Image processing device and computer program

Abstract

To suppress an edge composed of a specific color from becoming unclear.SOLUTION: A controller of an image processing device acquires target image data indicating a target image, executes a pixel number adjustment process which is either a process of increasing the number of pixels of the target image or a process of decreasing the number of pixels of the target image with respect to the target image data to generate the adjusted image data, and generates print data for causing a print execution unit to print the image, using the adjusted image data. In the pixel number adjustment process, a first adjustment process executed for the portion composed of a specific color in the target image adopts a value of one pixel selected from among one or more pixels corresponding to the target image, as a value of the adjusted pixels.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] This specification relates to an image processing technique for generating print data using image data, and in particular to an image processing technique that includes processing for adjusting the number of pixels of an image represented by image data when generating print data. [Background technology]

[0002] When generating print data for printing an image in a print execution unit such as an inkjet printer, an adjustment process (e.g., enlargement process or reduction process) is performed to adjust the number of pixels of the image according to the printing resolution of the print execution unit (e.g., Patent Document 1). Due to such an adjustment process, for example, a gray area, which is an intermediate color between black and white, may occur between the black characters and the white background, making the edge composed of black and white unclear. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-193231 A Summary of the Invention [Problem to be solved by the invention]

[0004] This specification discloses a new technology that can prevent edges formed of specific colors such as black and white from becoming unclear in an image printed using print data. [Means for solving the problem]

[0005] The technology disclosed in this specification has been made to solve at least a part of the above-mentioned problems, and can be realized as the following application examples.

[0006] [Application Example 1] An image processing device having a controller, wherein the controller acquires target image data indicating a target image, performs a pixel number adjustment process on the target image data, which is either a process for increasing the number of pixels of the target image or a process for decreasing the number of pixels of the target image, to generate adjusted image data, and generates print data using the adjusted image data for causing a print execution unit to print an image, and a first adjustment process of the pixel number adjustment process, which is performed on a portion of the target image that is composed of a specific color, is a process of adopting the value of one pixel selected from one or more corresponding pixels of the target image as the value of the adjusted pixel.

[0007] According to the above configuration, the first adjustment process performed on the portion configured with the specific color is a process of adopting the value of one pixel selected from one or more corresponding pixels of the target image as the value of the pixel after the adjustment process. As a result, it is possible to prevent pixels of a color different from the specific color from appearing in the portion configured with the specific color. Therefore, it is possible to prevent the edge configured with the specific color from becoming unclear. [Application Example 2] The image processing apparatus according to Application Example 1, wherein the specific colors are white and black, the image processing apparatus. [Application Example 3] The image processing apparatus according to Application Example 2, wherein the printing execution unit performs printing using a black coloring material and a plurality of colored coloring materials, wherein the target image data and the adjusted image data are image data indicating the color of each pixel with color values in a first color system, wherein the controller executes a process including a color conversion process on the adjusted image data to generate the print data, wherein the color conversion process is a process of converting the color values in the first color system included in the adjusted image data into color values in a second color system, wherein the color values in the second color system are color values including a plurality of component values corresponding to the black coloring material and the plurality of colored coloring materials, the image processing apparatus. [Application Example 4] The image processing apparatus according to Application Example 3, wherein the printing execution unit, a print head including a first nozzle row corresponding to the black coloring material and a plurality of second nozzle rows corresponding to the plurality of colored coloring materials, a sub-scanning unit that executes sub-scanning for relatively moving a print medium in a first direction with respect to the print head, a main-scanning unit that executes main-scanning for relatively moving the print head in a second direction intersecting the first direction with respect to the print medium, and includes, wherein the printing execution unit executes printing by repeatedly performing partial printing for discharging the coloring material from the print head while performing the main scanning and the sub-scanning using the print data, the number of nozzles for discharging the black coloring material in the first nozzle row is larger than the number of nozzles for discharging the colored coloring material in one of the second nozzle rows, an image having a predetermined width printed using only the black coloring material is printed by the partial printing n times (n is an integer of 1 or more), an image having the predetermined width printed using at least one of the colored coloring materials is printed by the partial printing m times (m is an integer satisfying n < m), the image processing apparatus. [Application Example 5] The image processing apparatus according to any one of Application Examples 1 to 4, wherein, among the pixel number adjustment processes, the second adjustment process executed on a portion including a color different from the specific color in the target image adopts, as the value of the adjusted pixel, a value obtained by interpolation using the values of two or more corresponding pixels of the target image. The image processing apparatus.

[0008] The technology disclosed in this specification can be realized in various forms, such as a printing device, a printing method, an image processing method, a computer program for realizing the functions of these devices or the above methods, a recording medium on which the computer program is recorded, etc. [Brief description of the drawings]

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

[0010] A. First Example: A-1: Configuration of Printer 200 Next, an embodiment of the present invention will be described based on an example of the present invention. Fig. 1 is a block diagram showing the configuration of a printer 200 as an image processing apparatus according to the example of the present invention.

[0011] The printer 200 includes, for example, a print mechanism 100 as a print execution unit, a CPU 210 as a controller for the print mechanism 100, a non-volatile storage device 220 such as a hard disk drive, a volatile storage device 230 such as a hard disk or flash memory, an operation unit 260 such as buttons or a touch panel for acquiring operations by a user, a display unit 270 such as a liquid crystal display, and a communication unit 280. The printer 200 is connected to an external device, for example, a user's terminal device (not shown) via the communication unit 280 so as to be able to communicate with the external device.

