JP2007136845A - Printing system, image processor, printer driver, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printing system or the like that eliminates color unevenness due to a difference in overlapping order of coloring agents in reciprocation printing without reducing printing speed. <P>SOLUTION: A printing system is provided with a color processing LUT composed of color processing LUTs 33a, 33b, which are for deciding a blend ratio of the coloring agents of multiple colors, and an interpolation calculation module 27, which executes interpolation calculation processing for estimating a value not existing on the color processing LUT, so as to execute color matching processing S02 corresponding to the coloring agents of multiple colors to image data by using the color processing LUT and the interpolation calculation module. The color processing LUT is composed of two color processing LUTs respectively for forward printing and backward printing. Color conversion processing is executed by referring to the color processing LUT for the forward printing and that of for the backward printing respectively after decomposing the image data into forward image-data for the forward printing and backward image-data for the backward printing in the color matching processing. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  Printing system, image processing apparatus, and printer driver comprising a host computer that stores or generates image data to be printed and a printer that performs reciprocal printing using a plurality of colorants based on instructions from the host computer , Related to the program.

Conventionally, in a printer that performs printing in synchronization with the operation of the print head in the main scanning direction and the paper feeding operation in the sub-scanning direction, reciprocal printing that performs printing in both the forward and backward paths of the print head in order to improve the printing speed Bidirectional printing) is known. This reciprocating printing is a technology that is widely used in ink jet printers that are widely used in recent years. However, the print head of an inkjet printer generally has nozzle rows corresponding to each color of K (black), M (magenta), Y (yellow), and C (cyan) arranged in the main scanning direction (each nozzle row is Therefore, when a color image is printed, there is a problem that uneven color occurs due to a difference in the overlapping order of ink in the forward path and the backward path. Therefore, if the number of ink dots of the color tone that forms the achromatic color component is calculated from the image data and it is determined that color unevenness is unlikely to occur, reciprocal printing is performed, and conversely if color unevenness is likely to occur, A solution for performing unidirectional printing has been proposed (see, for example, Patent Document 1).
JP 2003-305838 A

  However, in the above method, it is necessary to determine whether or not color unevenness is likely to occur, and depending on the determination result, unidirectional printing is performed, so that the throughput is significantly reduced depending on the color tone of the image data. There is. In other words, there is a contradiction that despite the use of reciprocating printing to improve printing speed, it cannot be used effectively.

  In view of such problems, the present invention eliminates color unevenness due to the difference in the order of colorant overlap in reciprocating printing without reducing the printing speed, and can contribute to further improvement in image quality. It is an object to provide a processing device, a printer driver, and a program.

  A printing system according to the present invention includes a host computer that stores or generates image data to be printed, and a printer that performs reciprocal printing using a plurality of colorants based on instructions from the host computer. A color processing table for determining a mixing ratio of a plurality of colorants, an interpolation calculation module for performing an interpolation calculation process for estimating a value that does not exist on the color processing table, and image data, A color conversion processing unit that performs color conversion processing according to a plurality of colorants using a color processing table and an interpolation calculation module; a printing unit that performs reciprocal printing by a printer based on the data after the color conversion processing; The color processing table is composed of two color processing tables for forward printing and for backward printing, and the color conversion processing means Decomposed into return image data of the forward image data and backward printing for printing, respectively with reference to the color processing table and for forward printing and backward printing, and performs the color conversion process.

  According to this configuration, the image data is separated into forward image data for forward printing and backward image data for backward printing, and color conversion processing is performed with reference to the color processing tables for forward printing and backward printing, respectively. Therefore, by designing each color processing table so as to eliminate the color unevenness based on the experimental value, it is possible to prevent the image quality from being deteriorated in the reciprocating printing. In addition, since values that do not exist on the color processing table are estimated by the interpolation calculation processing of the interpolation calculation module, the amount of data to be described on the color processing table can be reduced. Note that the color processing table, the interpolation calculation module, and the color conversion processing means may be mounted on either the host computer or the printer.

  In the printing system described above, the color conversion processing means includes an additive color mixture ratio determining means for determining the additive color mixture ratio for each pixel of the forward pass image data or the return pass image data, and the determined additive color mixture ratio. Color processing table discrimination means for discriminating whether or not the corresponding subtractive color mixing value exists on the color processing table for forward pass printing or return pass printing, and the ratio of subtractive color mixing exists on the color processing table The color reduction mixing ratio that determines the ratio of color reduction mixing by performing interpolation calculation processing using an interpolation calculation module when the value is determined as the ratio of color reduction mixing and there is no ratio of color reduction mixing on the color processing table. And determining means.

  According to this configuration, since the interpolation calculation process using the interpolation calculation module is performed only when the ratio of the subtractive color mixture does not exist on the color processing table, the memory capacity for storing the color processing table and the interpolation calculation process are controlled. The data amount of the color processing table can be determined according to the balance with the control capability. That is, when there is no limit on the memory capacity, the control load can be reduced by increasing the data amount of the color processing table. When a high-performance CPU is used, the data amount of the color processing table can be reduced. Can do.

  In the printing system described above, it is preferable that the interpolation calculation module performs the interpolation calculation process by using any one of cubic interpolation, triangular prism interpolation, tetrahedral interpolation, and hexahedral interpolation.

  According to this configuration, highly accurate color conversion processing can be performed by an interpolation method such as cubic interpolation, triangular prism interpolation, tetrahedral interpolation, or hexahedral interpolation.

  In the printing system described above, the first halftone processing unit that performs halftone processing on the forward image data and the backward image data after the color conversion processing by the color conversion processing unit, and the processing by the first halftone processing unit, respectively. Prior to the second halftone processing means for performing halftone processing for error calculation and the preceding error value generated by the processing of the forward image data by the second halftone processing means, the first half of the forward image data A forward error buffer for storing an error value generated by the halftone processing means, and a preceding error value generated by processing of the return image data by the second halftone processing means, followed by the first halftone processing means for the return image data. A return path error buffer for storing error values generated by the first halftone processing means; Stored in the forward data buffer for storing the processing results of the forward image data, the backward data buffer for storing the processing results of the backward image data by the first halftone processing means, the forward data buffer, and the backward data buffer. Data output means for alternately switching and outputting the processed results as data for printing by the printing means, and the first halftone processing means is stored in the forward path error buffer and the backward path error buffer. It is preferable to start halftone processing of the forward pass image data and the return pass image data, respectively, using the preceding error value.

  According to this configuration, when the processed data after the halftone processing is alternately output from the two data buffers of the forward pass data buffer and the return pass data buffer, the normal halftone processing of each image data is preceded. Halftone processing for error calculation is performed, and the preceding error value generated thereby is stored in the forward error buffer or the backward error buffer, so that the error buffer is not cleared when the data buffer is switched. (Because the preceding error value is already stored immediately after switching). That is, the first halftone processing unit starts the halftone process upon receiving the propagation of the preceding error value calculated by the second halftone processing unit (using the preceding error value stored in the error buffer in advance). Therefore, even when two data buffers are switched and used, the problem of image quality degradation caused by initialization of the error buffer can be solved.

