Printer, printing system, printing method and print control program

Abstract

To realize multi-screening of a printer with a simple circuit.SOLUTION: A printer is provided with: a threshold matrix set 710 containing at least one threshold matrix 71 composed of a plurality of thresholds to compare with the gradation values of a plurality of pixels contained in raster data 64 for printing; a threshold set containing at least one threshold 72 to compare with the gradation value of each pixel contained in the raster data 64; and a half-tone processing unit 52 for generating half-tone image data 65 on the basis of the comparison result of a threshold with the gradation value of each pixel contained in the raster data 64. For each pixel, the half-tone processing unit 52 switches a reference destination of a threshold that is compared with the gradation value in the raster data 64 between the threshold matrix set 710 and the threshold set 720, depending on the gradation value in the raster data 64.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a printing device that prints by ejecting ink onto a printing medium, and more particularly to halftone processing (screening processing) that converts multi-tone data into halftone dot data when printing is performed by the printing device. [Background technology]

[0002] Inkjet printing devices that perform printing by ejecting ink onto a printing medium such as printing paper or film using heat or pressure are known. Inkjet printing devices are provided with a head unit consisting of a plurality of ink ejection heads extending in a direction perpendicular to the transport direction of the printing medium, for example, for each color of ink. Each ink ejection head includes a number of nozzles that eject ink. The gradation of a printed image is expressed by controlling the on / off state of ink ejection from each of the plurality of nozzles, or by controlling the drop size of the ink ejected from each of the plurality of nozzles in multiple stages.

[0003] When printing is performed by an inkjet printing device, first, a rasterization process is performed on input data described in, for example, a page description language. After that, the multi-tone data after the rasterization process is converted into data indicating whether or not ink is to be ejected from each nozzle, or data indicating the drop size of ink ejected from each nozzle. That is, a halftone process (also called a "screening process") is performed to convert data representing a grayscale image in continuous tones into halftone data representing the grayscale image with halftone dots. Then, a grayscale image is formed on the printing medium by controlling the ejection of ink from each nozzle based on the data obtained by the halftone process.

[0004] Incidentally, one specific method of halftone processing is known in which a threshold matrix in which a large number of thresholds are arranged in a matrix (two-dimensionally) is prepared, and halftone dot data is generated by comparing the gradation values ​​in the multi-gradation data after rasterization processing with the thresholds in the threshold matrix for each pixel. In this regard, when only one size is provided as the drop size of the ink ejected from each nozzle, one type of threshold matrix is ​​prepared, and when, for example, three types (three levels) of sizes are provided as the drop size, three types of threshold matrices are prepared. The threshold matrix is ​​also called a "screen pattern."

[0005] FIG. 16 shows a configuration for halftone processing in the case where three drop sizes (S, M, and L) are provided. In this configuration, a threshold matrix set 910 is provided, which includes a threshold matrix 91(S) for S size, a threshold matrix 91(M) for M size, and a threshold matrix 91(L) for L size. For reference, an example of the threshold matrix 91(S) for S size is shown in FIG. 17, an example of the threshold matrix 91(M) for M size is shown in FIG. 18, and an example of the threshold matrix 91(L) for L size is shown in FIG. 19. The halftone processing unit 900 compares the gradation value of each pixel in the input data (multiple gradation data after rasterization processing) 98 with the corresponding threshold value in each of the three threshold matrices 91. Then, depending on the comparison result, the data value of the pixel in the halftone image data (halftone dot data) 99, which is the output data, is determined, for example, as follows. For pixels whose gradation values ​​in the input data 98 ​​are equal to or greater than the threshold value in the threshold matrix 91(L) for L size, the data value in the halftone image data 99 is set to a value representing application of L size ink (e.g., "3"). For pixels whose gradation values ​​in the input data 98 ​​are equal to or greater than the threshold value in the threshold matrix 91(M) for M size and less than the threshold value in the threshold matrix 91(L) for L size, the data value in the halftone image data 99 is set to a value representing application of M size ink (e.g., "2"). For pixels whose gradation values ​​in the input data 98 ​​are equal to or greater than the threshold value in the threshold matrix 91(S) for S size and less than the threshold value in the threshold matrix 91(M) for M size, the data value in the halftone image data 99 is set to a value representing application of S size ink (e.g., "1"). For pixels whose gradation values ​​in the input data 98 ​​are less than the threshold value in the threshold matrix 91(S) for S size, the data value in the halftone image data 99 is set to a value representing no application of ink (e.g., "0"). In this manner, halftone image data 99 for controlling the ejection of ink from each nozzle is generated.

[0006] Also, a technique has been proposed in which two types of threshold matrix sets are prepared and used depending on the attribute of data to be processed. An example of a configuration using this technique is shown in FIG. 20. In the configuration shown in FIG. 20, a first threshold matrix set 930 consisting of a threshold matrix 93(S) for S size, a threshold matrix 93(M) for M size, and a threshold matrix 93(L) for L size, and a second threshold matrix set 940 consisting of a threshold matrix 94(S) for S size, a threshold matrix 94(M) for M size, and a threshold matrix 94(L) for L size are provided. The halftone processing unit 920 is provided with tone value data 981 and attribute data 982 as input data 98. The attribute data 982 has different data values ​​for line drawings (including characters) and images, for example. The halftone processing unit 920 is composed of a reference destination switching unit 921 and a drop size determination unit 922. The reference switching unit 921 switches the reference of the data (threshold) to be compared with the gradation value of each pixel between the first threshold matrix set 930 and the second threshold matrix set 940 based on the attribute data 982. The drop size determination unit 922 compares the gradation value of each pixel in the gradation value data 981 with the corresponding thresholds in each of the three threshold matrices included in the reference threshold matrix set. Depending on the comparison result, the data value of the pixel in the halftone image data 99, which is the output data, is determined. Note that this method of performing halftone processing (screening processing) using different data depending on the attribute of the data to be processed is called "multi-screening." An invention regarding an inkjet printing device that performs such multi-screening is disclosed in JP 2010-221584 A. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2010-221584 A Summary of the Invention [Problem to be solved by the invention]

[0008] According to conventional multi-screening employing the configuration shown in Fig. 20, data (attribute data 982) for switching the reference threshold matrix set is required for each pixel. This causes problems such as insufficient data bandwidth in an inkjet printing device that performs high-speed printing, and high costs to ensure sufficient data bandwidth. In addition, a large-capacity memory is required to simultaneously read out data from two types of threshold matrix sets, and the circuit for comparing the gradation values ​​in the input data 98 ​​with the thresholds is also large-scale. From these perspectives, the cost is high.

