Method for generating dot data, and printing apparatus

Abstract

This design minimizes the degradation of fine lines caused by incomplete ink ejection across the entire edge, while also suppressing the decline in print quality due to ink bleeding. [Solution] A dot data generation method for generating dot data indicating the position of dots formed by ink from a print head, comprising: a first detection step of detecting at least one of the edges in a detection target area of ​​an image having a plurality of pixels arranged in a first direction and a second direction intersecting the first direction, which is located on one side of a region that is darker than the surrounding area in the first direction, and a second edge of a region that is darker than the surrounding area in the second direction, as a first processing target edge; and a generation step of generating the dot data from the image such that the amount of ink ejected from the print head to the first processing target edge is reduced.

Description

Technical Field

[0001] The present invention relates to a dot data generation method for generating dot data indicating the positions of dots formed by ink from a print head, and a printing apparatus.

Background Art

[0002] As a printing apparatus, an inkjet printer that forms a printed image by ejecting ink droplets from a print head onto a printing medium is known. Since the ink droplets are liquid, the print quality may deteriorate due to bleeding of the edges of areas that are darker than the surroundings, such as characters and barcodes, on the printing medium. To prevent such a decrease in print quality, it is conceivable to suppress the ejection of ink over the entire edge of the dark area. In the method for generating ejection position data disclosed in Patent Document 1, a process is performed to change the pixel values from ejection values to non-ejection values by one pixel on each side for a line having a width of three or more pixels.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, if the pixel values are changed from ejection values to non-ejection values over the entire edge of a barcode, the barcode may become too thin to be read. In the above-described method for generating ejection position data, the possibility of the barcode becoming unreadable is not considered. Further, when the above-described process is performed when a thin line is three pixels wide, the width of the line becomes only one pixel, so that the deterioration of an object including a thin line such as small characters becomes conspicuous.

Means for Solving the Problems

[0005] The present invention is a dot data generation method that generates dot data indicating the position of dots formed by ink from a print head, A first detection step in which, among the edges in a detection target area of ​​an image having a plurality of pixels arranged in a first direction and a second direction intersecting the first direction, at least one of a first edge portion located on one side of a region that is darker than the surrounding area in the first direction and a second edge portion located on one side of a region that is darker than the surrounding area in the second direction is detected as a first processing target edge portion; The embodiment includes a generation step of generating dot data from the image such that the amount of ink ejected from the print head to the first processing target edge portion is reduced.

[0006] Furthermore, the present invention relates to a printing apparatus that forms a printed image on a printing medium using ink, A print head capable of ejecting the aforementioned ink, The system includes a control unit that controls the ejection of ink from the print head to the printing medium so that dots constituting the printed image are formed on the printing medium, The control unit, A first detection process that detects, as a first processing target edge portion, at least one of the edges in a detection target region of an image having a plurality of pixels arranged in a first direction and a second direction intersecting the first direction, a first edge portion located on one side of a region that is darker than the surrounding area in the first direction, and a second edge portion located on one side of a region that is darker than the surrounding area in the second direction. The present invention includes an ejection control process that controls the ejection of ink from the print head to the printing medium so that the amount of ink ejected to the first processing target edge portion is reduced. [Brief explanation of the drawing]

[0007] [Figure 1] A schematic diagram showing an example of the configuration of a printing device. [Figure 2]A schematic diagram showing an example of the nozzle surface of a print head. [Figure 3] A flowchart schematically illustrating an example of print control processing. [Figure 4] This diagram schematically illustrates an example of forming a printed image from an input image with reduced ink volume in the first processing target edge area. [Figure 5] This diagram schematically illustrates an example of generating dot data with reduced ink volume in the edges targeted for secondary processing from an extracted image. [Figure 6] Figure 6A schematically shows an example of the edge detection processing specification screen, Figure 6B schematically shows an example of the media type specification screen, and Figure 6C schematically shows an example of the density area specification screen. [Figure 7] Figure 7A schematically shows an example of the edge width specification screen, and Figure 7B schematically shows an example of a 5x5 reference pattern. [Figure 8] Figure 8A schematically shows an example of the object selection screen, and Figure 8B schematically shows an example of a detection target area included in an image. [Figure 9] A schematic diagram illustrating a comparative example of forming a printed image from an input image. [Modes for carrying out the invention]

[0008] The embodiments of the present invention will be described below. Of course, the following embodiments are merely illustrative of the present invention, and not all of the features shown in the embodiments are necessarily essential to the solution of the invention.

[0009] (1) Summary of embodiments included in the present invention: First, an overview of the embodiments included in the present invention will be described with reference to the examples shown in Figures 1 to 9. Note that the figures in this application are schematic examples, and the scale of each part may differ from reality in order to make each part recognizable, the magnification in each direction shown in these figures may differ, and the figures may not be consistent. Of course, the elements of this embodiment are not limited to the specific examples indicated by the reference numerals. In "Overview of Embodiments Included in the Present Invention," the text in parentheses indicates supplementary explanation of the preceding word. In the present application, the numerical range "Min~Max" means not less than the minimum value Min and not more than the maximum value Max.

[0010] [Aspect 1] As illustrated in FIGS. 2 to 4, a dot data generation method according to one aspect is a dot data generation method for generating dot data DA2 indicating the positions of dots 38 formed by ink 36 from a print head 30, and includes the following steps. (a1) First detection step ST1 of detecting at least one of a first edge portion E11 existing on one side of a thick region (e.g., thick region AR3) that is thicker than the surrounding area (e.g., surrounding region AR2) in the first direction D1 and a second edge portion E12 existing on one side of a thick region (AR3) that is thicker than the surrounding area (AR2) in the second direction D2, among edges E0 existing in at least a partial detection target region AR1 of an image IM1 having a plurality of pixels PX0 arranged in a first direction D1 and a second direction D2 intersecting the first direction D1, as a first processing target edge portion E1. (a2) Generation step ST3 of generating the dot data DA2 from the image IM1 such that the amount of the ink 36 ejected from the print head 30 to the first processing target edge portion E1 is reduced.

