JP2009077343A - Color conversion circuit and color printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color conversion circuit capable of realizing a color printer which can always perform ground tint printing (ground tint printing which does not show ground tint embedded) successfully. <P>SOLUTION: A color conversion circuit carries out color conversion of RGBX data for color printers into CMYK data by using LUT (Look Up Table) depending on X data. The color conversion circuit is designed and manufactured as a circuit generating a CMYK data group in which (a part of) ground tint data is embedded by processing only RGBX data relating to pixels (with a predetermined attribute) to which color conversion into CMYK is carried out by a predetermined color and a predetermined LUT. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a color conversion circuit for a color printer and a color printer.

  In recent color printers, in order to prevent unauthorized copying, etc., printing embedded with an image that is not visible to the human eye (hereinafter referred to as background pattern) (unauthorized copy suppression background pattern printing, forgery suppression) There is an apparatus capable of performing what is called background pattern printing (hereinafter referred to as background pattern printing).

  Such a color printer generates RGB image data obtained by synthesizing RGB image data of an image to be printed and copy-forgery-inhibited pattern data (image data of the copy-forgery-inhibited pattern), and converts the RGB image data into CMYK image data to thereby generate a copy-forgery-inhibited pattern data. It is a device that performs printing (for example, refer to Patent Document 1), and always has a complicated process (each copy-forgery-inhibited pattern printing and normal printing) in which each RGB data is converted into CMYK data using an LUT corresponding to the attribute. The apparatus converts RGB image data into CMYK image data by color conversion processing. The attribute is information indicating which type of object (character, graphic, etc.) the pixel is associated with.

  Since the apparatus adopts such a configuration, an existing color printer capable of printing a background pattern is an apparatus in which a portion of the background pattern may be printed in a visible form when the background pattern is printed. ing.

JP 2005-94326 A

  Accordingly, an object of the present invention is to always provide a color printer capable of performing excellent background pattern printing (background pattern printing in which it is not known that the background pattern is embedded) and to easily manufacture such a color printer. A color conversion circuit is provided.

  In order to solve the above problems, a color conversion circuit according to the present invention, a copy-forgery-inhibited pattern data storage circuit for storing copy-forgery-inhibited pattern data as image data to be embedded in a print result, and RGB indicating the color of a certain pixel For each RGBX data in RGBX image data including RGBX data composed of data and X data indicating the attribute of the pixel for each of a plurality of pixels, the RGBX data is data relating to a pixel having a predetermined color and a predetermined attribute. A determination / color conversion circuit that converts the RGBX data into CMYK data using an LUT corresponding to the X data in the RGBX data, and a determination / color conversion circuit to determine a predetermined color and , Each CM generated by the determination / color conversion circuit from each RGBX data determined to be data relating to a pixel having a predetermined attribute For K data, a predetermined calculation is performed using the CMYK data and data relating to the pixel corresponding to the pixel in which the CMYK data indicates the color in the tint block data stored in the tint block data storage circuit as parameters. A CMYK data output circuit that performs a process of generating and outputting CMYK data by performing the process and outputting other CMYK data generated by the determination / color conversion circuit as it is is provided.

  That is, the color conversion circuit of the present invention processes only the RGBX data relating to pixels (predetermined attribute pixels) that are subjected to color conversion to CMYK using a predetermined color and a predetermined LUT (lookup table). A circuit that generates a CMYK data group in which (a part of) the data is embedded [the CMYK data group related to the copy-forgery-inhibited pattern portion in the processing result is converted into CMYK by an LUT for an attribute different from “predetermined attribute”. Circuit that does not include data]. Therefore, if the color conversion circuit of the present invention is used, a color printer (color printer or the like according to claim 3) capable of always performing good background pattern printing (background pattern printing in which the background pattern is not embedded) is manufactured. It will be possible.

  In realizing the color conversion circuit of the present invention, it is not necessary to set the “predetermined color” as one color, and a color satisfying a certain condition is handled as the “predetermined color” (the determination / color conversion circuit is changed). If the color of a certain RGBX data satisfies a certain condition, the circuit can determine that the color of the RGBX data is a “predetermined color”. When implementing the color conversion circuit of the present invention, the determination / color conversion circuit is a circuit that can set a predetermined color and a predetermined attribute (a circuit that can change the predetermined color and the predetermined attribute from the outside). You can also.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, a color printer 10 according to an embodiment of the present invention includes a control unit 12 including a CPU, a RAM 14, a ROM, a printer ASIC 15 and the like as main components, and an operation panel 11. And a color printing engine 13.