[0009] In view of the above circumstances, an object of the present invention is to realize multi-screening in an inkjet printing device using a simple circuit. [Means for solving the problem]

[0010] A first aspect of the present invention is a printing device that has a plurality of nozzles and performs printing by ejecting ink from the plurality of nozzles onto a printing medium, a threshold matrix set including at least one threshold matrix consisting of a plurality of thresholds arranged two-dimensionally, the plurality of thresholds being used for comparison with the gradation values ​​of a plurality of pixels included in the raster data for printing; a threshold set including at least one threshold for comparing with a gradation value of each pixel included in the raster data; a halftone processing unit that generates halftone image data based on a result of comparing the gradation value of each pixel included in the raster data with a threshold value; Equipped with The halftone processing unit is characterized in that, when generating the halftone image data, for each pixel, the reference for the threshold value to be compared with the gradation value in the raster data is switched between the threshold matrix set and the threshold set depending on the magnitude of the gradation value in the raster data.

[0011] The second invention is the first invention, The halftone processing unit is characterized in that, for pixels in the raster data whose gradation value is (K-1) or less, the halftone processing unit references the threshold matrix set as a reference for the threshold to be compared with the gradation value in the raster data, where K is a predetermined gradation value, and, for pixels in the raster data whose gradation value is K or more, the halftone processing unit references the threshold set as a reference for the threshold to be compared with the gradation value in the raster data.

[0012] The third invention is the first or second invention, Each of the plurality of nozzles is capable of ejecting ink in N different drop sizes, The at least one threshold matrix included in the threshold matrix set is N threshold matrices, The at least one threshold included in the threshold set is characterized by N thresholds.

[0013] The fourth invention relates to the third invention, The halftone processing unit is characterized in that, for pixels in the raster data whose gradation value is (MN) or less, the halftone processing unit references the threshold matrix set as a reference for the threshold to be compared with the gradation value in the raster data, where the maximum gradation value is M, and, for pixels in the raster data whose gradation value is (M-N+1) or more, the halftone processing unit references the threshold set as a reference for the threshold to be compared with the gradation value in the raster data.

[0014] A fifth aspect of the present invention is a printing system including the printing device according to the first aspect of the present invention and a printing raster data generating device that generates the raster data based on input data including a plurality of objects, the plurality of objects are classified into a first type of object and a second type of object according to a predetermined condition; Let M be the maximum value of the gradation value, and K be a given gradation value, the threshold matrix set corresponds to a first gradation range, which is a range of gradation values ​​from 0 to (K-1), the threshold set is associated with a second tone range, which is a range of tone values ​​from K to M, inclusive; The printing raster data generating device includes: a gradation value conversion unit that converts gradation values ​​of the first type objects of the plurality of objects into gradation values ​​within the first gradation range and converts gradation values ​​of the second type objects of the plurality of objects into gradation values ​​within the second gradation range, thereby generating intermediate data; a rasterization processing unit that generates the raster data by performing a rasterization process on the intermediate data; The present invention is characterized by comprising:

[0015] The sixth aspect of the present invention relates to the fifth aspect of the present invention, the plurality of objects includes at least an image object and a line drawing object; the graphical object is classified into the first type of object; The line drawing object is characterized in that it is classified into the second type of object.

[0016] The seventh aspect of the present invention is the fifth or sixth aspect of the present invention, Each of the plurality of nozzles is capable of ejecting ink in N different drop sizes, The at least one threshold matrix included in the threshold matrix set is N threshold matrices, The at least one threshold included in the threshold set is characterized by N thresholds.

[0017] The eighth aspect of the present invention relates to the seventh aspect of the present invention, The halftone processing unit is characterized in that for pixels in the raster data whose gradation value is (MN) or less, the threshold matrix set is used as a reference for the threshold to be compared with the gradation value in the raster data, and for pixels in the raster data whose gradation value is (M-N+1) or more, the threshold set is used as a reference for the threshold to be compared with the gradation value in the raster data.

[0018] A ninth aspect of the present invention is a printing method using a printing device having a plurality of nozzles that eject ink onto a printing medium, comprising: a halftone processing step of generating halftone image data based on a result of comparing the tone value of each pixel included in the raster data for printing with a threshold value; an ink ejection control step of controlling the ejection of ink from the plurality of nozzles based on the halftone image data; Including, The printing device includes: a threshold matrix set including at least one threshold matrix consisting of a plurality of thresholds arranged two-dimensionally, the plurality of thresholds being used for comparison with the gradation values ​​of a plurality of pixels included in the raster data; a threshold set including at least one threshold for comparing with a tone value of each pixel included in the raster data; Including, The halftone processing step is characterized in that, when generating the halftone image data, for each pixel, the reference for the threshold value to be compared with the gradation value in the raster data is switched between the threshold matrix set and the threshold set depending on the magnitude of the gradation value in the raster data.

[0019] A tenth aspect of the present invention relates to the ninth aspect of the present invention, In the halftone processing step, for pixels in the raster data whose gradation value is (K-1) or less, the threshold matrix set is used as a reference for the threshold to be compared with the gradation value in the raster data, where K is a predetermined gradation value, and for pixels in the raster data whose gradation value is K or more, the threshold set is used as a reference for the threshold to be compared with the gradation value in the raster data.

[0020] The eleventh aspect of the present invention is the ninth aspect of the present invention, The printing method includes: an input step of receiving input data including a plurality of objects; a gradation value conversion step of converting gradation values ​​of the plurality of objects to generate intermediate data; a rasterization processing step of generating the raster data by performing a rasterization process on the intermediate data; Further comprising: the plurality of objects are classified into a first type of object and a second type of object according to a predetermined condition; Let M be the maximum value of the gradation value, and K be a given gradation value, the threshold matrix set corresponds to a first gradation range, which is a range of gradation values ​​from 0 to (K-1), the threshold set is associated with a second tone range, which is a range of tone values ​​from K to M, inclusive; In the gradation value conversion step, the gradation values ​​of the first type objects among the plurality of objects are converted to gradation values ​​within the first gradation range, and the gradation values ​​of the second type objects among the plurality of objects are converted to gradation values ​​within the second gradation range.

[0021] A twelfth aspect of the present invention relates to the eleventh aspect of the present invention, the plurality of objects includes at least an image object and a line drawing object; the graphical object is classified into the first type of object; The line drawing object is characterized in that it is classified into the second type of object.

[0022] A thirteenth aspect of the present invention is any one of the ninth to twelfth aspects of the present invention, Each of the plurality of nozzles is capable of ejecting ink in N different drop sizes, The at least one threshold matrix included in the threshold matrix set is N threshold matrices, The at least one threshold included in the threshold set is characterized by N thresholds.

