JP7626969B2 - Image processing device and computer program - Google Patents

Description

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 a process for adjusting the number of pixels of an image represented by the image data when generating print data.

When generating print data for printing an image on a print execution unit such as an inkjet printer, an adjustment process (e.g., enlargement or reduction process) is performed to adjust the number of pixels of the image according to the printing resolution of the print execution unit (see, for example, Patent Document 1). This adjustment process can result in, for example, a gray area, which is an intermediate color between black and white, being generated between the black text and the white background, making the edge composed of black and white unclear.

JP 2011-193231 A

This specification discloses a new technology that can prevent edges consisting of specific colors, such as black and white, from becoming blurred in images printed using print data.

The technology disclosed in this specification has been made to solve at least some of the problems described above, and can be realized as the following application examples.

[Application Example 1] An image processing device including a controller, the controller acquires target image data indicating a target image, performs a pixel count 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 for printing an image using the adjusted image data, and a first adjustment process performed on a portion of the target image that is made up 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 a pixel that has been adjusted.

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 that has been adjusted. 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 device according to Application Example 1,
The specific colors are white and black.
[Application Example 3]
The image processing device according to the second aspect of the present invention,
the printing unit performs printing 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 controller executes a process including a color conversion process on the adjusted image data to generate the print data;
the color conversion process is a process of converting color values in the first color system included in the adjusted image data into color values in a second color system;
An image processing apparatus, wherein the color values of the second color system are color values including a plurality of component values corresponding to the black colorant and the plurality of chromatic colorants.
[Application Example 4]
The image processing device according to Application Example 3,
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 performs a sub-scan to move a print medium relative to the print head in a first direction;
a main scanning unit that executes a main scan by moving the print head relatively to the print medium in a second direction that intersects with 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).
[Application Example 5]
The image processing device according to any one of Application Examples 1 to 4,
An image processing device, comprising: an image processing apparatus, a pixel number adjustment process, a second adjustment process performed on a portion of the target image that includes a color different from the specific color, the second adjustment process being a process of adopting a value obtained by interpolation using values of two or more corresponding pixels of the target image as the value of a pixel that has been subjected to the adjustment process.

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.

FIG. 2 is a block diagram showing the configuration of a printer 200 as an image processing apparatus according to the embodiment. FIG. 2 is a diagram showing a schematic configuration of a printing mechanism 100. 3 is an explanatory diagram of the operation of the printing mechanism 100. 4 is a flowchart of a printing process. FIG. 13 is a flowchart of a reduction process.

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

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 a button or 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.

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 when the printer 200 is shipped. Alternatively, the computer program CP may be provided in a form in which it is downloaded from a server, or in a form in which it is 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 the printing process described below.

The printing mechanism 100 prints by ejecting ink (droplets) of each of the following 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.

Figure 2 is a diagram showing a schematic configuration of the printing mechanism 100. As shown in Figure 2 (A), the main scanning unit 130 includes a carriage 133 that carries the print head 110, 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 Figure 2). The main scanning unit 130 uses the power of a main scanning motor (not shown) to move the carriage 133 back and forth along the sliding shaft 134. This achieves main scanning, which moves the print head 110 back and forth along the main scanning direction relative to the paper M.

The transport unit 140 holds the paper M and transports the paper M in a transport direction AR (the +Y direction in FIG. 2) that intersects with the main scanning direction. As shown in FIG. 2A, the transport unit 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 transport direction AR will also be referred to simply as the upstream side, and the downstream side (+Y side) of the transport direction AR will also be referred to simply as the downstream side.

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 positioned opposite the nozzle formation surface 111 of the print head 110. The paper M is transported by driving the downstream roller pair 141 and the upstream roller pair 142 by a transport motor (not shown).

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

Figure 2 (B) shows the configuration of the print head 110 as viewed from the -Z side (the bottom side in Figure 2). As shown in Figure 2 (B), the nozzle forming surface 111 of the print head 110 has multiple nozzle rows formed thereon, each consisting of multiple nozzles; that is, the nozzle rows NC, NM, NY, and NK that eject the above-mentioned C, M, Y, and K inks. Each nozzle row includes multiple nozzles NZ aligned along the transport direction AR.

The nozzles NZ in one nozzle row are positioned differently in the transport direction AR (+Y direction) and are arranged at a predetermined nozzle interval along the transport direction AR. 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 K. Additionally, the number of nozzles in the K nozzle row NK is three times greater than the number of nozzles in the chromatic nozzle rows NC, NM, and NY. 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 images of the same resolution at higher speeds than printing using chromatic inks (CMY).

