JP2006043975A - Color conversion method, image output system, color conversion program, and storage medium storing program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology which enables constantly proper color reproduction, without reference to a relationship between a screen direction of a halftone image and an image output and scanning direction, when the halftone image is output onto recording paper. <P>SOLUTION: The halftone image with the predetermined screen direction is obtained by applying RIP processing and halftone processing to image data and outputting the image data onto recording paper. Before the halftone image is output in the predetermined direction of the recording paper, color conversion is pre-applied to the image data. The pre-applied color conversion is color conversion for adjusting the characteristics of a color, and the adjustment of the characteristics of the color is applied depending on the relationship between the screen direction of the halftone image on the recording paper and the image output and main-scanning direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method of generating network image data having a predetermined screen direction and outputting a network image from the network image data, and to a method of outputting a network image after performing color conversion.

  In recent years, with the spread of DTP (Desk Top Publishing) and the like, print orderers use their own terminals to edit images input from scanners on computer software and perform page imposition. Editing is no longer unusual.

  In such a printing plate making process, image setter output for directly outputting image data with page imposition on a film, CTP (Computer to Plate) output for directly recording an image on a printing plate, and further on a cylinder of a printing press. CTC (Computer to Cylinder) for directly recording an image on the rolled printing plate is performed.

  In addition, a DCP (Digital Color Proof), which is a color sample that reproduces the image setter, CTP, and CTC, is created in order to calibrate the pattern and color tone. Furthermore, along with such full digitization, the final printed matter can be directly output to a recording sheet without going through the plate making process, so that the printed matter can be produced in a small lot or used for POD (Print On Demand). Are also being used.

  In this printing plate making process, an image forming apparatus such as a color laser printer or a multifunction machine has been used exclusively for color comps. However, these image forming apparatuses in recent years have many demands for use in POD and DCP applications because of their performance improvement and cost reduction.

  Unlike offset printing, POD and DCP require a required amount of printing when necessary, and also require variable printing with different printing contents for each sheet. Accordingly, there is a great demand for image forming apparatuses such as color laser printers and multifunction machines.

  Here, the image forming apparatus in the POD application outputs an image as a final printed matter, and is required to have extremely high color tone identity within a lot. In addition, an image forming apparatus for DCP use, unlike color comp output, has a very high target setting for color tone and is strictly required for color reproducibility.

  Therefore, conventionally, a color conversion method called CMS (Color Management System) is widely known, and color tone is corrected by the CMS to achieve color tone identity and color reproducibility (see, for example, Patent Document 1). ).

  Also, image forming apparatuses such as color laser printers and multi-function machines generally have a maximum outputable size of A3 wide at the maximum. When outputting an image, the purpose is to save the recording paper depending on the size of the image data. Therefore, it is necessary to rotate the image data to match the output possible size of the image forming apparatus. In many cases, recording paper of the same size can be loaded in both the vertical and horizontal directions, and is not always output in the same direction during output.

  In this case, the network image data obtained by screening the image data has a predetermined screen direction. However, with the rotation of the image data, the relationship between the screen direction of the halftone image and the main scanning direction in the image output of the image forming apparatus changes, and moire occurs. Therefore, conventionally, considering the rotation of the image, the screen direction of the halftone image data is changed to prevent the occurrence of moiré and avoid the deterioration of the image quality (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 3-158075 JP 2003-51955 A

  Image forming apparatuses such as color laser printers and multi-function machines generally include a photoreceptor and a laser diode. The surface of the photosensitive member is charged, and the laser diode irradiates the photosensitive member that has been charged with a laser beam. At the same time, an electrostatic latent image is formed on the surface of the photosensitive member by scanning the laser beam and rotating the photosensitive member. That is, it is an electrophotographic system. An image forming apparatus such as an electrophotographic color laser printer or a multifunction peripheral generally has a scanning direction for image output, with a scanning direction of laser light as a main scanning direction and a rotation direction of a photosensitive member as a sub-scanning direction.

  When there is a lot of continuous data with output in the main scanning direction, the laser beam will keep the laser beam on, so the amount of laser beam irradiation increases, and the negative potential charged on the photoconductor is reduced. There is a tendency to lower. On the other hand, laser light blinks more frequently when there is less continuous output data in the main scanning direction. Therefore, the amount of laser light irradiation decreases, and the negative potential charged on the photosensitive member decreases. There is a tendency to decrease.

  Therefore, when the data with output is continuously arranged in the main scanning direction, which is the scanning direction of the laser beam, the laser beam forms an electrostatic latent image while maintaining the lighting. Due to the characteristics of the laser light, the density of the output pixels corresponding to the output presence data arranged side by side tends to be higher than the density value attached to the output data.

  On the other hand, when the data with output is arranged in a direction different from the main scanning direction, the laser light continuously blinks in order to output the arranged data with output. Due to the characteristics of the laser beam, the density of the output image is lower than the density value attached to the output data.

  As described above, when an image forming apparatus such as a color laser printer or a multifunction peripheral is applied to POD or DCP applications, the image may need to be rotated. The rotation of the image leads to a change in the relationship between the screen direction of the image and the main scanning direction in image output. Usually, since output data is arranged in the screen direction, if the relationship is changed, the relationship between the arrangement direction of output data and the scanning direction of the laser light is changed, resulting in a problem that the image density is changed.

  For example, as shown in FIG. 5, a case where image data screened by a line network is output is considered. This image data is image data in which a certain color plate is set at a screen angle of 90 degrees. As shown in FIG. 5A, when the image is output as it is on the recording paper in the vertical direction without being rotated, the screen direction coincides with the sub-scanning direction and is directed in a different direction from the main scanning direction. When this image data is rotated by 90 degrees, the screen direction is the same as the main scanning direction as shown in FIG. In this case, the same direction and the different direction are classified by setting the main scanning direction to 0 degree, −45 degrees to 45 degrees and 135 degrees to 225 degrees in the same direction, and the other directions in different directions.

  In FIG. 5A, since the output data arrangement direction of the image data is different from the main scanning direction, the laser light repeatedly blinks for image output, and the image density becomes lower than the desired density.

  For example, assuming that the arrangement direction of the image data shown in FIG. 5A is a normal arrangement direction in which the image is not rotated, in Patent Document 2, color conversion is performed in consideration of the fact that this image density is lower than a desired density. As a result, a decrease in image density can be prevented.