[0023] A fourteenth aspect of the present invention relates to the thirteenth aspect of the present invention, In the halftone processing step, for pixels in the raster data having a gradation value of (MN) or less, the threshold matrix set is used as a reference for the threshold to be compared with the gradation value in the raster data, and for pixels in the raster data having a gradation value of (M-N+1) or more, the threshold set is used as a reference for the threshold to be compared with the gradation value in the raster data.

[0024] A fifteenth aspect of the present invention is a print control program for controlling the operation of a printing device having a plurality of nozzles that eject ink onto a printing medium, comprising: a threshold matrix set including at least one threshold matrix consisting of a plurality of thresholds arranged two-dimensionally to be compared with the gradation values ​​of a plurality of pixels included in raster data for printing, and a threshold set including at least one threshold to be compared with the gradation values ​​of each pixel included in the raster data; a halftone processing step for generating halftone image data based on a result of comparing the gradation value of each pixel included in the raster data with a threshold value; an ink ejection control step of controlling the ejection of ink from the plurality of nozzles based on the halftone image data; Run the command, The halftone processing step is characterized in that, when generating the halftone image data, for each pixel, the reference for the threshold value to be compared with the gradation value in the raster data is switched between the threshold matrix set and the threshold set depending on the magnitude of the gradation value in the raster data. Effect of the Invention

[0025] According to the first aspect of the present invention, a printing device that prints by ejecting ink from a nozzle is provided with a threshold matrix set including at least one threshold matrix consisting of a plurality of thresholds arranged two-dimensionally, and a threshold set including at least one threshold, as data to be compared with the gradation value of each pixel during halftone processing. Then, during halftone processing, the reference destination of the data (threshold) to be compared with the gradation value of each pixel is switched between the threshold matrix set and the threshold set according to the magnitude of the gradation value of each pixel. In this way, the reference destination is switched based on the gradation value of each pixel. That is, the reference destination is switched without adding special data for switching the reference destination to the raster data for printing. Therefore, there is no need to expand the data bandwidth to realize multiscreening. Also, the data provided to be compared with the gradation value of each pixel is not a plurality of threshold matrix sets, but a threshold matrix set and a threshold set. Therefore, multiscreening can be performed by only making a slight change to a general configuration that does not employ multiscreening. As described above, it is possible to realize multiscreening in a printing device with a simpler circuit than before.

[0026] According to the second aspect of the present invention, for pixels with high gradation levels, the data (thresholds) to be compared with the gradation value of the pixel during halftone processing are referenced to a threshold set rather than a threshold matrix set. This allows the gradation value of the pixel in high gradation areas to be compared with a constant threshold. As a result, the uniformity of the contours of line drawing objects is improved, and the print quality of high gradation areas is improved.

[0027] According to the third aspect of the present invention, when multiple drop sizes are available, it is possible to eject ink from each nozzle at an appropriate drop size both in an area where halftone processing has been performed with reference to a threshold matrix set and in an area where halftone processing has been performed with reference to a threshold set.

[0028] According to the fourth aspect of the invention, it is possible to associate the N maximum gradation values ​​with N drop sizes. For example, if three drop sizes (S, M, L) are prepared and the maximum gradation value is 255, it is possible to associate the gradation value "255" with the L size, the gradation value "254" with the M size, and the gradation value "253" with the S size. This allows ink to be ejected in a specific drop size according to the gradation value in high gradation regions, improving the print quality in high gradation regions.

[0029] According to the fifth aspect of the invention, the same effects as those of the first aspect of the invention can be obtained.

[0030] According to the sixth aspect of the present invention, it is possible to make the reference destination of the data (threshold value) to be compared with the gradation value of each pixel different between the image data and the line drawing data, thereby making it possible to eject ink in an appropriate drop size from each nozzle in both the image area and the line drawing area.

[0031] According to the seventh aspect of the present invention, the same effects as those of the third aspect of the present invention can be obtained.

[0032] According to the eighth aspect of the invention, the same effects as those of the fourth aspect of the invention can be obtained.

[0033] According to the ninth aspect of the invention, the same effects as those of the first aspect of the invention can be obtained.

[0034] According to the tenth aspect of the present invention, the same effects as those of the second aspect of the present invention can be obtained.

[0035] According to the eleventh aspect of the invention, the same effects as those of the first aspect of the invention can be obtained.

[0036] According to the twelfth aspect of the present invention, the same effects as those of the sixth aspect of the present invention can be obtained.

[0037] According to the thirteenth aspect of the present invention, the same effects as those of the third aspect of the present invention can be obtained.

[0038] According to the fourteenth aspect of the present invention, the same effects as those of the fourth aspect of the present invention can be obtained.

[0039] According to the fifteenth aspect of the present invention, the same effects as those of the first aspect of the present invention can be obtained. [Brief description of the drawings]

[0040] [Figure 1] 1 is a diagram illustrating the overall configuration of a printing system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing a configuration example of an inkjet printing apparatus in the embodiment. [Diagram 3] FIG. 4 is a plan view showing one configuration example of a recording unit in the embodiment. [Figure 4] FIG. 4 is a diagram for explaining an example of nozzle arrangement in the embodiment. [Diagram 5] FIG. 2 is a block diagram showing a hardware configuration of the print control device in the embodiment. [Figure 6] 3 is a block diagram showing a schematic functional configuration of a control unit realized by execution of a print control program in the print control device in the embodiment. FIG. [Figure 7] FIG. 2 is a block diagram showing a configuration related to halftone processing in the embodiment. [Figure 8] 10 is a diagram for explaining a reference destination of data (threshold value) to be compared with the gradation value of each pixel in the embodiment. FIG. [Figure 9] 10A to 10C are diagrams for explaining halftone processing for pixels included in a line drawing region in the embodiment. [Figure 10] 10A to 10C are diagrams for explaining halftone processing for pixels included in an image area in the embodiment. [Figure 11] FIG. 2 is a block diagram showing a functional configuration of the print data generating device in the embodiment. [Figure 12] FIG. 11 is a diagram for explaining tone value conversion of a first type object in the embodiment. [Figure 13] FIG. 11 is a diagram for explaining tone value conversion of a second type object in the embodiment. [Figure 14] 6 is a flowchart showing the overall procedure for print output in the embodiment. [Figure 15] FIG. 11 is a block diagram showing a configuration relating to halftone processing in a modified example of the embodiment. [Figure 16] FIG. 1 is a block diagram showing a typical conventional configuration relating to halftone processing. [Figure 17] FIG. 13 is a diagram illustrating an example of a threshold matrix for an S size. [Figure 18] FIG. 13 is a diagram showing an example of a threshold matrix for M size. [Figure 19] FIG. 13 is a diagram illustrating an example of a threshold matrix for an L size. [Figure 20] FIG. 1 is a block diagram showing a conventional configuration for realizing multi-screening. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] An embodiment of the present invention will be described below with reference to the accompanying drawings. In the following embodiment (including modified examples), it is assumed that the minimum gradation value is 0 and the maximum gradation value is 255.