  An image processing apparatus according to the present invention includes a color conversion processing unit in the printing system described above.

  A printer driver according to the present invention includes a color conversion processing unit in the printing system described above.

  The program of the present invention is a program for causing a computer to function as color conversion processing means in the printing system described above.

  By using these, color unevenness due to the difference in the order of colorant overlap in reciprocal printing can be eliminated and the image quality can be further improved without reducing the printing speed.

  Hereinafter, a printing system, an image processing apparatus, a printer driver, and a program according to an embodiment of the present invention will be described with reference to the accompanying drawings. The present invention decomposes image data into forward image data for forward printing and backward image data for backward printing, and performs color conversion processing with reference to color processing tables for forward printing and backward printing, respectively. Thus, it is an object to prevent the occurrence of color unevenness in the main scanning direction in reciprocating printing. Therefore, a case where the color conversion processing means in the printing system of the present invention is installed in a computer as a printer driver will be described as an example, and a printing system including the computer (host computer) and a printer will be described. As an example of the printer, an inkjet printer is used.

  FIG. 1 is a block diagram of a printing system 10 according to an embodiment of the present invention. As shown in FIG. 1, the printing system 10 stores or generates various data and converts the data into print data (ink discharge data), and performs printing based on the print data output from the host computer 20. Printer 40 to be performed.

  The host computer 20 controls an application 21 that is a program for generating various data (hereinafter referred to as “image data”) that requires halftone processing (binarization processing), and the host computer 20. An OS (operating system) 22 that is a basic program, a printer driver 23 that performs image processing and command conversion processing including color conversion processing and halftone processing, and print data (processed data after image processing) are sent to the printer 40. And a print data output unit 24 for outputting.

  The printer driver 23 includes a driver upper layer 25 that performs rendering processing and the like, and an image processing module 26. The image processing module 26 includes three modules: a control module 30, a color matching & halftone module (color conversion processing means, first halftone processing means, second halftone processing means) 31 and a command conversion module 32. Yes.

  The control module 30 performs overall control of the color matching & halftone module 31 and the command conversion module 32 and performs control for supplementing the functions of the modules 31 and 32.

  The color matching & halftone module 31 performs color matching processing (color conversion processing) with reference to the color processing LUT (color processing table) 33 and determines the presence / absence of dots of the colorant with reference to the dot generation LUT 34. To do. Examples of dot types include four types: level 0: no dot, level 1: small dot, level 2: medium dot, and level 3: large dot. Of these, you can decide what level to use and what percentage. When aiming for high image quality, not only four types but also more detailed dot stages may be set. The color matching & halftone module 31 has an interpolation calculation module 27, and estimates a value that does not exist on the color processing LUT 33 by the interpolation calculation during the color matching process (details will be described later). ).

  Further, the color matching & halftone module 31 performs halftone processing (error diffusion processing) using the error diffusion method, stores the error value generated by the halftone processing in the error buffer 35, and the processing result of the halftone processing Is stored in the data buffer 36. The data stored in the data buffer 36 is output to a storage area called a command conversion buffer 37 every predetermined amount for subsequent command processing.

  Further, the command conversion module 32 refers to the command conversion table 38, performs command processing for conversion into a command format that can be decoded by the printer 40, and outputs the data after the command processing to the command processing buffer 39.

  On the other hand, the printer 40 stores a print data input unit 41 that inputs (acquires) print data output from the host computer 20, a print buffer 42 that temporarily stores the input print data, and the print buffer 42. And a printing unit 43 that performs reciprocal printing based on the print data.

  The printing unit 43 includes a carriage 44, a carriage motor 46, a print head (inkjet head) 47, and a paper feed motor 48. The carriage motor 46 reciprocates the carriage 44 on which the print head 47 is mounted in the main scanning direction. Let Further, the paper feed motor 48 transports the print medium (paper) 51 (see FIG. 3) in the sub-scanning direction. A desired print image is formed on the print medium 51 by synchronizing the drive of the carriage motor 46 and the paper feed motor 48 with the ink ejection operation from the print head 47.

  Next, the configuration of the carriage 44 (print head 47) will be described with reference to FIG. This figure is a plan view of the carriage 44 as seen from the nozzle surface side. In this embodiment, K (black), M (magenta), Y (yellow), and C (cyan) are formed on one carriage 44. Four print heads 47 corresponding to each color are mounted.

  The print heads 47 are arranged in the main scanning direction (movement direction of the carriage 44) in the order of K → M → Y → C. In forward printing, ink is ejected in the order of K → M → Y → C. In return pass printing, ink is ejected in the order of C → Y → M → K. Therefore, since the ink ejection order is different between the forward path and the backward path, the ink stacking order is changed, and the color development characteristics are changed between the forward path and the backward path. Therefore, when the same image processing (color conversion processing) is performed in both directions, color unevenness occurs between the forward printing area and the backward printing area. For this reason, in this embodiment, in the color matching process, two color processing LUTs 33a and 33b (see FIG. 4) for forward pass printing and reverse pass printing are used, and color unevenness caused by the difference in the ink ejection order is used. (The details will be described later).

  Each print head 47 is formed with two nozzle rows 52 along the sub-scanning direction, and 180 nozzles 53 are arranged in each nozzle row 52 at a pitch of 180 dpi. In addition, since the two nozzle rows 52 of each print head 47 are shifted from each other by half a pixel, the nozzles 53 are substantially arranged in a row at a pitch of 360 dpi. It is in the same state as that.

  Next, the operation of the carriage 44 will be described with reference to FIG. This figure shows the relative positional relationship between the print medium 51 and the carriage 44, and the carriage 44 moves relative to the print medium 51 in the direction of the arrow shown. If the position indicated by the dotted line in the figure is the print start position (home position) P, first, printing is performed while moving the carriage 44 to the right in the main scanning direction. Further, when printing is completed up to the right end of the print image, the carriage 44 is temporarily stopped to move, waits for paper feeding in the upward direction in the figure, and is then printed while moving to the left in the main scanning direction. When printing is completed up to the left end of the print image, the carriage 44 stops moving, and after the paper is fed in the upward direction in the figure, printing is performed again toward the right in the main scanning direction.

  In this way, printing is performed while repeating the printing in the main scanning direction and the paper feeding operation in the sub-scanning direction. Hereinafter, printing when moving to the right in the main scanning direction is referred to as “outward printing”. Printing when moving to the left in the scanning direction is referred to as “return printing”. Further, image data for one pass corresponding to a print image in a print area printed by forward printing or backward printing is referred to as “partial image data”.