  In FIG. 5B, the output data arrangement direction of the image data is oriented in the same direction as the main scanning direction, the laser light is kept on for image output, the image density becomes higher than the desired density, and the color tone increases. End up. In this case, since the image data has been rotated by 90 degrees, in Japanese Patent Application Laid-Open No. 2004-260, color conversion considering that the image density is lower than the desired density is a laser whose image density is higher than the desired density. This causes a further color misregistration than the light characteristics. In addition to the density, the color saturation and lightness change in addition to the laser light characteristics, that is, the color characteristics including density, saturation, and lightness change.

  As described above, when an image forming apparatus such as a color laser printer or a copying machine is applied to POD or DCP applications, it is necessary to rotate image data. In the conventional image forming apparatus, if the image is rotated, the relationship between the screen direction of the halftone image and the main scanning direction of the image output may change, and the color characteristics may change such that the image density deviates from the desired density. There is.

  The present invention has been made in view of the above-described problems, and an object of the present invention is a technique capable of always achieving good color reproduction regardless of the relationship between the screen direction of the halftone image and the image output scanning direction. Is to provide.

  In order to solve the above problem, the invention described in claim 1 is to perform color conversion on the image data in advance before outputting the network image having the predetermined screen direction based on the image data in the predetermined direction of the recording paper. The color conversion method is characterized in that the color conversion for adjusting color characteristics according to the relationship between the screen direction of the halftone image and the image output main scanning direction is performed.

  The invention according to claim 2 is a color conversion method in which color conversion is performed on image data in advance before outputting a network image having a predetermined screen direction based on the image data in a predetermined direction on a recording sheet. In advance, an input color-side device profile that defines a color system value for each combination of a plurality of input color separation image information is stored, and color characteristics for each relationship between the screen direction of the halftone image and the image output scanning direction are stored. Is stored in advance, and a plurality of output color side device profiles defining color system values for each combination of the plurality of output color separation image information are stored in advance, and when the screen direction of the halftone image is determined, the input Following the reference to the color side device profile, the color of the image data with reference to the output color side device profile corresponding to the relationship between the determined screen direction and the image output scanning direction Performing the conversion, characterized by.

  The invention according to claim 3 is a color conversion method in which a color image is preliminarily subjected to color conversion before outputting a network image having a predetermined screen direction based on the image data in a predetermined direction on a recording sheet. A plurality of combinations of a plurality of output color separation image information for each combination of a plurality of input color separation image information in which color characteristics are set for each relationship between the screen direction of the halftone image and the image output scanning direction. A device link profile is stored in advance, and when the screen direction of the halftone image is determined, color conversion of the image data is performed with reference to the device link profile corresponding to the relationship between the determined screen direction and the image output scanning direction. It is characterized by this.

  According to a fourth aspect of the present invention, there is provided a color conversion method in which color conversion is performed on image data in advance before outputting a network image having a predetermined screen direction based on the image data in a predetermined direction on a recording sheet. A plurality of outputs in which an input color side device profile that prescribes a color system value for each combination of a plurality of input color separation image information is stored in advance, and color characteristics are set depending on whether or not the image data is rotated A plurality of output color side device profiles defining color system values for each combination of color separation image information are stored in advance, image rotation information indicating whether or not the image data needs to be rotated is acquired, and the image rotation information Is obtained, the color of the image data is referred to with reference to the output color side device profile corresponding to the obtained image rotation information following the reference of the input color side device profile. Performing the conversion, characterized by.

  The invention according to claim 5 is a color conversion method for performing color conversion on image data in advance before outputting a network image having a predetermined screen direction based on the image data in a predetermined direction on the recording paper. A device link profile that prescribes each combination of a plurality of pieces of output color separation image information for each combination of a plurality of pieces of input color separation image information in which color characteristics are set depending on whether or not the image data is rotated, and Image rotation information indicating whether or not image data needs to be rotated is acquired, and the device link profile corresponding to the acquired image rotation information is referred to.

  According to a ninth aspect of the present invention, there is provided an image output system for outputting a network image having a predetermined screen direction based on image data in a predetermined direction of recording paper, wherein the screen direction of the network image is output with respect to the image data. And color conversion means for performing color conversion for adjusting color characteristics in accordance with the relationship between the image output scanning direction and the image output scanning direction.

  According to a tenth aspect of the present invention, there is provided an image output system for outputting a network image having a predetermined screen direction in a predetermined direction on a recording sheet based on image data, wherein each combination of a plurality of pieces of input color separation image information is previously provided. A plurality of outputs in which color characteristics are set for each relationship between the screen direction of the halftone image and the image output scanning direction; A second storage means for preliminarily storing a plurality of output color side device profiles defining color system values for each combination of color separation image information; and when the screen direction of the halftone image is determined, the input color side Following the reference to the device profile, the output color side device profile corresponding to the determined relationship between the screen direction and the image output scanning direction is referred to, and the image data Further comprising a color converter to convert, and characterized.

  According to an eleventh aspect of the present invention, there is provided an image output system for outputting a halftone image having a predetermined screen direction in a predetermined direction on a recording sheet based on image data, wherein the screen direction of the halftone image and the image output scanning direction are output. Storage means for preliminarily storing a plurality of device link profiles defining each combination of a plurality of output color separation image information for each combination of a plurality of input color separation image information, in which color characteristics are set for each relationship Color conversion means for performing color conversion of the image data with reference to a device link profile corresponding to the relationship between the determined screen direction and the image output scanning direction when the screen direction of the image is determined; Features.

  According to a twelfth aspect of the present invention, there is provided an image output system for outputting a network image having a predetermined screen direction in a predetermined direction on a recording sheet based on image data, and each combination of a plurality of pieces of input color separation image information in advance. A first storage unit that stores an input color side device profile that defines a value of a color system for the image data, and a combination of a plurality of pieces of output color separation image information in which color characteristics are set by the presence or absence of rotation of the image data Second storage means for preliminarily storing a plurality of output color side device profiles defining values of the color system, acquisition means for acquiring image rotation information indicating whether or not the image data needs to be rotated, and the image rotation When the information is acquired, the output color side device corresponding to the relationship between the acquired arrangement direction information and the image output scanning direction is followed by reference to the input color side device profile. The reference to the profile and a color conversion unit that performs color conversion of the image data, characterized by.

  According to a thirteenth aspect of the present invention, there is provided an image output system for outputting a halftone image having a predetermined screen direction in a predetermined direction of recording paper based on image data, wherein color characteristics are set depending on whether or not the image data is rotated. Storage means for storing in advance a device link profile defining each combination of a plurality of pieces of output color separation image information for each combination of a plurality of pieces of input color separation image information, and an image indicating the necessity of rotation of the image data An acquisition means for acquiring rotation information, and color conversion of the image data is performed with reference to the device link profile corresponding to the previously acquired image rotation information.