[0042] <1. Overall configuration of the printing system> FIG. 1 is an overall configuration diagram of a printing system according to an embodiment of the present invention. This printing system is composed of an inkjet printing device 10 and a print data generating device 30. The inkjet printing device 10 and the print data generating device 30 are connected to each other by a LAN 4. The print data generating device 30 generates raster data for printing by performing a rasterization process or the like on the input data. In this embodiment, it is assumed that a PDF file is provided as the input data to the print data generating device 30. The raster data generated by the print data generating device 30 is transferred to the inkjet printing device 10 via the LAN 4. The inkjet printing device 10 is composed of a printing machine main body 200 and a print control device 100 that controls the operation of the printing machine main body 200. The inkjet printing device 10 outputs a print image on a printing paper as a printing medium based on the raster data transferred from the print data generating device 30 without using a printing plate. The present invention can also be applied to a case where a printing medium other than printing paper (for example, a film) is used.

[0043] <2. Structure of the main body of the inkjet printing device> 2 is a schematic diagram showing an example of the configuration of the inkjet printing apparatus 10. As described above, the inkjet printing apparatus 10 is made up of the print control device 100 and the printing machine main body 200.

[0044] The printing press main body 200 includes a paper feed section 21 that supplies the printing paper 5 to the printing mechanism 22, the printing mechanism 22 that prints on the printing paper 5, and a paper winding section 28 that winds up the printing paper 5 into a roll after printing.

[0045] The printing mechanism 22 includes a first driving roller 221 for transporting the printing paper 5 to the inside, a plurality of support rollers 222 for transporting the printing paper 5 inside the printing mechanism 22, a recording unit 223 for recording a print image on the printing paper 5, a drying mechanism 224 for drying the printing paper 5 on which the print image has been recorded, an in-line scanner 225 as an imaging device for capturing an image of the printing image recorded on the printing paper 5 by the recording unit 223, and a second driving roller 226 for outputting the printing paper 5 from inside the printing mechanism 22. The imaging data obtained by capturing the print image with the in-line scanner 225 is sent to the print control device 100. The recording unit 223 is composed of a K-color head unit 23K that ejects K-color (black) ink, a C-color head unit 23C that ejects C-color (cyan) ink, an M-color head unit 23M that ejects M-color (magenta) ink, and a Y-color head unit 23Y that ejects Y-color (yellow) ink. In the following description, when there is no need to distinguish between the colors of ink ejected from the head units, the head units will be given the reference numeral 23.

[0046] 3 is a plan view showing an example of the configuration of the recording unit 223. As shown in FIG. 3, the recording unit 223 is composed of a K-color head unit 23K, a C-color head unit 23C, an M-color head unit 23M, and a Y-color head unit 23Y, which are arranged in a row in the transport direction (sub-scanning direction) of the print paper 5. Each head unit 23 is composed of a plurality of ink ejection heads (print heads) 231 arranged in a staggered pattern. Each ink ejection head 231 includes a large number of nozzles (not shown in FIG. 3) that eject ink. Each nozzle of the ink ejection head 231 included in the K-color head unit 23K ejects K-color ink, each nozzle of the ink ejection head 231 included in the C-color head unit 23C ejects C-color ink, each nozzle of the ink ejection head 231 included in the M-color head unit 23M ejects M-color ink, and each nozzle of the ink ejection head 231 included in the Y-color head unit 23Y ejects Y-color ink.

[0047] FIG. 4 is a diagram for explaining an example of the arrangement of nozzles in the ink ejection head 231. The ink ejection head 231 shown in FIG. 4 includes four rows of nozzle groups each consisting of a plurality of nozzles arranged in a main scanning direction (a direction perpendicular to the transport direction of the print paper 5). In FIG. 4, the portion marked with the reference numeral 41 shows a schematic diagram of the landing position of the ink ejected from each nozzle on the print paper 5. The nozzles in the ink ejection head 231 are arranged so that the landing position of the ink ejected from the nozzles included in the first row of nozzle groups, the landing position of the ink ejected from the nozzles included in the second row of nozzle groups, the landing position of the ink ejected from the nozzles included in the third row of nozzle groups, and the landing position of the ink ejected from the nozzles included in the fourth row of nozzle groups are different from each other. For example, the landing position of the ink ejected from each nozzle included in the first row of nozzle groups is between the landing position of the ink ejected from the nozzles included in the third row of nozzle groups and the landing position of the ink ejected from the nozzles included in the fourth row of nozzle groups. In the example shown in Figure 4, the landing position 42 of ink ejected from the nozzle labeled 26(p) is a position between the landing position 43 of ink ejected from the nozzle labeled 26(q) and the landing position 44 of ink ejected from the nozzle labeled 26(r).

[0048] It should be noted that the configurations shown in FIGS. 2 to 4 are merely examples, and the specific configurations of the print mechanism 22, the recording unit 223, and the ink ejection head 231 are not particularly limited.

[0049] <3. Print control device> <3.1 Hardware configuration> FIG. 5 is a block diagram showing a hardware configuration of the print control device 100. As shown in FIG. 5, the print control device 100 includes a main body 110, an auxiliary storage device 121, an optical disk drive 122, a display unit 123, a keyboard 124, and a mouse 125. The main body 110 includes a CPU 111, a memory 112, a first disk interface unit 113, a second disk interface unit 114, a display control unit 115, an input interface unit 116, and a communication interface unit 117. The CPU 111, the memory 112, the first disk interface unit 113, the second disk interface unit 114, the display control unit 115, the input interface unit 116, and the communication interface unit 117 are connected to each other via a system bus. The auxiliary storage device 121 is connected to the first disk interface unit 113. The optical disk drive 122 is connected to the second disk interface unit 114. The display unit (display device) 123 is connected to the display control unit 115. A keyboard 124 and a mouse 125 are connected to the input interface unit 116. The printer main body 200 is connected to the communication interface unit 117 via a communication cable. The communication interface unit 117 is also connected to the LAN 4. The auxiliary storage device 121 is a magnetic disk device or the like. An optical disk 19 serving as a computer-readable recording medium such as a CD-ROM or DVD-ROM is inserted into the optical disk drive 122. The display unit 123 is a liquid crystal display or the like. The display unit 123 is used to display information desired by the operator. The keyboard 124 and the mouse 125 are used by the operator to input instructions to this print control device 100.

