JP2008118447A - Image forming apparatus, image forming method, and its program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus for eliminating the performance of uselessly highly accurate processing, so as to attain more quick RIP, and to provide an image forming method and its program. <P>SOLUTION: A table is generated which associates a conversion source color space with a conversion destination color space, based on a conversion source profile and a conversion destination profile. The smoothness of color change in the conversion destination color space relative to the color change in the conversion source color space is calculated by using the generated table. The color conversion accuracy, upper limit bit depth, or interpolation accuracy of gradation plotting is determined based on the calculated smoothness, and an image is formed in response to the determination result. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and an image forming method for executing color conversion processing at high speed using a multidimensional table, and a program for executing the image forming method.

  Currently, page printers that print out using a print engine such as electrophotography are widely known. In this page printer, RIP processing is performed in which data described in a page description language (PDL) is received via a communication medium such as a network, and is interpreted by a dedicated interpreter to form an image. The page description language data is generated from the original electronic document by cooperation between the application, the operating system, and the driver. LIPS developed by Canon, PCL developed by HP, PostScript developed by Adobe, ESC / P developed by Epson, etc. are widely known as page description languages.

  In RIP processing of page description language data, intermediate data is often output by a PDL interpreter by software processing, and a bitmap image is generated from the intermediate data by a renderer by hardware processing or software processing. In addition, a direct mapping method using a multi-dimensional lookup table and interpolation processing is applied as a high-speed, high-precision color conversion process for nonlinear color space conversion, such as color matching and conversion from RGB color space to CMYK color space. May be. Some devices can realize color management desired by a user by downloading and using an ICC profile as a multi-dimensional lookup table.

  The profile stores data describing the input / output characteristics of an input device such as a monitor and a scanner, and an output device such as a printer. In particular, an ICC profile is often used as an industry standard. In the ICC profile, a color space that does not depend on an input / output color space called Profile Connection Space (PCS) is defined in the CIE XYZ color space and the CIE L * a * b * color space. When color matching is performed between the input device and the output device, the color space depending on the input device is first converted from PCS to PCS, and then the PCS is converted to the color space depending on the output device.

  The profile consists of a 3-input N-output look-up table as a database for converting from PCS to input / output device-dependent color space, or from input / output device-dependent color space to PCS. Data is stored. This multi-dimensional lookup table stores multiple grid points that uniquely determine the output color for the input color. When there is no continuity of color values between adjacent grid points and surrounding grid points, gradation drawing was performed. There is a possibility of problems such as gradation skipping. Therefore, a method for smoothing the lattice points has been devised (for example, see Patent Document 1).

  On the other hand, in recent years, a color space exceeding 8 bits for each conventional color such as 16 bits for each color such as scRGB is being introduced. The purpose of introducing such a multi-bit color space is to increase the color gamut and improve the gradation.

JP 2004-320624 A

  However, such a multi-bit color space greatly increases RIP performance because it causes an increase in the amount of processing data. If the actual printer engine does not have the ability to reproduce such gradation, the output image is not effective, and it is expected that only the RIP time will be unnecessarily increased. In addition to the performance of the printer engine, the following problems can be considered.

  For one thing, depending on the smoothness of the multi-dimensional table in the ICC profile used for color management (details will be described later), the accuracy of color management is reduced, and the gradation of the input color space is faithful to the output color after color management. It is expected that it cannot be reproduced. That is, an increase in the number of bits of the input color value may be wasted. Further, when the smoothness of the multidimensional table in the ICC profile is low, color management processing with high calculation accuracy and gradation drawing with high interpolation accuracy may be wasted.

  In order to solve the problems and problems described above, an image forming apparatus according to the present invention has the following configuration.

  Means for obtaining a conversion source profile for color conversion from a device-specific color space to a device-independent color space, and a conversion destination profile for color conversion from a device-independent color space to a device-specific color space Obtaining a table that associates a conversion source color space with a conversion destination color space from the conversion source profile and the conversion destination profile, and using the generated table, the conversion source color According to the means for calculating the smoothness of the color change in the conversion destination color space with respect to the color change in the space, the means for determining the color conversion accuracy based on the calculated smoothness, according to the determined color conversion accuracy, Means for performing color conversion on the print data from the conversion source color space to the conversion destination color space; and an image format according to the print data subjected to the color conversion. Characterized in that it comprises a means for.