  That is, the image data generated by the application 21 is divided into n partial image data (however, an integer satisfying n ≧ 1) by the printer driver 23, and among these, the first partial image data (first partial data) Image data) is printed by the first forward printing. Further, the second partial image data (second partial image data) is printed by the subsequent backward printing, and the third partial image data (third partial image data) is printed by the subsequent forward printing. That is, odd-numbered partial image data is printed by forward printing, and even-numbered partial image data is printed by backward printing. When printing of all print images based on the image data (n partial image data) is completed, the carriage 44 is moved to the print start position P and waits for the next print instruction.

  Next, with reference to FIG. 4, the outline and process of various processes in the printer driver 23 will be described. When acquiring the image data D generated by the application 21 (see FIG. 1), the printer driver 23 first performs rendering by the driver upper layer 25 (S01). Rendering is a process of imaging information related to an object or a figure given as numerical data by calculation. This process is executed when the acquired image data corresponds to numerical data.

  Subsequently, the printer driver 23 performs color matching processing by the image processing module 26 (S02). Here, the RGB multi-value data is color-converted into CMYK ink multi-value data by using the two color processing LUTs 33a and 33b for the forward pass printing and the return pass print and the interpolation calculation module 27.

  When the color matching process is finished, a halftone process is subsequently performed (S03). Here, halftone processing using the error diffusion method is performed for each partial image data based on the processing result of the color matching processing and the reference results of the two dot generation LUTs 34a and 34b for forward pass printing and return pass printing.

  In the present embodiment, since the two dot generation LUTs 34a and 34b for forward pass printing and reverse pass printing have the same contents, only one is provided in the image processing module 26 and is used for bidirectional printing. Anyway. Further, the contents of the dot generation LUTs 34a and 34b may be changed for forward printing and for backward printing to further improve the image quality.

  When the halftone processing is completed, the binarized data (for example, four types of data of level 0: no dot, level 1: small dot, level 2: medium dot, level 3: large dot. Aiming for high image quality). In this case, the command conversion process is performed based on the data in which not only the four types but also the dot stage is set more finely (S04), and the data is output to the printer 40. Note that the processes from S02 to S04 are all executed by the image processing module 26.

  Next, the color matching process (S02) will be described in detail with reference to FIGS. FIG. 5 shows an example of two color processing LUTs (outbound path color processing LUT 33a and inbound path color processing LUT 33b) for forward path printing and backward path printing. The color processing LUTs 33a and 33b are color conversion tables for converting RGB (additional color mixture ratio) to CMYK (subtractive color mixture ratio) as described above, and each RGB 8-bit (decimal 0 to 255) data. Are assigned to each 8 bits of CMYK (0 to 255 in decimal). When aiming for high image quality, resolution can be improved by assigning multiple bits such as 16 bits instead of 8 bits. Further, the color processing LUTs 33a and 33b are composed of a list of binary data, and the data are listed in the order of CMYK as shown (C1M1Y1K1, C2M2Y2K2... CnMnYnKn).

  However, since there are 256 (0 to 255) cubes = about 16.77 million combinations of all RGB, it is not practical to describe all these combinations on the table. Therefore, specific RGB values are determined in advance, and only the CMYK values (values for determining the ink ejection amount) corresponding to these values are described in the color processing LUTs 33a and 33b. Therefore, for example, when RGB is set to 10 grids, the color processing LUTs 33a and 33b are configured with 10 3 = 1000 grids. The number of grids affects the accuracy of the color to be output. The larger the number of grids, the better the accuracy, but there are also adverse effects such as an increase in capacity, so the number of grids is determined in consideration of the balance with the product. FIGS. 7A and 7B show a part of the color processing LUTs 33a and 33b.

  For example, as shown in FIG. 6A, the ratio of the additive color mixture of arbitrary pixels included in the image data (odd-numbered partial image data) to be subjected to forward printing is R = 100, G = 30, When B = 90 (decimal system) and the corresponding color reduction mixing ratio (CMYK combination) is present in the outbound color processing LUT 33a, the ratio of color reduction mixing (C = 40, M = 120, Y = 34, B = 63 (decimal system)), the ink amount of each color is determined.

  Further, as shown in FIG. 5B, the ratio of the additive color mixture of arbitrary pixels included in the partial image data (even-numbered partial image data) to be subjected to the backward printing is similarly R = 100, G = 30 and B = 90 (decimal system), and if the corresponding color reduction mixing ratio (CMYK combination) exists in the return color processing LUT 33b, the ratio of the color reduction mixing (C = 35, M = 128, Y = 35, B = 66 (decimal system)), the ink amount of each color is determined.

  As described above, even when the ratio of the additive color mixture is the same, the ratio of the subtractive color mixing described in the forward color processing LUT 33a and the backward color processing LUT 33b does not necessarily match. This is in consideration of the difference in the overlapping order of inks (in the order of K → M → Y → C in forward printing, and in the order of C → Y → M → K in backward printing, FIG. 2). As a result, color unevenness between the print area where the forward printing is performed and the printing area where the backward printing is performed is prevented.

  By the way, as described above, when each color processing LUT 33a, 33b is 1000 grids, this number of grids cannot cope with the actual processing, so the number of grids needs to be expanded to a combination of all RGB. Therefore, in the present embodiment, interpolation calculation is performed using the interpolation calculation module 27 (see FIG. 4), and CMYK values based on RGB values not existing on the grid are estimated. First, the processing steps of the color matching process by the color matching & halftone module 31 will be described with reference to the flowchart of FIG.

  The color matching & halftone module 31 determines (calculates) RGB values (additional color mixture ratio) based on the rendered image data (S06, additive color mixture ratio determining means). Next, it is determined whether or not the CMYK value corresponding to the RGB value is a value on the grid of each of the color processing LUTs 33a and 33b (S07, color processing table determination means). When CMYK values corresponding to RGB values exist as in the example shown in FIG. 5 (S07: Yes), CMYK values are determined with reference to the values of the color processing LUTs 33a and 33b (S08, color reduction). Mixing ratio determining means). On the other hand, if the value is not on the grid (S07: No), the CMYK value is determined (estimated) by the interpolation calculation by the interpolation calculation module 27 (S09, subtractive color mixture ratio determining means).

  Here, the principle of the interpolation calculation process will be briefly described with reference to FIGS. Here, a case where “tetrahedral interpolation” is employed as an interpolation method is illustrated. FIG. 3A shows the color processing LUTs 33a and 33b three-dimensionally. As shown in the figure, when each axis of RGB is divided into ten, CMYK values are stored in advance at each lattice point. Now, assuming that the determined RGB value is O on the three-dimensional orthogonal coordinates, there is a unit cube containing O, and its vertices A to H are output values stored at lattice points, that is, values on the grid. (Refer to FIG. 2B).