[0050] The auxiliary storage device 121 stores a print control program (program for controlling the execution of print processing by the printer body 200) 13. The CPU 111 reads the print control program 13 stored in the auxiliary storage device 121 into the memory 112 and executes it to realize various functions of the print control device 100. The memory 112 includes a RAM (Random Access Memory) and a ROM (Read Only Memory). The memory 112 functions as a work area for the CPU 111 to execute the print control program 13 stored in the auxiliary storage device 121. The print control program 13 is stored in the computer-readable recording medium (non-transient recording medium) and provided. That is, the user, for example, purchases an optical disk 19 as a recording medium for the print control program 13, inserts it into the optical disk drive 122, reads out the print control program 13 from the optical disk 19, and installs it in the auxiliary storage device 121.

[0051] In the example shown in FIG. 5, the print control device 100 is provided with only one CPU 111 as a processor, but the present invention is not limited to this. A configuration using multiple processors, such as a configuration using multiple CPUs, can also be adopted. As the processor, in addition to the CPU 111, an MPU (Micro Processing Unit), a GPU (Graphics Processing Unit), a DSP (Digital Signal Processor), etc. can also be adopted. A combination of multiple types of processors can also be used. For example, with regard to the internal components of the control unit 50 described later (see FIG. 6), some of the components and the remaining components may be realized by different processors. Furthermore, a configuration including an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit) can also be adopted.

[0052] <3.2 Configuration of the control unit> FIG. 6 is a block diagram showing a schematic functional configuration of the control unit 50 realized by executing the print control program 13 in the print control device 100. As shown in FIG. 6, the control unit 50 generally includes a transport control unit 51, a halftone processing unit 52, an ink ejection control unit 53, a drying control unit 54, and an image capture control unit 55. The transport control unit 51 controls the speed (transport speed) at which the transport mechanism 29 transports the print paper 5. In this embodiment, the transport mechanism 29 is realized by the paper delivery unit 21, the first driving roller 221, the multiple support rollers 222, the second driving roller 226, and the paper winding unit 28 (see FIG. 2). The halftone processing unit 52 performs halftone processing on the printing raster data 64 transmitted from the print data generating device 30 to generate halftone image data (halftone dot data) 65 including information indicating the ink drop size corresponding to each pixel. In this embodiment, three types of ink drop sizes (S size, M size, and L size) are prepared. In other words, each of the multiple nozzles included in the recording unit 223 is capable of ejecting ink in three different drop sizes. The halftone processing unit 52 will be described in detail later. The ink ejection control unit 53 controls the ejection of ink from each nozzle of each ink ejection head 231 included in each head unit 23 constituting the recording unit 223 based on halftone image data 65. For example, the ink ejection timing and drop size are controlled. The drying control unit 54 controls the temperature (drying temperature) when the drying mechanism 224 dries the printing paper 5 after printing. The imaging control unit 55 controls the imaging timing of the print image by the inline scanner 225.

[0053] Generally, RGB format data is sent as raster data 64 for printing from the print data generating device 30 to the print control device 100, and color conversion processing is performed in the print control device 100 to convert the RGB format data into CMYK format data before halftone processing is executed. However, since the color conversion processing is not directly related to the present invention, a description of the color conversion processing is omitted.

[0054] <4. Halftone processing> Next, the halftone processing in this embodiment will be described in detail. FIG. 7 is a block diagram showing a configuration related to the halftone processing. The halftone processing unit 52 is composed of a reference destination switching unit 521 and a drop size determination unit 522. As can be seen from FIG. 7, a threshold matrix set 710 consisting of a threshold matrix 71(S) for S size, a threshold matrix 71(M) for M size, and a threshold matrix 71(L) for L size, and a threshold set 720 consisting of a threshold matrix 72(S) for S size, a threshold matrix 72(M) for M size, and a threshold matrix 72(L) for L size are provided. Each threshold matrix 71 constituting the threshold matrix set 710 is composed of a plurality of thresholds arranged two-dimensionally, which are used for comparison with the gradation values ​​of a plurality of pixels contained in the raster data 64 for printing, as in the conventional case. The threshold matrix set 710 and the threshold set 720 are stored in, for example, the auxiliary storage device 121, and are read out to the memory 112 and referred to when print output is executed. As described above, in the conventional configuration shown in FIG. 20, two types of threshold matrix sets are provided to realize multi-screening, whereas in this embodiment, one type of threshold matrix set 710 and one type of threshold set 720 are provided to realize multi-screening.

[0055] The reference destination switching unit 521 switches the reference destination of the data (threshold value) to be compared with the gradation value of each pixel between the threshold matrix set 710 and the threshold set 720 based on the gradation value of each pixel in the raster data 64. Meanwhile, in this embodiment, the reference destination is switched depending on whether each pixel is included in an image area or a line drawing area (including a character area). In this regard, pixels in the raster data 64 with a gradation value of 252 or less are considered to be included in the image area, and pixels in the raster data 64 with a gradation value of 253 or more are considered to be included in the line drawing area. Then, the threshold matrix set 710 is referred to when processing pixels included in the image area, and the threshold set 720 is referred to when processing pixels included in the line drawing area. That is, as shown in FIG. 8, the reference destination switching unit 521 sets the reference destination to the threshold matrix set 710 when processing pixels in the raster data 64 with a gradation value of 252 or less, and sets the reference destination to the threshold set 720 when processing pixels in the raster data 64 with a gradation value of 253 or more.

[0056] The drop size determination unit 522 determines a drop size corresponding to each pixel based on the gradation value in the raster data 64 (in other words, determines the data value of each pixel in the halftone image data 65, which is the output data). With regard to the processing of each pixel, if the reference destination is set to the threshold matrix set 710 by the reference destination switching unit 521, the drop size determination unit 522 compares the gradation value in the raster data 64 with the corresponding threshold value in each of the three threshold matrices 71 included in the threshold matrix set 710, and if the reference destination is set to the threshold set 720 by the reference destination switching unit 521, the drop size determination unit 522 compares the gradation value in the raster data 64 with the three threshold values ​​72 included in the threshold set 720. Depending on the comparison result, the data value of each pixel in the halftone image data 65 is determined.

[0057] Incidentally, as described above, pixels in the raster data 64 with a gradation value of 253 or more are considered to be included in a line drawing region, and threshold set 720 is referenced when processing pixels included in the line drawing region. With regard to threshold set 720, threshold 72(S) for S size is set to "253," threshold 72(M) for M size is set to "254," and threshold 72(L) for L size is set to "255." By defining the thresholds in this manner, as shown in Fig. 9, the drop size is set to S for pixels in the raster data 64 with a gradation value of 253, the drop size is set to M for pixels in the raster data 64 with a gradation value of 254, and the drop size is set to L for pixels in the raster data 64 with a gradation value of 255.