  Means for obtaining a conversion source profile for color conversion from a device-specific color space to a device-independent color space, and a conversion destination profile for color conversion from a device-independent color space to a device-specific color space Obtaining a table that associates a conversion source color space with a conversion destination color space from the conversion source profile and the conversion destination profile, and using the generated table, the conversion source color Means for calculating a smoothness of a color change in the conversion destination color space with respect to a color change in the space; a means for determining an upper limit bit depth based on the calculated smoothness; and a bitmap for forming print data into an image RIP means for converting to data, and the bit depth of the bitmap data generated by the RIP means is combined with the upper limit bit depth. Characterized in that it comprises means for.

  Means for obtaining a conversion source profile for color conversion from a device-specific color space to a device-independent color space, and a conversion destination profile for color conversion from a device-independent color space to a device-specific color space Obtaining a table that associates a conversion source color space with a conversion destination color space from the conversion source profile and the conversion destination profile, and using the generated table, the conversion source color Means for calculating a smoothness of a color change in the conversion destination color space with respect to a color change in the space; a means for determining an interpolation accuracy of gradation drawing based on the calculated smoothness; and according to the determined interpolation accuracy Means for performing gradation drawing.

  The image forming method of the present invention has the following configuration.

  A step of obtaining a conversion source profile for color conversion from a device-specific color space to a device-independent color space, and a conversion destination profile for color conversion from a device-independent color space to a device-specific color space Generating a table that associates a conversion source color space with a conversion destination color space from the conversion source profile and the conversion destination profile, and using the generated table, the conversion source color Calculating the smoothness of the color change in the conversion destination color space with respect to the color change in the space, determining the color conversion accuracy based on the calculated smoothness, and according to the determined color conversion accuracy, Performing color conversion on the print data from the conversion source color space to the conversion destination color space, and the print data subjected to the color conversion; Characterized in that it comprises a step of image formation in accordance with data.

  A step of obtaining a conversion source profile for color conversion from a device-specific color space to a device-independent color space, and a conversion destination profile for color conversion from a device-independent color space to a device-specific color space Generating a table that associates a conversion source color space with a conversion destination color space from the conversion source profile and the conversion destination profile, and using the generated table, the conversion source color Calculating a smoothness of a color change in the destination color space with respect to a color change in the space; determining an upper limit bit depth based on the calculated smoothness; and determining the output bit depth Generating and outputting bitmap data for image formation in accordance with an upper limit bit depth, and That.

  A step of obtaining a conversion source profile for color conversion from a device-specific color space to a device-independent color space, and a conversion destination profile for color conversion from a device-independent color space to a device-specific color space Generating a table that associates a conversion source color space with a conversion destination color space from the conversion source profile and the conversion destination profile, and using the generated table, the conversion source color Calculating a smoothness of a color change in the conversion destination color space with respect to a color change in the space; means for determining an interpolation accuracy of gradation drawing based on the calculated smoothness; and according to the determined interpolation accuracy And a step of performing gradation drawing.

  The present invention can also be realized as a program including a program code for causing a computer to execute each step of the image forming method.

  The image processing method of the present invention evaluates the smoothness of a table obtained based on a profile, stores the evaluation result corresponding to the profile, and print data based on color conversion accuracy determined according to the smoothness. It is characterized by determining the accuracy in the color conversion processing for.

  According to the present invention, based on the smoothness of the color change in the conversion destination color space with respect to the color change in the conversion source color space, the bit depth of the optimum color value, the calculation accuracy of color management (color conversion accuracy), gradation The drawing interpolation accuracy is selected. As a result, high-precision processing is not performed unnecessarily, and high-speed RIP is realized.

  Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a system configuration diagram showing a configuration of the entire system including image forming apparatuses according to an embodiment of the present invention.

  The image forming apparatus 200 includes a scanner unit 2070 that is an image input device, a printer unit 2095 that is an image output device, a controller unit 2000, and an operation unit 2012 that is a user interface. The scanner unit 2070, the printer unit 2095, and the operation unit 2012 are each connected to a controller unit 2000, and the controller unit 2000 is connected to a network transmission unit such as a LAN 2011. Further, other image forming apparatuses 220 and 230 having the same device configuration as the image forming apparatus 200 are connected to the LAN 2011. The image forming apparatuses 220 and 230 have scanner units 2270 and 2370, printer units 2295 and 2395, and operation units 2212 and 2312, which are connected to corresponding controller units 2200 and 2300, respectively. A host computer 2100 is connected to the LAN 2011.