The positions of the nozzle rows NC, NM, NY, and NK in the main scanning direction (X direction in FIG. 2B) are different from each other, and their positions in the transport direction AR (Y direction in FIG. 2B) overlap with each other. For example, in the example of FIG. 2B, the nozzle row NM is arranged in the +X direction of the nozzle row NY that ejects Y ink.

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

Figure 3 is an explanatory diagram of the operation of the printing mechanism 100. Figure 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 Figure 3) and a resolution of 300 dpi in the transport direction AR (Y direction in Figure 3). The print image OI extends in the main scanning direction and includes multiple raster lines RL (for example, RL1 in Figure 3) that differ from one another in position in the transport direction AR. Each raster line RL is a line on which multiple dots can be formed.

The print image OI includes multiple 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 of the nozzle rows NC, NM, NY, and NK in the transport direction AR (nozzle length).

Each partial print image PI is printed by one partial print or three partial prints. The printing direction of the partial print is either the forward pass direction or the return pass direction. That is, 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 return pass printing, in which dots are formed while performing a main scan in the return pass direction (+X direction in FIG. 3). In FIG. 3, solid arrows pointing in the +X or -X direction are indicated within the partial images. Partial images with one arrow (for example, PI1 and PI2 in FIG. 3) are printed by one partial print. Partial images with three arrows (for example, PI3 to PI5 in FIG. 3) are printed by three partial prints.

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) inches, which is an interval equivalent to 300 dpi. As described above, in this embodiment, the nozzle spacing 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 spacing 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 spacing NTk equivalent to 300 dpi) transported in between. 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.

For this reason, the partial print images PI1 and PI2 containing only K dots are printed in one partial print, and the partial print images PI3 to PI5 containing CMY dots are printed in three partial prints. Note that the K dots contained in the partial print images PI3 to PI5 containing CMY dots are printed, for example, in one of the three partial prints. 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.

A-3. Printing process The printing process for executing the printing described 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 the user. The printing instruction includes the designation of image data showing the image to be printed. FIG. 4 is a flowchart of the printing process. In S110 of FIG. 3, the CPU 210 acquires the 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 value is, for example, a color value 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 converted into RGB image data.

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 with 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.

In S120, the CPU 210 selects one target partial image from among the multiple partial images PRI of the RGB image RI. In the example of FIG. 3, five partial images PRI1 to PRI5 are selected as target partial images in sequence from the downstream side of the transport direction AR (the upper side of FIG. 3). Hereinafter, the RGB image data showing the target partial image is also referred to as target partial image data. Furthermore, 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.

In S130, the CPU 210 performs a reduction process on the target portion image data. In this specification, a process of reducing 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 performed to halve the number of pixels in the transport direction AR without changing the number of pixels in the main scanning direction. By performing a reduction process according to the print resolution in this way, 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.

In S140, the CPU 210 executes a color conversion process on the image data of the portion of interest that has been reduced by the reduction process. The color conversion process is a process for converting the RGB values of multiple pixels that make up the image of the portion of interest into CMYK values. The CMYK values are color values in the CMYK color system that include component values (in this embodiment, the 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.

In the color conversion process of this embodiment, RGB values that indicate achromatic colors with a density equal to or greater than the standard (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, RGB values that indicate achromatic colors with a density less than the standard except for white (e.g., light gray and medium gray) are converted to CMYK values that include 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 performed so that achromatic colors with a density equal to or greater than the reference value are printed using only K dots, and achromatic colors with a density less than the reference value are printed using CMY dots as well. If achromatic colors with a density less than the reference value 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.

In S150, halftone processing is performed on the color-converted image data of the portion of interest (CMYK image data). This generates dot data that indicates the partial print image PI that corresponds to the image of the portion of interest. 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 values of each pixel of the dot data are two levels, "no dot" and "dot present". Alternatively, the component values 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 known techniques such as dithering and error diffusion.

In S160, the CPU 210 determines whether the partial print image PI corresponding to the target partial image will be printed using only K ink, based on the dot data generated in S150. Specifically, if the CMY component values of all pixels in the dot data generated in S150 are values indicating "no dots" and only the K component value contains a value indicating "dots present", it is determined that the partial print image PI corresponding to the target partial image will be printed using only K ink. If the CMY component values of at least some pixels in the dot data are values indicating "dots present", it is determined that the partial print image PI corresponding to the target partial image will be printed using chromatic ink.