[0058] As described above, pixels in the raster data 64 with a gradation value of 252 or less are considered to be included in the image area, and the threshold matrix set 710 is referenced when processing pixels included in the image area. The three threshold matrices 71 constituting the threshold matrix set 710 (threshold matrix 71(S) for S size, threshold matrix 71(M) for M size, and threshold matrix 71(L) for L size) can be substantially the same as those used in the past (see Figs. 17 to 19) (however, the maximum gradation value is 252). By determining the drop size using the three threshold matrices 71, the relationship between the printing rate of S size, the printing rate of M size, and the printing rate of L size for each gradation value becomes, for example, as shown in Fig. 10. In Fig. 10, the solid line labeled with reference numeral 81 represents the printing rate of S size, the thick dotted line labeled with reference numeral 82 represents the printing rate of M size, and the thick solid line labeled with reference numeral 83 represents the printing rate of L size.

[0059] As described above, in this embodiment, during halftone processing, the reference destination of the data (thresholds) to be compared with the gradation value of each pixel is switched between the threshold matrix set 710 and the threshold set 720 depending on the magnitude of the gradation value.

[0060] According to this embodiment, for pixels in the raster data 64 whose gradation value is 252 or less, the halftone processor 52 refers to the threshold matrix set 710 as the threshold to be compared with the gradation value, and for pixels in the raster data 64 whose gradation value is 253 or more, the halftone processor 52 refers to the threshold set 720 as the threshold to be compared with the gradation value. However, the present invention is not limited to this. With K as a predetermined gradation value, the halftone processor 52 may refer to the threshold matrix set 710 as the threshold to be compared with the gradation value for pixels in the raster data 64 whose gradation value is (K-1) or less, and refer to the threshold set 720 as the threshold to be compared with the gradation value for pixels in the raster data 64 whose gradation value is K or more.

[0061] Furthermore, in this embodiment, three ink drop sizes are provided, and the maximum tone value is 255, but the present invention is not limited to this. In a case where N ink drop sizes (N is a natural number) are provided, and the maximum tone value is M, halftone processing unit 52 may refer to threshold matrix set 710 as the threshold value to be compared with the tone value for pixels in raster data 64 whose tone value is (MN) or less, and refer to threshold set 720 as the threshold value to be compared with the tone value for pixels in raster data 64 whose tone value is (M-N+1) or more.

[0062] <5. Configuration of the print data generating device> In the halftone processing unit 52, pixels in the raster data 64 with a tone value of 252 or less are considered to be included in the image area, and pixels in the raster data 64 with a tone value of 253 or more are considered to be included in the line drawing area. However, for the submitted data (PDF file) provided to the print data generating device 30, both the line drawing data and the image data can have tone values ​​of 0 to 255. Therefore, for the image data, values ​​of 0 to 255 must be converted to values ​​of 0 to 252, and for the line drawing data, values ​​of 0 to 255 must be converted to values ​​of 253 to 255. Therefore, in this embodiment, the print data generating device 30 performs a process of converting tone values ​​for the submitted data. The configuration of the print data generating device 30 will be described below. In this embodiment, the print data generating device 30 realizes a printing raster data generating device.

[0063] The hardware configuration of the print data generating device 30 is almost the same as the hardware configuration (see FIG. 5) of the print control device 100. However, unlike the print control device 100, the communication interface unit 117 is not connected to the printer main body 200 via a communication cable, and the auxiliary storage device 121 stores a program for generating raster data 64 for printing from input data.

[0064] Fig. 11 is a block diagram showing the functional configuration of the print data generating device 30. As shown in Fig. 11, the print data generating device 30 functionally includes a PDF analysis unit 310, a tone value conversion unit 320, and a rasterization processing unit 330. Note that Fig. 11 shows only the components related to the present invention.

[0065] The PDF analysis unit 310 analyzes internal data constituting a PDF file as the submitted data 61. This identifies the type of each of a plurality of objects included in the submitted data 61. The PDF analysis unit 310 outputs a PDF analysis result 62 including object type information indicating the type of each object.

[0066] The gradation value conversion unit 320 generates intermediate data 63 by converting the gradation values ​​of the multiple objects included in the submitted data 61 based on the object type information included in the PDF analysis result 62. In this embodiment, the multiple objects included in the submitted data 61 are classified into a first type object and a second type object according to a predetermined condition. For example, an image object and a background object are classified into a first type object, and a line drawing object and a character object are classified into a second type object. For the first type objects among the multiple objects included in the submitted data 61, the gradation value conversion unit 320 converts the gradation value in the submitted data 61 to a value between 0 and 252. The conversion is performed so that the relationship between the gradation value before conversion and the gradation value after conversion is, for example, as shown in FIG. 12. For the second type objects among the multiple objects included in the submitted data 61, the gradation value conversion unit 320 converts the gradation value in the submitted data 61 to a value between 253 and 255. The conversion is performed so that the relationship between the gradation values ​​before and after the conversion is as shown in FIG. 13, for example.

[0067] Generally speaking, with the maximum gradation value being M and K being a predetermined gradation value, the threshold matrix set 710 can be associated with a first gradation range that is a range of gradation values ​​from 0 to (K-1) inclusive, and the threshold set 720 can be associated with a second gradation range that is a range of gradation values ​​from K to M inclusive. Under this premise, the gradation value conversion unit 320 generates intermediate data 63 by converting the gradation values ​​of a first type of object among the multiple objects included in the submitted data 61 to gradation values ​​within the first gradation range, and converting the gradation values ​​of a second type of object among the multiple objects included in the submitted data 61 to gradation values ​​within the second gradation range.

[0068] The rasterization processing unit 330 performs rasterization processing on the intermediate data 63 by referring to the PDF analysis result 62. This generates raster data 64 for printing. The raster data 64 is transferred from the print data generating device 30 to the print control device 100.

[0069] <6. Print output procedure> The overall procedure (printing method) for print output in this printing system will be described with reference to the flowchart shown in Fig. 14. First, a PDF file including a plurality of objects is provided as input data 61 to the print data generating device 30 (step S10).

[0070] Next, in the print data generating device 30, the gradation value conversion unit 320 generates intermediate data 63 by converting the gradation values ​​of a plurality of objects included in the PDF file, which is the input data 61 (step S20). In this step S20, as described above, the gradation values ​​of the first type objects are converted to values ​​within the range of 0 to 252, and the gradation values ​​of the second type objects are converted to values ​​within the range of 253 to 255.

[0071] Next, in the print data generating device 30, the rasterization processing unit 330 performs a rasterization process on the intermediate data 63 generated in step S20 to generate raster data 64 for printing (step S30). Then, the raster data 64 is transferred from the print data generating device 30 to the print control device 100 in the inkjet printing device 10 (step S40).