  The operation panel 11 is a unit provided in the color printer 10 as an interface means with the user. The operation panel 11 is a unit composed of an LCD, a plurality of push button switches, and the like.

  The color printing engine 13 is a printing engine capable of color printing. Note that the color printer 10 according to the present embodiment is an apparatus in which an electrophotographic printer is used as the print engine 13.

  The control unit 12 is a unit for operating the color printer 10 as an apparatus capable of normal printing and tint block printing. When the control unit 12 receives print data (page description language format) for instructing copy-forgery-inhibited pattern printing, the control unit 12 generates RGBX image data on the RAM 14 based on the print data, and performs copy-forgery-inhibited pattern print for the RGBX image data. By causing the printer ASIC 15 to perform this process, the color print engine 13 is a unit that performs tint block printing. Note that the RGBX image data includes, for each pixel, RGB data indicating the color of the pixel (in this embodiment, a total of 24 bits of data of 8 bits for each color) and some bits (in this embodiment, the first bit). 6th and 7th bits; hereinafter referred to as attribute bits) indicates the attribute of the pixel (information indicating whether the pixel is a character, graphic, image, or other pixel). X data (in this embodiment, 8-bit data including unused bits).

  Like the existing printer ASIC, the printer ASIC 15 used in the color printer 10 converts the RGBX image data into CMYK image data (CMYK data group) from the color conversion circuit in the self ASIC, and then the CMYK. This is a circuit that generates screen data for driving the color printing engine 13 by performing screen processing (processing called halftone processing) on the image data and supplies the data to the color printing engine 13.

  However, the printer ASIC 15 is an ASIC equipped with the color conversion circuit 20 having the configuration shown in FIG. 2 as a color conversion circuit.

  The first comparison circuit 21 in the color conversion circuit 20 has all the R, B, and G component values of the RGBX data to be processed (RGBX data to be processed this time in the RGBX image data on the RAM 14) “FF”. Only when “(= 255)”, this is a circuit that sets “1” to a predetermined unused bit (hereinafter referred to as a color bit) of X data.

  The second comparison circuit 22 is a circuit (a circuit having a color register in which an external circuit (CPU) can write data) that can set colors (R value, G value, and B value). is there. In the second comparison circuit 22, each color component value of the input RGBX data (RGBX data for which the processing (comparison) by the first comparison circuit 21 has been completed) is greater than or equal to the corresponding color component value of the set color. In this case, the circuit sets the color bit of X data to “1”.

  The RGB / CMYK color conversion circuit 23 converts the input RGBX data (RGBX data for which processing (comparison) by the second comparison circuit 22 has been completed) into the value of its attribute bits (sixth and seventh bits in the X data). Is a circuit that converts data into CMYK data using an LUT (Look Up Table) according to the above.

  The embedding necessity determination circuit 24 has a circuit (a register for embedding attribute bit value) in which an embedding attribute bit value (2-bit value) can be set, and an external circuit (CPU) writes data to the register. Circuit). Then, the embedding necessity determination circuit 24 has the color bit value of RGBX data (the X data in the RGBX data) in which the color conversion by the RGB / CMYK color conversion circuit 23 has been completed, and the value of the attribute bit However, if it matches the set embedding attribute bit value, “1” is output, and if not, “0” is output.

  The four selectors 27 to which the output of the embedding necessity determination circuit 24 and the like are input are output from the RGB / CMYK color conversion circuit 23 when “0” is input from the embedding necessity determination circuit 24. When 8-bit data (C, M, Y, or K data) is output and “1” is input from the embedding necessity determination circuit 24, 8-bit data from the OR gate 26 (for details, see FIG. Is a circuit that outputs (described later).

  The copy-forgery-inhibited pattern data supply circuit 25 includes image data (a kind of monochrome image data) including 2-bit pixel data for each pixel, LX and LY indicating the size of the image data, and X0 for designating an embedding start position. And Y0 can be set. The copy-forgery-inhibited pattern data supply circuit 25 receives, from the RGB / CMYK color conversion circuit 23, coordinates (x0, Y0) and coordinates (x0 + LX-1, Y0 + LY-1) in a rectangular area having diagonal vertices. , Y) is a circuit configured to output “FF-n (x−X0, y−Y0)” when the CMYK data regarding the pixel of (y) is output. Note that n (x−X0, y−Y0) is pixel data (2-bit data) relating to the pixel at coordinates (x−X0, y−Y0) in the image data set in the tint block data supply circuit 25. ).