FIG. 2 is a block diagram illustrating a configuration of the image forming apparatus 200.
The controller unit 2000 is a controller for inputting and outputting image information and device information. The controller unit 2000 is connected to a scanner 2070 as an image input device and a printer 2095 as an image output device, and is also connected to a LAN 2011 and a public line (WAN) 2051. A CPU 2001 is a controller that controls the entire system.

  A RAM 2002 is a system work memory for operating the CPU 2001, and is also an image memory for temporarily storing image data. A ROM 2003 is a boot ROM, and stores a system boot program. An HDD 2004 is a hard disk drive that stores system software and image data. An operation unit I / F 2006 is an interface unit with the operation unit (UI) 2012 and outputs image data to be displayed on the operation unit 2012 to the operation unit 2012. Also, it plays a role of transmitting information input by the user of the system from the operation unit 2012 to the CPU 2001.

  A network interface (I / F) 2010 is connected to the LAN 2011 and inputs / outputs information. A modem 2050 is connected to the public line 2051 and inputs / outputs information. The above devices are arranged on the system bus 2007. An image bus I / F (Image Bus I / F) 2005 is a bus bridge that connects a system bus 2007 and an image bus 2008 that transfers image data at high speed, and converts a data structure. The image bus 2008 is configured by a PCI bus or IEEE1394. The following devices are arranged on the image bus 2008.

  An image processor (RIP) 2060 expands the display list into a raster image. The device I / F unit 2020 connects the scanner 2070 and the printer 2095, which are image input / output devices, and the controller 2000, and performs synchronous / asynchronous conversion of image data. A scanner image processing unit 2080 corrects, processes, and edits input image data. The printer image processing unit 2090 performs correction, resolution conversion, halftoning, and the like on the print output image data. The image rotation unit 2030 rotates image data. The image compressing unit 2040 performs JPEG, MMR, and MH compression / decompression processing on multi-valued image data and binary image / image data.

The appearance of the image forming apparatus 200 is shown in FIG.
The scanner unit 2070 serving as an image input device illuminates an image on paper as a document and scans it using a CCD line sensor (not shown), thereby converting the image into raster signal data 2071 into an electrical signal. The original paper is set on the tray 2073 of the original feeder 2072. When the user of the apparatus gives an instruction to start reading from the operation unit 2012, the controller CPU 2001 gives an instruction to the scanner 2070 (2071), and the feeder 2072 feeds original sheets one by one and performs an original image reading operation.

  The printer unit 2095 serving as an image output device is a part that converts raster image data 2096 into an image on paper. The method used in the printer unit 2095 includes an electrophotographic method using a photosensitive drum or a photosensitive belt, and an ink jet method in which an ink is ejected from a minute nozzle array to directly print an image on a sheet. I do not care. The printing operation is started by an instruction 2096 from the controller CPU 2001. The printer unit 2095 has a plurality of paper feed stages so that different paper sizes or different paper orientations can be selected, and has paper cassettes 2101, 2102, and 2103 corresponding thereto. A paper discharge tray 2111 receives paper that has been printed.

The configuration of the operation unit 2012 is shown in FIG.
The LCD display unit 2013 has a touch panel sheet 2019 affixed on the LCD, displays a system operation screen and soft keys, and transmits position information to the controller CPU 2001 when the displayed keys are pressed. A start key 2014 is used to start a document image reading operation. At the center of the start key 2014, there is a green and red two-color LED 2018, which indicates whether or not the start key 2014 is in a usable state. A stop key 2015 serves to stop an operation in operation. The ID key 2016 is used when inputting the user ID of the user. A reset key 2017 is used when initializing settings from the operation unit.

FIG. 5 is a software block diagram of the image forming apparatus according to the embodiment of the present invention.
Reference numeral 1501 denotes a UI, that is, a user interface, and is a module that mediates with an apparatus when an operator performs various operations and settings of the image forming apparatus. This module transfers input information to various modules, which will be described later, and requests processing or sets data in accordance with the operation of the operator.

  Reference numeral 1502 denotes an address-book, that is, a database module that manages a data transmission destination, a communication destination, and the like. The contents of the Address-Book are used to add, delete, and acquire data by operations from the UI 1501 and to provide data sending / communication destination information to each module described later by the operations of the operator. .