[0072] After that, in the print control device 100, the halftone processing unit 52 generates halftone image data 65 based on the result of comparing the tone value of each pixel included in the raster data 64 with the threshold value (step S50). That is, halftone processing is performed. At that time, the reference destination of the threshold value to be compared with the tone value in the raster data 64 for each pixel is switched between the threshold matrix set 710 and the threshold set 720 according to the magnitude of the tone value in the raster data 64. Specifically, as described above, the threshold matrix set 710 is referenced when processing pixels in the raster data 64 whose tone value is 252 or less, and the threshold set 720 is referenced when processing pixels in the raster data 64 whose tone value is 253 or more.

[0073] After the halftone process is completed, the ink ejection control unit 53 controls the ejection of ink from each nozzle included in the recording unit 223 based on the halftone image data 65 generated in step S50 (step S60). As a result, a print image is recorded on the printing paper 5 (step S70).

[0074] In this embodiment, the submission step is realized by step S10, the tone value conversion step is realized by step S20, the rasterization processing step is realized by step S30, the halftone processing step is realized by step S50, and the ink ejection control step is realized by step S60.

[0075] <7. Effects> According to this embodiment, the inkjet printing device 10 has three drop sizes when ink is ejected from the nozzles, and is provided with a threshold matrix set 710 including three threshold matrices 71 consisting of a plurality of thresholds arranged two-dimensionally, and a threshold set 720 including three thresholds 72 as data to be compared with the gradation value of each pixel during halftone processing. Then, during halftone processing, the reference destination of the data (threshold) to be compared with the gradation value of each pixel is switched between the threshold matrix set 710 and the threshold set 720 according to the magnitude of the gradation value of each pixel. In this way, the reference destination is switched based on the gradation value of each pixel. That is, the reference destination is switched without adding special data for switching the reference destination, such as the attribute data 982 shown in FIG. 20, to the raster data 64 for printing. Therefore, there is no need to expand the data bandwidth to realize multiscreening. Also, the data provided for comparison with the gradation values ​​of pixels in the line drawing area is not a threshold matrix set, but a threshold value for each drop size. Therefore, multiscreening can be performed by simply making a slight change to a general configuration that does not employ multiscreening. As described above, according to this embodiment, multi-screening in the inkjet printing apparatus 10 can be achieved with a simpler circuit than in the past.

[0076] Furthermore, according to this embodiment, in each line image area, the nozzles eject ink in a fixed drop size of either S size, M size, or L size. Therefore, when, for example, a certain line image is recorded on the printing paper 5, the ink ejected from the nozzles does not have a mixture of multiple drop sizes. In other words, when a line image is recorded on the printing paper 5, ink of a fixed drop size is ejected from the nozzles. This improves the print quality of the line image area.

[0077] <8. Variations> In the above embodiment, three types (three stages) of sizes are provided as the drop size of ink ejected from each nozzle. Correspondingly, the threshold matrix set 710 is composed of three threshold matrices 71, and the threshold set 720 is composed of three thresholds 72. However, the present invention is not limited to this. The present invention can also be applied to a case where only one type of size is provided as the drop size of ink ejected from each nozzle. Therefore, as a modification of the above embodiment, a case where only one type of size is provided as the drop size of ink ejected from each nozzle will be described.

[0078] 15 is a block diagram showing the configuration related to halftone processing in this modified example. As in the above embodiment, halftone processing unit 52 is made up of reference destination switching unit 521 and drop size determination unit 522. In this modified example, the data value of each pixel in halftone image data 65 generated by drop size determination unit 522 is a value that indicates whether or not ink is to be ejected.

[0079] In this modification, since there is only one type of drop size, threshold matrix set 710 is made up of one threshold matrix 71, and threshold set 720 is made up of one threshold 72. In this modification as well, when processing pixels included in an image region, reference destination switching unit 521 sets the reference destination to threshold matrix set 710, and when processing pixels included in a line drawing region, reference destination switching unit 521 sets the reference destination to threshold set 720. Then, with regard to the processing of each pixel, if the reference destination is set to threshold matrix set 710, drop size determination unit 522 compares the gradation value in raster data 64 with the corresponding threshold in threshold matrix 71, and if the reference destination is set to threshold set 720, drop size determination unit 522 compares the gradation value in raster data 64 with threshold 72. Depending on the comparison result, the data value of each pixel in halftone image data 65 is determined.

[0080] According to this modification, the reference data to be compared with the gradation value of each pixel during halftone processing is switched between threshold matrix 71 and threshold 72 depending on the magnitude of the gradation value of each pixel. With this configuration, like the above embodiment, there is no need to expand the data bandwidth to achieve multi-screening, and multi-screening can be performed by simply making slight changes to a general configuration that does not employ multi-screening. As described above, this modification also makes it possible to achieve multi-screening in inkjet printing device 10 with simpler circuitry than in the past.

[0081] <9.Other> The present invention is not limited to the above embodiment (including the modified example), and various modifications can be made without departing from the spirit of the present invention. For example, in the above embodiment (including the modified example), an inkjet printing apparatus 10 that performs color printing is adopted. However, the present invention is not limited to this, and an inkjet printing apparatus that performs monochrome printing may be adopted. Also, in the above embodiment (including the modified example), an inkjet printing apparatus 10 that uses water-based ink is adopted. However, the present invention is not limited to this, and an inkjet printing apparatus that uses UV ink (ultraviolet light curable ink) such as an inkjet printing apparatus for label printing may be adopted. In this case, an ultraviolet light irradiation mechanism that cures the UV ink on the printing paper 5 by irradiating ultraviolet light is provided inside the printing mechanism 22 (see FIG. 2) instead of the drying mechanism 224. [Explanation of symbols]

[0082] 10...Inkjet printing device 30...Print data generating device 50...Control unit 52...Halftone processing unit 61...Submission data 64...Raster data 65...Halftone image data 71...Threshold matrix 72...Threshold 100...Print control device 200…Printing machine body 310...PDF analysis department 320... Gradation value conversion unit 330...Rasterization processing unit 521...Reference destination switching section 522: Drop size determination unit 710...Threshold matrix set 720…Threshold set

Claims

1. A printing device having a plurality of nozzles and performing printing by ejecting ink from the plurality of nozzles onto a printing medium, a threshold matrix set including at least one threshold matrix consisting of a plurality of thresholds arranged two-dimensionally, the plurality of thresholds being used for comparison with the gradation values ​​of a plurality of pixels included in the raster data for printing; a threshold set including at least one threshold for comparing with a gradation value of each pixel included in the raster data; a halftone processing unit that generates halftone image data based on a result of comparing the gradation value of each pixel included in the raster data with a threshold value; Equipped with A printing device characterized in that, when generating the halftone image data, the halftone processing unit switches, for each pixel, the reference for the threshold value to be compared with the gradation value in the raster data between the threshold matrix set and the threshold set depending on the magnitude of the gradation value in the raster data.