  According to a seventeenth aspect of the present invention, the image output control device performs color conversion on the image data in advance before outputting the network image having the predetermined screen direction based on the image data in the predetermined direction of the recording paper. A color conversion program for executing a process for performing color conversion for adjusting color characteristics in accordance with a relationship between a screen direction of the halftone image and an image output scanning direction. It is characterized by.

  The invention according to claim 18 is the first storage means for storing the input color side device profile that prescribes the color system value for each combination of the plurality of input color separation image information, and the recording of the network image. A plurality of output color side device profiles that prescribe color system values for each combination of a plurality of output color separation image information, in which color characteristics are set for each relationship between the screen direction on the paper and the image output scanning direction, A second storage means for storing the halftone image having a predetermined screen direction based on the image data to an image output control device before outputting the image in the predetermined direction on the recording paper. A color conversion program for executing a process for performing color conversion, wherein when the relationship between the screen direction of the halftone image and the image output scanning direction is determined, the input color from the first storage unit Referring to the device profile and executing the process of performing color conversion of the image data with reference to the output color side device profile corresponding to the relationship between the determined screen direction and the image output scanning direction from the second storage means It is characterized by making it.

  According to a nineteenth aspect of the present invention, a plurality of output color separation images for each combination of a plurality of pieces of input color separation image information in which color characteristics are set for each relationship between the screen direction of the halftone image and the image output scanning direction. A network image having a predetermined screen direction based on image data is output in a predetermined direction on a recording sheet to an image output control device including a storage unit that stores a plurality of device link profiles that prescribe each combination of information in advance. A color conversion program for executing a process for performing color conversion on the image data in advance, and when the screen direction of the halftone image is determined for the image output control device, the determined screen direction and image Performing a process of performing color conversion of the image data with reference to a device link profile corresponding to a relationship with an output scanning direction. That.

  The invention according to claim 20 is the first storage means for storing the input color side device profile that prescribes the color system value for each combination of the plurality of input color separation image information, and the rotation of the image data. And a second storage unit that stores in advance a plurality of output color side device profiles that define color system values for each combination of a plurality of output color separation image information in which color characteristics are set depending on the presence or absence of A color conversion program for causing an output control device to execute a process of performing color conversion on image data in advance before outputting a network image having a predetermined screen direction based on the image data in a predetermined direction on a recording sheet. When the image output control apparatus acquires the image rotation information by causing the image output control device to execute processing for acquiring image rotation information indicating whether or not the image data needs to be rotated. The color of the image data by referring to the input color side device profile from the first storage means and the output color side device profile corresponding to the acquired image rotation information from the second storage means A process for performing the conversion is executed.

  According to a twenty-first aspect of the present invention, a plurality of output colors for each combination of a plurality of input color separation image information set for each relationship between an arrangement direction of the halftone image on the recording paper and an image output scanning direction. A network image having a predetermined screen direction based on the image data is output in a predetermined direction on a recording sheet to an image output control apparatus including a storage unit that stores in advance a device link profile that defines each combination of decomposed image information. A color conversion program that executes a process for performing color conversion on the image data in advance, and that obtains image rotation information indicating whether the image data needs to be rotated from the image output control device When the image rotation information is acquired, the device link profile corresponding to the acquired image rotation information is referred to from the storage unit. Possible to execute a process for performing color conversion of the image data, characterized by.

  According to a twenty-fifth aspect of the invention, the image output program according to any of the seventeenth to twenty-fourth aspects is stored so as to be readable by the image output control device.

  In the color conversion, when the screen direction of the halftone image and the image output main scanning direction are the same direction, the image density of the image data is lowered, and the screen direction of the halftone image and the image output main scanning direction are In the case of a different direction, the image density of the image data may be increased (corresponding to the inventions of claims 5, 13, and 21).

  The plurality of output-side device profiles include a first output color-side device profile set corresponding to a case where the screen direction of the halftone image and the image output main scanning direction are the same direction, and the screen of the halftone image. A second output color side device profile set corresponding to the case where the direction and the image output main scanning direction are different directions, and the color conversion is performed when the screen direction of the halftone image and the image output main scanning direction are If determined in the same direction, the reference is made with reference to the first output color side device profile following reference to the input color side device profile, and the screen direction of the halftone image and the image output main scanning direction are different directions. Then, following the reference of the input color side device profile, the reference may be made with reference to the second output color side device profile (see FIG. Corresponds to the invention of Motomeko 6,14,22).

  Further, the plurality of device link profiles include a first device link profile set corresponding to a case where the screen direction of the halftone image and the image output main scanning direction are the same direction, the screen direction of the halftone image, and the image A second device link profile set corresponding to a case where the output main scanning direction is different, and the color conversion is determined so that the screen direction of the halftone image and the image output main scanning direction are the same direction. Then, it is performed with reference to the first device link profile, and when the screen direction of the halftone image and the image output main scanning direction are determined to be different directions, the second device link profile is referred to. (It is equivalent to the invention of claims 7, 15 and 23).

  According to the color conversion method, the image output system, the color conversion program, and the storage medium storing the program according to the present invention, the color characteristics are adjusted according to the relationship between the screen direction of the halftone image and the image output main scanning direction. By performing color conversion, changes in color characteristics such as changes in image density can be corrected in advance by color conversion, and color reproducibility can be improved.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a preferred embodiment of a color conversion method, an image output system, a color conversion program, and a storage medium storing the program according to the present invention will be specifically described with reference to the drawings. The color conversion method according to the present invention will be described for a case where a halftone image is output in an image forming apparatus capable of rotating an image. FIG. 1 is a block diagram of a color conversion apparatus that performs color conversion on image data that is the basis of a halftone image.

  Here, a halftone image is an image formed by a group of halftone dots or halftone lines, and is an image output on a recording sheet. This halftone image is output based on halftone image data having a predetermined screen direction for each color plate. The halftone image data is data in which halftone dots or halftone lines are arranged in the screen direction, and output data is continuously arranged in the screen direction. The screen direction is the direction in which the continuous arrangement of the data with output becomes the maximum, and in the case of multi-valued network image data, the screen direction is the maximum in consideration of the output intensity given to the data with output. Usually, the screen direction is based on the screen angle and indicates unidirectionality.

  The image output main scanning direction is the direction of an output line when outputting an image on a recording sheet. When the image forming apparatus is a color laser printer, the scanning direction of the laser light corresponds to the main scanning direction, and the rotation direction of the photoconductor is the sub-scanning direction. When the image forming apparatus is an ink jet printer, the direction is substantially perpendicular to the nozzle arrangement direction.