[0011] As described above, not the entire edge E0 existing in the detection target region AR1, but at least one of the first edge portion E11 existing on one side of a thick region (AR3) that is thicker than the surrounding area (AR2) in the first direction D1 and the second edge portion E12 existing on one side of a thick region (AR3) that is thicker than the surrounding area (AR2) in the second direction D2 is ejected with a reduced amount of the ink 36. Thereby, while obtaining the effect of suppressing the deterioration of print quality due to bleeding of the ink 36, it is possible to avoid the inconvenience that objects such as barcodes and fine characters become too thin. Therefore, the above aspect can provide a dot data generation method capable of suppressing the deterioration of thin lines due to non-ejection of ink over the entire edge and suppressing the deterioration of print quality due to bleeding of the ink.

[0012] Various examples can be considered in the above-described aspect. The size of the dots may be changeable. Therefore, the dot data may be binary data representing the presence or absence of dot formation, or may be multi-valued data of three or more values representing the formation state of the dots. The detection target area may be the entire image or a part of the image. For example, when the first direction is horizontal, the first edge portion does not mean that it exists on both the left and right sides of the region darker than the surroundings, but means that it exists on the left side or the right side of the region darker than the surroundings. When the second direction is vertical, the second edge portion does not mean that it exists on both the upper and lower sides of the region darker than the surroundings, but means that it exists on the upper side or the lower side of the region darker than the surroundings. Of course, the first direction may be vertical, and the second direction may be horizontal. The reduction in the amount of ink ejected to the first processing target edge portion includes the case where no ink is ejected to the first processing target edge portion. In the present application, "first", "second",... are terms for identifying each component included in a plurality of components having similarities, and do not mean an order. Of course, the above-mentioned remarks are also applicable in the following aspects.

[0013] [Aspect 2] As illustrated in FIGS. 3 and 5, this dot data generation method may further include the following steps. (a3) A second detection step ST2 of detecting at least a part of the edges existing in the extraction image IM2 representing the portion other than the first processing target edge portion E1 in the detection target area AR1 as the second processing target edge portion E2. In the generation step ST3, the dot data DA2 may be generated from the image IM1 such that the ink 36 is not ejected from the print head 30 to the first processing target edge portion E1, the ink 36 is ejected from the print head 30 to the second processing target edge portion E2, and the amount of the ink 36 ejected from the print head 30 to the second processing target edge portion E2 is reduced.

[0014] If the ink 36 that lands on the printing medium ME0 is prone to bleeding, even if the portion of the edge E0 in the detection target area AR1 that does not eject ink 36 is limited to the first processing target edge portion E1, the bleeding of the ink 36 may still be noticeable. In such cases, the bleeding of the ink 36 is suppressed by reducing the amount of ink 36 ejected to the second processing target edge portion E2, while keeping it within a range that does not become zero. Therefore, the above embodiment can suppress ink bleeding while leaving fine lines when the ink that lands on the printing medium is prone to bleeding.

[0015] [Aspect 3] As illustrated in Figures 3, 5, and 6B, this dot data generation method may further include the following steps. (a4) A printing step ST4 in which the ink 36 is ejected from the print head 30 onto the printing medium ME0 based on the dot data DA2. (a5) A media type designation step ST5 that accepts the designation of a type to be used from among a plurality of types 220 that can be used for the printing medium ME0, the plurality of types 220 including a first type 221 and a second type 222 in which the ink 36 is more likely to bleed than the first type 221. (a6) When the second type 222 is specified, a second detection step ST2 is performed to detect edges in the extracted image IM2 that represent the portion of the detection target area AR1 other than the first processing target edge portion E1 as the second processing target edge portion E2. In the generation step ST3, if the first type 221 is specified, the dot data DA2 may be generated from the image IM1 such that the ink 36 is not ejected from the print head 30 to the first processing target edge portion E1. Also, in the generation step ST3, if the second type 222 is specified, the dot data DA2 may be generated from the image IM1 such that the ink 36 is not ejected from the print head 30 to the first processing target edge portion E1, and the amount of ink 36 ejected from the print head 30 to the second processing target edge portion E2 is reduced to a range that is not zero.

[0016] When the second type 222, which is more prone to ink bleeding than the first type 221, is specified as the printing medium ME0 to be used, the amount of ink 36 ejected to the second processing target edge portion E2 is reduced to a range that does not become zero, thereby suppressing ink bleeding while leaving fine lines. On the other hand, when the first type 221 is specified as the printing medium ME0 to be used, the amount of ink 36 ejected to the pixels PX0 that can become the second processing target edge portion E2 is maintained, so that the edges present in the extracted image IM2 are clearly displayed. Therefore, the above embodiment can improve the image quality of the printed image according to the user's intentions.

[0017] [Aspect 4] As illustrated in Figure 6C, this dot data generation method may further include the following steps. (a7) A color specification step ST6 that accepts the specification of an option to be applied to the dark area (AR3) from among a plurality of options 240, which include a predetermined color (e.g., "black only" item 241) and a predetermined color range (e.g., "other than white" item 242). In the first detection step ST1, if the predetermined color (241) is specified, at least one of the edges E0 present in the detection target area AR1, namely the first edge portion E11 located on one side of the dark area (AR3) which is the predetermined color (241) in the first direction D1, and the second edge portion E12 located on one side of the dark area (AR3) which is the predetermined color (241) in the second direction D2, may be detected as the first processing target edge portion E1. In addition, in the first detection step ST1, if the predetermined color range (242) is specified, at least one of the edges E0 present in the detection target area AR1, namely the first edge portion E11 located on one side of the dark area (AR3) which is in the predetermined color range (242) in the first direction D1, and the second edge portion E12 located on one side of the dark area (AR3) which is in the predetermined color range (242) in the second direction D2, may be detected as the first processing target edge portion E1.

