JP4539458B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that generates a color profile based on a color chart formed on a medium.

  2. Description of the Related Art In recent years, when color printed matter such as a magazine is generated, the color state is confirmed using an image forming apparatus such as a printer before printing by a printing machine.

In this case, since it is necessary to match the color reproducibility of the printing press and the color reproducibility of the image forming apparatus, data called a color profile is generated, and processing for matching the color reproducibility is performed using this color profile. It has been broken.
JP 2003-66546 A

  However, in recent printing sites, images are also formed on relatively thin paper. In such a case, the contents of printing on another page can be seen through the paper, for example, on the back side. A phenomenon such as reflection has occurred.

  For such show-through, the saturation of image data to be formed on the other surface is reduced by a predetermined value and synthesized with the image data formed on one surface, regardless of the color reproducibility processing. There were times when it was simulated by the method of doing.

  However, in spite of the fact that the state of show-through is different depending on, for example, the paper and the characteristics of the printing machine, this method does not take such circumstances into consideration, so in the final printed matter, The effects of show-through are not accurately reproduced.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of improving show-through reproduction accuracy in a final printed matter.

  The present invention for solving the problems of the above-described conventional example is an image forming apparatus that generates a color profile based on a color measurement result of a color chart, and a medium on which the color chart is formed is a color measurement target. Means for acquiring color measurement data by optically reading a color chart to be measured from a surface side different from the surface on which the color chart is formed, and the acquired color measurement data; And a color profile generating means for generating a show-through color profile.

  An image forming apparatus according to an aspect of the present invention is characterized in that image data of a predetermined color chart is reversed and formed on a medium as a color chart to be measured.

  Furthermore, an image forming apparatus according to an aspect of the present invention forms image data of a predetermined color chart on one surface of a medium, and on the other surface side different from the one surface, A color chart in which the image data of the predetermined color chart is reversed left and right is formed at a position not opposite to the formed color chart.

  Further, in the medium according to one embodiment of the present invention, the color chart image data is formed on the first surface, and the second surface different from the first surface is at a position not facing the formed color chart. A reverse color chart is formed by reversing the image data of the color chart formed on the first surface to the left and right.

  Furthermore, the color profile generating method according to another aspect of the present invention uses a computer, and the medium on which the color chart is formed is different from the side on which the color chart to be colorimetric is formed, Via the medium, obtaining a color measurement data by optically reading a color chart to be measured, and generating a show-through color profile based on the obtained color measurement data; It is characterized by performing.

  Furthermore, a program according to another aspect of the present invention provides a computer with a medium on which a color chart is formed from a side different from the side on which the color chart to be colorimetric is formed via the medium. Performing a procedure for acquiring color measurement data by optically reading a color chart to be measured, and a procedure for generating a show-through color profile based on the acquired color measurement data. It is a feature.

  Embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the image forming apparatus 1 according to the embodiment of the present invention includes a control unit 11, a storage unit 12, an operation unit 13, a display unit 14, a printer unit 15, and a color measurement unit 16. And.

  The control unit 11 is realized by a CPU (Central Processing Unit) or the like, and operates according to a program stored in the storage unit 12. The specific contents of the processing performed by the control unit 11 will be described in detail later.

  The storage unit 12 can be realized by a memory element such as a random access memory (RAM) or a read only memory (ROM), a hard disk, or the like. The storage unit 12 stores a program (software) executed by the control unit 11. The storage unit 12 also operates as a work memory that holds various data used in the process of the control unit 11.

  The operation unit 13 is a mouse, a keyboard, or the like. The operation unit 13 receives an instruction input from the user and outputs the content of the instruction to the control unit 11. The display unit 14 is a color display device or the like, and displays an image in accordance with an instruction input from the control unit 11.

  The printer unit 15 is a color printer and can be realized by an output device such as a laser printer or an inkjet printer. The printer unit 15, for example, in accordance with an instruction input from the control unit 11, an image based on the image data input from the control unit 11 (for example, text, graphics, etc.) on a sheet-like medium such as paper or synthetic resin film. A color or monochrome printed original image including a photograph or the like) is formed.

  The color measurement unit 16 can be realized by a scanner device or the like provided with a spectrophotometer. The color measurement unit 16 optically scans an image formed on a medium that is a color measurement target according to an instruction input from the control unit 11, and generates color measurement data representing the color of the image. And output to the control unit 11.

  Next, the content of the process which the control part 11 performs is demonstrated. The control unit 11 according to the present embodiment executes color chart formation processing, color profile generation processing, and show-through simulation processing.