  As shown in FIG. 8A, in tetrahedral interpolation, a unit cube is divided into six tetrahedrons, and the region where O exists is determined by the boundary condition shown in FIG. 8B. For example, when O belongs to the region shown in FIG. 7A, that is, when DL * ≧ Da *: True, Da *> Db *: True, Db *> DL *: False and belongs to the BADH region ( The value of CMYK corresponding to the position of O can be obtained by the calculation formula shown in FIG. 8C.

  In the above example, the interpolation calculation is performed by tetrahedral interpolation. However, other interpolation methods such as cubic interpolation, triangular prism interpolation, and hexahedral interpolation may be used. Moreover, although each color processing LUT33a, 33b illustrated the case where RGB was each 10 grids, you may set the number of grids more or less. Also, the number of grids after expansion is not limited to 256 (0 to 255) to the third power = about 16.77 million grids, which is a combination of all RGB, and may be set to less than that or input RGB May be further expanded by performing interpolation calculation processing a plurality of times.

  Further, the grid intervals of the color processing LUTs 33a and 33b may be set at equal intervals, or may be set at irregular intervals based on empirical rules. Further, the grid interval may be changed for each of the color processing LUTs 33a and 33b, or the number of grids themselves may be changed.

  Next, halftone processing (see S03 in FIG. 4) will be described in detail with reference to FIGS. FIG. 9 is a block diagram (hereinafter, referred to as “halftone processing block”) schematically showing each component related to the halftone processing. As shown in the figure, the halftone processing block 100 includes two halftone processing means 110 and 120, two handles 130a and 130b, and data output for outputting processed data after halftone processing in the next step. Means 140.

  Each of the two halftone processing means 110 and 120 has a color matching & halftone module 31 (see FIG. 1) as a main component, and performs halftone processing using an error diffusion method. The first halftone processing unit 110 performs normal halftone processing on the partial image data obtained by dividing the image data into n pieces, and the second halftone processing unit 120 performs processing at the front end of each partial image data. Halftone processing for error calculation (hereinafter also referred to as “overlap”) is performed on predetermined data.

  The two handles 130a and 130b have LUT groups 131a and 131b and work areas 132a and 132b, respectively. Reference number 130a is a forward handle used for processing of partial image data for forward printing (odd-numbered partial image data (see FIG. 3), hereinafter referred to as “forward image data”), and reference number 130b is This is a return path handle used in processing of partial image data for return pass printing (even-numbered partial image data (see FIG. 3), hereinafter referred to as “return pass image data”).

  The forward path LUT group 131a includes an outbound path color processing LUT 33a and an outbound path dot generation LUT 34a, and is used during halftone processing of outbound path image data. Similarly, the return pass LUT group 131b includes a return pass color processing LUT 33b and a return pass dot generation LUT 34b, and is used during halftone processing of the return pass image data.

  The forward path work area 132a includes an forward path error buffer (odd error buffer) 35a and a forward path data buffer (odd data buffer) 36a, and includes error values generated by the halftone process of the forward path image data, and the forward path. The halftone processing result of the image data is stored. Similarly, the return path work area 132b includes a return path error buffer (even error buffer) 35b and a return path data buffer (even data buffer) 36b, and error values generated by halftone processing of the return path image data, The halftone processing result of the return path image data is stored.

  The data output means 140 alternately switches the processing results stored in the forward path data buffer 36a and the backward path data buffer 36b and outputs them to the command conversion buffer 37 (see FIG. 1).

  Here, the overall processing in the halftone processing block 100 will be described. When the halftone processing block 100 acquires the first partial image data (outbound image data) after the color matching processing, the first halftone processing unit 110 first refers to the outbound LUT group 131a and performs halftone processing for each raster. Execute the process. The error value generated by the halftone process is stored in the forward path error buffer 35a, and the binarized data as the processing result is stored in the forward path data buffer 36a. As shown in FIG. 2, since the nozzle row 52 of each color has 360 nozzles 53 arranged therein, each partial image data is composed of 360 raster data corresponding to the number of nozzles of each color. . Therefore, the halftone process for 360 rasters is executed here. In this embodiment, when each partial image data is recorded, all the number of nozzles of each color is used. However, the present invention is not limited to this, and a numerical value equal to or less than the number of nozzles of each color is configured. The number of rasters may be used.

  Generally (conventionally), after the halftone processing of 360 rasters of the first partial image data is finished, the halftone processing of the second partial image data is started. When starting the remaining three rasters of the image data, the second halftone processing unit 120 simultaneously performs the halftone processing of the second partial image data with reference to the return LUT group 131b. That is, in the processing after the second partial image data, halftone processing of the remaining three rasters by the first halftone processing unit 120 and half of three rasters at the leading end of the subsequent partial image data by the second halftone processing unit 120 The tone processing is performed simultaneously (overlapping processing is performed). Note that the process by the second halftone processing unit 120 is not performed on the first partial image data (first partial image data). This is because the first partial image data does not need to consider continuity with the previous image data (because deterioration in image quality does not pose a problem even when the error buffers 35a and 35b are initialized). ).

  The error value (hereinafter referred to as “preceding error value”) of the second partial image data generated by the second halftone processing means 120 is stored in the return path error buffer 35b. Is not used (it is temporarily stored in the return path data buffer 36b, but the processing result of the first halftone processing means 110 is overwritten later). That is, the first halftone processing unit 110 sequentially performs halftone processing on the partial image data, and precedes this (for the next partial image data processed by the first halftone processing unit 110). 2 Halftone processing means 120 performs halftone processing only for calculating the preceding error value.

  Then, when the processing of the second partial image data by the first halftone processing unit 120 is completed, the first halftone processing unit 110 subsequently refers to the return path LUT group 131b in accordance with the switching of the printing direction. Start halftone processing of partial image data. At this time, since the previous error value generated by the second halftone processing unit 120 is already stored in the forward error buffer 35b, the first halftone processing unit 110 uses the error value to generate the second part. Start halftone processing of image data. When the first halftone processing unit 110 starts processing the remaining three rasters of the second partial image data, the second halftone processing unit 120 starts processing the first three rasters of the third partial image data. . In this way, the processing by the two halftone processing means 110 and 120 is repeated up to the nth partial image data.

  FIG. 10 illustrates the processing by the two halftone processing means 110 and 120 in an easy-to-understand manner. Here, the image data is shown as D, and the partial image data are shown as D1 to Dn. As described above, in the halftone processing block 100, processed data after halftone processing is output for each of the partial image data D1, D2,... Dn obtained by dividing the image data D into n pieces ( In the halftone process (shown as “HT1, HT2”) and the halftone process (shown as “output data”), the tip part (for three rasters) of each partial image data is overlapped after the second partial image data. That is, the data for three rasters corresponding to “HT2” shown in the figure is processed by the second halftone processing means 120, and the data for 360 rasters corresponding to “HT1” shown in the figure is used by using the error value generated by the processing. The first halftone processing unit 110 performs processing.