  Reference numeral 1504 denotes a universal-send, that is, a module that manages data distribution, and distributes data instructed to the operator by the UI 1501 to a communication (output) destination similarly designated. When the operator uses the scanner function of the device to generate distribution data, the device is operated via a control-API 1519 described later to generate data.

  A module 1505 is executed when a printer is specified as an output destination in the Universal-Send 1504. A module 1506 is executed when an E-mail address is designated as a communication destination in the Universal-Send 1504. A module 1507 is executed when a database is designated as an output destination in the Universal-Send 1504. Reference numeral 1508 denotes a module that is executed when an image forming apparatus similar to this apparatus is designated as an output destination in the Universal-Send 1504.

  A PDL module 1509 realizes a function of printing a PDL (Page Description Language) document transmitted from the outside of the image forming apparatus by using the print function of the image forming apparatus. 1531 inside the PDL module 1509 is a Job-Ticket-Parser, which is a module that interprets the Job-Ticket data received together with the PDL data.

  In Job-Ticket, print media, the number of copies, post-processing, various color processing, and image processing method can be specified. These pieces of information are analyzed by 1531 Job-Ticket-Parser. After being analyzed, the data is transmitted to a later-described Job-Manager 1520, a Printer-Manager 1526, and a PDL-Interpreter 1527 via a later-described Control-API 1519. Further, it also provides a function of taking out and printing an electronic document stored in an external Web server using the 1512 HTTP module.

A copy module 1510 uses the printer function and the scanner function of the image forming apparatus and executes a copy operation based on a UI instruction.
A box module (Box) 1511 stores a scanned image or a PDL print image in the HDD and provides the following management functions. That is, it provides management functions such as printing of stored images using a printer function, transmission using a Universal-Send function, deletion of documents stored in the HDD, grouping (storage in individual BOX), movement between BOXes, and copying between BOXes.

Reference numeral 1512 denotes a module used when the image forming apparatus performs communication by HTTP, and provides communication to the above-described PDL 1509 module by a TCP / IP 1517 module described later.
Reference numeral 1513 denotes an lpr module which provides communication to the printer module 1505 in the above-described Universal-Send 1504 by a TCP / IP 1517 module described later.

Reference numeral 1514 denotes an SMTP module, which provides communication to the E-mail module 1506 in the above-mentioned Universal-Send 1504 by a TCP / IP 1517 module described later.
Reference numeral 1515 denotes an SLM, that is, a Salutation-Manager module. This provides communication to the database module 1517 and the DP module 1518 in the above-mentioned Universal-Send 1504 by a TCP / IP 1517 module described later.

An LPD module 1516 provides communication to the PDL 1509 module described above by a TCP / IP 1517 module described later.
Reference numeral 1517 denotes a TCP / IP communication module, which provides network communication to the various modules described above using a network-driver 1518 described later.
Reference numeral 1518 denotes a network driver that controls a portion physically connected to the network.

  Reference numeral 1519 denotes a Control-API. This provides higher-level modules such as Universal-Send 1504, PDL 1509, Copy 1510, and Box 1511 with interfaces with lower-level modules such as Job-Manager 1520 described later. This alleviates the dependency between the upper and lower modules and increases their applicability.

Reference numeral 1520 denotes a job manager, which interprets processing instructed from the various modules described above via the control-API 1519 and gives instructions to each module described later. Further, this module centrally manages hardware processing executed in the image forming apparatus.
A CODEC-Manager 1521 manages and controls various compression / decompression of data in the process instructed by the Job-Manager 1520.

Reference numeral 1522 denotes an FBE-Encoder that compresses data read by a scan process executed by the Job-Manager 1520 and the Scanner-Manager 1525 using the FBE format.
1523 is JPEG-CODEC. This is a JPEG compression process of the read data in the scan process executed by the Job-Manager 1520 and the Scanner-Manager 1525. In the printing process executed by the Printer-Manager 1526, JPEG expansion processing of print data is performed.

  1524 is MMR-CODEC. This is the MMR compression processing of the read data in the scan processing executed by the Job-Manager 1520 and the Scanner-Manager 1525. In the printing process executed by the Printer-Manager 1526, the print data is subjected to the MMR expansion process.

  Reference numeral 1525 denotes a scanner-manager, which manages and controls scan processing instructed by the job-manager 1520. Reference numeral 1528 denotes a scanner I / F, which provides an interface between the scanner-manager 1524 and the scanner unit to which the image forming apparatus is internally connected.