[0012] The volatile storage device 230 provides a buffer area 231 for temporarily storing various intermediate data generated when the CPU 210 performs processing. The non-volatile storage device 220 stores a computer program CP. In this embodiment, the computer program CP is a control program for controlling the printer 200. The computer program CP may be provided by being stored in the non-volatile storage device 220 at the time of shipment of the printer 200. Alternatively, the computer program CP may be provided in a form downloaded from a server, or in a form stored on a DVD-ROM or the like. By executing the computer program CP, the CPU 210 controls, for example, the print mechanism 100 to perform a print process described below.

[0013] The printing mechanism 100 performs printing by ejecting ink (droplets) of each of the colors cyan (C), magenta (M), yellow (Y), and black (K). The printing mechanism 100 includes a print head 110, a head drive unit 120, a main scanning unit 130, and a transport unit 140.

[0014] Fig. 2 is a diagram showing a schematic configuration of the printing mechanism 100. As shown in Fig. 2(A), the main scanning unit 130 includes a carriage 133 on which the print head 110 is mounted, and a sliding shaft 134 that holds the carriage 133 so that it can move back and forth along the main scanning direction (the X-axis direction in Fig. 2). The main scanning unit 130 uses the power of a main scanning motor (not shown) to reciprocate the carriage 133 along the sliding shaft 134. This achieves main scanning, which reciprocates the print head 110 along the main scanning direction relative to the paper M.

[0015] The conveying section 140 holds the paper M and conveys the paper M in a conveying direction AR (+Y direction in FIG. 2) intersecting the main scanning direction. As shown in FIG. 2A, the conveying section 140 includes a paper tray 145, an upstream roller pair 142, and a downstream roller pair 141. Hereinafter, the upstream side (-Y side) of the conveying direction AR will also be simply referred to as the upstream side, and the downstream side (+Y side) of the conveying direction AR will also be simply referred to as the downstream side.

[0016] The upstream roller pair 142 holds the paper M upstream (-Y side) of the print head 110, and the downstream roller pair 141 holds the paper M downstream (+Y side) of the print head 110. The paper platform 145 is located between the upstream roller pair 142 and the downstream roller pair 141, and is disposed in a position facing the nozzle forming surface 111 of the print head 110. The downstream roller pair 141 and the upstream roller pair 142 are driven by a transport motor (not shown), whereby the paper M is transported.

[0017] While the main scanning unit 130 is performing a main scan of the print head 110, the head driving unit 120 (FIG. 1) supplies a driving signal to the print head 110 to drive the print head 110. In accordance with the driving signal, the print head 110 ejects ink onto the paper being transported by the transport unit 140 to form dots.

[0018] Fig. 2(B) shows the configuration of the print head 110 as viewed from the -Z side (the bottom side in Fig. 2). As shown in Fig. 2(B), a plurality of nozzle rows consisting of a plurality of nozzles, that is, nozzle rows NC, NM, NY, and NK that eject the above-mentioned C, M, Y, and K inks, are formed on the nozzle forming surface 111 of the print head 110. Each nozzle row includes a plurality of nozzles NZ aligned along the transport direction AR.

[0019] The nozzles NZ in one nozzle row are arranged at a predetermined nozzle interval along the transport direction AR, with their positions in the transport direction AR (+Y direction) different from one another. The nozzle interval is the length in the transport direction AR between two nozzles NZ adjacent to each other in the transport direction AR among the nozzles NZ in one nozzle row. The nozzle interval NTc of the nozzle rows NC, NM, and NY of the chromatic colors C, M, and Y is, for example, an interval equivalent to 100 dpi, that is, (1 / 100) inch. The nozzle interval NTk of the nozzle row NK of the achromatic color K is, for example, an interval equivalent to 300 dpi, that is, (1 / 300) inch. Therefore, in the second embodiment, the nozzle interval NTc of the nozzle rows NC, NM, and NY of the chromatic colors is three times longer than the nozzle interval NTk of the nozzle row NK of the K. Also, the number of nozzles in the nozzle row NK of the K is three times greater than the number of nozzles in the nozzle rows NC, NM, and NY of the chromatic colors. For example, the nozzle row NK includes three nozzle rows that are shifted in the transport direction AR by a nozzle spacing NTk, thereby achieving a shorter nozzle spacing. This allows, for example, printing using only K ink to print an image of the same resolution at a higher speed than printing using chromatic color (CMY) inks.

[0020] The nozzle rows NC, NM, NY, and NK are positioned differently in the main scanning direction (X direction in FIG. 2B), and overlap each other in the transport direction AR (Y direction in FIG. 2B). For example, in the example of FIG. 2B, the nozzle row NM is disposed in the +X direction of the nozzle row NY that ejects Y ink.

[0021] A-2. Printing Overview The printing mechanism 100 prints a print image OI on paper M by alternately performing partial printing multiple times, in which ink is ejected from the print head 110 to form dots on paper M while main scanning is performed by the main scanning unit 130, and sub-scanning (transporting paper M) by the transport unit 140.

[0022] FIG. 3 is an explanatory diagram of the operation of the printing mechanism 100. FIG. 3 shows a print image OI printed on paper M. In this embodiment, the print image OI has a resolution of 600 dpi in the main scanning direction (X direction in FIG. 3) and a resolution of 300 dpi in the transport direction AR (Y direction in FIG. 3). The print image OI extends in the main scanning direction and includes multiple raster lines RL (for example, RL1 in FIG. 3) that are positioned differently from one another in the transport direction AR. Each raster line RL is a line on which multiple dots can be formed.

[0023] The print image OI includes a plurality of partial print images PI. In the example of Fig. 3, the print image OI includes partial print images PI1 to PI5. The length of one partial print image PI in the transport direction is approximately equal to the length (nozzle length) of the nozzle rows NC, NM, NY, and NK in the transport direction AR.