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 amount of transport of the paper M to be performed after one partial printing to the dot data generated in S150, and outputs the data 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.

If it is determined that the partial print image PI corresponding to the target partial image is printed using chromatic ink (S160: NO), in S180, the CPU 210 controls the printing mechanism 100 to print the partial print image PI in three partial prints. For example, the CPU 210 separates the dot data generated in S150 into three data corresponding to the three partial prints, adds control data to each of the 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 to print the partial print image PI.

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

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

The reduction process by simple thinning will be described with reference to FIG. 5(A). An example of the 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 transport direction AR (Y direction in FIG. 5) and the main scanning direction (X direction in FIG. 5).

The reduced partial image RDIa is shown on the right side of FIG. 5(A). This reduced partial image RDIa is an image obtained by reducing the unreduced partial image PRI through a reduction process using simple thinning. The reduced partial image RDIa includes a number of pixels Poa arranged in a matrix along the transport direction AR and the main scanning direction.

In the following, the pixel Pi of the partial image PRI before reduction is also referred to as the input pixel Pi, and the pixel Poa of the reduced partial image RDIa is also referred to as 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.

The partial image PRI before reduction in FIG. 5(A) contains 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 the two corresponding input pixels Pi. Generally, of the one or more corresponding input pixels Pi, the 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., the pixel on the upper side (+Y side)) is selected.

As shown in FIG. 5A, 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.

The reduction process using 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 below, if the partial image PRI before reduction contains only white pixels PiW and black pixels PiB, the reduction process using linear interpolation is not performed. However, in order to make it easier to 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.

The right side of FIG. 5B shows the 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, similar to FIG. 5A, the output pixel Pob is illustrated with the length of the output pixel Pob in the transport direction AR twice the length in the main scanning direction. 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.

In the reduction process using 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 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.

As shown in FIG. 5B, in a 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 that have a density intermediate between white and black.

Next, we will explain the specific processing content of the reduction process in this embodiment, which uses these two types of reduction processes. Figure 6 is a flowchart of the reduction process.

In S200, the CPU 210 prepares canvas data in memory (specifically, in the buffer area of the volatile storage device 230) for generating image data indicating the reduced partial image RDI. 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 that constitutes the canvas is a predetermined initial value (for example, (R, G, B) = (0, 0, 0)).

In S205, the CPU 210 selects one output pixel of interest from among the multiple output pixels Po that make up the canvas.

In S210, the CPU 210 identifies two corresponding input pixels Pi that correspond 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, the two input pixels Pi that overlap the target output pixel when completely overlapped are identified as the corresponding input pixels.

In S220, it is determined whether all of the identified corresponding input pixels are black pixels PiB or white pixels PiW as described above.

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

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 target output pixel by linear interpolation. In this embodiment, as described above, the value of the target output pixel 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 target pixel are determined to be Ro = (R1 + R2) / 2, Go = (G1 + G2) / 2, Bo = (B1 + B2) / 2.

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

As can be seen from the above explanation, in the partial image PRI before reduction, the part that is made up only of black pixels PiB and white pixels PiW is reduced by the reduction process using simple thinning (Figure 5 (A)). As a result, in the partial image PRI before reduction, the part that is made up only of black pixels PiB and white pixels PiW is also made up only of black pixels PoB and white pixels PoW in the reduced partial image RDI.

In the partial image PRI before reduction, a portion that includes pixels of a color different from the black pixels PiB and the white pixels PiW (e.g., gray pixels or chromatic pixels) is reduced by a reduction process using linear interpolation (Figure 5 (B)). For this reason, a portion that includes pixels of a color different from the black pixels PiB and the white pixels PiW (e.g., gray pixels or chromatic pixels) in the partial image PRI before reduction may include pixels in the reduced partial image RDI that have different RGB values from the pixels of the partial image PRI before reduction.

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 on the RGB image data, which is a process for reducing the number of pixels in the RGB image RI, 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).

The reduction process (Figure 5(A)) by simple thinning, which is performed on a portion of the RGB image RI that is made up of specific colors (black and white in this embodiment), is a process in which the value of a pixel that has been reduced is determined by using the value of one pixel selected from one or more corresponding pixels in the RGB image RI before reduction.

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). This prevents 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. 5B, gray pixels may appear between black and white in the reduced RGB image, causing the edge between black and white to become unclear. This embodiment prevents such inconvenience.