[0018] If an object such as text or a barcode is of a predetermined color (241) and that predetermined color (241) is specified, a high-quality printed image IM5 can be obtained for objects of that predetermined color (241) by reducing the amount of ink in the first processing target edge portion E1. If an object is included in a predetermined color range (242) and that predetermined color range (242) is specified, a high-quality printed image IM5 can be obtained for objects within that predetermined color range (242) by reducing the amount of ink in the first processing target edge portion E1. Therefore, the above embodiment can obtain a high-quality printed image depending on the color of the object such as text or a barcode.

[0019] [Aspect 5] As illustrated in Figures 7A and 7B, this dot data generation method may further include the following steps. (a8) Edge width specification step ST7 for receiving the width of the first processing target edge portion E1. In the first detection step ST1, the first processing target edge portion E1 may be detected to have the specified width.

[0020] In the above case, the width of the detected first processing target edge portion E1 can be adjusted to the user's intent. Therefore, the above embodiment can improve the image quality of the printed image according to the user's intent.

[0021] [Aspect 6] As illustrated in Figures 8A and 8B, this dot data generation method may further include the following steps. (a9) Object specification step ST8, which specifies an object included in the image IM1 (for example, item 281, "text and lines"). In the first detection step ST1, the first processing target edge portion E1 may be detected using the region of the specified object (281) (for example, the character region AR1c and the line region AR1b) as the detection target region AR1.

[0022] In the above case, the detection target area AR1 can be adjusted to the user's intent. Therefore, the above embodiment can improve the image quality of the printed image according to the user's intent.

[0023] [Aspect 7] Incidentally, as illustrated in Figures 1 and 2, a printing apparatus 1 according to one embodiment is a printing apparatus 1 that forms a print image IM5 on a printing medium ME0 using ink 36, and comprises a print head 30 and a control unit U1. The print head 30 is capable of ejecting the ink 36. The control unit U1 controls the ejection of the ink 36 from the print head 30 to the printing medium ME0 so that dots 38 constituting the print image IM5 are formed on the printing medium ME0. The control unit U1 performs the following processing as illustrated in Figures 3 and 4. (b1) A first detection process (for example, step S102 in Figure 3) in which at least one of the edges E0 present in a detection target region AR1 of an image IM1 having a plurality of pixels PX0 arranged in a first direction D1 and a second direction D2 intersecting the first direction D1 is detected as the first processing target edge portion E1, which is located on one side of a region (AR3) that is darker than the surrounding area (AR2) in the first direction D1, and the second edge portion E12 that is located on one side of a region (AR3) that is darker than the surrounding area (AR2) in the second direction D2. (b) Discharge control processing (for example, steps S108 to S114 in Figure 3) that controls the discharge of the ink 36 from the print head 30 to the printing medium ME0 so that the amount of ink 36 discharged to the first processing target edge portion E1 is reduced.

[0024] The above embodiment can provide a printing apparatus that can suppress the deterioration of fine lines due to insufficient ink ejection across the entire edge, while also suppressing the reduction in print quality due to ink bleeding. Furthermore, the control unit U1 may perform at least a portion of the second detection process corresponding to the second detection process ST2, the media type specification process corresponding to the media type specification process ST5, the color specification process corresponding to the color specification process ST6, the edge width specification process corresponding to the edge width specification process ST7, and the object specification process corresponding to the object specification process ST8.

[0025] Furthermore, the above-described embodiments are applicable to a printing method including the dot data generation method described above, a printing system including the printing apparatus described above, a control method for the printing apparatus described above, a control program for the printing apparatus described above, a computer-readable non-temporary medium on which the control program is recorded, and so on. In addition, the aforementioned printing apparatus may be composed of multiple distributed parts.

[0026] (2) Specific examples of printing devices: Figure 1 schematically illustrates the configuration of the printing device 1. In this specific example, the printing device 1 is assumed to be the printer 2 itself, but the printing device 1 may also be a combination of the printer 2 and a host device HO1. The host device HO1 shown in Figure 1 is equipped with a display device DU1. The printer 2 shown in Figure 1 is an inkjet printer that ejects ink 36 as ink droplets 37 from a print head 30. The printer 2 may also be a line printer in which the printing medium ME0 moves in the feed direction D3 without the print head 30 moving, or a serial printer, etc., and the printing device 1 may include additional elements not shown in Figure 1. Figure 2 schematically illustrates the nozzle surface 30a of the print head 30.

[0027] Printer 2 forms a print image IM5 on the printing medium ME0 using ink 36 ejected from the print head 30. The printer 2 shown in Figure 1 includes a controller 10, a semiconductor memory RAM (Random Access Memory) 21, a communication I / F (interface) 22, a storage unit 23, an operation panel 24, a print head 30, a drive unit 50, etc. The controller 10 and the drive unit 50 are examples of the control unit U1. The controller 10, RAM 21, communication I / F 22, storage unit 23, and operation panel 24 are connected to a bus and are able to input and output information from each other.

[0028] The controller 10 includes a processor, a CPU (Central Processing Unit) 11, an edge correction unit 12, a color conversion unit 13, a halftone processing unit 14, a drive signal transmission unit 15, etc. The controller 10 controls the drive unit 50 and the print head 30 so that a print image IM5 is formed on the print medium ME0 based on an image acquired from either the host device HO1, a memory card (not shown), etc. The acquired image includes, for example, two colors for each pixel: R (red), G (green), and B (blue). 8 Tone (or 2 16 An RGB image, represented by RGB data with integer values ​​for gradation, etc., can be applied. The controller 10 can be configured using an SoC (System on a Chip) or the like.