  When the image data for each color plate of C (cyan), M (magenta), Y (yellow), and K (sumi) is supplied, the color conversion device supplies the image data to the color conversion unit 6 to generate a new image for each color plate. The data is converted into image data for each color plate of C′M′Y′K ′. At the time of color conversion, color conversion for adjusting color characteristics is performed according to the relationship between the screen direction of the halftone image and the image output main scanning direction.

  Note that the classification of the relationship between the screen direction of the halftone image and the image output main scanning direction differs depending on the precision to be adjusted. For example, the relationship between the screen direction of the halftone image and the image output main scanning direction is divided into only two ways. Specifically, the screen direction of the halftone image is −45 degrees or more with the image output main scanning direction set to 0 degree. The case of 45 degrees or less and 135 degrees or more and 225 degrees or less is set to be the same direction as the main scanning direction of the image output and the other directions are set to different directions, and the adjustment amount of the color characteristic is changed according to these two ways. Also good. Further, when the angle is −45 ° or more and 45 ° or less, the case where the angle is 135 ° or more and 225 ° or less may be divided. Therefore, it is effective. Further, it may be finely set in increments of 10 degrees, and the adjustment amount of the color characteristic may be changed accordingly.

  The supplied image data may be image data for printing, raster image data, or network image data. That is, color conversion may be performed in parallel with generation of raster image data, and raster image data subjected to color conversion may be generated. Further, new raster image data may be generated by color conversion after the raster image data is generated. Alternatively, color conversion may be performed in parallel with the generation of the network image data, and the network image data subjected to the color conversion may be generated.

  The degree of color conversion of the color conversion unit 6 is determined by selecting and referring to one LUT among a plurality of LUTs (Look Up Tables) 8a to 8c stored in the storage unit 8. The plurality of LUTs are stored according to the relationship between the screen direction of the halftone image and the image output main scanning direction, and correct the change in color tone caused by the difference between the screen direction of the halftone image and the image output main scanning direction. This is a reference table.

  This LUT is a device profile, and is composed of two device profiles: CMYK → L * a * b * and L * a * b * → C′M′Y′K ′. Each of CMYK is input color separation image information. L * a * b * is a device-independent color space that controls the amount of light with the spectral characteristics of x-bar, y-bar, and z-bar defined by the CIE (Commission International del'Eclairage). It is a general value based on the values of the XYZ color system obtained by integration and is a value of the color system. C′M′Y′K ′ is output color separation image information that reflects the output characteristics of a device that outputs a halftone image. The output color separation image information reflects a change in color tone caused by the relationship between the screen direction of the halftone image and the image output main scanning direction.

  For example, as shown in FIG. 5A, when the screen direction is orthogonal to the main scanning direction on the recording paper, that is, the color conversion unit 6 selects and refers to the LUT of the relationship. At the same time, color conversion is performed based on the adjustment amount of the color characteristic defined in the LUT. That is, first, CMYK, which is input color separation image information of supplied image data, is converted into L * a * b *, and then L * a * b * is output color separation image information, and in accordance with the relationship. To C′M′Y′K ′ reflecting the color characteristics. In this case, since the data with output is discontinuous in the main scanning direction, the image density tends to be thin. The LUT corresponding to this relationship is set so as to increase the image density as an adjustment amount of the color characteristic, and the conversion unit performs color conversion so that the image density becomes high.

  As shown in FIG. 5B, when the screen direction of the halftone image is the same as the image output main scanning direction, the color conversion unit 6 specifies the LUT while selecting and referring to the LUT of the relationship. The color conversion is performed based on the adjustment amount of the color characteristics. In this case, since the data with output is arranged with continuity in the main scanning direction, the image density tends to increase. The LUT corresponding to this relationship is set so as to reduce the image density as the adjustment amount of the color characteristic, and the conversion unit performs color conversion so that the image density is lowered.

  Therefore, if there are a plurality of combinations of the relationship between the screen direction of the halftone image and the image output main scanning direction, a plurality of LUTs exist accordingly. When a device profile includes an LUT, only a plurality of device profiles on the L * a * b * → C′M′Y′K ′ side may be stored.

  These LUTs are created by preparing a plurality of relationships between the screen direction of the halftone image and the image output main scanning direction, outputting each as a color chart in which color patches are arranged, and measuring the color with a spectral densitometer.

  The relationship between the screen direction of the halftone image and the image output main scanning direction is acquired by the relationship acquisition unit 7, and the color conversion unit 6 selects and refers to the LUT from the storage unit 8 based on the acquired relationship.

  The LUT may be a device link profile. The device link profile is one profile of CMYK → C′M′Y′K, and directly associates input color separation image information and output color separation image information between devices.

  Regarding the acquisition of the relationship between the screen direction of the halftone image and the main scanning direction of the image output, in the case of the screen direction of the halftone image, the screen angle included in the information referred to when generating the halftone image data and the rotation of the halftone image data are Determined by presence or absence. That is, the screen direction of the halftone image is determined by acquiring the screen angle and the image rotation information. If the screen angle is constant, only image rotation information needs to be acquired.

  The image output main scanning direction is the scanning line direction of the image forming apparatus, for example, the scanning direction of laser light when the image forming apparatus is an electrophotographic system. If the image output main scanning direction is fixed, this information need not be acquired.

  Based on the screen direction of the acquired halftone image and the image output main scanning direction, the relationship between the directions is determined.

  As described above, this color conversion method acquires the relationship between the screen direction of the halftone image and the image output scanning direction, and adjusts the degree of color conversion according to the relationship, and corresponds to the acquired relationship. The color characteristics are adjusted by referring to the device profile or the device link profile.

  Description will be made based on an image output system using the color conversion method according to the present invention. As shown in FIG. 2, the image output system 1 is a system for POD or CTP, and includes a client terminal 2 that performs image data editing processing, a control device 3 that is an image output control device, and a color laser that is an image forming device. The printer 4 is configured to be connected via a network such as a public line such as a LAN or the Internet or a dedicated line. Further, a CTP RIP 5 is connected as necessary.

  The image output system 1 edits print image data for POD or CTP use at the client terminal 2 and transmits it directly or via the CTP RIP 5 to the control device 3 (hereinafter, POD and CTP use are the configuration and The operation is the same and is omitted for CTP applications).

  The control device 3 receives and stores the printing image data, performs RIP processing and screen processing on the printing image data, performs color conversion in parallel, and generates network image data. The halftone image data is transmitted to the color laser printer 4 and a halftone image based on the halftone image data is output on a recording sheet. When the RIP process is performed in the CTP RIP 5, the RIP process is omitted in the control device 3.