Reference numeral 1526 denotes a Printer-Manager that manages and controls printing processing instructed by the Job-Manager 1519.
Reference numeral 1529 denotes an engine-I / F driver which provides an interface between the printer-manager 1526 and the printing unit.

Reference numeral 1527 denotes a PDL interpreter. This interprets a PDL or electronic document format such as LIPS, PostScript, PCL, PDF, SVG or the like according to an instruction from Job-Manager 1520. Then, a display list which is a common expression format independent of the type of PDL or electronic document format is generated.
Reference numeral 1530 denotes a renderer, which expands the display list generated by the PDL Interpreter 1527 to a raster image memory using an image processor in accordance with an instruction from the Printer-Manager 1520.

Next, a rough processing flow of this embodiment will be described with reference to FIG.
As a first step, the ICC profile 3105 is downloaded from the host computer 3102 to the image forming apparatus 3103.
Next, as a second step, the image forming apparatus 3103 examines (evaluates) the smoothness (details will be described later) of the multidimensional table stored in the ICC profile 3105, and checks the upper limit bit depth used during RIP and color management calculation. Determine accuracy and shading interpolation accuracy. Then, the ICC profile 3105 is stored in a predetermined position in the HDD 3106.

  As a third step, a PostScript print job 3104 is input from the host computer 3101 to the image forming apparatus 3103. After the print job 3104 is input, the image forming apparatus 3103 performs RIP processing based on the upper limit bit depth, color management calculation accuracy, and shading interpolation accuracy determined in the second step, and prints out. The first step and the second step are executed continuously, and the third step is executed as a process when the print job is finally input.

Next, a method for examining the smoothness of the multidimensional table from the ICC profile and determining the upper limit bit depth, color management calculation accuracy, and shading interpolation accuracy used in RIP will be described with reference to FIGS.
FIG. 7 is a processing flowchart.

The process starts from step S3201, and the output profile received in step S3202 is stored in a predetermined position on the HDD.
In step S3203, the received output profile is combined with the RGB input profile built in the device in advance to generate a single multidimensional table. The synthesis of the RGB input profile and the output profile is executed by sampling the result of actual color conversion using a table group included in each profile. Values are assigned to 33 levels between 0 and 255 for the three RGB axes, and output CMYK values are obtained for 33 × 33 × 33 RGB values. The RGB input profile is a conversion source profile for performing color conversion from a device-specific conversion source color space to a device-independent color space. A conversion destination profile for performing color conversion from a device-independent color space to a device-specific conversion color space is an output profile.

  Next, proceeding to step S3204, using the synthesized multidimensional table, the input value is displaced from the origin of the three-dimensional space made up of RGB values toward the diagonal of the RGB cube in this space, and the corresponding CMYK output value Is sampled. As shown in FIG. 8, the RGB values are simultaneously displaced in 256 steps from 0 to 255 from the origin (white) to the diagonal point (black) of the RGB cube, and 256 CMYK output values are obtained. Since the three-dimensional table is composed of 33 × 33 × 33 lattice points, the output values of points that do not match the lattice points are obtained by interpolation.

  In step S3205, an average line is derived from the sampled values. FIG. 9 shows an example in which sampling values are plotted. Reference numeral 3301 denotes an actual output line, and 3302 denotes an average line. The actual output line shows the output value of cyan when the value is displaced from black to white. 3303 is an enlarged view of a specific portion of the actual output line and the average line, and 7 points from C (n−3) to C (n + 3) are shown as actual output values. When C (n) is an attention point, the average point A (n) on the average line corresponding to this is obtained by the following equation.

  A (n) = (0.3 × C (n−2) + 0.7 × C (n−1) + C (n) + 0.7 × C (n + 1) + 0.3 × C (n + 2)) / 3

Values are obtained by the above calculation for all output values where n is 0 to 255, and finally an average line is derived.
In step S3206, the average error of the sampling values is obtained with the average line as a reference, and this is used as the smoothness.

  In step S3207, the upper limit bit depth at the time of rendering is determined from the smoothness. The upper limit bit depth is 8 bits, 10 bits, and 12 bits, and the smoothness value is small, that is, 12 bits are adopted when smooth, and the smoothness value is large, that is, 8 bits when smooth. When the smoothness value is intermediate, 10 bits are used. In order to determine whether the smoothness is large, small, or intermediate, threshold values Th1 and Th2 may be used.