[0024] Each partial print image PI is printed by one partial printing or three partial printings. The printing direction of the partial printing is either the forward pass direction or the backward pass direction. That is, the partial printing is either forward pass printing in which dots are formed while performing a main scan in the forward pass direction (-X direction in FIG. 3) or backward pass printing in which dots are formed while performing a main scan in the backward pass direction (+X direction in FIG. 3). In FIG. 3, a solid arrow in the +X direction or -X direction is added within the partial image. A partial image with one arrow added (for example, PI1, PI2 in FIG. 3) is printed by one partial printing. A partial image with three arrows added (for example, PI3 to PI5 in FIG. 3) is printed by three partial printings.

[0025] In the printing of this embodiment, as described above, the resolution in the transport direction AR is 300 dpi. That is, the multiple raster lines RL included in the partial print image PI are arranged in the transport direction AR at intervals of (1 / 300) inch, which is an interval equivalent to 300 dpi. As described above, in this embodiment, the nozzle interval NTk of the K nozzle row NK is an interval equivalent to 300 dpi, so the K dots of one partial print image PI are formed in one partial print. The nozzle interval NTc of the chromatic color (CMY) nozzle row NK is an interval equivalent to 100 dpi, so the chromatic color dots of one partial print image PI are formed in three partial prints. These three partial prints are performed, for example, with a small amount of paper M (for example, nozzle interval NTk equivalent to 300 dpi) transported between them. As a result, the chromatic dots of the 3nth (n is an integer equal to or greater than 0) raster line RL, the chromatic dots of the (3n+1)th raster line RL, and the chromatic dots of the (3n+2)th raster line RL included in one partial print image PI are each formed by different partial printing. As a result, the chromatic dots are formed at intervals equivalent to 300 dpi.

[0026] For this reason, the partial print images PI1 and PI2 containing only K dots are printed in one partial printing, and the partial print images PI3 to PI5 containing CMY dots are printed in three partial printings. Note that the K dots contained in the partial print images PI3 to PI5 containing CMY dots are printed in, for example, one of the three partial printings. Therefore, the time required to print the partial print images PI1 and PI2 containing only K dots is shorter than the time required to print the partial print images PI3 to PI5 containing CMY dots.

[0027] A-3. Printing process A printing process for executing the printing described above with reference to FIG. 3 will be described. The CPU 210 (FIG. 1) of the printer 200 executes the printing process based on a printing instruction from a user. The printing instruction includes designation of image data showing an image to be printed. FIG. 4 is a flowchart of the printing process. In S110 of FIG. 3, the CPU 210 acquires image data designated by the printing instruction from the non-volatile storage device 220. The acquired image data is, for example, RGB image data. The RGB image data is bitmap data including RGB values ​​for each pixel. The RGB values ​​are, for example, color values ​​of the RGB color system including three component values ​​of red (R), green (G), and blue (B). Note that if the image data is data in a format different from RGB image data (for example, image data described in a page description language), a rasterization process is executed in this step and the image data is converted into RGB image data.

[0028] The RGB image RI shown by the acquired RGB image data corresponds to the print image OI in Fig. 3. For this reason, Fig. 3 can also be said to be a diagram showing the RGB image RI. The RGB image RI includes a plurality of partial images PRI corresponding to the plurality of partial print images PI (images formed by dots) described above. In the example of Fig. 3, the RGB image RI includes five partial images PRI1 to PRI5 corresponding to the five partial print images PI1 to PI5.

[0029] In S120, the CPU 210 selects one partial image of interest from among a plurality of partial images PRI of the RGB image RI. In the example of Fig. 3, five partial images PRI1 to PRI5 are selected as partial images of interest in sequence from the downstream side of the transport direction AR (upper side of Fig. 3). Hereinafter, the RGB image data indicating the partial image of interest is also referred to as partial image data of interest. In addition, in the RGB image RI, the direction corresponding to the transport direction AR of the print image OI is referred to as the transport direction AR in the RGB image RI, and the direction corresponding to the main scanning direction of the print image OI is referred to as the main scanning direction in the RGB image RI.

[0030] In S130, the CPU 210 executes a reduction process on the target portion image data. In this specification, a process of decreasing at least one of the number of pixels in the main scanning direction and the number of pixels in the transport direction is called a reduction process. A process of increasing at least one of the number of pixels in the main scanning direction and the number of pixels in the transport direction is called an enlargement process. In this embodiment, as described above, the print resolution (300 dpi) in the transport direction AR (sub-scanning direction) is half the print resolution (600 dpi) in the main scanning direction. For this reason, in S130 of this embodiment, a reduction process is executed to halve the number of pixels in the transport direction AR without changing the number of pixels in the main scanning direction. In this way, by executing a reduction process according to the print resolution, it is possible to print a print image OI that appropriately expresses the RGB image RI. Details of the reduction process will be described later.

[0031] In S140, the CPU 210 executes a color conversion process on the target portion image data that has been reduced by the reduction process. The color conversion process is a process for converting the RGB values ​​of a plurality of pixels that constitute the target portion image into CMYK values. The CMYK values ​​are color values ​​of the CMYK color system that include component values ​​(in this embodiment, component values ​​of C, M, Y, and K) that correspond to the inks used in printing. The color conversion process is executed, for example, by referring to a lookup table that specifies the correspondence between RGB values ​​and CMYK values.