  Since there is no subsequent partial image data for the last partial image data (nth partial image data Dn), the last three rasters of the nth partial image data are processed by the first halftone processing unit 110 alone. (The overlap processing by the second halftone processing means 120 is not executed).

  Next, switching between the forward handle 130a and the return handle 130b shown in FIG. 9 will be described in more detail with reference to FIGS. As shown in FIG. 11, for example, when “during forward printing” is assumed, the forward handle 130 a functions for printing, and the backward handle 130 b functions for error calculation. That is, the first halftone processing unit 110 uses the forward handle 130a, and the second halftone processing unit 120 uses the forward handle 130b. The illustrated example shows a state in which halfway processing of forward image data is being performed and the remaining three rasters are not reached. Therefore, the return path handle 130b has not yet functioned, and the data buffer 36b and the error buffer 35b are in an initialized state (no data is written). When the data buffer 36a reaches a predetermined amount (for example, 32 rasters), binarized data that is processed data is output to the command conversion buffer 37. When the output of the processed data for all rasters of the forward path image data is finished, the handles 130a and 130b are switched, and the forward path handle 130a functions for error calculation and the return path handle 130b functions for printing.

  As described above, since the data buffers 36a and 36b output data every predetermined amount, the capacity can be arbitrarily set. However, the error buffers 35a and 35b have three rasters for the preceding error value and one. A capacity capable of storing error values for bands (360 rasters in this embodiment) is required.

  FIG. 12 is a diagram for explaining the initialization timing of the error buffers 35a and 35b. For example, at the time of “outward printing”, as described above, the forward handle 130a functions for printing and the backward handle 130b functions for error calculation, but the first halftone processing means 110 performs all rasters of the forward image data. When the minute processing is finished, the state shown in FIG. That is, the error values of all the forward path image data (360 rasters) are written in the error buffer 35a, and the preceding error values of 3 rasters are also written in the error buffer 35b.

  Here, when the printing direction is switched, the data in the data buffer 36a, which is the processing result of the first halftone processing means 110, is output to the command conversion buffer 37, and the functions of the handles 130a and 130b are switched. FIG. 5B shows a state immediately after the printing direction is switched. That is, when the forward path handle 130a is switched for error calculation, the data buffer 36a and the error buffer 35a are initialized. On the other hand, the processing result and error value for three rasters are written in the data buffer 36b and the error buffer 35b, respectively, in the return path handle 130b, but the processing result of the subsequent return path image data is stored in the data buffer 36b. Overwritten. That is, the processing result obtained by the second halftone processing unit 120 performed in advance is not used. Therefore, the data buffer 36a may be initialized when switching to error calculation. Further, the error value written in the error buffer 35b remains as it is, and using this, the first halftone processing unit 110 starts the halftone processing of the return path image data. Therefore, the error value of the first raster when the return path handle 130b functions for printing is written in the fourth raster of the error buffer 35b.

  Next, the print job processing by the printer driver 23 (mainly the image processing module 26) (see FIG. 1) will be described with reference to the flowcharts of FIGS.

  As shown in FIG. 13, the print job processing steps include initial setting of a print job (S 10), initial setting for each page (S 20), and each band (area that can be printed by one main scan of the print head 47). Print processing (S30), page-by-page end processing (S40), and print job end processing (S50).

  In the initial setting of the print job (S10), first, the LUT switching flag is initialized (S11). This LUT switching flag is effective when the color processing LUTs 33a and 33b referred to as described above are used by switching between forward printing and backward printing. This flag can be switched using a GUI provided by the printer driver 23 (valid / invalid can be set), but here a print mode (a mode that can be set by the user according to print quality and print medium). ). That is, for example, in the printing modes A to D, when the A or B is set, the LUT switching flag is enabled, and when the C or D is set, the LUT switching flag is disabled. Do. Therefore, after initialization of the LUT switching flag (S11), the LUT switching setting based on the print mode is confirmed (S12). If the LUT switching flag is valid (S12: valid), the setting of the LUT switching flag is set to “true”. "(S13).

  Subsequently, in the initial setting for each page (S20), the LUT switching flag is confirmed (S21). If invalid (S21: false), the forward handle 130a of the halftone processing block 100 (see FIG. 9). Is designated (S22). That is, in this case, the handle 130a for the forward path is used in both the forward printing and the backward printing, and the handles 130a and 130b are not switched. Also, the halftone processing for error calculation by the second halftone processing unit 120 is not performed, and the first halftone processing unit 110 processes all partial image data using the forward handle 130a.

  On the other hand, the LUT switching flag is confirmed (S21). If it is valid (S21: true), the two handles 130a and 130b for the forward printing and the backward printing of the halftone processing block 100 are designated (S23, S24). ), The previous moving direction of the print head 47 is set to “return”, and the start raster position of the latest output band is set to “−1” (S25). This is because (the movement direction of the print head 47 is set to “return”), the movement direction of the print head 47 with respect to the first partial image data D1 is always the forward direction (move from the print start position P to the right in the main scanning direction). Yes, see FIG. 3), since the movement direction of the print head 47 is switched for every one-pass printing, if the movement direction of the print head 47 so far, that is, “the movement direction of the previous print head 47” is defined, it is virtually This is because the “return path” must be set (the same applies when blank skip occurs before the first printing on the print medium 51 is started). Thereby, the process for discriminating the head of the page can be omitted. The reason why the starting raster position of the latest output band is set to “−1” is for initial setting of the page (to make the raster position to be executed from now the first raster of the output band).

  Subsequently, the printing process for each band is performed (S30), and it is determined whether or not the band remains (S31). If the band remains (S31: Yes), the printing process for each band is repeated (S30). If no band remains (S31: No), an end process is performed for each page (S40), and it is determined whether or not a page remains (S41). If a band remains (S41: Yes). The initial setting for each page is performed (S20). If no page remains (S41: No), a print job end process is performed (S50).

  Here, the print processing (S30) for each band will be described with reference to the flowcharts of FIGS. As shown in FIG. 14, the printing process for each band is repeatedly executed for the raster of the bitmap that forms the image data (S301). First, the direction at which the bitmap raster is printed is defined as the head moving direction at the time of printing so far, that is, the “return path” (see S25 in FIG. 13), and further defined as not being the first raster in that direction. (S302).

  Subsequently, the state of the LUT switching flag is confirmed (S303). When the LUT switching flag is not valid (S303: false), normal halftone processing is executed (S304). That is, the same determination as S12 and S21 in FIG. 13 is performed, and if the LUT switching setting is invalid, halftone processing using only the forward handle 130a is performed. Then, it is determined whether or not the raster remains (S305). If the raster remains (S305: Yes), the processing after S301 is repeated. If no raster remains (S305: No), the band-by-band printing process (S30) is terminated.

