. Further, the CPU 3 executes the pixel-specific image data correction program 55 based on the information relating to the corrected pixel color acquired in step S5 and stored in the RAM 4, thereby changing the pixel color. The pixel-specific image data is corrected by replacing the color (step S8; pixel-specific image data correction step).

  Next, the CPU 3 determines whether or not all the pixels have been selected. If the CPU 3 determines that all the pixels have been selected (step S9; Yes), the CPU 3 reads the color characteristic information acquisition program 56 and reads a predetermined work area in the RAM 4. In accordance with the developed color characteristic information acquisition program 56, the color collection TBL 58 is read out, and color density data corresponding to the color of the pixel specified in the corrected pixel-specific image data is acquired from the color collection TBL 58. And it memorize | stores in RAM4 (step S10; color characteristic information acquisition process). If the CPU 3 determines in step S7 that the pixel is not a special color edge pixel (step S7; No), the pixel-by-pixel image data is not corrected, and the process proceeds to step S9 to select all the pixels. A determination of whether or not has been made is performed.

  If the CPU 3 determines that all the pixels are not selected (step S9; No), the process returns to the step S6 again to acquire the pixels of the pixel-specific image data, and whether or not the CPU 3 is the edge image of the spot color. The process of step 8 or step S9 is executed.

  When the color density data is acquired in step S10, the CPU 3 executes a process for setting the exposure amount applied to each of the Y, M, and C photosensitive layers for each pixel of the silver halide photosensitive material. (Step S11). Specifically, the CPU 3 reads an exposure amount setting program (not shown) from the ROM 5 and develops it in the RAM 4, reads the material characteristic TBL59, and from this material characteristic TBL59, the color density for each pixel acquired in step S10. The exposure level of each photosensitive layer corresponding to the data is acquired. The exposure amount under the control of the CPU 3 is set for each pixel in accordance with the pixel number, and the exposure amount is set for all pixels, thereby exposing each pixel and its Y, M, and C photosensitive layers. Exposure amount data for each pixel associated with the amount is generated.

  Next, the CPU 3 transfers the generated exposure amount data for each pixel to the image output unit 7 (step S12), and sets the exposure unit 71 of the image output unit 7 in accordance with the exposure amount data for each pixel. By controlling, the exposure part 71 exposes the silver halide photosensitive material to form a latent image related to the proof image on the silver halide photosensitive material, and further, the silver halide photosensitive material on which the latent image is formed Is developed in a development processing unit (not shown) to form a proof image (step S13).

According to the image forming apparatus 1 of the first embodiment described above, the color of the edge of the halftone dot made up of the special color is changed to a color having a color difference of 5 or more different from the color of the special color. The visual effect changes. That is, it is possible to obtain a visual effect that emphasizes the brightness and vividness of the spot color.
Further, since the width of the area formed by the color different from the halftone dot, that is, the border area is 10 to 50 μm, the influence of the border can be ignored, and the deviation as a measured value is kept small. At the same time, it is possible to obtain different visual effect changes that can greatly affect the overall tone of the halftone dots.

<Embodiment 2>
The image forming apparatus 100 according to the second embodiment will be described below. The image forming apparatus 100 is different from the image forming apparatus 1 according to the first embodiment in the program stored in the ROM 5. Therefore, in the description of the second embodiment, the same components as those of the first embodiment are denoted by the same reference numerals and the description thereof is omitted.

As shown in FIG. 10, the ROM 105 in the image forming apparatus 100 according to the second embodiment stores a complementary color determination program 153 instead of the color determination program 53 in the ROM 5 according to the first embodiment.
The complementary color determination program 153 is a program for determining a complementary color of a spot color included in the spot color halftone dot using a hue ring sheet (not shown) based on the information on the spot color tone acquired by the spot color tone acquisition program 51. It is. The CPU 3 functions as a complementary color determination unit by executing the complementary color determination program 153.

  Hereinafter, an example of the area gradation image creation operation by the image forming apparatus 100 will be described with reference to the flowchart shown in FIG.

As in the first embodiment, the original image is read (step S14), and area gradation processing is performed by the RIP 6 to obtain area gradation image data. (Step S15).
The CPU 3 acquires the special color tone data (step S16), determines the border method (step S17), and determines the complementary color by executing the complementary color determination program 153 based on the special color tone data acquired in step S16. (Step S18; complementary color determination step). The CPU 3 stores information related to the edging method and complementary colors in the RAM 4.
Next, the CPU 3 acquires pixel-specific image data (step S19), determines whether or not it is a spot color edge image (step S20), and if it is an edge image (step S20; Yes), step S17. Based on the bordering method acquired in step S1 and the complementary color acquired in step S18, the pixel-specific image data is corrected by executing the pixel-specific image data correction program 55 (step S21).
Hereinafter, the steps from step S22 to step S26 correspond to the steps from step S9 to step S13 in the first embodiment, and are therefore omitted.