[0032] In the color conversion process of this embodiment, RGB values ​​indicating achromatic colors with a density equal to or greater than the reference density (e.g., black and dark gray) are converted to CMYK values ​​in which only the K component value is greater than 0 and the CMY component values ​​are 0. For example, an RGB value (R, G, B)=(0, 0, 0) indicating black is converted to a CMYK value (C, M, Y, K)=(0, 0, 0, 255). In contrast, an RGB value indicating achromatic colors with a density less than the reference density except for white (e.g., light gray or medium gray) is converted to a CMYK value including CMY component values ​​greater than 0. For example, an RGB value (R, G, B)=(127, 127, 127) indicating medium gray is converted to a CMYK value (C, M, Y, K)=(127, 128, 130, 5). In other words, in this embodiment, the color conversion process is executed so that achromatic colors with a density equal to or greater than the reference density are printed using only K dots, and achromatic colors with a density less than the reference density are printed using CMY dots as well. If achromatic colors with a density less than the reference density were represented using only black dots, the roughness of the black parts of the printed image would be noticeable, and image quality would be easily degraded.

[0033] In S150, halftone processing is performed on the color-converted image data of the portion of interest (CMYK image data). This generates dot data indicating the partial print image PI corresponding to the portion of interest image. The dot data is data that indicates the dot formation state for each pixel for each color component of CMYK. In this embodiment, the component value of each pixel of the dot data is two-level, "no dot" and "dot present". Alternatively, the component value of each pixel of the dot data may indicate the dot formation state in four levels, "no dot", "small", "medium", and "large". The halftone processing is performed using a known method such as a dither method or an error diffusion method.

[0034] In S160, the CPU 210 judges whether the partial print image PI corresponding to the partial image of interest is printed using only K ink based on the dot data generated in S150. Specifically, if the CMY component values ​​of all pixels of the dot data generated in S150 are values ​​indicating "no dot" and only the K component value contains a value indicating "dot presence", it is judged that the partial print image PI corresponding to the partial image of interest is printed using only K ink. If the CMY component values ​​of at least some pixels of the dot data are values ​​indicating "dot presence", it is judged that the partial print image PI corresponding to the partial image of interest is printed using chromatic ink.

[0035] If the partial print image PI corresponding to the target partial image is printed using only K ink (S160: YES), in S170 the CPU 210 controls the printing mechanism 100 to print the partial print image PI in one partial printing. For example, the CPU 210 adds control data indicating the transport amount of the paper M to be transported after one partial printing to the dot data generated in S150, and outputs the result to the printing mechanism 100. The printing mechanism 100 executes one partial printing based on the dot data to print the partial print image PI.

[0036] If it is determined that the partial print image PI corresponding to the target partial image is printed using chromatic inks (S160: NO), in S180, the CPU 210 controls the printing mechanism 100 to print the partial print image PI by three partial prints. For example, the CPU 210 divides the dot data generated in S150 into three data corresponding to the three partial prints, adds control data indicating the transport amount of the paper M to be transported after the partial print, and outputs the result to the printing mechanism 100. The printing mechanism 100 executes three partial prints based on the three data corresponding to the three partial prints, and prints the partial print image PI.

[0037] In S190, the CPU 210 judges whether or not all partial print images PI of the print image OI to be printed have been printed by the printing mechanism 100. If there are partial print images PI that have not been printed, the CPU 210 returns to S120. If all partial print images PI have been printed by the printing mechanism 100 (S190: YES), the CPU 210 ends the printing process.

[0038] A-4. Reduction processing The reduction process in S130 in Fig. 4 will be described below. Fig. 5 is an explanatory diagram of the reduction process. In the reduction process of this embodiment, two types of reduction process are used: reduction process by simple thinning and reduction process by linear interpolation.

[0039] The reduction process by simple thinning will be described with reference to Fig. 5(A). An example of a partial image PRI before reduction is shown on the left side of Fig. 5(A). The partial image PRI before reduction includes a plurality of pixels Pi arranged in a matrix along the conveying direction AR (Y direction in Fig. 5) and the main scanning direction (X direction in Fig. 5).

[0040] The right side of Fig. 5(A) shows a reduced partial image RDIa. This reduced partial image RDIa is an image obtained by reducing the unreduced partial image PRI by a reduction process using simple thinning. The reduced partial image RDIa includes a plurality of pixels Poa arranged in a matrix along the transport direction AR and the main scanning direction.

[0041] In the following, the pixel Pi of the partial image PRI before reduction is also called the input pixel Pi, and the pixel Poa of the reduced partial image RDIa is also called the output pixel Poa. As described above, in the reduction process of this embodiment, in order to reduce the partial image PRI according to the print resolution, the number of pixels in the main scanning direction is not changed, and the number of pixels in the transport direction AR is halved. For this reason, in FIG. 5B, the output pixel Poa is illustrated with the length of the output pixel Poa in the transport direction AR twice the length in the main scanning direction so that the correspondence between the input pixel Pi and the output pixel Poa can be easily understood. For example, two input pixels Pi located in the area Ai of the partial image PRI before reduction correspond to one output pixel Poa located in the area Aoa of the reduced partial image RDIa.

[0042] The partial image PRI before reduction in FIG. 5(A) includes only white (e.g., (R, G, B)=(255, 255, 255)) pixels PiW and black (e.g., (R, G, B)=(0, 0, 0)) pixels PiB. In reduction processing by simple thinning, the value of the output pixel Poa is set to the value of one pixel selected from two corresponding input pixels Pi. In general, of the one or more corresponding input pixels Pi, a pixel closest to the output pixel Poa is selected (the so-called nearest neighbor method). In this embodiment, the distance between the output pixel Poa and each of the two corresponding input pixels Pi is equal. For this reason, of the two corresponding input pixels Pi, a pixel at a predetermined position (e.g., a pixel on the upper side (+Y side)) is selected.