  The color laser printer 4 is an electrophotographic color laser printer having a plurality of paper feed cassettes. A plurality of paper feed cassettes (not shown) that store recording papers of different sizes in different storage directions (vertical and horizontal), and the size and storage direction of the recording paper stored in each of the paper feed cassettes Is an image forming apparatus provided with storage means (not shown) or the like. The color laser printer 4 outputs the network image data transmitted from the control device 3 onto a recording sheet, and rotates the network image as necessary based on the size and storage direction of the recording sheet and outputs the rotated image. . Since the color laser printer 4 of this embodiment is an electrophotographic system, the image output main scanning direction is the scanning direction of the laser beam, and the sub-scanning direction is the rotation direction of the photosensitive member.

  The control device 3 includes a CPU, ROM, RAM, HDD, and I / F (not shown). The control device 3 executes a program including a color conversion program stored in the ROM or HDD, and the CPU performs an operation while performing the calculation. Each process is executed by inputting / outputting data to / from other devices as appropriate using / F. In addition, a man-machine interface such as a display and a keyboard (not shown) is provided, which can be operated by the user.

  As shown in FIG. 3, the control device 3 includes an image data storage unit 30, an image data processing unit 31, an image rotation information acquisition unit 32, an LUT storage unit 33, and a transmission / reception unit 34.

  In such a control device 3, the printing image data transmitted from the client terminal 2 is stored in the image data storage unit 30. The image data for printing stored in the image data storage unit 30 is transferred to the image data processing unit 31, and is subjected to RIP processing, screen processing, and color conversion processing in parallel therewith, and the network image data subjected to color conversion. Is generated.

  At the time of color conversion, the relationship between the screen direction of the halftone image and the image output main scanning direction is acquired from the image rotation direction acquisition unit 32, and the corresponding LUT stored in the LUT storage unit 33 is obtained based on this relationship. The color characteristics are adjusted with reference to this LUT. That is, the control device 3 includes the color conversion device shown in FIG.

  The network image data subjected to the color conversion is transferred to the transmission / reception unit 34 and transmitted to the color laser printer 4 by the transmission / reception unit 34.

  That is, the image data storage unit 30 includes, for example, an I / F among the hardware resources of the control device 3. The image data storage unit 30 stores the print image data transmitted from the client terminal 1.

  The image data processing unit 31 includes, for example, a CPU among the hardware resources of the control device 3. The image data processing unit 31 reads the printing image data from the image data storage unit 30, and performs RIP processing, screen conversion processing, and color conversion processing in parallel therewith. That is, it corresponds to the color conversion unit 6 shown in FIG.

  RIP processing interprets print image data described in PostScript, and raster image data that matches the image data with the output resolution of an image forming apparatus such as the color laser printer 4, that is, a bitmap that is a collection of points. This is data conversion, so-called rasterization. Raster image data is generated for each color plate of four colors of CMYK and special colors (hereinafter also referred to as “special colors”) 1 and 2 such as gold and silver, and is composed of pixels according to the output resolution of the color laser printer 3. In this case, density value data indicating the gradation value of the image is assigned to each pixel.

  In the screen processing, halftone dots or halftone lines are formed in a predetermined pixel group following the RIP process, and multi-value halftone dot image data for each color plate formed by halftone dots or halftone lines is generated. This screen processing is performed by comparing the density value data of each pixel included in the raster image data with the threshold value matrix threshold value in which predetermined threshold values are arranged in a matrix.

  In the threshold matrix, threshold data is arranged based on the shape of halftone dots or halftone lines, the screen angle of halftone dots or halftone lines, the number of lines, and the density of halftone dots or halftone lines. This threshold matrix determines the screen direction of the network image data.

  The color conversion process is the same as that of the color conversion unit 6 shown in FIG. That is, raster image data for each color plate of CMYK is converted into raster image data for each color plate of C′M′Y′K ′ in parallel with raster image data subjected to RIP processing or screen processing, or The image data is converted into halftone image data for each color plate of C′M′Y′K ′. The simultaneous and parallel with the screen processing is to perform the screen processing while referring to the LUT stored in the LUT storage unit 33. In this color conversion, one LUT is selected from the plurality of LUTs stored in the LUT storage unit 33 and the color characteristics are adjusted. In selecting one LUT, the image data processing unit 31 acquires the relationship between the screen direction of the halftone image and the image output main scanning direction from the image rotation direction acquisition unit 32, and selects the LUT corresponding to this relationship.

  The image rotation information acquisition unit 32 acquires the relationship between the screen direction of the halftone image and the image output main scanning direction. In the color laser printer 4 in this embodiment, the scanning direction of the laser beam, that is, the main scanning direction of the image output is fixed, and the screen direction of the network image data is determined to be a predetermined direction by the threshold matrix. Therefore, the image rotation information acquisition unit 32 acquires the size information and storage direction information of the recording paper stored in the color laser printer 4, and acquires the image rotation information based on these information, thereby screen image of the halftone image. The relationship between the direction and the image output main scanning direction is acquired.

  The storage direction information is information indicating whether the storage direction of the recording paper is the vertical direction or the horizontal direction. The image rotation information is information that the image data is rotated if the image data needs to be rotated according to the storage direction of the recording paper. If it is necessary to rotate the image data by comparing the size information of the recording paper and the size of the image data, the image rotation information is information with rotation.

  The LUT storage unit 33 stores a plurality of LUTs according to the relationship between the screen direction of the halftone image and the image output main scanning direction. The same function as the storage unit 8 shown in FIG. 1 is realized. The plurality of LUTs are stored as a device profile or a device link profile. In this embodiment, a device profile A corresponding to the presence of rotation and a device profile B corresponding to the absence of rotation are stored, and the input color side device profile CMYK → L * a * b * and L * a *, respectively. b * → C′M′Y′K ′ and the output color side device profile.

  The transmission / reception unit 34 transmits the network image data subjected to color conversion to the color laser printer 4, and mediates acquisition of storage direction information acquired by the image rotation information acquisition unit 32.

  Next, the operation of such an image output system will be described in detail with reference to FIG. Here, from the printing image data, it is assumed that the network image data shown in FIG. 5A is generated, and the recording paper is stored in the horizontal direction. Therefore, the network image data shown in FIG. It shall be rotated 90 degrees.

  First, print image data is transmitted from the client terminal 2. The control device 3 receives the print image data and stores the print image data in the image data storage unit 30 (S100).

  When the printing image data is stored, the image rotation information acquisition unit 32 inquires and acquires the size information and storage direction information of the recording paper stored in the color laser printer 4 (S101). By this acquisition, it is acquired that the recording paper is stored in the horizontal direction.