[0029] The CPU 11 is the device that primarily handles information processing and control in the printer 2. The edge correction unit 12 may convert the resolution of the acquired image to the print resolution if the acquired image differs from the print resolution. This image adjusted to the print resolution will be called image IM1. The edge correction unit 12 detects the processing target edges (E1, E2) from image IM1 in units of pixels PX0 (see Figure 4) and generates a corrected image IM3 that reduces the amount of ink 36 ejected to the processing target edges (E1, E2). As will be described in more detail later, the processing target edges (E1, E2) refer collectively to the first processing target edge E1 shown in Figure 4 and the second processing target edge E2 shown in Figure 5. If image IM1 is an RGB image, the corrected image IM3 will also be an RGB image. Alternatively, the edge correction unit 12 may generate the corrected image IM3 before the resolution conversion and convert the resolution of the corrected image IM3 to the print resolution.

[0030] The color conversion unit 13 refers to a color conversion LUT (lookup table) which defines the correspondence between the gradation values ​​of R, G, and B and the gradation values ​​of C (cyan), M (magenta), Y (yellow), and K (black), and converts the RGB data representing the corrected image IM3 into ink amount data DA1. The ink amount data DA1 is, for example, set for each pixel PX0 to C, M, Y, and K 8 Tone (or 2 16 It has integer values ​​for gradation, etc. The ink amount data DA1 represents the amount of C, M, Y, and K ink 36 used in units of pixel PX0. The halftone processing unit 14 reduces the number of gradations in the gradation values ​​of each pixel PX0 constituting the ink amount data DA1 by performing halftone processing using one of the following methods: dithering, error diffusion, etc., thereby generating dot data DA2. The dot data DA2 represents the formation state of the dots 38 of the ink droplets 37 in units of pixel PX0, and indicates the position of the dots 38 formed by the ink 36 from the print head 30. The dot data DA2 may be binary data representing the presence or absence of dot formation, or it may be multi-level data with three or more gradations that can handle dots of different sizes, such as small, medium, and large.

[0031] The drive signal transmission unit 15 generates a drive signal SG1 from the dot data DA2 and outputs it to the drive circuit 31 of the print head 30. The drive signal SG1 corresponds to the voltage signal applied to the drive element 32 of the print head 30. For example, if the dot data DA2 is "dot formation", the drive signal transmission unit 15 outputs a drive signal SG1 that ejects ink droplets for dot formation. Also, if the dot data DA2 is data with three or more values, the drive signal transmission unit 15 outputs a drive signal SG1 that ejects ink droplets for large dots if the dot data DA2 is "large dot formation", and outputs a drive signal SG1 that ejects ink droplets for small dots if the dot data DA2 is "small dot formation".

[0032] Each of the above parts 11 to 15 may be composed of an ASIC (Application Specific Integrated Circuit), and may directly read the data to be processed from RAM 21 or directly write the processed data to RAM 21.

[0033] As shown in Figure 2, the print head 30 has multiple nozzle rows 33 on its nozzle surface 30a, each row having multiple nozzles 34 capable of ejecting ink droplets 37 onto the printing medium ME0, arranged in the nozzle alignment direction D4 at a predetermined nozzle pitch interval. Here, a nozzle means a small hole from which ink droplets are ejected, and a nozzle row means an arrangement of multiple nozzles. The nozzle surface 30a is the ejection surface for the ink droplets 37. The multiple nozzles 34 in each nozzle row 33 may be arranged in a staggered pattern in the nozzle alignment direction D4, or in other words, in two rows in the nozzle alignment direction D4. The nozzle alignment direction D4 may intersect with the feed direction D3, or it may intersect with the main scanning direction which intersects with the feed direction D3, as in a serial printer, etc. The multiple nozzle rows 33 include a C nozzle row 33C capable of ejecting C ink 36, an M nozzle row 33M capable of ejecting M ink 36, a Y nozzle row 33Y capable of ejecting Y ink 36, and a K nozzle row 33K capable of ejecting K ink 36. Each ink droplet 37 is ejected from the nozzle 34 onto the printing medium ME0, targeting the pixel PX0. Naturally, a C dot 38 is formed on the printing medium ME0 from a C ink droplet 37, an M dot 38 is formed on the printing medium ME0 from an M ink droplet 37, a Y dot 38 is formed on the printing medium ME0 from a Y ink droplet 37, and a K dot 38 is formed on the printing medium ME0 from a K ink droplet 37. The printer 2 may have multiple print heads 30.

[0034] The drive unit 50, controlled by the controller 10, moves the printing medium ME0 along the transport path 59 in the feed direction D3 by driving the roller drive unit 55. The roller drive unit 55 includes a transport roller pair 56 and a discharge roller pair 57. The roller drive unit 55 is composed of a servo motor and moves the printed medium ME0 in the feed direction D3 by rotating the drive transport roller of the transport roller pair 56 and the drive discharge roller of the discharge roller pair 57 according to the control of the controller 10. The control unit U1 can be said to control the relative positional relationship between the print head 30 and the printing medium ME0. The printing medium ME0 is the substrate that holds the printed image. The material of the printing medium ME0 is not particularly limited and can be various materials such as paper, resin, or metal. The shape of the printing medium ME0 is also not particularly limited and can be various shapes such as rectangles or rolls, and it may also be three-dimensional.

[0035] The platen 58 is located below the transport path 59 and supports the printing medium ME0 by contacting it in the transport path 59. The print head 30, controlled by the controller 10, is equipped with a drive circuit 31 and drive elements 32, etc., and adheres ink 36 to the printing medium ME0 supported by the platen 58 by ejecting ink droplets 37 toward the printing medium ME0. Therefore, it can be said that the control unit U1 controls the ejection of ink droplets 37 from the print head 30. The drive circuit 31 applies a voltage signal to the drive element 32 according to the drive signal SG1 input from the drive signal transmission unit 15. The drive element 32 may be a piezoelectric element that applies pressure to the ink 36 in a pressure chamber communicating with the nozzle 34, or it may be a drive element that generates bubbles in the pressure chamber using heat to eject ink droplets 37 from the nozzle 34. Ink 36 is supplied to the pressure chamber of the print head 30 from an ink supply unit 35, such as an ink cartridge or ink tank. The ink 36 in the pressure chamber is ejected as ink droplets 37 from the nozzle 34 toward the printing medium ME0 by the drive element 32. As a result, dots 38 of ink droplets 37 are formed on the printing medium ME0, and a printed image IM5 represented by a pattern of dots 38 is formed on the printing medium ME0. Therefore, it can be said that the control unit U1 controls the ejection of ink 36 from the print head 30 to the printing medium ME0 so that the dots 38 constituting the printed image IM5 are formed on the printing medium ME0.