[Color chart formation processing]
The control unit 11 forms a color chart including a plurality of patches (color patches) colored in different colors on the medium. Here, the color and arrangement of the color patches are determined in advance and stored in the storage unit 12. Here, with respect to the color patches to be included in the color chart, identification information uniquely assigned to each color patch, color patch color information, and information indicating the arrangement position are associated with each other as shown in FIG. Is stored as

  Here, it is assumed that the color patches are arranged in a matrix of m rows and n columns, and information indicating the arrangement position of each color patch is set according to the arrangement.

  Based on the color patch information illustrated in FIG. 2, the control unit 11 arranges the color patch of the color specified by the color information at a position based on the arrangement position information associated with the color information, Image data of a color chart as shown in FIG. 5 is generated. The control unit 11 outputs the color chart image data generated here to the printer unit 15 to form it on the medium. The color chart formed here is hereinafter referred to as a device chart.

[Color profile generation processing]
The control unit 11 also performs color profile generation processing. First, the user operates the color measurement unit 16 to read each color patch of the device chart in a predetermined order. For example, the color patches arranged in m × n are read sequentially from left to right starting from the upper left corner, then moved down one line and then sequentially read from left to right (hereinafter referred to as scan line order). Read to the lower right corner.

  The control unit 11 converts the reading results of the color patches sequentially input from the color measurement unit 16 into values in a device-independent color space (for example, the Lab color space), and sequentially stores them in the storage unit 12 as device profile information. Store.

  Further, the user turns over the medium on which the device chart is formed, operates the color measurement unit 16, and the back side through the medium (the side different from the side on which the color chart to be measured) is formed. Then, each color patch of the device chart is read in a predetermined order. For example, color patches arranged in m × n are read sequentially from right to left starting from the upper right corner, and then read down to the lower left corner in the order of moving down one row and sequentially from right to left.

  The control unit 11 converts the reading results of the color patches sequentially input from the colorimetric unit 16 in this way into values in a device-independent color space, and sequentially stores them in the storage unit 12 as show-through device profile information. In other words, the show-through device profile information includes the color information of each color patch (for example, information in a CMYK color space including cyan C, magenta M, yellow Y, and black K). When printing is performed on the back side of the medium, the conversion table is converted into color values (values in the Lab color space) that do not depend on the device when viewed from the front side through the medium.

[Back-through simulation processing]
Using this device profile information and show-through device profile information, the control unit 11 generates and outputs an image schematically showing show-through. For example, it is assumed that a profile (target profile) of a printing press serving as a simulation target is stored in the storage unit 12 in advance, and an example of simulating the show-through state at the time of printing on the printing press serving as the target is described. .

  The target profile associates each color value (for example, a Lab value) in a device-independent color space with a color value (for example, a CMYK value) reproduced by a target printing machine.

  The control unit 11 includes device profile information for associating each color value (for example, Lab value) in a device-independent color space with a color value (for example, CMYK value) reproduced by the target image forming apparatus 1, Using these profiles, a device link profile in which CMYK values associated with a common Lab value are associated with each other in the two pieces of profile information is generated. For example, as shown in FIG. 3, when the image forming apparatus 1 outputs a color having a specific CMYK value (Cp, Mp, Yp, Kp) in the device profile information, the Lab value of the color is L0, a0, Assume that b0. Further, it is assumed that the CMYK values of the target printing press corresponding to L0, a0, and b0 are CT, MT, YT, and KT from the target profile.

  Then, in order to simulate the output result when outputting the colors of CT, MT, YT, and KT to the target printing machine, Cp, Mp, Yp on the image forming apparatus 1 side. , Kp color may be output. A conversion table for performing this conversion is defined by the device link profile.

  That is, this device link profile associates color values (CMYK values) reproduced by the image forming apparatus 1 with corresponding color values (CMYK values) reproduced by the target printer. . Since this device link profile generation method is widely known, detailed description thereof is omitted here.

  Next, the control unit 11 uses the generated device link profile and the show-through device profile information to reproduce the color value (CMYK value) reproduced on the target printing machine and the show-through color value ( Information associated with a value in the Lab color space). Further, the control unit 11 refers to the device profile and converts the show-through color value (the value in the Lab color space) into a color value (CMYK value) for reproduction by the image forming apparatus 1. Thus, the control unit 11 reproduces the color (CMYK value) printed on the back side of the medium in the target printing machine and the color when the image is viewed from the front side (CMYK value). A show-through device link profile is generated.