  In step S3208, the color management calculation accuracy (color conversion accuracy) is determined from the smoothness. The calculation accuracy of color management is 8 bits, 10 bits, and 12 bits in the number of bits when quantizing a color value input in floating point, and the smoothness value is small, that is, 12 bits when smooth. Is adopted. On the other hand, 8 bits are adopted when the smoothness value is large, that is, not smooth, and 10 bits is adopted when the smoothness value is intermediate.

  In step S3209, the shading interpolation accuracy is determined from the smoothness. In the PostScript language used in the present invention, the setsmoothness operator is prepared as a command for setting the smoothness when gradation drawing is performed. In this operator, an allowable error between the color value and the theoretical value at the time of interpolation is specified as a percentage. it can. The default value is changed to one of three levels of 2%, 1%, and 0.5% according to the smoothness obtained above. 0.5% is adopted when the smoothness value is small, ie, smooth, 2% is adopted when the smoothness value is large, ie, not smooth, and 1% when the smoothness value is intermediate. Is adopted. Note that the three values of the upper limit bit depth, color management calculation accuracy, and shading interpolation accuracy used during RIP are managed and stored in combination with the downloaded ICC profile.

Next, the flow of RIP processing for interpreting the page description language and forming an image will be described with reference to FIG.
The PostScript interpreter 3001 is one of the PDL Interpreters 1527 of FIG. 5, and interprets data 3015 described in the PostScript language to generate a display list 3017 that is intermediate language data. Each module in the PostScript interpreter 3001 is executed by pipeline, and each module from 3004 to 3011 is repeatedly executed for each drawing object. A display list for one page is generated when the processing for all the drawing objects in the same page is completed.

  The RIP detailed parameter 3016 is a parameter group applied at the time of RIP processing among information specified by the job ticket. The parameters given here include an output color mode, an RGB source profile, a CMYK simulation profile, and an output profile. As described above, the Job Ticket is interpreted by the Job-Ticket-Parser 1531 in FIG.

  Here, the description will be made on the assumption that the output color mode setting Auto for determining whether the entire page is color or monochrome depending on the color of the drawing object included in each page.

The language processing unit 3004 interprets the PostScript language data and issues a drawing request to each drawing processing unit of the character processing unit 3005, the graphics processing unit 3006, and the image processing unit 3007 in accordance with the drawing operator.
The character processing unit 3005 generates a character bitmap from a specified font. The graphics processing unit 3006 controls vector graphics drawing, and the image processing unit 3007 performs processing for converting image data into a common internal data format.

  The CMS engine 3008 is a module that performs color management, and generates an output color (CMYK) specific to the printer engine after converting the input color into an absolute color space. In the PostScript language, various color spaces such as a device (Device) color space, a CIEBased color space, and a special color space are defined. For the input color specified in the device color space, color conversion is performed using a specified one of ICC profile groups prepared in advance such as an RGB source profile and a CMYK simulation profile.

  For input colors specified in the CIEBased color space, color conversion is performed according to the conversion table, conversion function, and conversion matrix specified in the color space. Conversion from the absolute color space to the color space specific to the printer engine is performed using an output profile or CRD (Color Rendering Dictionary) defined by PostScript. Regarding the output profile, a gray compensation profile giving priority to expressing the gray scale in K single color and a normal profile expressing the gray scale in four colors of CMYK are prepared in advance. In addition to these two profiles, any of the profiles downloaded by the user can be selectively used.

  The spot color specified in the Separation color space or the DeviceN color space is converted into a process color (CMYK) using a Named ICC profile. When the designated output profile is a profile downloaded by the user, the following is performed. That is, the upper limit bit depth, color management calculation accuracy, and shading interpolation accuracy that are managed in combination with the profile and used during RIP are read and changed from the default values.

  The shading interpolation accuracy is referred to by the graphics processing unit 3006. When the shading designation is included in the print data, the shading interpolation accuracy is used for processing. The color management calculation accuracy is referred to when the input color value is color-converted, and is handled as the number of bits when the color value specified by the floating point is quantized. Further, the number of bits of the output value after color conversion differs depending on the upper limit bit depth, and the number of bits is used in the subsequent rendering processing.