[0036] RAM 21 stores images and other data received from the host device HO1 or memory (not shown). The communication interface 22 is connected to the host device HO1 by wire or wireless connection and inputs and outputs information to the host device HO1. The host device HO1 includes computers such as personal computers and tablet terminals, mobile phones such as smartphones, digital cameras, digital video cameras, etc. The storage unit 23 may be a non-volatile semiconductor memory such as flash memory, or a magnetic storage device such as a hard disk. The operation panel 24 includes an output unit 25 such as a liquid crystal panel for displaying information, an input unit 26 such as a touch panel for receiving operations on the display screen, etc.

[0037] Incidentally, as illustrated in Figure 9, when dots 38 originating from liquid ink droplets expand beyond pixel PX0, it is conceivable that the dark areas surrounded by white areas, such as black areas, may expand. In particular, when ink droplets that land on the printing medium ME0 bleed, the dark areas may expand too much, which can lead to a decrease in the print quality of characters or cause barcodes to become non-standard. Figure 9 schematically shows a comparative example of forming printed images (IM95, IM96) from an input image IM91, which is an RGB image. In the images shown in Figure 9 (IM91, IM92), pixels PX0 in the black region are hatched. The gradation values ​​(R,G,B) of pixel PX0 in the white region are assumed to be (255,255,255), and the gradation values ​​(R,G,B) of pixel PX0 in the black region are assumed to be (0,0,0).

[0038] The input image IM91 shown in Figure 9 has a black line consisting of three pixels in the X direction, which is an example of the first direction D1. This black line is oriented in the Y direction, which is an example of the second direction D2, which is perpendicular to the first direction D1. When dots 38 of color K, for example, large dots, are formed on the printing medium ME0 from each pixel PX0 of this black line, the ink droplets bleed, and a printed image IM95 with a black line wider than three pixels is formed on the printing medium ME0. To prevent a decrease in print quality due to ink droplet bleeding, the edge E0 of the black area is detected, and it is assumed that ink droplets will not be ejected across the entire edge E0. In the corrected image IM92 shown in Figure 9, the pixel values ​​of edge E0 in the input image IM91 are replaced from (0,0,0) to (255,255,255). As a result, the width of the black line is reduced from 3 pixels to 1 pixel, and a printed image IM96 with a black line of 1 dot row is formed on the printing medium ME0. If the black line is a barcode, the barcode may become too thin to be read. If the black line is an object containing thin lines such as letters, the degradation of the object will be noticeable.

[0039] In this specific example, by limiting the reduction in ink volume to certain edges, the deterioration of fine lines is suppressed while preventing a decrease in print quality due to ink bleeding. The following describes specific examples of print control processes for implementing the dot data generation method, referring to Figures 3-8B.

[0040] (3) Specific examples of print control processing: Figure 3 schematically illustrates the print control process performed by the controller 10. Figure 4 schematically illustrates how a printed image IM5 is formed from the input image with reduced ink volume at the first processing target edge E1. The input image is assumed to be an RGB image, and the images (IM1, IM2) shown in Figure 4 are assumed to be RGB images. In the images (IM1, IM2) shown in Figure 4, the surrounding region AR2 is a white region with pixel values ​​(R, G, B) of (255, 255, 255), and the darker region AR3, which is darker than the surrounding region AR2, is a black region with pixel values ​​(R, G, B) of (0, 0, 0). Figure 4 also shows the reference pattern P0 applied to image IM1. In Figure 4, the pixels PX0 in the dark region AR3, including the reference pattern P0, are hatched. In Figure 3, step S102 corresponds to the first detection step ST1 and the first detection process. Step S106 corresponds to the second detection step ST2 and the second detection process. Steps S108 to S112 correspond to the generation step ST3. Step S114 corresponds to the printing step ST4. Steps S108 to S114 correspond to the ejection control process. Hereafter, the term "step" may be omitted, and the step number may be indicated in parentheses.

[0041] When the print control process shown in Figure 3 starts, the controller 10 performs a first detection process in the edge correction unit 12, which detects a portion of edge E0 from the RGB image IM1 as the first processing target edge portion E1 (S102). As shown in Figure 4, the image IM1 has multiple pixels PX0 arranged in the X direction as an example of the first direction D1, and in the Y direction as an example of the second direction D2 intersecting the first direction D1. The feed direction D3 shown in Figures 1 and 2 may be either the X direction or the Y direction. In Figure 4, the X direction and the Y direction are orthogonal to each other. Note that the Y direction may be applied to the first direction D1, and the X direction may be applied to the second direction D2. In Figure 4, the detection target area AR1 of the first processing target edge portion E1 is the entire image IM1. The edge E0 present in the detection target area AR1 is a 1-pixel area adjacent to the surrounding area AR2 in the X or Y direction in the dense area AR3, as shown in the extracted image IM2.