[0043] As shown in FIG. 5(A), in a reduction process using simple thinning, if the partial image PRI before reduction contains only white pixels PiW and black pixels PiB, the reduced partial image RDIa also contains only white pixels PoW and black pixels PoB.

[0044] The reduction process by linear interpolation will be described with reference to Fig. 5(B). The left side of Fig. 5(B) shows a partial image PRI before reduction that is the same as the partial image PRI1 on the right side of Fig. 5(A). In this embodiment, as described later, if the partial image PRI before reduction contains only white pixels PiW and black pixels PiB, the reduction process by linear interpolation is not executed. However, in order to easily understand the difference between the two types of reduction processes, the case where the partial image PRI before reduction contains only white pixels PiW and black pixels PiB will be described as an example.

[0045] The right side of FIG. 5B shows a reduced partial image RDIb. This reduced partial image RDIb is an image obtained by reducing the unreduced partial image PRI by a reduction process using linear interpolation. The reduced partial image RDIb includes a plurality of pixels Pob arranged in a matrix along the transport direction AR and the main scanning direction, similar to the partial image RDIa in FIG. 5A. The pixels Pob of the reduced partial image RDIb are also called output pixels Pob. In FIG. 5B, the output pixels Pob are illustrated with the length of the output pixels Pob in the transport direction AR twice as long as that in the main scanning direction, similar to FIG. 5A. For example, two input pixels Pi located in the area Ai of the unreduced partial image PRI correspond to one output pixel Pob located in the area Aob of the reduced partial image RDIb.

[0046] In the reduction process by linear interpolation, the value of the output pixel Pob is calculated by interpolation using two corresponding input pixels Pi. For example, the value of the output pixel Pob is calculated as a weighted average value using the values ​​of two or more corresponding input pixels Pi and a weight according to the distance from the output pixel Pob. In this embodiment, the distance between the output pixel Pob and each of the two corresponding input pixels Pi is equal. For this reason, the simple average of the two corresponding input pixels Pi is adopted as the value of the output pixel Pob.

[0047] As shown in Fig. 5B, in the reduction process using linear interpolation, even if the partial image PRI before reduction contains only white pixels PiW and black pixels PiB, the reduced partial image RDIb may contain colors different from the white pixels PoW and black pixels PoB. In the example of Fig. 5B, the reduced partial image RDIb contains gray pixels PoG having a density intermediate between white and black.

[0048] Next, the specific processing contents of the reduction processing in this embodiment, which uses these two types of reduction processing, will be described with reference to the flowchart of FIG.

[0049] In S200, the CPU 210 prepares canvas data for generating image data indicating the reduced partial image RDI in a memory (specifically, in a buffer area of ​​the volatile storage device 230). The canvas (initial image) indicated by the canvas data is an image of the same size as the reduced partial image RDI to be generated, i.e., an image with the same number of pixels. The value of each output pixel Po constituting the canvas is a predetermined initial value (for example, (R, G, B)=(0, 0, 0)).

[0050] In S205, the CPU 210 selects one output pixel of interest from among a plurality of output pixels Po that form the canvas.

[0051] In S210, the CPU 210 identifies two corresponding input pixels Pi corresponding to the target output pixel from among the multiple input pixels Pi of the partial image PRI before reduction. In this embodiment, assuming that the partial image PRI before reduction and the canvas image are images of the same size and completely overlap each other, two input pixels Pi that overlap with the target output pixel when completely overlapped are identified as the corresponding input pixels.

[0052] In S220, it is determined whether or not all of the identified corresponding input pixels are the above-mentioned black pixels PiB or white pixels PiW.

[0053] If all the identified corresponding input pixels are black pixels PiB or white pixels PiW (S220: YES), in S230, the CPU 210 determines the target output pixel to be a white pixel PoW or a black pixel PoB. For example, if the pixel on the upper side (the +Y side in FIG. 5) of the two corresponding input pixels is a black pixel PiB, the target output pixel is determined to be a black pixel PoB, and if the pixel on the upper side is a white pixel PiW, the target output pixel is determined to be a white pixel PoW. That is, in this case, the RGB value of the target output pixel is determined to be either a value indicating white (e.g., (255, 255, 255)) or a value indicating black (e.g., (0, 0, 0)).

[0054] If at least one of the identified corresponding input pixels is neither a black pixel PiB nor a white pixel PiW (S220: NO), in S240, the CPU 210 determines the value of the output pixel of interest by linear interpolation. In this embodiment, as described above, the value of the output pixel of interest is determined to be the simple average value of the values ​​of the two corresponding input pixels. For example, if the RGB values ​​of the two corresponding input pixels are (R1, G1, B1) and (R2, G2, B2), the RGB values ​​(Ro, Go, Bo) of the corresponding pixel of interest are determined to be Ro=(R1+R2) / 2, Go=(G1+G2) / 2, and Bo=(B1+B2) / 2.

[0055] In S250, the CPU 210 judges whether or not all output pixels Po of the canvas image have been processed as the output pixel of interest. If there are unprocessed output pixels Po (S250: NO), the CPU 210 returns to S205. If all output pixels Po have been processed as the output pixel of interest (S250: YES), the CPU 210 ends the reduction process.

[0056] As can be seen from the above explanation, in the partial image PRI before reduction, the part consisting of only black pixels PiB and white pixels PiW is reduced by the reduction process by simple thinning (FIG. 5(A)). Therefore, in the partial image PRI before reduction, the part consisting of only black pixels PiB and white pixels PiW is also consisting of only black pixels PoB and white pixels PoW in the reduced partial image RDI.