  For example, when a color color patch of Cp, Mp, Yp, Kp formed by the image forming apparatus 1 on the back side of the medium is read from the medium surface side through the medium, Lab values are Ls, as, bs. Suppose there is. At this time, if the device link profile stipulates that the colors of Cp, Mp, Yp, Kp of the image forming apparatus 1 correspond to the colors of CT, MT, YT, KT in the target printer, the target printing is performed. In the machine, it can be assumed that the show-through color when the colors CT, MT, YT, and KT are output is Ls, as, and bs. In this way, a show-through profile (show-through target profile) relating to the target printing machine can be generated.

  On the other hand, the output value (CMYK value) of the image forming apparatus 1 for outputting the color of the Lab value of Ls, as, bs can be obtained from the device profile. Here, assuming that the values are Cq, Mq, Yq, and Kq, the image forming apparatus 1 is used to simulate the case where the colors of CT, MT, YT, and KT are output in the target printing machine. It is sufficient to instruct to output the colors Cq, Mq, Yq, and Kq.

  The control unit 11 receives input of image data to be formed on the front side of the medium (referred to as first data) and image data to be formed on the back side of the medium (referred to as second data) from the user. Accept and do the following:

  The control unit 11 converts the color information of the first data into CMYK values. Further, the control unit 11 uses the device link profile to convert the output of the target printing press based on the CMYK value into a CMYK value for the image forming apparatus 1 to simulate.

  Further, the control unit 11 converts the color information of the second data into CMYK values. Further, the control unit 11 uses the show-through device link profile to convert the output of the target printing press based on the CMYK value into a CMYK value to be simulated by the image forming apparatus 1. The control unit 11 performs left-right reversal processing on the second data.

  Then, the control unit 11 converts these color values, and translucently synthesizes the second data subjected to the left / right reversal processing and the first data after converting the color values. Here, the semi-transparent composition is a process of adding corresponding pixel values in the first data and the second data. The control unit 11 outputs the image data obtained as a result of the semitransparent composition to the printer unit 15 (FIG. 4).

  According to the present embodiment, a show-through device link profile representing the color reproducibility of show-through in an actual printing press is generated, and the show-through state is simulated using the show-through device link profile. The accuracy of show-through reproduction in can be improved.

  Further, in the description so far, when the show-through profile is generated in the image forming apparatus 1, the user turns over the color chart for generating a normal device profile and reads it in the reverse order from that at the time of generating the device profile. However, the control unit 11 of the image forming apparatus 1 may perform a color chart forming process as follows in order to reduce the work burden on the user. That is, based on the color patch information illustrated in FIG. 2, the control unit 11 arranges the color patch of the color specified by each color information at a position based on the arrangement position information associated with the color information. Thus, image data for the first page is generated. Next, the image data of the first page of the color patch is subjected to left / right reversal processing to generate image data of the second page. Then, the control unit 11 outputs the image data for two pages generated here to the printer unit 15 to form it on the medium. Here, two media are formed. For the image on the first page, the user reads each color patch in the order of scan lines from the side on which they are formed. The control unit 11 converts the reading results of the color patches sequentially input from the color measurement unit 16 into values in a color space that does not depend on the device, and sequentially stores them in the storage unit 12 as device profile information.

  In addition, for the image on the second page, the user reads each color patch in the order of scan lines from the surface (back surface) opposite to the surface on which the color patch is formed via the medium. Here, the left and right sides are reversed so that they can be read in the same order as the first page. The control unit 11 converts the reading results of the color patches sequentially input from the color measurement unit 16 into values in a color space that does not depend on the device, and sequentially stores them in the storage unit 12 as show-through profile information.

  Further, the control unit 11 may form the image of the first page and the image of the second page (the one obtained by performing left-right reversal processing) on the front and back of one medium. In this case, it is assumed that the image of the color patch arranged in m × n has a size less than ½ of the printing surface of the medium. Then, an image of a color patch to be formed on the first page is formed on one surface of the medium, and an image (color chart) of the formed color patch is formed on the other surface side different from the one surface. Forms an image of the color patch to be formed on the second page at a position that does not oppose (FIG. 6). In FIG. 6, the color of the color patch at the position (x, y) on the m × n array is denoted as Cxy, and the color that appears when this color shows through is denoted as C′xy.

  When formed in this way, the user reads each color patch formed on the first page in the order of scan lines from the side on which the color patches are formed. The control unit 11 converts the reading results of the color patches sequentially input from the color measurement unit 16 into values in a color space that does not depend on the device, and sequentially stores them in the storage unit 12 as device profile information. Further, the user can turn each color patch formed on the second page as it is through the medium from the side on which the color patch on the first page is formed without turning the medium over. Read in scan line order. Also in this case, since the color patch image is formed by reversing the left and right, it can be read in the same order as the first page, and the control unit 11 sequentially inputs from the color measurement unit 16. The read result of the color patch is converted into a value in a color space independent of the device, and sequentially stored in the storage unit 12 as show-through profile information.