For example, the RGB image RI in FIG. 3 includes black characters TX placed 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 in the printed image OI, the edges of the black characters TX become unclear, preventing the characters TX from becoming difficult to read.

In addition, in this embodiment, white and black are set as the specific colors to which the reduction process by simple thinning is applied, so that, for example, blurring of edges can be more appropriately prevented. For example, parts consisting of only black and white (e.g., black text or the borders of diagrams) often require sharp edges more than other objects (e.g., photographs). In this embodiment, it is possible to appropriately prevent the edges of parts that require sharp edges from becoming blurred.

Furthermore, according to this embodiment, the CPU 210 executes a process 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 the 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 by the color conversion process into CMYK values in which the CMY component values are not 0. For this reason, if a specific part in the RGB image RI before reduction is composed of black and white, but the specific part in the reduced RGB image contains pixels of other colors such as gray, chromatic (CMY) inks may be used to print the specific part. In this case, chromatic inks, which are more expensive than K ink, are wasted. In addition, the appearance of the edges of black objects can be diminished by the appearance of chromatic dots at the edges between black and white. In this embodiment, this problem can be prevented from occurring.

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 (e.g., nozzle row NC) (Fig. 2B). 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).

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 (CMY) inks 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, if 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 if the entire image is printed in color, the partial print images PI1 and PI2 containing only black text TX are printed faster than the partial print images PI3 to PI5 containing the photo PC, so that the printing speed of the entire image can be improved.

Furthermore, according to this embodiment, the process of the reduction process that is performed on a portion of the RGB image RI before reduction that contains a color (e.g., gray or a chromatic color) different from a specific color (e.g., black and white) is a process that adopts a value obtained by interpolation using the values of two or more corresponding pixels of the RGB image RI before reduction as the value of the reduced pixel (S240 in FIG. 6). As a result, it is possible to prevent the image quality of an object (e.g., the photo PC in FIG. 3) that contains a color different from the specific color from deteriorating. For example, an object that contains 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 reduction processing by interpolation is used than when reduction processing by simple thinning is used.

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. Furthermore, 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. Furthermore, 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.

B. Modification (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 according to the print resolution, or may be a process of reducing both the number of pixels in the main scanning direction and the number of pixels in the transport direction AR. In place of the reduction process, an enlargement process may be performed, which is a process of increasing the number of pixels in the RGB image RI. For example, if the number of pixels in the RGB image data acquired in S110 in FIG. 4 is small and a sufficiently large print image OI cannot be printed when used as is, an enlargement process may be performed on the acquired RGB image data. In this case, the enlargement process may be a process of increasing the number of pixels in the main scanning direction according to the print resolution, or may be a process of increasing the number of pixels in the transport direction AR. In either case, it is preferable that a reduction process or an enlargement process using the nearest neighbor method is performed on a portion of the RGB image RI that is composed of only specific colors (for example, white and black). Furthermore, it is preferable to perform a reduction or enlargement process using an interpolation process (for example, linear interpolation or bicubic interpolation) on a portion of the RGB image RI that includes a color different from the specific color.

(2) In the reduction process of the above embodiment (S130 in FIG. 4), 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 other than white, black, and the primary colors of C, M, and Y. In this case, for example, it is possible to prevent the edge between two colors among white, black, and the primary colors of C, M, and Y from becoming unclear.

(3) The specific configuration of the printing mechanism 100 in the above embodiment is 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 maintain good gradation of photographs that include gray while suppressing the edges of black characters from becoming unclear. Furthermore, the printing mechanism 100 may be an electrophotographic printer that prints using toner as a color material.

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 spacing NTk of the black nozzle row NK is shorter than the nozzle spacing 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 spacing of the black nozzle row and the nozzle spacing of the chromatic nozzle rows may be equal to each other. 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.

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 spacing of the black nozzle row and the nozzle spacing 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 a single partial print.

(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

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

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

(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 sending print data to the printer 200.

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 multiple computers that can communicate with each other via a network.

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

The present invention has been described above based on examples and modifications, but the above-mentioned embodiments of the invention are intended to facilitate understanding of the present invention and do not limit the present invention. The present invention may be modified or improved without departing from the spirit and scope of the claims, and the present invention includes equivalents thereof.

100...printing mechanism, 110...printing head, 111...nozzle formation surface, 120...head drive unit, 130...main scanning unit, 133...carriage, 134...sliding shaft, 140...transport unit, 141...downstream roller pair, 142...upstream roller pair, 145...paper tray, 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...transport 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 (3)

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 that includes 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. 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 printing 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). 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