[0042] Here, in the X direction, the edge present on one side of the dense region AR3, which is on both the left and right sides, is defined as the first edge E11. In the Y direction, the edge present on one side of the edge present on both the upper and lower sides of the dense region AR3 is defined as the second edge E12. Figure 4 shows that the first edge E11 is on the right side of the dense region AR3, and the second edge E12 is on the lower side of the dense region AR3. The first edge E11 may also be on the left side of the dense region AR3 instead of the right side. That is, the first edge E11 is not present on both sides of the dense region AR3 in the X direction. The second edge E12 may also be on the upper side of the dense region AR3 instead of the lower side. That is, the second edge E12 is not present on both sides of the dense region AR3 in the Y direction. Figure 4 shows that both the first edge portion E11 and the second edge portion E12 are detected as the first edge portion E1 to be processed. The controller 10 may detect the first edge portion E11 as the first edge portion E1 to be processed without including the second edge portion E12, or it may detect the second edge portion E12 as the first edge portion E1 to be processed without including the first edge portion E11. When the Y direction is longer than the X direction, as in the dense region AR3 shown in Figure 4, it is preferable that the first edge portion E1 to be processed includes the first edge portion E11.

[0043] The first target edge E1 can be detected by pattern matching using the reference pattern P0 shown in Figure 4. Here, a pattern refers to a set of features such as signals or images, and the relationships between these features. Pattern matching means comparing a given pattern with a set of pre-prepared patterns based on predetermined evaluation criteria. Pattern matching is not limited to comparing images; it can be any pattern that allows the state of a pixel of interest and its surrounding pixels to be compared based on evaluation criteria, such as signals represented by 0s and 1s. The reference pattern P0 shown in Figure 4 is a collective term for rectangular (including square) reference patterns P1 to P5, and can be considered the training image for image IM1. The reference patterns P1 to P5 shown in Figure 4 are 3x3 pixel squares. For the sake of explanation, pixels PX0 included in the surrounding region AR2 will be called faint pixels, and pixels PX0 included in the dark region AR3 will be called dark pixels. The light pixels shown in Figure 4 are white pixels with pixel values ​​(R,G,B) of (255,255,255), and the pixel values ​​of the light pixels in reference patterns P1 to P5 are also (R,G,B)=(255,255,255). The dark pixels shown in Figure 4 are black pixels with pixel values ​​(R,G,B) of (0,0,0), and the pixel values ​​of the dark pixels in reference patterns P1 to P5 are also (R,G,B)=(0,0,0). Furthermore, in addition to reference patterns P1 to P5, reference pattern P0 may also include reference patterns not shown that match diagonal edges corresponding to the first edge E11 and second edge E12, such as the diagonal edge on the lower right side. Also, the size of the reference pattern may be 5x5 pixels, or it may be a non-square size such as 3x5 pixels or 5x3 pixels.

[0044] The controller 10 sequentially selects a target pixel PX1 from among multiple pixels PX0 contained in the image IM1, and performs pattern matching by applying the reference pattern P0 to a rectangular determination region AD0 centered on the target pixel PX1. The determination region AD0 is the same size as the reference patterns P1 to P5, and in the example shown in Figure 4, it is a 3x3 pixel region centered on the target pixel PX1. If the arrangement of light and dark pixels in the determination region AD0 matches the arrangement of light and dark pixels in any of the reference patterns P1 to P5, the controller 10 detects the target pixel PX1 as the first processing target edge E1. If the pixel arrangement of the determination region AD0 does not match any of the pixel arrangements of the reference patterns P1 to P5, the target pixel PX1 is not the first processing target edge E1. For example, since the pixel arrangement of the determination region AD1 matches the pixel arrangement of the reference pattern P1, the target pixel PX1 in the determination region AD1 is detected as the first processing target edge E1. Since the pixel arrangement of the determination region AD2 matches the pixel arrangement of the reference pattern P2, the pixel PX1 of interest in the determination region AD2 is detected as the first processing target edge portion E1. As described above, the controller 10 detects at least one of the edges E0 present in the detection target area AR1 as the first processing target edge portion E1, which is a first edge portion E11 located on one side of the dense area AR3 in the first direction D1, and a second edge portion E12 located on one side of the dense area AR3 in the second direction D2.

[0045] After processing in S102 in Figure 3, the controller 10 branches the processing in the edge correction unit 12 depending on whether or not it detects an edge in the extracted image IM2, which represents the part of the detection target region AR1 other than the first processing target edge E1, as the second processing target edge E2 (S104). If the edge correction unit 12 detects the second processing target edge E2, the controller 10 performs the second detection processing in S106, and if it does not detect the second processing target edge E2, it skips S106 and proceeds to processing in S108. The second detection processing in S106 will be described later.

[0046] In S108, the controller 10 performs an edge correction in the edge correction unit 12 to reduce the amount of ink in the processing target edge areas (E1, E2). As a result, the process in S108 can be described as a process of thinning or reducing the size of the dots 38 in the processing target edge areas (E1, E2). If the second processing target edge area E2 is not detected, the controller 10 performs a correction to reduce the amount of ink only in the first processing target edge area E1. As shown in Figure 4, if the first processing target edge area E1 is detected, the controller 10 generates dot data DA2 from the image IM1 so that ink 36 is not ejected from the print head 30 to the first processing target edge area E1. For example, the controller 10 generates extracted image IM2 by replacing the pixel values ​​(R, G, B) of the first processing target edge area E1 in the image IM1 from (0, 0, 0) to (255, 255, 255). Note that the amount of ink in the first processing target edge area E1 may be reduced to, for example, 1 to 50% of the amount before correction. For example, the pixel values ​​(R, G, B) of the first processing target edge E1 may be replaced with values ​​(128, 128, 128) that represent approximately 50% of the ink amount based on the pre-correction values. Note that the pixel values ​​shown in this specification are merely examples to illustrate this specific example and can be changed in various ways. The same applies to the following steps. If the second detection process in S106 is not performed, the controller 10 uses the extracted image IM2 as the corrected image IM3 and performs the processing from S110 onward.