  On the other hand, if the LUT switching flag is valid (S303: true), it is determined whether or not the first output or rasters equal to or greater than the number of rasters (360 rasters) for the height of the print head 47 has been processed. (S306). In this embodiment, the number of rasters corresponding to the height of the print head 47 (360 rasters) is used. However, as described in the raster configuration of the partial image data, a value equal to or less than the number of nozzles of the print head 47 is used. It doesn't matter if it is high. In this case, printing is performed in a state where all the nozzles of the print head 47 are not used (a state where some of the nozzles are used). Here, for example, when it is the first raster of the band (S306: Yes), it is the first raster in that direction, and the direction when printing the bitmap raster is opposite to the current direction (return path, see S302). Direction, i.e., "outward" (S307). However, at this stage, the print direction is assumed only, and it is S316 (see FIG. 15) described later that actually determines the print direction.

  Subsequently, the handle of the halftone processing block 100 for printing is defined as the forward handle 130a, and the handle of the halftone processing block 100 for overlap (for error calculation) is defined as the handle 130b for returning (S308). . That is, it is assumed that the first halftone processing means 110 uses the forward handle 130a and the second halftone processing means 120 uses the return handle 130b. If it is determined as “No” in S306, it is assumed that the moving direction of the print head 47 does not change, S307 is omitted, and the process proceeds to S308.

  Subsequently, it is determined whether or not the bitmap raster printing direction is “return” (S309). For example, in the case of the first raster of the band, since “outbound” is defined in S307, “No” is determined in S309. On the other hand, when the bitmap raster printing direction is “return”, the handle of the halftone processing block 100 for printing is set to the handle 130b for returning, and the handle of the halftone processing block 100 for overlap is further used. Is defined as a forward handle 130a (S310).

  Subsequently, it is determined whether the number of rasters remaining until the raster corresponding to the height of the head is not the first output or less is equal to or less than the number of rasters to be overlapped (3 rasters) (S311). For example, if it is the first raster of the band, it is determined as “false” because it is the first output, and halftone processing is performed using the handle of the halftone processing block 100 for printing (S312). That is, S312 is processing by the first halftone processing unit 110. If it is determined as “true” in S311, halftone processing is performed using the handle of the overlapping halftone processing block 100 (S313). That is, S312 is processing by the second halftone processing unit 120, and the processing result is not used (although it is once written in the data buffers 36a and 36b, it is overwritten later). If it is determined as “true” in S311, the processing in S312 (processing by the first halftone processing unit 110) is also performed (overlap processing).

  Subsequently, it is determined whether or not it is the first raster in that direction (S314). If it is the first raster (for example, the first raster of the band) (S314: true), the halftone result is blank. It is determined whether or not (S315). Here, the reason why the determination is made based on the halftone result is that there is a possibility that an effective pixel is generated at a place where the blank raster is supposed to be generated by the halftone process. Here, if the halftone result is not blank, that is, if there is an effective pixel to be printed (S315: No), the head moving direction is determined as the direction for printing the bitmap raster, and the latest (previous) The starting raster position of the output band is rewritten to the current raster position, and the process returns to S305 (see FIG. 14). Note that the head movement direction determined in S316 is the direction assumed in S307 (see FIG. 14), that is, the “outward path”.

  If it is determined as “false” in S314, that is, if it is not the first raster, the blank check (S315) is unnecessary, and the process directly returns to S305 to avoid useless processing. Also, if “Yes” is determined in S315, that is, in the case of a blank raster, S316 is omitted and the process returns to S305.

  As described above, according to the present embodiment, in the color matching processing, the forward color processing LUT 33a and the backward color processing LUT 33b are referred to for the forward image data and the backward image data, respectively. By designing each color processing LUT so that unevenness can be eliminated, it is possible to eliminate unevenness in color caused by a difference in printing direction. In addition, since values that do not exist on the color processing tables 33a and 33b are estimated by the interpolation calculation process of the interpolation calculation module 27, it is not necessary to use the color processing LUTs 33a and 33b describing a huge color conversion pattern.

  The interpolation calculation module 27 executes the interpolation calculation process only when there is no CMYK value corresponding to the determined RGB value on each color processing LUT 33a, 33b, and the CMYK value exists on each color processing LUT 33a, 33b. In this case, since the ink discharge amount is determined using the value, useless processing can be omitted. Also, the data amount of each color processing LUT 33a, 33b can be determined according to the memory capacity (stores the color processing LUTs 33a, 33b) and the control capability (controlling the interpolation calculation processing) of the installed device. That is, when the memory capacity is not limited, the control load can be reduced by increasing the data amount of the color processing LUTs 33a and 33b. When a high-performance CPU is used, the data amount of the color processing LUTs 33a and 33b. Can be reduced.

  Further, in the halftone process, the halftone process for error calculation is performed prior to the normal halftone process of the forward path image data or the backward path image data, and the preceding error value generated thereby is used as the forward path error buffer 35a or the backward path data. Since it is stored in the error buffer 35b, the error buffers 35a and 35b are not cleared when the data buffers 36a and 36b are switched. That is, if the error diffusion process is started when the moving direction of the print head 47 is switched, the error is cleared, so that the delay of dot generation becomes significant. However, the first halftone processing unit 110 does not perform the second halftone. Since the halftone process can be started by receiving the propagation of the preceding error value calculated by the processing means 120 (using the preceding error value stored in the error buffers 35a and 35b in advance), it is not displayed on the printed image. It is possible to prevent natural discontinuities from occurring. Accordingly, even when the two data buffers 36a and 36b for forward printing and backward printing are switched and used, it is possible to prevent the image quality from being deteriorated when the data buffers 36a and 36b are switched.

  Further, since the halftone processing for error calculation by the second halftone processing unit 120 may be only three rasters at the front end of each partial image data, the second halftone processing unit 120 processes all rasters (360 rasters). The control load can be reduced to 1/120 (3/360) as compared with the case of performing.

  Further, since the two data buffers 36a and 36b are divided into forward printing and backward printing, the data buffers 36a and 36b to be used may be switched in synchronization with the switching of the printing direction, and the control is easy. is there.

  Next, a second embodiment of the present invention will be described with reference to FIG. In the first embodiment, the two data buffers 36a and 36b are used for the forward pass printing and the backward pass printing during the halftone process (see FIG. 11). However, in the present embodiment, the data buffer 236 is used. It is different in that it is one. Therefore, the description will focus on the differences from the first embodiment.