  Here, according to the example of forming on one medium, for example, even when reading color patches all at once with a scanner or the like, processing such as turning over the medium is unnecessary.

  Here, the color patch image of the second page is formed by reversing left and right. However, the control unit 11 causes the user to read the color patches formed on the back side in the order of the scan lines. The reading result of the color patches sequentially input from the color unit 16 may be processed by inverting the order in units of each line.

  Similarly, for example, when the image is read all at once by a scanner, the color patch image formed on the back surface side of the reading surface may be reversed left and right, and then these colors may be subjected to colorimetric processing.

  As described above, instead of performing the horizontal reversal process at the time of formation, a process corresponding to the horizontal reversal process at the time of reading may be performed.

  In the above description, the image forming apparatus 1 includes the printer unit 15. However, the printer unit 15 may be a separate device from the image forming apparatus 1. In other words, the image forming apparatus 1 may be a so-called printer server or a computer system that outputs a print instruction to the printer apparatus.

1 is a configuration block diagram of an image forming apparatus according to an embodiment of the present invention. It is explanatory drawing showing the example of the information which prescribes | regulates a color chart. It is explanatory drawing which concerns on the production | generation of a show-through device link profile. It is explanatory drawing showing the example of the simulation of show-through. It is explanatory drawing showing the example which formed the color chart used for the production | generation of a device profile. It is explanatory drawing showing the example which formed the color chart used for the production | generation of a show-through device profile.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Image forming apparatus, 11 Control part, 12 Storage part, 13 Operation part, 14 Display part, 15 Printer part, 16 Colorimetry part.

Claims (5)

An image forming apparatus that generates a color profile based on a color measurement result of a color chart,
Color measurement is performed by optically reading the color chart of the color measurement target from the side different from the surface on which the color chart to be color measurement is formed through the medium. Means for obtaining data;
A color profile generating means for generating a show-through color profile based on the acquired colorimetric data;
Based on the data indicating the image of the first surface of the medium, the data indicating the image of the second surface different from the first surface of the medium, and the color profile for show-through, the image of the first surface And a composite image forming means for forming a semi-transparent composite image on the medium, which reproduces the color of the show-through of the image on the second surface and is reversed left and right , and
An image forming apparatus comprising: A printing system for generating a color profile based on a color measurement result of a color chart,
Color measurement is performed by optically reading the color chart of the color measurement target from the side different from the surface on which the color chart to be color measurement is formed through the medium. Means for obtaining data;
A color profile generating means for generating a show-through color profile based on the acquired colorimetric data;
Based on the data indicating the image of the first surface of the medium, the data indicating the image of the second surface different from the first surface of the medium, and the color profile for show-through, the image of the first surface And a composite image forming means for forming a semi-transparent composite image on the medium, which reproduces the color of the show-through of the image on the second surface and is reversed left and right , and
A system characterized by including. Based on the show-through color profile, the color value that is printed on one side of the medium by the target printing machine, and the color obtained by viewing the printed color from the side different from the one side of the medium are combined. A show-through device link profile generating means for generating a show-through device link profile that associates color values to be reproduced by the image forming means;
The composite image forming means is based on data indicating an image of a first surface of a medium, data indicating an image of a second surface different from the first surface of the medium, and the show-through device link profile, Forming an image on the medium by translucently combining the image of the first surface and the image of the second surface image that reproduces the color of the show-through and is horizontally reversed ;
The image forming apparatus according to claim 1. Based on the show-through color profile, the color value that is printed on one side of the medium by the target printing machine, and the color obtained by viewing the printed color from the side different from the one side of the medium are combined. A show-through device link profile generating means for generating a show-through device link profile that associates a color value to be reproduced by the image forming means,
The composite image forming means is based on data indicating an image of a first surface of a medium, data indicating an image of a second surface different from the first surface of the medium, and the show-through device link profile, Forming an image on the medium by translucently combining the image of the first surface and the image of the second surface image that reproduces the color of the show-through and is horizontally reversed ;
The system according to claim 2. On the computer,
Color measurement is performed by optically reading the color chart of the color measurement target from the side different from the surface on which the color chart to be color measurement is formed through the medium. The steps to get the data,
A procedure for generating a show-through color profile based on the acquired colorimetric data;
Based on the data indicating the image of the first surface of the medium, the data indicating the image of the second surface different from the first surface of the medium, and the color profile for show-through, the image of the first surface And forming a translucent composite image on the medium that reproduces the color of the show-through of the image on the second surface and reverses the image horizontally ;
A program characterized by having executed.

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