2. The printing device described in claim 1, characterized in that, for pixels in the raster data whose gradation value is (K-1) or less, K is a predetermined gradation value, and the halftone processing unit uses the threshold matrix set as a reference for thresholds to be compared with the gradation value in the raster data, and for pixels in the raster data whose gradation value is K or more, uses the threshold set as a reference for thresholds to be compared with the gradation value in the raster data.

3. Each of the plurality of nozzles is capable of ejecting ink in N different drop sizes, The at least one threshold matrix included in the threshold matrix set is N threshold matrices, 3. The printing device according to claim 1, wherein the at least one threshold included in the threshold set is N thresholds.

4. 4. The printing device according to claim 3, wherein the maximum value of the gradation value is M, and the halftone processing unit references the threshold matrix set as a reference for thresholds to be compared with the gradation value in the raster data for pixels in the raster data whose gradation value is (M-N) or less, and references the threshold set as a reference for thresholds to be compared with the gradation value in the raster data for pixels in the raster data whose gradation value is (M-N+1) or more.

5. 2. A printing system including the printing device according to claim 1 and a printing raster data generating device that generates the raster data based on input data including a plurality of objects, the plurality of objects are classified into a first type of object and a second type of object according to a predetermined condition; Let M be the maximum value of the gradation value, and K be a predetermined gradation value, the threshold matrix set corresponds to a first gradation range, which is a range of gradation values ​​from 0 to (K−1), the threshold set is associated with a second tone range, which is a range of tone values ​​from K to M, inclusive; The printing raster data generating device includes: a gradation value conversion unit that converts gradation values ​​of the first type objects of the plurality of objects into gradation values ​​within the first gradation range and converts gradation values ​​of the second type objects of the plurality of objects into gradation values ​​within the second gradation range, thereby generating intermediate data; a rasterization processing unit that generates the raster data by performing a rasterization process on the intermediate data; A printing system comprising:

6. the plurality of objects includes at least an image object and a line drawing object; the graphical objects are classified into the first type of objects; 6. The printing system of claim 5, wherein the line drawing objects are classified as objects of the second type.

7. Each of the plurality of nozzles is capable of ejecting ink in N different drop sizes, The at least one threshold matrix included in the threshold matrix set is N threshold matrices, 7. The printing system according to claim 5, wherein the at least one threshold included in the threshold set is N thresholds.

8. The printing system described in claim 7, characterized in that the halftone processing unit uses the threshold matrix set as a reference for thresholds to be compared with the gradation values ​​in the raster data for pixels whose gradation values ​​in the raster data are (M-N) or less, and uses the threshold set as a reference for thresholds to be compared with the gradation values ​​in the raster data for pixels whose gradation values ​​in the raster data are (M-N+1) or more.

9. A printing method using a printing device having a plurality of nozzles that eject ink onto a printing medium, comprising: a halftone processing step of generating halftone image data based on a result of comparing the tone value of each pixel included in the raster data for printing with a threshold value; an ink ejection control step of controlling the ejection of ink from the plurality of nozzles based on the halftone image data; Including, The printing device includes: a threshold matrix set including at least one threshold matrix consisting of a plurality of thresholds arranged two-dimensionally, the plurality of thresholds being used for comparison with the gradation values ​​of a plurality of pixels included in the raster data; a threshold set including at least one threshold for comparing with a tone value of each pixel included in the raster data; Including, A printing method characterized in that in the halftone processing step, when generating the halftone image data, the reference for the threshold value to be compared with the gradation value in the raster data for each pixel is switched between the threshold matrix set and the threshold set depending on the magnitude of the gradation value in the raster data.

10. 10. The printing method according to claim 9, wherein in the halftone processing step, for pixels in the raster data whose gradation value is (K-1) or less, the threshold matrix set is used as a reference for the threshold to be compared with the gradation value in the raster data, where K is a predetermined gradation value, and for pixels in the raster data whose gradation value is K or more, the threshold set is used as a reference for the threshold to be compared with the gradation value in the raster data.

11. an input step of receiving input data including a plurality of objects; a gradation value conversion step of converting gradation values ​​of the plurality of objects to generate intermediate data; a rasterization processing step of generating the raster data by performing a rasterization process on the intermediate data; Further comprising: the plurality of objects are classified into a first type of object and a second type of object according to a predetermined condition; Let M be the maximum value of the gradation value, and K be a predetermined gradation value, the threshold matrix set corresponds to a first gradation range, which is a range of gradation values ​​from 0 to (K−1), the threshold set is associated with a second tone range, which is a range of tone values ​​from K to M, inclusive; 10. The printing method of claim 9, wherein in the gradation value conversion step, the gradation values ​​of the first type objects among the plurality of objects are converted to gradation values ​​within the first gradation range, and the gradation values ​​of the second type objects among the plurality of objects are converted to gradation values ​​within the second gradation range.

12. the plurality of objects includes at least an image object and a line drawing object; the graphical objects are classified into the first type of objects; 12. The method of claim 11, wherein the line drawing objects are classified as objects of the second type.

13. Each of the plurality of nozzles is capable of ejecting ink in N different drop sizes, The at least one threshold matrix included in the threshold matrix set is N threshold matrices, 13. The printing method according to claim 9, wherein the at least one threshold value included in the threshold set is N threshold values.

14. 14. The printing method according to claim 13, wherein in the halftone processing step, for pixels in the raster data whose gradation value is (M-N) or less, the threshold matrix set is used as a reference for the threshold to be compared with the gradation value in the raster data, and for pixels in the raster data whose gradation value is (M-N+1) or more, the threshold set is used as a reference for the threshold to be compared with the gradation value in the raster data.

15. A print control program for controlling the operation of a printing device having a plurality of nozzles that eject ink onto a print medium, a threshold matrix set including at least one threshold matrix consisting of a plurality of thresholds arranged two-dimensionally for comparing with the gradation values ​​of a plurality of pixels included in raster data for printing, and a threshold set including at least one threshold for comparing with the gradation values ​​of each pixel included in the raster data; a halftone processing step for generating halftone image data based on a result of comparing the gradation value of each pixel included in the raster data with a threshold value; an ink ejection control step of controlling the ejection of ink from the plurality of nozzles based on the halftone image data; Run the command, A printing control program characterized in that, in the halftone processing step, when generating the halftone image data, the reference for the threshold value to be compared with the gradation value in the raster data for each pixel is switched between the threshold matrix set and the threshold set depending on the magnitude of the gradation value in the raster data.

Images