  A color determination unit 3009 examines CMYK colors, which are output values of the CMS engine, and determines whether the currently processed page is a color page or a monochrome page. The color determination is executed only when Auto is designated by the output color mode of the RIP detailed parameter. In addition to the output color mode, color and monochrome can be specified, but color determination is not executed when color or monochrome is specified. Details of the color determination method will be described later.

  The display list generator 3011 generates a display list 3017 that is intermediate language data. The display list 3017 includes an attribute flag for each object, and identifies whether the object is a graphic, an image, or a character. The attributes notified from the character processing unit 3005, the graphics processing unit 3006, and the image processing unit 3007 are used as they are. The attribute flag is used for subsequent image processing via the render 3002. The display list 3017 includes raster operation information for each object, and identifies whether the object needs raster operation processing.

  The renderer 3002 interprets the display list 3017 and generates CMYK bitmaps 3018 each having a bit depth of M × 4, and performs most of the processing using the RIP 2060 of FIG. The bit depth M is 8, 10, or 12, depending on the value of the upper limit bit depth. The renderer 3002 has raster operation modes such as Mask (result = src & dest), Copy (result = src), and Merge (result = src | dest). The renderer 3002 executes a raster operation process between the already drawn drawing object (background, dest) and the drawing object to be drawn next (foreground, src) in accordance with the raster operation mode specified for each drawing object. . Then, the drawing result (result) is developed on the page memory.

  Also, the renderer 3002 generates an object attribute map 3019 indicating attributes for each device pixel unit as the fifth version based on the attribute flags included in the display list 3017. Here, the object attribute map has attribute information of bit depth 2 (graphics 01, image 10, character 11) for each pixel. Next, the CMYK bitmap 3018 and the object attribute map (object attribute information) 3019 are sent to the image processor 3003.

  The image processor 3003 is controlled by the Printer Manager 1526 shown in FIG. The image processor 3003 performs image processing such as density / color balance adjustment 3012, output gamma correction 3013, and halftoning 3014 on the CMYK bitmap 3018 generated by the render 3002.

  Halftoning 3014 refers to the object attribute map 3019 and applies different halftoning for each object attribute. Specifically, a resolution-prioritized high-frequency screen is used for graphics attribute image areas, a gradation-priority low-resolution screen is used for image attribute image areas, and character attribute image areas. Applies error diffusion.

  If the color determination unit 3009 determines that the page is a monochrome page, only the K version bitmap of the CMYK bitmap 3018 created by the render 3002 is sent to the image processor 3004 and used in the final output. A map 3021 is generated. If the color determination unit 3009 determines that the page is a color page, the CMYK bitmap 3018 generated by the render 3002 is sent to the image processor 3002 as it is, and a CMYK bitmap 3020 used for final output is generated. The

  In this way, the CMYK bitmap 3020 or the K bitmap 3021 generated by the image processor 3003 is transferred to the printer engine via the engine I / F 1529 of FIG. 5 and printed out on a desired medium.

  The present invention may be applied to a system including a plurality of devices including a printer (for example, a host computer, an interface device, a scanner, a printer, etc.), or may be applied to a single printer device.

The processing method for storing the program for operating the configuration of the above-described embodiment so as to realize the function of the above-described embodiment in a storage medium, reading the program stored in the storage medium as a code, and executing the program on the computer is also described above. It is included in the category of the embodiment. In addition to the storage medium storing the above program, the program itself is included in the above embodiment.
As such a storage medium, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a magnetic tape, a nonvolatile memory card, and a ROM can be used.
In addition, the processing is not limited to a single program stored in the above-described storage medium, but operates on the OS in cooperation with other software and expansion board functions to execute the operations of the above-described embodiments. Those are also included in the category of the embodiment described above.

1 is a diagram illustrating a configuration of an entire system including an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration within a controller unit of the image forming apparatus. 2 is an external view of the image forming apparatus. FIG. 2 is an external view of an operation unit of the image forming apparatus. FIG. 2 is a software block diagram of the image forming apparatus. FIG. It is a system flow figure of the embodiment. It is a smoothness determination flowchart in the same embodiment. It is a figure which shows the three-dimensional table in the same embodiment. It is a figure which shows the example of output sampling in the same embodiment. It is a data flow figure of the embodiment.