According to the image forming apparatus 100 of the second embodiment described above, the above-described bordering effect can be obtained also by changing the color of the halftone dot edge using the complementary color of the spot color halftone dot color. Thereby, the color reproducibility of the spot color can be improved.
Next, examples of the present invention described above will be described together with comparative examples.

[Examples 1 to 14]
[Sample preparation]
First, the silver halide photosensitive material No. 1 described in Example 1 of JP-A-2002-341470 is disclosed. 101 was created.
Next, an image forming apparatus having the following exposure unit and development unit was prepared. The exposure unit arranged 10 B (Blue) LEDs (Light Emitting Diodes) as light sources in the main scanning direction and adjusted the exposure so that the same place could be exposed with 10 LEDs by gradually delaying the exposure timing. In addition, an exposure head was prepared in which 10 LEDs were arranged in the sub-scanning direction and exposure for 10 adjacent pixels could be performed at once. Similarly, G (green) and R (red) were combined with LEDs to prepare exposure heads. The diameter of each beam was about 10 μm, the beams were arranged at this interval, and the sub-scanning pitch was about 100 μm. The exposure time per pixel was about 100 nanoseconds.
The exposed portion of the silver halide photosensitive material after the exposure was prepared so as to perform the development processing described in Example 1 of the publication.

As an image, a flat mesh having a mesh percentage of 30% is prepared as a 100 × 100 mm patch, and the solid color tone of the image is L ^* = 53.5, a ^* = 4.3, and b ^* = 38.7. The prepared sample was used as a reference sample. Samples were prepared by setting the border color shown in Table 1 to be reproduced in the dots outside the halftone dots of the image of the reference sample (Examples 1 to 5; Samples No. 1 to No. 5). The solid color tone is a color inspired by gold. 1 and sample no. For No. 2, a complementary color was used as the border color.
Next, as a 100 × 100 mm patch, a flat mesh having a halftone dot percentage of 30% is prepared, and the solid color tone is L ^* = 57.1, a ^* = − 2.2, and b ^* = 4.2. did. Using this as a reference sample, settings were made so that the border colors shown in Table 1 were reproduced, and samples were prepared (Examples 6 to 9; Samples No. 6 to No. 9). The solid color tone is a color inspired by silver. In particular, sample no. 6 and sample no. For 8, a complementary color was used as the border color.
Furthermore, sample no. 1-No. The same sample as the reference sample used in the preparation of No. 5 (100 × 100 mm patch as a flat mesh with a mesh percentage of 30%, solid color tone L ^* = 53.5, a ^* = 4.3, (image with b ^* = 38.7) is set as a reference sample, and the border color shown in Table 1 is set to be reproduced in the dots outside the halftone dot, and the border is 1 dot (Example 10; Sample No.) 10) 3 dots (Example 11; Sample No. 11) 4 dots (Example 12; Sample No. 12) 5 dots (Example 13; Sample No. 13) ) And 6 dots (Example 14; Sample No. 14) were prepared. The solid color tone is a color inspired by gold.

Sample No. 1-No. 14 was evaluated by 10 subjects. The content of the evaluation is 1 for the equivalent, 2 for which the difference is recognized, and the one that emphasizes the feeling of the special color (gold / silver) compared to the reference sample used in the preparation of each sample. It was set to 3.
The results are shown in Table 1. Here, ΔE is a color difference between the reference sample and each sample, and Δh is a hue difference between the reference sample and each sample.

[Comparative Examples 1-4]
[Sample preparation]
Then, sample No.1-No. 5 as a reference sample when creating image 5 (a patch of 100 × 100 mm, mesh percentage is 30%, solid color tone is L ^* = 53.5, a ^* = 4.3, b ^* = 38. 7 was prepared as a sample (comparative example 1; sample No. 15). This image was a color resembling gold and represented as “G” in Table 1 below. And sample no. A sample was prepared by setting so that the border color shown in Table 1 was reproduced in dots outside the 15 dots (Comparative Example 2; Sample No. 16).
Furthermore, sample no. 6-No. 9 as a reference sample for creating 9 (100 × 100 mm patch, 30% mesh, solid color tone L ^* = 57.1, a ^* = − 2.2, b ^* = 4 2 was prepared as a sample (Comparative Example 3; Sample No. 17). And sample no. A sample was prepared by setting so that the border color shown in Table 1 was reproduced in dots outside the 17 dot (Comparative Example 4; Sample No. 18).

Sample No. 16, no. 18 was evaluated by 10 subjects. The contents of evaluation are as follows. 16 is sample No. In comparison with Sample No. 15, Sample No. No. 18 is sample no. Compared to 17, the equivalent is 1, the difference is recognized 2, the special color (gold / silver) feeling is emphasized 3. The results are shown in Table 1.