  As shown in FIG. 16, the halftone processing block 200 of the present embodiment includes a first halftone processing unit 210 that performs normal halftone processing and a second halftone processing unit 220 that performs halftone processing for error calculation. And two handles 230a and 230b. In addition, the first halftone processing unit 210 and the second halftone processing unit 220 switch and use the handles 230a and 230b, respectively, and each handle 230a and 230b has an error buffer (odd error buffer and even error buffer). About the point provided with 235a, 235b, it is the same as that of 1st Embodiment. In addition, as in the first embodiment, the handles 230a and 230b may be provided with color processing LUTs 33a and 33b and dot generation LUTs 34a and 34b, respectively, and the common color processing LUT and dot generation LUT are provided in the first half. Both the tone processing unit 210 and the second halftone processing unit 220 may be referred to.

  Here, the processing of the halftone processing block 200 in the present embodiment will be described. When the halftone processing block 200 acquires the first partial image data (outbound image data) after the color matching processing, first, the first halftone processing unit 210 performs normal halftone processing, and the error value generated as a result is displayed. And stored in the error buffer 235a in the handle 230a for the forward path. The processing result of the first halftone processing unit 210 is stored in the data buffer 236.

  Then, when processing of the remaining third raster (358th raster) of the first partial image data is started, halftone processing for error calculation of the second partial image data by the second halftone processing unit 220 is started at the same time. . The error value (preceding error value) generated as a result is stored in the error buffer 235b in the return path handle 230b, and the processing result is stored in another storage area (not shown). Thereafter, the processing results for three rasters by the second halftone processing means 220 are written in the other storage area, but the processing results are overwritten sequentially and are not particularly used.

  Subsequently, when the processing of the first partial image data by the first halftone processing unit 210 is completed, the first halftone processing unit 210 stores the error buffer 235b in the return path handle 230b as the printing direction is switched. The processing of the second partial image data is started using the error values for the three rasters already stored. This figure shows a state at the start of processing of the second partial image data by the first halftone processing means 210. In this way, since the processing of each partial image data is started using the error values already stored in the error buffers 235a and 235b, the error values are not cleared and a good image quality can be obtained. . The processing result of the second partial image data by the first halftone processing unit 210 is also stored in the data buffer 236 continuously with the processing result of the first partial image data, and the data buffer 236 stores a predetermined amount of data. At this point, data is output to the command conversion buffer 37 (data output means). Each error buffer 235a, 235b is initialized at the time of switching to error calculation.

  As described above, according to this embodiment, halftone processing for error calculation is performed prior to normal halftone processing, and the preceding error value generated thereby is stored in each error buffer 235a, 235b. Since these are used to start normal halftone processing of partial image data, the error buffers 235a and 235b are not cleared at the start of halftone processing (immediately after switching, the error buffers 235a and 235b are not cleared). Because the leading error value is already stored in That is, the first halftone processing unit 210 has received the propagation of the preceding error value calculated by the second halftone processing unit 220 only by switching the error buffers 235a and 235b to be referred to according to the partial image data to be processed. Since the halftone process (using the preceding error value stored in advance in the error buffers 235a and 235b) can be started, it is possible to eliminate the deterioration in image quality caused by the initialization of the error buffers 235a and 235b.

  Further, since only one data buffer 236 is required as compared with the first embodiment, there is an advantage that the configuration of the halftone processing block 200 can be simplified.

  In the above example, the partial image data is divided in units of bands (areas that can be printed by one main scan of the print head), but may be in units of multiple bands or in units of pages. . That is, the image data can be divided into partial image data having an arbitrary data size in accordance with the use form of the data after image processing and the image processing performance. According to this configuration, since the capacities of the two error buffers 235a and 235b can be determined according to the data amount of the partial image data, the memory capacity required for the error buffers 235a and 235b can be saved. That is, when the partial image data is in units of pages, the capacity may be sufficient to store an error value for one page, and a continuous image across a plurality of pages may be printed as in the case of long printing. There is no need to provide an assumed large-capacity error buffer.

  Next, a third embodiment of the present invention will be described with reference to FIG. In the second embodiment, an error buffer for forward printing (an error buffer for storing error values of odd-numbered partial image data) 235a and an error buffer for backward printing (error values of even-numbered partial image data are stored). (Error buffer to be stored) 235b, and the error buffers 235a and 235b to be referred to (written to) by the first halftone processing unit 210 and the second halftone processing unit 220 are switched. A normal error buffer 331 and a preceding error buffer 332, the error value generated by the first halftone processing unit 310 is stored in the normal error buffer 31, and the error value generated by the second halftone processing unit 320 is stored in the preceding error buffer. It is different in that the data is written to 332. Therefore, the description will focus on the differences from the second embodiment.

  As shown in FIG. 17, the halftone processing block 300 of this embodiment includes a first halftone processing unit 310 that performs normal halftone processing and a second halftone processing unit 320 that performs halftone processing for error calculation. A normal error buffer 331 and a preceding error buffer 332. As in the second embodiment, the error buffers 331 and 332 may be provided in the handle having the color processing LUT and the dot generation LUT, or the common color processing LUT and the dot generation LUT are each halftone processed. The means 310 and 320 may be referred to.

  Here, the processing of the halftone processing block 300 in the present embodiment will be described. When the halftone processing block 300 obtains the first partial image data (outbound image data) after the color matching processing, the first halftone processing means 310 first performs normal halftone processing, and the error value generated as a result is displayed. And stored in the normal error buffer 331. Further, the processing result of the first halftone processing means 310 is stored in the data buffer 336.

  When the first halftone processing unit 310 starts processing the remaining third raster (358th raster) of the first partial image data, the second halftone processing unit 320 calculates the error of the second partial image data at the same time. Start halftone processing for The error value (preceding error value) generated as a result is stored in the preceding error buffer 332, and the processing result is stored in another storage area (not shown) as in the second embodiment.

  Subsequently, when the processing of the first partial image data by the first halftone processing unit 310 is completed, the normal error buffer 331 is initialized as the printing direction is switched. The first halftone processing unit 310 reads out the error values for three rasters already stored in the preceding error buffer 332, writes them into the normal error buffer 331, and processes the second partial image data using the error values. To start. The first halftone processing unit 310 starts processing the second partial image data while referring to the preceding error value stored in the preceding error buffer 332, instead of writing the read error value in the normal error buffer 331. You may make it do. In this way, the first halftone processing unit 310 uses the preceding error value stored in the preceding error buffer 332 to start processing each partial image data. Therefore, good image quality can be obtained. The preceding error buffer 332 is not initialized because the preceding error values stored in the preceding error buffer 332 are sequentially overwritten.

  As described above, the preceding error value generated by the halftone processing for error calculation is stored in the preceding error buffer 332, and the normal halftone processing is started using this, so that the preceding error value is propagated. (The halftone process can be started using the preceding error value stored in advance in the preceding error buffer 332). That is, since the halftone process of the partial image data can be continued without losing the continuity of the error value, it is possible to eliminate the deterioration in image quality caused by the initialization of the normal error buffer 331. Further, since the capacity of the preceding error buffer 332 may be small enough to store error values for three rasters, the memory capacity required for the preceding error buffer 332 can be saved.