[0047] After processing in S108, the controller 10 performs a color conversion process in the color conversion unit 13 to convert the corrected image IM3 into ink amount data DA1 (S110). For the pixel PX0 of the first processing target edge part E1, if the pixel value (R,G,B) of the corrected image IM3, which is an RGB image, is (255,255,255), it is converted to a pixel value where no ink droplet 37 is ejected, for example, (C,M,Y,K)=(0,0,0,0). After the color conversion process, the controller 10 performs a halftone process in the halftone processing unit 14 to convert the ink amount data DA1 into dot data DA2 (S112). For the pixel PX0 of the first processing target edge part E1, if the pixel value (C,M,Y,K) of the ink amount data DA1 is (0,0,0,0), C, M, Y, and K are all converted to a value indicating no dot, for example, 0. Figure 4 shows schematic dot data DA2 in the print medium ME0, where dots 38, for example, large dots, are formed on the dark pixels of the corrected image IM3. As described above, the controller 10 generates dot data DA2 from the image IM1 such that the amount of ink 36 ejected from the print head 30 to the first processing target edge E1 is reduced, including 0. In this specification, "such as reducing the amount of ink 36 ejected to the first processing target edge E1, including 0" means "reducing the amount of ink ejected" or "preventing ejection altogether" compared to the case without correction.

[0048] After halftone processing, the controller 10 generates a drive signal SG1 based on the dot data DA2 and transmits the drive signal SG1 to the drive circuit 31 of the print head 30 (S114), thereby ending the print control process. The print head 30 ejects K ink droplets 37 according to the drive signal SG1 so that multiple dots 38 are formed in the dark pixels, as shown in the print medium ME0 of Figure 4. As a result, a print image IM5 represented by a pattern of dots 38 is formed on the print medium ME0. The printer 2 ejects ink 36 from the print head 30 onto the print medium ME0 based on the dot data DA2.

[0049] As explained above, the amount of ink 36 ejected to at least one of the edge portions (E11, E12) on one side of the dense area AR3 is reduced, rather than the entire edge E0 present in the detection target area AR1. This makes it possible to suppress the deterioration of print quality due to ink bleeding 36 while avoiding the inconvenience of objects such as barcodes and small characters becoming too thin.

[0050] If the ink 36 that lands on the printing medium ME0 is prone to bleeding, even if the portion of the edge E0 in the detection target area AR1 that does not eject ink 36 is limited to the first processing target edge portion E1, the bleeding of the ink 36 may still be noticeable. In this case, the second detection process S106 shown in Figure 3 is performed to suppress the bleeding of the ink 36 while leaving fine lines. Therefore, the second detection process S106 in Figure 3 will be explained with reference to Figure 5.

[0051] Figure 5 schematically illustrates how dot data DA2 is generated from the extracted image IM2 with reduced ink volume in the second processing target edge area E2. In the images (IM2, IM3) shown in Figure 5, the surrounding area AR2 is a white area with pixel values ​​(R, G, B) of (255, 255, 255), and the hatched pixel PX0 is a black area with pixel values ​​(R, G, B) of (0, 0, 0). In S106 shown in Figure 3, the controller 10 performs a second detection process in the edge correction unit 12 to detect edges present in the extracted image IM2, which represents the portion of the detection target area AR1 other than the first processing target edge portion E1, as the second processing target edge portion E2. The second processing target edge portion E2 shown in Figure 5 is the entire edge of the portion of the dense area AR3 excluding the first processing target edge portion E1, as shown in the corrected image IM3. The controller 10 may also detect only a portion of the edge of the portion of the dense area AR3 excluding the first processing target edge portion E1 as the second processing target edge portion E2. The controller 10 can detect the second processing target edge portion E2 by pattern matching using a reference pattern that can detect all or part of the edges of the extracted image IM2, for example. This pattern matching is particularly effective when detecting edges present on one side in the first direction D1 of the dense area excluding the first processing target edge portion E1, or edges present on one side in the second direction D2 of the dense area excluding the first processing target edge portion E1, as the second processing target edge portion E2. Furthermore, the controller 10 may detect the second processing target edge portion E2 by filtering using a known edge detection filter. For detecting the entire edge, a Laplacian filter or the like can be used as the edge detection filter.

[0052] After the second detection process, the controller 10 performs correction in the edge correction unit 12 to reduce the amount of ink in both the first processing target edge E1 and the second processing target edge E2 (S108). In this specific example, the controller 10 generates dot data DA2 from image IM1 such that no ink 36 is ejected from the print head 30 to the first processing target edge E1, and the amount of ink 36 ejected from the print head 30 to the second processing target edge E2 is reduced to a range that is not zero. For example, the controller 10 generates extracted image IM2 by replacing the pixel values ​​(R,G,B) of the first processing target edge E1 in image IM1 from (0,0,0) to (255,255,255). The controller 10 also generates corrected image IM3 by replacing the pixel values ​​of the second processing target edge E2 in extracted image IM2 such that the amount of ink is, for example, 1 to 50% of the amount before correction. For example, the pixel values ​​(R, G, B) of the second processing target edge E2 may be replaced with values ​​(128, 128, 128) that represent approximately 50% of the ink amount based on the pre-correction values.

[0053] After processing in S108, the controller 10 performs a color conversion process in the color conversion unit 13 to convert the corrected image IM3 into ink amount data DA1 (S110). For pixels PX0 of the first target edge E1, if the pixel value (R,G,B) of the corrected image IM3, which is an RGB image, is (255,255,255), it is converted to a pixel value where no ink droplet 37 is ejected, for example, (C,M,Y,K)=(0,0,0,0). For pixels PX0 of the second target edge E2, if the pixel value (R,G,B) of the corrected image IM3 is (128,128,128), it is converted to a pixel value where the size of the K ink droplet 37 becomes smaller, for example, from the equivalent of a large dot to the equivalent of a medium dot, for example, (C,M,Y,K)=(0,0,0,127). After the color conversion process, the controller 10 performs a halftone processing in the halftone processing unit 14 to convert the ink amount data DA1 to dot data DA2 (S112). For pixels PX0 of the first target edge E1, if the pixel value (C,M,Y,K) of the ink amount data DA1 is (0,0,0,0), C, M, Y, and K are all converted to a value indicating no dot, for example, 0. For dark pixels of the corrected image IM3, K is converted to a value indicating a large dot, for example, 3. For pixels PX0 of the second target edge E2, if the pixel value (C,M,Y,K) of the ink amount data DA1 is (0,0,0,127), K is converted to a value indicating a medium dot, for example, 2.