  The image rotation information acquisition unit 32 determines the arrangement direction on the recording paper from the size information and storage direction information of the recording paper and the size of the printing image data, and outputs a halftone image on the recording paper. Then, it is determined whether to rotate and output the network image data, and the presence / absence of rotation of the network image data is acquired as image rotation information (S102). Since the acquired storage direction information is the horizontal direction, it is determined that the network image data is rotated 90 degrees and output, and the presence of rotation of the network image data is acquired as image rotation information.

  When the image rotation information is acquired, the image data processing unit 31 selects an LUT corresponding to the image rotation information based on the image rotation information in the LUT storage unit 33 (S103). In the present embodiment, the presence or absence of rotation is directly associated with the LUT as a flag. In the present embodiment, the device profile is stored as the LUT. The image data processing unit 31 reads the device profile A from the LUT storage unit using the image rotation information with image rotation as a flag.

  The image data processing unit 31 sequentially performs RIP processing on the description content of the printing image data, and generates raster image data for each CMYK color plane. Further, following the RIP processing, the input color side device profile is sequentially referred to, and then the output color side device profile is referred to, CMYK → L * a * b * → C′M′Y′K ′ conversion is performed, and the image is rotated. Raster image data of C′M′Y′K ′ reflecting the color characteristics corresponding to the presence is generated (S104). As shown in FIG. 5B, this C′M′Y′K ′ has an image density higher than that of CMYK in consideration of the screen direction of the halftone image and the image output main scanning direction being the same direction. Thinly produced.

  Next, following RIP processing and color conversion processing, screen processing is performed on raster image data for each color plate of C′M′Y′K ′, and C′M′Y′K ′ for each color plate having a predetermined screen direction. Network image data is generated (S105). This halftone image data is transferred to the LUT storage unit 34 and transmitted from the LUT storage unit 34 to the color laser printer 4 (S106). At this time, the network image data is rewritten to data rotated by 90 degrees.

  The color laser printer 4 outputs a halftone image along the longitudinal direction of the recording paper in the horizontal direction based on the halftone image data. That is, the screen direction of the halftone image is rotated by 90 degrees and is the same as the image output main scanning direction which is the laser beam scanning direction of the color laser printer 4, and the image density is output darkly. The output halftone image is based on C′M′Y′K ′, and the image density is lightly converted in consideration of output of a high image density. Is reproduced with desired color characteristics.

  When the halftone image data does not rotate and the screen direction of the halftone image and the image output main scanning direction shown in FIG. 5B are different, the device profile for increasing the image density is referred to.

  In the following, color conversion was performed using an image output system to which the color conversion method of the present embodiment was applied, and four types of image output were performed, and these were compared.

  In color conversion, an ISO12642 color patch and a natural image including a person and a landscape were output on a recording sheet by an electrophotographic printer. This natural image data is multivalued network image data formed by a mesh line having a predetermined screen direction.

  There are four output methods in combination of the following cases 1 and 2, and the relationship (relation between the screen direction of the halftone image and the image output main scanning direction) 1 and 2.

Case 1: A device link profile was created for each of the two relationships, and the corresponding device link profile was referenced during the color conversion process. One is a case where the screen direction of the network image in which the network image data is not rotated and the image output main scanning direction are the same direction. The other is a case where the screen direction of the halftone image and the image output main scanning direction are different from each other assuming that the halftone image data is rotated 90 degrees.
Case 2: A device link profile is created only when the screen direction of the halftone image and the image output main scanning direction are the same, and this device link profile is used regardless of the relationship between the screen direction of the halftone image and the image output scanning direction. The color conversion processing was performed with reference to FIG.
Direction 1: The halftone image was output so as to be parallel to the main scanning direction (the screen direction of the halftone image and the image output main scanning direction were the same direction without rotating the halftone image data).
Direction 2: Output was performed so that the halftone image was orthogonal to the main scanning direction (the halftone image data was rotated 90 degrees, and the screen direction of the halftone image and the image output main scanning direction were different directions).

  In each of the above combinations, 928 color patches of ISO12642 were measured with a Greda Macbeth I1 colorimeter, and the difference from the output color patch was determined as an average ΔE. Further, the visual approximation of natural images was evaluated (rank evaluation was performed in 10 stages. Rank 10 was the highest evaluation, and practical upper and lower limits were rank 5. Rank is an average value of evaluation by five evaluators. Was used). The results are shown in Table 1.

  As can be seen from Table 1, in case 1, favorable evaluation was obtained in ΔE and the visual rank even if the image was not rotated. That is, color reproducibility was ensured. However, in the case 2, in the direction 2 in which the screen direction of the halftone image and the image output main scanning direction were not substantially taken into consideration, although the practical rank was reached, the color reproducibility was inferior compared with the others.

  In this way, the continuity of the data with the output of the network image data changes, so that the blinking pattern in the main scanning direction of the laser light also changes, thereby changing the exposure amount and accompanying changes in the image density, etc. Changes in color characteristics occur. However, as in the present invention, by adjusting the color characteristics according to the relationship between the screen direction of the halftone image and the main scanning direction of the image output, changes in image density and the like can be corrected in advance by color conversion. The color reproducibility can be improved. In particular, this color conversion can be easily performed by using a device profile or a device link profile. In addition, when the screen direction of the network image data is determined in advance, the LUT to be referred to may be selected depending on the presence / absence of image rotation, and the change in image density caused by the image rotation can be corrected, and the paper direction can be changed. It is also suitable for changing and re-outputting.

  Here, in the present embodiment, the color conversion program stored in the HDD or ROM is executed so that the control device 3 has the above-described functions. However, such an image output program is stored in the control device. 3 can be stored in a readable storage medium such as an optical disk, a magneto-optical disk (CD-ROM / DVD-RAM / DVD-ROM / MO, etc.), or a magnetic storage medium (hard disk / floppy (registered trademark) disk / ZIP, etc.). You may be made to do. In the present embodiment, the control device 3 is provided with the above-described function by executing a color conversion program, but may be provided with the above-described function by including a dedicated circuit.