  Similar to the second embodiment, in this embodiment, the partial image data can be set in arbitrary units according to the use form of the data after image processing and the image processing performance.

  Although the present invention has been described with three embodiments, the image processing module 26 that realizes color conversion processing and halftone processing is not provided in the host computer 20 as in the above embodiments (FIG. 1). For example, the printer 40 may be provided. That is, the image processing module 26 may be mounted as a part of the firmware of the printer 40. In addition to the printing system 10, the present invention can be applied to any system or apparatus that can execute image processing.

  Further, the halftone processing for error calculation is assumed to be 3 rasters at the tip of each partial image data, but the value thereof can be changed as appropriate, such as 4 rasters or 5 rasters. However, considering the control load, it is preferably 10 rasters or less.

  Further, it is preferable to provide means for setting the number of rasters for performing the error calculation, that is, means for allowing the user to easily change the number of rasters by using a GUI or the like. According to this configuration, the number of rasters can be set according to the user's preference and the type of image data.

  It is also possible to provide the function of the image processing module 26 shown in the above embodiment as a program. Further, the program can be provided by being stored in a recording medium (not shown). CD-ROM, flash ROM, memory card (compact flash (registered trademark), smart media, memory stick, etc.), compact disk, magneto-optical disk, digital versatile disk, flexible disk, hard disk, etc. can be used as the recording medium. is there.

  Further, regardless of the example of the printing system 10 and the halftone processing blocks 100, 200, and 300 in the above-described embodiment, the apparatus configuration, system configuration, printing method, processing process, and the like are within the scope not departing from the gist of the present invention. Changes can be made as appropriate. That is, the present invention may be applied not only to the ink jet printer described above but also to a printing method such as a thermal transfer method or a wire dot method. Also, the print medium may be a receipt paper instead of a cut sheet, or a recording medium other than paper.

  In the above-described embodiment, the image formation by ejecting ink from the print head 47 is referred to as “printing”. However, whether or not characters or figures are formed and whether or not the formed one is visually visible. Regardless of this, the present invention can also be applied to the case where images and patterns are widely formed on a recording medium. In addition, “ink” widely includes a colorant, and the type (dye ink, pigment ink, etc.) does not matter.

1 is a block diagram of a printing system according to an embodiment of the present invention. It is a figure which shows the structure of a carriage. It is a figure for demonstrating operation | movement of a carriage. 3 is a flowchart illustrating an overview of various processes in a printer driver. It is a figure which shows an example of a color processing LUT. It is a flowchart which shows a color matching process. It is a figure for demonstrating an interpolation calculation process. It is explanatory drawing following FIG. It is a block diagram of a halftone processing block. It is a figure for demonstrating a halftone process. It is a figure for demonstrating switching of a handle | steering-wheel. It is explanatory drawing following FIG. 6 is a flowchart illustrating processing of a print job. 6 is a flowchart of print processing for each band, which is a part of print job processing. It is a flowchart following FIG. It is a figure for demonstrating the halftone process which concerns on 2nd Embodiment of this invention. It is a figure for demonstrating the halftone process which concerns on 3rd Embodiment of this invention.

Explanation of symbols

  10: printing system, 20: host computer, 23: printer driver, 26: image processing module, 31: color matching & halftone module, 33: color processing LUT, 34: dot generation LUT, 35: error buffer, 36: data Buffer: 40: Printer, 43: Printing section, 44: Carriage, 47: Print head, 51: Print medium, 100: Halftone processing block, 110: First halftone processing means, 120: Second halftone processing means, 130: Handle, D: Image data, D1 to Dn: Partial image data

Claims (7)

A printing system comprising: a host computer that stores or generates image data to be printed; and a printer that performs reciprocal printing using a plurality of colorants based on instructions from the host computer,
A color processing table for determining a mixing ratio of the colorants of the plurality of colors;
An interpolation calculation module that performs an interpolation calculation process for estimating a value that does not exist on the color processing table;
Color conversion processing means for performing color conversion processing on the image data according to the colorants of the plurality of colors using the color processing table and the interpolation calculation module;
Printing means for performing the reciprocal printing by the printer based on the data after the color conversion processing,
The color processing table comprises two color processing tables for forward printing and for backward printing.
The color conversion processing means includes
The image data is divided into forward image data for forward printing and backward image data for backward printing, and color conversion processing is performed with reference to the color processing tables for forward printing and backward printing, respectively. A printing system characterized by that. The color conversion processing means includes
Additive color mixing ratio determining means for determining a ratio of additive color mixing for each pixel of the forward path image data or the backward path image data;
Color processing table determining means for determining whether or not a value of subtractive color mixing corresponding to the determined ratio of additive color mixing exists on the color processing table for the forward printing or the backward printing, respectively;
When the ratio of subtractive color mixing is present on the color processing table, the value is determined as the ratio of subtractive color mixing, and when the ratio of subtractive color mixing is not present on the color processing table, the interpolation calculation module is used. The printing system according to claim 1, further comprising: a subtractive color mixing ratio determining unit configured to determine a subtractive color mixing ratio by performing the interpolation calculation process.   3. The printing according to claim 1, wherein the interpolation calculation module performs the interpolation calculation processing using any one of cubic interpolation, triangular prism interpolation, tetrahedral interpolation, and hexahedral interpolation. system. First halftone processing means for performing halftone processing on the forward pass image data and the return pass image data after color conversion processing by the color conversion processing means;
Prior to processing by the first halftone processing means, second halftone processing means for performing halftone processing for error calculation;
A forward error buffer for storing an error value generated by the first halftone processing unit of the forward image data following the preceding error value generated by the processing of the forward image data by the second halftone processing unit;
A return error buffer for storing an error value generated by the first halftone processing unit of the return image data following the preceding error value generated by the processing of the return image data by the second halftone processing unit;
A forward data buffer for storing a processing result of the forward image data by the first halftone processing unit;
A return data buffer for storing the processing result of the return image data by the first halftone processing means;
Data output means for alternately switching and outputting the processing results stored in the forward path data buffer and the backward path data buffer as data for printing by the printing means,
The first halftone processing means starts halftone processing of the forward path image data and the backward path image data using the preceding error values stored in the forward path error buffer and the backward path error buffer, respectively. The printing system according to claim 1, 2, or 3.   An image processing apparatus comprising color conversion processing means in the printing system according to claim 1, 2 or 3.   A printer driver comprising color conversion processing means in the printing system according to claim 1.   The program for functioning a computer as a color conversion process means in the printing system of Claim 1, 2, or 3.

Images