  The OR gate 26 for each color in the color conversion circuit 20 includes 8-bit data from the tint block data supply circuit 25 and 8-bit data (C, M, Y, or K data) from the RGB / CMYK color conversion circuit 23. Is a circuit that performs an OR operation for each bit and outputs the operation result.

  In short, the color conversion circuit 20 mounted on the printer ASIC 15 is configured to display RGBX data (the attribute bit value of which is the same as the embedded attribute bit value) for a predetermined color and a pixel whose color conversion to CMYK is performed by a predetermined LUT. By processing only the RGBX data), a CMYK data group in which the copy-forgery-inhibited pattern data (a part of) is embedded is generated. The printer ASIC 15 is a circuit that generates data for driving the color print engine 13 by performing screen processing on the CMYK data group generated by the color conversion circuit 20 and supplies the data to the color print engine 13. Therefore, it can be said that the color printer 10 according to the present embodiment is a device that can always perform good background pattern printing (background pattern printing in which it is not known that the background pattern is embedded).

<Deformation>
The color printer 10 and the color conversion circuit 20 described above can be modified in various ways. For example, the color conversion circuit 20 can be modified to a circuit that does not include the second comparison circuit 22. When the color conversion circuit 20 is modified to such a circuit, the tint block data supply circuit 25 can be modified to a circuit that can store only 1-bit pixel data.

  In addition, the color conversion circuit 20 can be modified into a circuit that can set color image data as copy-forgery-inhibited pattern data. However, since the color conversion circuit 20 capable of setting color image data as the copy-forgery-inhibited pattern data has to be large in scale, it is desirable to adopt the above configuration.

  The color conversion circuit 20 is a circuit that embeds copy-forgery-inhibited pattern data in white and a portion close to white. However, the color conversion circuit 20 is replaced with black ((R, G, B) = (0, 0, 0)) or It can be modified to a circuit that embeds copy-forgery-inhibited pattern data in a portion close to black or a circuit that can embed copy-forgery-inhibited pattern data in a portion close to black or black. Further, the color printer 10 is an apparatus having only a printing function, but it is natural that the color printer 10 may be transformed into an apparatus (such as a multifunction machine) having other functions.

1 is a configuration diagram of a color printer according to an embodiment of the present invention. FIG. 1 is a configuration diagram of a color conversion circuit mounted on a printer ASIC in a color printer according to an embodiment. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Color printer, 11 Operation panel, 12 Control part 13 Color printing engine, 14 RAM, 15 ASIC for printers
20 color conversion circuit, 21 first comparison circuit, 22 second comparison circuit, 23 RGB / CMYK color conversion circuit, 24 embedding necessity judgment circuit, 25 tint block data supply circuit, 26 OR gate, 27 selector

Claims (3)

A color conversion circuit used in a color printing apparatus,
A tint block data storage circuit for storing tint block data which is image data to be embedded in the print result;
For each RGBX data in RGBX image data including RGBX data composed of RGB data indicating the color of a pixel and X data indicating the attribute of the pixel for each of a plurality of pixels, the RGBX data has a predetermined color, and , A determination / color conversion circuit that determines whether or not the data relates to a pixel having a predetermined attribute, and converts the RGBX data into CMYK data using an LUT corresponding to the X data in the RGBX data;
For each CMYK data generated by the determination / color conversion circuit from each RGBX data determined by the determination / color conversion circuit as data relating to a pixel having a predetermined color and a predetermined attribute, the CMYK data and The CMYK data is generated by performing a predetermined calculation using as parameters the pixels for which the CMYK data indicates the color and the data relating to the corresponding pixels in the background pattern data stored in the background pattern data storage circuit. A color conversion circuit comprising: a CMYK data output circuit that performs a process for outputting the data and outputs the other CMYK data generated by the determination / color conversion circuit as it is. The determination / color conversion circuit is
The color conversion circuit according to claim 1, wherein the predetermined color and the predetermined attribute are settable. A color printing engine,
An RGBX image data representing an image to be printed on paper based on the print data when the print data is received when the color conversion circuit according to claim 1 or 2 is received. RGBX image data including RGBX data including RGB data indicating color and X data indicating the attribute of the pixel is generated for each of a plurality of pixels, and the RGBX image data is generated based on a processing result by the color conversion circuit. A color printer comprising: a control unit having a function of operating a color printing engine.

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