It is explanatory drawing in one Embodiment of the color conversion method which concerns on this invention. It is a block diagram of the image output system which concerns on this embodiment. It is a functional block diagram of a control device concerning this embodiment. It is an operation | movement flowchart of the image output system which concerns on this embodiment. It is a figure explaining the relationship between the screen direction of a halftone image, and an image output main scanning direction, (a) is a figure which shows the state output without rotating a halftone image, (b) is a figure which shows a halftone image. It is a figure which shows the state which rotated 90 degree | times and was output.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image output system 2 Client terminal 3 Control apparatus 30 Image data storage part 31 Image data processing part 32 Image rotation information acquisition part 33 LUT storage part 34 Transmission / reception part 4 Color laser printer 5 RIP for CTP
6 color conversion unit 7 relationship acquisition unit 8 storage unit

Claims (25)

A color conversion method for performing color conversion on image data in advance before outputting a network image having a predetermined screen direction based on image data in a predetermined direction on a recording sheet,
Performing the color conversion for adjusting color characteristics according to the relationship between the screen direction of the halftone image and the image output main scanning direction;
A color conversion method characterized by the above. A color conversion method for performing color conversion on image data in advance before outputting a network image having a predetermined screen direction based on image data in a predetermined direction on a recording sheet,
In advance, an input color side device profile that defines a color system value for each combination of a plurality of input color separation image information is stored,
A plurality of output color side device profiles that define color system values for each combination of a plurality of output color separation image information, in which color characteristics are set for each relationship between the screen direction of the halftone image and the image output scanning direction. Remember in advance,
When the screen direction of the halftone image is determined, the image data is referred to by referring to the output color side device profile corresponding to the relationship between the determined screen direction and the image output scanning direction following reference to the input color side device profile. The color conversion of the
A color conversion method characterized by the above. A color conversion method for performing color conversion on image data in advance before outputting a network image having a predetermined screen direction based on image data in a predetermined direction on a recording sheet,
A plurality of device links defining each combination of a plurality of output color separation image information for each combination of a plurality of input color separation image information, in which color characteristics are set for each relationship between the screen direction of the halftone image and the image output scanning direction Pre-store profile,
When the screen direction of the network image is determined, color conversion of the image data is performed with reference to a device link profile corresponding to the relationship between the determined screen direction and the image output scanning direction.
A color conversion method characterized by the above. A color conversion method for performing color conversion on image data in advance before outputting a network image having a predetermined screen direction based on image data in a predetermined direction on a recording sheet,
In advance, an input color side device profile that defines a color system value for each combination of a plurality of input color separation image information is stored,
A plurality of output color side device profiles defining color system values for each combination of a plurality of output color separation image information, in which color characteristics are set depending on the presence or absence of rotation of the image data, are stored in advance.
Obtaining image rotation information indicating whether or not the image data needs to be rotated;
When the image rotation information is acquired, following the reference of the input color side device profile, performing color conversion of the image data with reference to the output color side device profile corresponding to the acquired image rotation information,
A color conversion method characterized by the above. A color conversion method for performing color conversion on image data in advance before outputting a network image having a predetermined screen direction based on image data in a predetermined direction on a recording sheet,
A device link profile prescribing each combination of a plurality of output color separation image information for each combination of a plurality of input color separation image information, in which color characteristics are set depending on the presence or absence of rotation of the image data,
Obtaining image rotation information indicating whether or not the image data needs to be rotated;
Referring to the device link profile corresponding to the acquired image rotation information;
A color conversion method characterized by the above. The color conversion is
When the screen direction of the halftone image and the image output main scanning direction are the same direction, the image density of the image data is lowered,
If the screen direction of the halftone image and the image output main scanning direction are different directions, increasing the image density of the image data;
The color conversion method according to claim 1. The plurality of output side device profiles are:
A first output color side device profile set corresponding to a case where the screen direction of the halftone image and the image output main scanning direction are the same direction;
A second output color side device profile set corresponding to a case where the screen direction of the halftone image and the image output main scanning direction are different directions;
Including
The color conversion is
When the screen direction of the halftone image and the image output main scanning direction are determined to be the same direction, the reference is made with reference to the first output color side device profile following the input color side device profile,
When the screen direction of the halftone image and the image output main scanning direction are determined to be different directions, the reference is made with reference to the second output color side device profile following reference to the input color side device profile,
The color conversion method according to claim 2. The plurality of device link profiles are:
A first device link profile set corresponding to a case where the screen direction of the halftone image and the image output main scanning direction are the same direction;
A second device link profile set corresponding to the case where the screen direction of the halftone image and the image output main scanning direction are different directions;
Including
The color conversion is
When the screen direction of the halftone image and the image output main scanning direction are determined to be the same direction, it is performed with reference to the first device link profile,
When the screen direction of the halftone image and the image output main scanning direction are determined to be different directions, it is performed with reference to the second device link profile;
The color conversion method according to claim 3. An image output system for outputting a network image having a predetermined screen direction based on image data in a predetermined direction of a recording sheet,
Color conversion means for performing color conversion for adjusting color characteristics according to the relationship between the screen direction of the halftone image and the image output scanning direction for the image data;
An image output system characterized by An image output system for outputting a network image having a predetermined screen direction based on image data in a predetermined direction of a recording sheet,
First storage means for storing in advance an input color side device profile that defines a color system value for each combination of a plurality of input color separation image information;
A plurality of output color side device profiles that define color system values for each combination of a plurality of output color separation image information, in which color characteristics are set for each relationship between the screen direction of the halftone image and the image output scanning direction. Second storage means for storing in advance;
When the screen direction of the halftone image is determined, the image data is referred to by referring to the output color side device profile corresponding to the relationship between the determined screen direction and the image output scanning direction following reference to the input color side device profile. Color conversion means for performing color conversion of
Providing
An image output system characterized by An image output system for outputting a network image having a predetermined screen direction based on image data in a predetermined direction of a recording sheet,
A plurality of devices defining each combination of a plurality of output color separation image information for each combination of a plurality of input color separation image information, in which color characteristics are set for each relationship between the screen direction of the halftone image and the image output scanning direction Storage means for storing a link profile in advance;
When the screen direction of the halftone image is determined, a color conversion unit that performs color conversion of the image data with reference to a device link profile corresponding to the relationship between the determined screen direction and the image output scanning direction;
Providing
An image output system characterized by An image output system for outputting a network image having a predetermined screen direction based on image data in a predetermined direction of a recording sheet,
First storage means for storing in advance an input color side device profile that defines a color system value for each combination of a plurality of input color separation image information;
Second storage means for preliminarily storing a plurality of output color side device profiles defining color system values for each combination of a plurality of output color separation image information, in which color characteristics are set depending on the presence or absence of rotation of the image data When,
Acquisition means for acquiring image rotation information indicating whether or not the image data needs to be rotated;
When the image rotation information is acquired, the reference of the input color side device profile is followed by referring to the output color side device profile corresponding to the relationship between the acquired arrangement direction information and the image output scanning direction. Color conversion means for performing color conversion;