[0057] In the partial image PRI before reduction, a portion including pixels of a color different from the black pixels PiB and the white pixels PiW (for example, gray pixels or chromatic color pixels) is reduced by reduction processing using linear interpolation (FIG. 5(B)). For this reason, a portion including pixels of a color different from the black pixels PiB and the white pixels PiW (for example, gray pixels or chromatic color pixels) in the partial image PRI before reduction may include pixels in the reduced partial image RDI that have RGB values ​​different from the pixels of the partial image PRI before reduction.

[0058] According to the present embodiment described above, the CPU 210 acquires RGB image data as target image data (S110 in FIG. 4), and executes a reduction process, which is a process for reducing the number of pixels of the RGB image RI, on the RGB image data to generate reduced RGB image data (S130 in FIG. 4, FIG. 6). The CPU 210 uses the reduced RGB image data to generate dot data, which is print data for causing the print mechanism 100 to print the print image OI (S140, S150 in FIG. 4).

[0059] Among the reduction processes, the reduction process by simple thinning (Figure 5(A)) which is performed on a portion of the RGB image RI that is composed of specific colors (black and white in this embodiment) is a process in which the value of one pixel selected from one or more corresponding pixels in the RGB image RI before reduction is used as the value of the reduced pixel.

[0060] As a result, it is possible to prevent pixels of different colors (e.g., gray pixels) from appearing in a portion of the reduced RGB image that is composed of specific colors (e.g., black and white). Therefore, it is possible to prevent the edge between white and black from becoming unclear in the reduced RGB image, and in the print image OI. If a reduction process using linear interpolation is applied to a portion composed of black and white, as shown in FIG. 5(B), gray pixels may appear between black and white in the reduced RGB image, causing the edge between black and white to become unclear. According to this embodiment, it is possible to prevent such inconvenience.

[0061] For example, the RGB image RI in Fig. 3 includes black characters TX arranged on a white background. According to the reduction process of this embodiment, the black characters TX and the surrounding white background are reduced by simple thinning. As a result, in the reduced RGB image and, ultimately, in the printed image OI, the edges of the black characters TX become unclear, which can prevent the characters TX from becoming difficult to read.

[0062] In addition, in this embodiment, since white and black are set as the specific colors to which the reduction process by simple thinning is applied, for example, it is possible to more appropriately prevent edges from becoming blurred. For example, a part consisting of only black and white (for example, black text or the borders of a diagram) is often required to have sharp edges more than other objects (for example, photographs). In this embodiment, it is possible to appropriately prevent edges from becoming blurred in such a part that requires sharp edges.

[0063] Furthermore, according to this embodiment, the CPU 210 executes processing including a color conversion process (S140 in FIG. 4) on the reduced RGB image data to generate print data (S140 and S150 in FIG. 4). As described above, the color conversion process is a process for converting the RGB values ​​included in the reduced RGB image data into CMYK values ​​including multiple component values ​​corresponding to black (K) ink and chromatic (CMY) inks used in printing. As described above, RGB values ​​indicating achromatic colors of intermediate density different from black and white, such as gray, may be converted into CMYK values ​​having non-zero CMY component values ​​by the color conversion process. For this reason, if a specific portion in the RGB image RI before reduction is composed of black and white, but the specific portion in the reduced RGB image includes pixels of other colors such as gray, chromatic (CMY) inks may be used to print the specific portion. In this case, chromatic inks, which are more expensive than K ink, are wasted. In addition, chromatic dots are visible at the edge between black and white, which may reduce the appearance of the edge of a black object. In this embodiment, the occurrence of such inconvenience can be suppressed.

[0064] Furthermore, in the print head 110 of the printing mechanism 100 of this embodiment, the number of nozzles NZ for ejecting K ink in the nozzle row NK for K ink is greater than the number of nozzles NZ for ejecting chromatic color materials in one nozzle row for chromatic colors (for example, nozzle row NC) (FIG. 2(B)). For this reason, a partial print image PI of a predetermined width printed using only K ink is printed by one partial printing, and a partial print image PI of a predetermined width printed using at least one chromatic ink is printed by three partial printings (S160 to S180 in FIGS. 3 and 4).

[0065] In such a printing mechanism 100, the printing speed when printing using only K ink is faster than the printing speed when printing using chromatic inks. According to this embodiment, as described above, it is possible to suppress the inconvenience of using chromatic inks (CMY) to print a specific portion in the RGB image RI before reduction, even though the specific portion is composed of black and white. Therefore, for example, when the partial image PRI before reduction is composed of only black and white, it is possible to suppress the use of chromatic inks when printing the partial print image PI corresponding to the partial image PRI, so that it is possible to suppress a decrease in printing speed due to the use of chromatic inks. For example, as shown in FIG. 3, even in the case of color printing, the printing speed of the entire image can be improved because the partial print images PI1 and PI2 including only black characters TX are printed faster than the partial print images PI3 to PI5 including the photo PC.

[0066] Furthermore, according to this embodiment, the process of the reduction process that is executed on a portion that includes a color (e.g., gray or a chromatic color) different from a specific color (e.g., black and white) in the RGB image RI before reduction is a process that adopts a value obtained by interpolation using the values ​​of two or more corresponding pixels in the RGB image RI before reduction as the value of the reduced pixel (S240 in FIG. 6). As a result, it is possible to suppress the degradation of the image quality of an object that includes a color different from the specific color (e.g., the photo PC in FIG. 3). For example, an object that includes pixels of intermediate density such as gray or pixels of chromatic colors is likely to require good gradation (e.g., smoothness of gradation change) rather than sharpness of edges. The gradation in the reduced RGB image is better when a reduction process by interpolation is used than when a reduction process by simple thinning is used.