Explanation of symbols

3001 PostScript Interpreter 3002 Render 3003 Image Processor 3004 Language Processing Unit 3005 Character Processing Unit 3006 Graphics Processing Unit 3007 Image Processing Unit 3008 CMS Engine 3009 Color Determination Unit 3011 Display List Generator 3012 Density / Color Balance Adjustment Unit 3013 Output Gamma Correction Unit 3014 Halftoning section 3015 PostScript data 3016 RIP detailed parameters 3017 Display list 3018 CMYK bitmap 3019 Object attribute information 3020 CMYK bitmap 3021 K bitmap

Claims (8)

Means for obtaining a conversion source profile for color conversion from a device-specific conversion source color space to a device-independent color space;
Means for obtaining a conversion destination profile for color conversion from a device-independent color space to a device-specific conversion destination color space;
Means for creating a table associating the conversion source color space with the conversion destination color space from the conversion source profile and the conversion destination profile;
Means for calculating the smoothness of the color change in the conversion destination color space with respect to the color change in the conversion source color space using the created table;
Means for determining color conversion accuracy based on the calculated smoothness;
Means for performing color conversion on the print data from the conversion source color space to the conversion destination color space according to the determined color conversion accuracy;
An image forming apparatus comprising: means for forming an image in accordance with the print data subjected to the color conversion. Means for obtaining a conversion source profile for color conversion from a device-specific conversion source color space to a device-independent color space;
Means for obtaining a conversion destination profile for color conversion from a device-independent color space to a device-specific conversion destination color space;
Means for creating a table associating the conversion source color space with the conversion destination color space from the conversion source profile and the conversion destination profile;
Means for calculating the smoothness of the color change in the conversion destination color space with respect to the color change in the conversion source color space using the created table;
Means for determining an upper limit bit depth based on the calculated smoothness;
RIP means for converting print data into bitmap data for image formation;
An image forming apparatus comprising: means for matching a bit depth of bitmap data generated by the RIP means with the upper limit bit depth. Means for obtaining a conversion source profile for color conversion from a device-specific conversion source color space to a device-independent color space;
Means for obtaining a conversion destination profile for color conversion from a device-independent color space to a device-specific conversion destination color space;
Means for creating a table associating the conversion source color space with the conversion destination color space from the conversion source profile and the conversion destination profile;
Means for calculating the smoothness of the color change in the conversion destination color space with respect to the color change in the conversion source color space using the created table;
Means for determining the interpolation accuracy of gradation drawing based on the calculated smoothness;
An image forming apparatus comprising: means for performing gradation drawing according to the determined interpolation accuracy. Obtaining a conversion source profile for color conversion from a device-specific conversion source color space to a device-independent color space;
Obtaining a conversion destination profile for color conversion from a device-independent color space to a device-specific conversion destination color space;
Creating a table associating the conversion source color space with the conversion destination color space from the conversion source profile and the conversion destination profile;
Using the created table to calculate the smoothness of the color change in the destination color space with respect to the color change in the source color space;
Determining color conversion accuracy based on the calculated smoothness;
Performing color conversion from the conversion source color space to the conversion destination color space for the print data according to the determined color conversion accuracy;
Forming an image according to the print data subjected to the color conversion. Obtaining a conversion source profile for color conversion from a device-specific conversion source color space to a device-independent color space;
Obtaining a conversion destination profile for color conversion from a device-independent color space to a device-specific conversion destination color space;
Creating a table associating the conversion source color space with the conversion destination color space from the conversion source profile and the conversion destination profile;
Calculating the smoothness of the color change in the conversion destination color space with respect to the color change in the conversion source color space using the created table;
Determining an upper limit bit depth based on the calculated smoothness;
And a step of generating and outputting bitmap data for image formation by matching an output bit depth to the determined upper limit bit depth. Obtaining a conversion source profile for color conversion from a device-specific conversion source color space to a device-independent color space;
Obtaining a conversion destination profile for color conversion from a device-independent color space to a device-specific conversion destination color space;
Creating a table associating the conversion source color space with the conversion destination color space from the conversion source profile and the conversion destination profile;
Calculating the smoothness of the color change in the conversion destination color space with respect to the color change in the conversion source color space using the created table;
Means for determining the interpolation accuracy of gradation drawing based on the calculated smoothness;
And a step of performing gradation drawing according to the determined interpolation accuracy.   A program comprising program code for causing a computer to execute each step of the image forming method according to claim 4. Evaluate the smoothness of the table obtained based on the profile,
Storing the evaluation result corresponding to the profile;
An image processing method for determining accuracy in color conversion processing for print data based on color conversion accuracy determined according to the smoothness.

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