Each result was then evaluated.
[Evaluation]
[Golden color]
Sample No. which is a reference sample. Compared with the sample No. 15, the color difference is only 2.6. 16 is Sample No. The difference with 15 was hardly confirmed. However, the effects of the present invention were recognized in all the samples (samples No. 1 to No. 5) bordered by dots having a color difference of 5 or more.
Among them, the sample No. 1 and sample no. No. 2 had a significant effect. Sample No. 4 and sample no. No. 5, the difference as a color difference is small, but the sample No. 4 was confirmed to have a higher evaluation score.
That is, it has been found that it is preferable to make a difference in hue for a color having a large metric chroma, and it is particularly preferable to use a complementary color.

[Silver color]
Sample No. which is a reference sample. Compared with Sample No. 17, the sample No. 18 is Sample No. Although the difference with 17 was hardly recognized, it was confirmed that the samples of No. 6 to 9 having a color difference of 5 or more can obtain the effects of the present invention. When a complementary color is used as the border color, the effect tends to be slightly higher, but the effect is slight, and it is effective to change the brightness for a color with a small metric chroma. I understood.

[Border width]
In the case where the dots used for edging are 3 dots (sample No. 11), 4 dots (sample No. 12), and 5 dots (sample No. 13), the case of 1 dot (sample No. 10) is compared. In the case of 6 dots (sample No. 14), it was found that the effect on the color tone was seen and the effect of enhancing the golden feeling was weakened.

1 is a block diagram showing a schematic configuration of an image forming apparatus 1 in Embodiment 1 of the present invention. It is the figure which showed typically the image data which comprises a halftone dot for every color component. It is the figure which showed the color discrimination TBL typically. It is a figure which shows the image data classified by pixel. It is the figure which showed the color collection TBL typically. It is a figure which shows color density data. It is the figure which showed material characteristic TBL typically. It is the figure which showed the exposure amount data for every pixel. 4 is a flowchart showing a proof image forming process performed by the image forming apparatus 1. It is a block diagram which shows schematic structure of the image forming apparatus 100 in Embodiment 2 of this invention. 4 is a flowchart illustrating a proof image forming process performed by the image forming apparatus 100.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,100 Image forming apparatus 2 Image input part 3 CPU (Special color tone acquisition means, Border method determination means, Color determination means, Complementary color determination means, Special color halftone edge detection means, Pixel-specific image data correction means, Color characteristic information acquisition means )
4 RAM
5, 105 ROM
6 RIP
7 Image output section

Claims (7)

In an area gradation image forming method for forming an area gradation image expressed by gradation of a set of dots whose colors are variable based on image data including at least cyan, magenta, yellow, black, and a special color.
A method for forming an area gradation image, wherein the color of one or more dots inside and / or outside the edge of a halftone dot comprising the special color is changed to a color having a color difference of 5 or more from the special color. In an area gradation image forming method for forming an area gradation image expressed by gradation of a set of dots whose colors are variable based on image data including at least cyan, magenta, yellow, black, and a special color.
An area gradation image forming method, wherein a color of one or more dots inside and / or outside of an edge of a halftone dot made of the special color is changed to a complementary color of the special color. The area gradation image forming method according to claim 1 or 2,
The area gradation image forming method, wherein a width of one or more dot areas inside and / or outside the halftone dot edge is 10 μm to 50 μm. In an area gradation image forming apparatus that forms an area gradation image expressed by gradation of a set of dots whose colors are variable based on image data including at least cyan, magenta, yellow, black, and a special color.
Area gradation image formation comprising: changing means for changing the color of one or more dots inside and / or outside of the edge of the halftone dot made of the special color to a color different in color difference by 5 or more from the special color apparatus. In an area gradation image forming apparatus that forms an area gradation image expressed by gradation of a set of dots whose colors are variable based on image data including at least cyan, magenta, yellow, black, and a special color.
An area gradation image forming apparatus, comprising: changing means for changing a color of one or more dots inside and / or outside of a halftone dot edge made of the special color to a complementary color of the special color. Based on image data including at least cyan, magenta, yellow, black, and a special color, a computer that forms an area gradation image represented by gradation of a collection of dots whose colors are variable,
A program for realizing a function of changing the color of one or more dots inside and / or outside the edge of a halftone dot made of the special color to a color different in color difference by 5 or more from the special color. Based on image data including at least cyan, magenta, yellow, black, and a special color, a computer that forms an area gradation image represented by gradation of a collection of dots whose colors are variable,
A program for realizing a function of changing the color of one or more dots inside and / or outside the edge of a halftone dot made of the special color to a complementary color of the special color.

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