[0067] As can be seen from the above explanation, the reduction process in the embodiment is an example of pixel count adjustment process, and the dot data is an example of print data. Also, the RGB image data before reduction in the embodiment is an example of target image data, and the reduced RGB image data is an example of adjusted image data. Also, the reduction process by simple thinning in the embodiment is an example of a first adjustment process, and the reduction process by linear interpolation is an example of a second adjustment process.

[0068] B. Modifications (1) The reduction process (S130 in FIG. 4) in the above embodiment is an example, and is not limited thereto. For example, the reduction process may be a process of reducing only the number of pixels in the main scanning direction, or a process of reducing both the number of pixels in the main scanning direction and the number of pixels in the transport direction AR, depending on the print resolution. Also, instead of the reduction process, an enlargement process may be executed, which is a process of increasing the number of pixels of the RGB image RI. For example, if the number of pixels of the RGB image data acquired in S110 in FIG. 4 is small and if it is used as is, a sufficiently large print image OI cannot be printed, an enlargement process may be executed on the acquired RGB image data. In this case, the enlargement process may be a process of increasing only the number of pixels in the main scanning direction, or a process of increasing only the number of pixels in the transport direction AR, depending on the print resolution. In either case, it is preferable that a reduction process or an enlargement process using the nearest neighbor method is executed on a portion of the RGB image RI that is composed of only specific colors (for example, white and black). Furthermore, it is preferable that a reduction or enlargement process using an interpolation process (for example, linear interpolation or bicubic interpolation) is performed on a portion of the RGB image RI that includes a color different from the specific color.

[0069] (2) In the reduction process (S130 in FIG. 4) of the above embodiment, the specific colors are white and black, but the specific colors may include other colors in addition to white and black, or may include other colors instead of at least one of white and black. For example, the specific colors may include white, black, and the primary colors of C, M, and Y. In this case, for example, in the RGB image RI before reduction, a reduction process by simple thinning is performed on a portion consisting of all or a portion of pixels of white, black, and the primary colors of C, M, and Y, and a reduction process by linear interpolation is performed on a portion including pixels of colors different from any of white, black, and the primary colors of C, M, and Y. In this case, for example, it is possible to suppress the edge between two colors among white, black, and the primary colors of C, M, and Y from becoming unclear.

[0070] (3) The specific configuration of the printing mechanism 100 in the above embodiment is merely an example, and is not limited thereto. For example, the printing mechanism 100 may be a monochrome printer that prints using only K ink, instead of a color printer that prints using four colors of ink, CMYK. Even in this case, for example, it is possible to suppress the edges of black characters from becoming unclear, while maintaining good gradation of photographs including gray. Furthermore, the printing mechanism 100 may be an electrophotographic printer that prints using toner as a color material.

[0071] In the print head 110 of FIG. 2B, the nozzle length of the black nozzle row NK is equal to the nozzle length of the chromatic nozzle rows NC, NM, and NY, and the nozzle interval NTk of the black nozzle row NK is shorter than the nozzle interval NTc of the chromatic nozzle rows NC, NM, and NY. Alternatively, the nozzle length of the black nozzle row may be twice as long as the nozzle length of the chromatic nozzle rows, and the nozzle interval of the black nozzle row may be equal to the nozzle interval of the chromatic nozzle rows. In this case, the number of nozzles in the black nozzle row is twice the number of nozzles in the chromatic nozzle rows. In this case, for example, a partial print image printed using only black ink is printed in one partial print, and a partial print image printed using chromatic ink is printed in two partial prints.

[0072] In addition, the nozzle length of the black nozzle row may be equal to the nozzle length of the chromatic nozzle row, and the nozzle interval of the black nozzle row and the nozzle interval of the chromatic nozzle row may also be equal to each other. In this case, the number of nozzles in the black nozzle row is equal to the number of nozzles in the chromatic nozzle row, and all partial print images are printed in one partial printing.

[0073] (4) The reduction process in the above embodiment is performed on RGB image data, but it may also be performed on CMYK image data after color conversion. Even in this case, the edge between black and white

[0074] (5) As the print medium, instead of paper M, other media, such as OHP film, CD-ROM, or DVD-ROM, may be used.

[0075] (6) In the printing mechanism 100 of the above embodiment, the transport unit 140 transports the paper M, thereby moving the paper M in the transport direction relative to the print head 110. Alternatively, the paper M may be moved in the transport direction AR relative to the print head 110 by moving the print head 110 in the opposite direction to the transport direction AR with respect to the fixed paper M.

[0076] (7) In each of the above embodiments, the image processing device that executes the print process in Fig. 4 is the printer 200. Alternatively, a terminal device, such as a personal computer, connected to the printer 200 may execute the print process in Fig. 4. In this case, the CPU of the terminal device executes the print process in Fig. 4, for example, by executing a printer driver program. In this case, in S170 and S180 of Fig. 4, the CPU of the terminal device causes the printer 200, as a print execution unit, to execute printing by transmitting print data to the printer 200.

[0077] Furthermore, the device that executes the printing process in Fig. 4 may be, for example, a server that acquires image data from a printer or a terminal device and generates a print job using the image data. Such a server may be a plurality of computers that can communicate with each other via a network.