Providing
An image output system characterized by An image output system for outputting a network image having a predetermined screen direction based on image data in a predetermined direction of a recording sheet,
Storage means for preliminarily storing a device link profile that defines each combination of a plurality of pieces of output color separation image information for each combination of a plurality of pieces of input color separation image information in which color characteristics are set according to the presence or absence of rotation of the image data;
Acquisition means for acquiring image rotation information indicating whether or not the image data needs to be rotated;
Performing color conversion of the image data with reference to the device link profile corresponding to the previously acquired image rotation information;
An image output system characterized by The color conversion is
When the screen direction of the halftone image and the image output main scanning direction are the same direction, the image density of the image data is lowered,
If the screen direction of the halftone image and the image output main scanning direction are different directions, increasing the image density of the image data;
The image output system according to claim 9. The second storage means includes a plurality of output side device profiles.
A first output color side device profile set corresponding to a case where the screen direction of the halftone image and the image output main scanning direction are the same direction;
A second output color side device profile set corresponding to a case where the screen direction of the halftone image and the image output main scanning direction are different directions;
Remember
The color conversion means includes
When the screen direction of the halftone image and the image output main scanning direction are determined in the same direction, referring to the input color side device profile, referring to the first output color side device profile,
When the screen direction of the halftone image and the image output main scanning direction are determined to be different directions, referring to the input color side device profile, referring to the second output color side device profile,
The image output system according to claim 10. The storage means includes the plurality of device link profiles.
A first device link profile set corresponding to a case where the screen direction of the halftone image and the image output main scanning direction are the same direction;
A second device link profile set corresponding to the case where the screen direction of the halftone image and the image output main scanning direction are different directions;
Remember
The color conversion means includes
When the screen direction of the halftone image and the image output main scanning direction are determined to be the same direction, referring to the first device link profile,
When the screen direction of the halftone image and the image output main scanning direction are determined to be different directions, referring to the second device link profile,
The image output system according to claim 11. A color conversion program for causing an image output control device to execute a process of performing color conversion on image data in advance before outputting a network image having a predetermined screen direction based on the image data in a predetermined direction on a recording sheet. And
Causing the image data to undergo color conversion for adjusting color characteristics in accordance with the relationship between the screen direction of the halftone image and the image output scanning direction;
A color conversion program characterized by First storage means for storing in advance an input color side device profile that defines a color system value for each combination of a plurality of input color separation image information;
Multiple output color sides that specify color system values for each combination of multiple output color separation image information with color characteristics set for each relationship between the screen direction of the halftone image on the recording paper and the image output scanning direction Second storage means for storing a device profile in advance,
For image output control device
A color conversion program for executing a process for performing color conversion on the image data in advance before outputting the network image having a predetermined screen direction based on image data in a predetermined direction on a recording sheet,
When the relationship between the screen direction of the halftone image and the image output scanning direction is determined, the input color side device profile is referred to from the first storage unit, and the determined screen direction is determined from the second storage unit. Referring to an output color side device profile corresponding to the relationship with the image output scanning direction, causing the image data to undergo color conversion,
A color conversion program characterized by A plurality of devices defining each combination of a plurality of output color separation image information for each combination of a plurality of input color separation image information, in which color characteristics are set for each relationship between the screen direction of the halftone image and the image output scanning direction For an image output control device comprising storage means for storing a link profile in advance,
A color conversion program that executes a process of performing color conversion on image data in advance before outputting a network image having a predetermined screen direction based on image data in a predetermined direction on a recording sheet,
For the image output control device,
When the screen direction of the network image is determined, a process of performing color conversion of the image data with reference to a device link profile corresponding to the relationship between the determined screen direction and the image output scanning direction is executed.
A color conversion program characterized by First storage means for storing in advance an input color side device profile that defines a color system value for each combination of a plurality of input color separation image information;
Second storage means for preliminarily storing a plurality of output color side device profiles defining color system values for each combination of a plurality of output color separation image information, in which color characteristics are set according to the presence or absence of rotation of image data; Comprising
For image output control device
A color conversion program for executing a process of performing color conversion on the image data in advance before outputting a network image having a predetermined screen direction based on the image data in a predetermined direction on a recording sheet,
For the image output control device,
A process of acquiring image rotation information indicating whether or not rotation of the image data is necessary;
When the image rotation information is acquired, the output color side device profile corresponding to the acquired image rotation information from the second storage unit with reference to the input color side device profile from the first storage unit To perform a process of performing color conversion of the image data,
A color conversion program characterized by A device that defines each combination of a plurality of output color separation image information for each combination of a plurality of input color separation image information set for each relationship between the arrangement direction of the halftone image on the recording paper and the image output scanning direction. For an image output control device comprising storage means for storing a link profile in advance,
A color conversion program for executing a process of performing color conversion on the image data in advance before outputting a network image having a predetermined screen direction based on the image data in a predetermined direction on a recording sheet,
For the image output control device,
A process of acquiring image rotation information indicating whether or not rotation of the image data is necessary;
When the image rotation information is acquired, referring to the device link profile corresponding to the acquired image rotation information from the storage unit, causing the image data to undergo color conversion,
A color conversion program characterized by The color conversion is
When the screen direction of the halftone image and the image output main scanning direction are the same direction, the image density of the image data is lowered,
If the screen direction of the halftone image and the image output main scanning direction are different directions, increasing the image density of the image data;
The color conversion method according to claim 17. The second storage means includes a plurality of output side device profiles.
A first output color side device profile set corresponding to a case where the screen direction of the halftone image and the image output main scanning direction are the same direction;
A second output color side device profile set corresponding to a case where the screen direction of the halftone image and the image output main scanning direction are different directions;
Remember
The color conversion is
When the screen direction of the halftone image and the image output main scanning direction are determined to be the same direction, the first storage unit refers to the input color side device profile, and the second storage unit This process is performed by referring to the output color device profile.
When the screen direction of the halftone image and the image output main scanning direction are determined to be different directions, the second storage unit refers to the input color side device profile from the first storage unit, and the second storage unit This is a process performed by referring to the output color device profile.
The color conversion program according to claim 18. The storage means includes the plurality of device link profiles.
A first device link profile set corresponding to a case where the screen direction of the halftone image and the image output main scanning direction are the same direction;
A second device link profile set corresponding to the case where the screen direction of the halftone image and the image output main scanning direction are different directions;
Remember
The color conversion is
When the screen direction of the halftone image and the image output main scanning direction are determined to be the same direction, the processing is performed by referring to the first device link profile from the storage unit,
When the screen direction of the halftone image and the image output main scanning direction are determined to be different directions, the processing is performed by referring to the second device link profile from the storage unit,
The color conversion program according to claim 19. 25. A storage medium in which the image output program according to claim 17 is stored so as to be readable by the image output control device.

Images