[0078] (8) In each of the above embodiments, a part of the configuration realized by hardware may be replaced by software, and conversely, a part or all of the configuration realized by software may be replaced by hardware. For example, when the printing process of FIG. 4 is executed in the printer 200, the halftone process and color conversion process may be realized by a dedicated hardware circuit (e.g., ASIC) that operates according to instructions from the CPU 210 of the printer 200.

[0079] The present invention has been described above based on examples and modifications, but the above-described embodiments of the invention are intended to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit and scope of the claims, and equivalents thereof are included in the present invention. [Explanation of symbols]

[0080] 100...printing mechanism, 110...print head, 111...nozzle formation surface, 120...head drive unit, 130...main scanning unit, 133...carriage, 134...sliding shaft, 140...conveying unit, 141...downstream roller pair, 142...upstream roller pair, 145...paper stand, 200...printer, 210...CPU, 220...non-volatile storage device, 230...volatile storage device, 231...buffer area, 260...operation unit, 270...display unit, 280...communication unit, AR...conveying direction, CP...computer program, M...paper, NC, NM, NY, NK,...nozzle row, NZ...nozzle, OI...printed image, PI...partial printed image, PRI...partial image, RI...RGB image

Claims

1. An image processing device including a controller, The controller: Obtaining target image data representing a target image by reading the data from a storage device of the image processing device or by receiving the data from an external device; performing a pixel number adjustment process on the target image data, the pixel number adjustment process being either a process of increasing the pixel number of the target image or a process of decreasing the pixel number of the target image, to generate adjusted image data representing an adjusted image; performing a process including a color conversion process on the adjusted image data to generate print data for printing an image by a print execution unit that prints using a black color material and a plurality of chromatic color materials; the target image data and the adjusted image data are image data that indicate a color for each pixel using a color value in a first color system, the color conversion process is a process of converting color values ​​of the first color system included in the adjusted image data into color values ​​of a second color system including a plurality of component values ​​corresponding to the black color material and the plurality of chromatic color materials, In the color conversion process, a color value of the first color system that indicates an achromatic color of a density equal to or greater than a reference is converted to a color value of the second color system in which only a black component value is greater than 0 and component values ​​of a plurality of chromatic colors are 0, and a color value of the first color system that indicates an achromatic color of a density less than the reference except for white is converted to a color value of the second color system including component values ​​of the plurality of chromatic colors greater than 0, The pixel number adjustment process includes: determining, for each pixel of the adjusted image, whether or not two or more corresponding pixels of the target image are only white pixels and black pixels; a first adjustment process for adopting a value of one pixel selected from the two or more corresponding pixels of the target image as a pixel value of the adjusted image when the two or more corresponding pixels of the target image are only white pixels and black pixels; a second adjustment process for adopting, as a pixel value of the adjusted image, a value obtained by interpolation using values ​​of two or more corresponding pixels of the target image when the two or more corresponding pixels of the target image are not only white pixels and black pixels; 23. An image processing device comprising:

2. 2. The image processing device according to claim 1, The print execution unit is a print head including a first nozzle row corresponding to the black color material and a plurality of second nozzle rows corresponding to the plurality of chromatic color materials; a sub-scanning unit that executes a sub-scan for moving a print medium relative to the print head in a first direction that is a direction in which the nozzles of the first nozzle row and the second nozzle row are aligned; a main scanning unit that executes a main scan by moving the print head relatively to the print medium in a second direction perpendicular to the first direction; Equipped with the print execution unit executes printing by performing partial printing, in which the color material is ejected from the print head while performing the main scan, and the sub-scan, a plurality of times using the print data; the number of nozzles in the first nozzle row for ejecting the black color material is greater than the number of nozzles in one of the second nozzle rows for ejecting the chromatic color materials, The image having a predetermined width printed using only the black color material is printed by performing the partial printing n times (n is an integer equal to or greater than 1), An image processing apparatus, wherein the image of the predetermined width printed using at least one of the chromatic color materials is printed by the partial printing m times (m is an integer satisfying n<m).

3. A computer program for an image processing device, comprising: Obtaining target image data representing a target image by reading it from a storage device of the image processing device or by receiving it from an external device; performing a pixel number adjustment process on the target image data, the pixel number adjustment process being either a process of increasing the pixel number of the target image or a process of decreasing the pixel number of the target image, to generate adjusted image data representing an adjusted image; performing a process including a color conversion process on the adjusted image data to generate print data for printing an image by a print execution unit that prints using a black color material and a plurality of chromatic color materials; This is realized on a computer. the target image data and the adjusted image data are image data that indicate a color for each pixel using a color value in a first color system, the color conversion process is a process of converting color values ​​of the first color system included in the adjusted image data into color values ​​of a second color system including a plurality of component values ​​corresponding to the black color material and the plurality of chromatic color materials, In the color conversion process, a color value of the first color system that indicates an achromatic color of a density equal to or greater than a reference is converted to a color value of the second color system in which only a black component value is greater than 0 and component values ​​of a plurality of chromatic colors are 0, and a color value of the first color system that indicates an achromatic color of a density less than the reference except for white is converted to a color value of the second color system including component values ​​of the plurality of chromatic colors greater than 0, The pixel number adjustment process includes: determining, for each pixel of the adjusted image, whether or not two or more corresponding pixels of the target image are only white pixels and black pixels; a first adjustment process for adopting a value of one pixel selected from the two or more corresponding pixels of the target image as a pixel value of the adjusted image when the two or more corresponding pixels of the target image are only white pixels and black pixels; a second adjustment process for adopting, as a pixel value of the adjusted image, a value obtained by interpolation using values ​​of two or more corresponding pixels of the target image when the two or more corresponding pixels of the target image are not only white pixels and black pixels; A computer program comprising:

Images