[0054] After halftone processing, the controller 10 generates a drive signal SG1 based on the dot data DA2 and transmits the drive signal SG1 to the drive circuit 31 of the print head 30 (S114), thereby ending the print control process. As a result, a print image IM5, represented by a pattern of dots 38 corresponding to the pixel values ​​of the dot data DA2 shown in Figure 5, is formed on the print medium ME0. As explained above, if ink bleeding is noticeable when the amount of ink in the first target edge E1 is reduced to zero, the bleeding of the ink 36 is suppressed by reducing the amount of ink 36 ejected to the second target edge E2, while keeping the amount of ink 36 within a range that does not become zero. Therefore, when the ink 36 that lands on the printing medium ME0 is prone to bleeding, it is possible to suppress the bleeding of the ink 36 while leaving fine lines.

[0055] Furthermore, some of the above-described processes may be performed by the host device HO1. In this case, the combination of the controller 10, the drive unit 50, and the host device HO1 is an example of the control unit U1, and the combination of the printer 2 and the host device HO1 is an example of the printing device 1. The entity that performs the above-described processes is not limited to the CPU, but may be an electronic component other than the CPU, such as an ASIC. Of course, multiple CPUs may cooperate to perform the above-described processes, or a CPU and other electronic components (such as an ASIC) may cooperate to perform the above-described processes.

[0056] For the decision-making process S104 shown in Figure 3, the printing device 1 can display the screens (500, 520) exemplified in Figures 6A and 6B on at least one of the output unit 25 of the operation panel 24 and the display device DU1 of the host device HO1. Figure 6A schematically shows an example of the display of the edge detection processing specification screen 500. The edge detection processing specification screen 500 shown in Figure 6A includes items such as "Once only" item 201 and "Two-stage processing" item 202. In S104 shown in Figure 3, for example, the controller 10 displays the edge detection processing specification screen 500 on the output unit 25 and accepts the selection of one of the multiple options (201, 202) at the input unit 26 of the operation panel 24. If the selection of "Once only" item 201 is accepted, the controller 10 determines that the condition is not met and proceeds to S108, and if the selection of "Two-stage processing" item 202 is accepted, the controller 10 determines that the condition is met and proceeds to S106. When the host device HO1 performs the processing in S102 to S108, the host device HO1 displays the edge detection processing specification screen 500 on the display device DU1 and accepts the selection of one of the multiple options (201, 202) at an input unit (not shown). If the host device HO1 accepts the "only once" item 201, it determines that the condition is not met and proceeds to S108. If the "two-stage processing" item 202 is accepted, it determines that the condition is met and proceeds to S106.

[0057] Based on the above, if the "Once Only" item 201 is specified, the printer 1 does not detect the second processing target edge E2 and generates dot data DA2 from image IM1 in such a way that the amount of ink 36 ejected from the print head 30 to the first processing target edge E1 is reduced. If the "Two-Stage Processing" item 202 is specified, the printer 1 generates dot data DA2 from image IM1 in such a way that the amount of ink 36 ejected to both processing target edges (E1, E2) is reduced.

[0058] Figure 6B schematically shows an example of the display of the media type selection screen 520. The media type selection screen 520 shown in Figure 6B includes multiple types 220 that can be used for the printing medium ME0, such as the "photo paper" item as an example of the first type 221 and the "plain paper" item as an example of the second type 222. Plain paper is more prone to ink bleeding than photo paper (for example, glossy paper), so the second type 222 is more prone to ink bleeding than the first type 221. Fabrics can also be considered as a second type 222 that is prone to ink bleeding. In S104 shown in Figure 3, for example, the controller 10 displays the media type selection screen 520 on the output unit 25 and accepts the selection of the type to be used from among the multiple types (221, 222) at the input unit 26 of the operation panel 24. If the controller 10 accepts the selection of the first type 221, it determines that the condition is not met and proceeds to S108, and if the selection of the second type 222 is accepted, it determines that the condition is met and proceeds to S106. Of course, the host device HO1 may perform the processing in S102 to S108. In either case, a media type specification step ST5 is performed in S104 to accept the specification of the type to be used from among several types 220. If a second type 222 is specified, a second detection step ST2 (see Figures 3 and 5) is performed in S106 to detect edges in the extracted image IM2, which represents the part of the detection target area AR1 other than the first processing target edge part E1, as the second processing target edge part E2. In S108, the ink amount of the first processing target edge part E1 is corrected to 0, and the ink amount of the second processing target edge part E2 is reduced to a range where it does not become 0.

[0059] Therefore, when the first type 221 is specified, the printing device 1 does not detect the second processing target edge E2 and generates dot data DA2 from the image IM1 so that ink 36 is not ejected from the print head 30 to the first processing target edge E1. When the second type 222 is specified, the printing device 1 generates dot data DA2 from the image IM1 so that ink 36 is not ejected from the print head 30 to the first processing target edge E1, and the amount of ink 36 ejected from the print head 30 to the second processing target edge E2 is reduced to a range that is not zero. In the example shown in Figure 6B, if the second type 222, in which ink 36 is prone to bleeding, is specified as the printing medium ME0 to be used, the bleeding of ink 36 can be suppressed while retaining fine lines. On the other hand, if the first type 221, in which ink 36 does not bleed easily, is specified as the printing medium ME0 to be used, the amount of ink 36 ejected to the pixel PX0, which can become the second processing target edge E2, is maintained, so that the edges present in the extracted image IM2 are clearly displayed. Therefore, the image quality of the printed image is improved according to the user's intention.

[0060] Furthermore, in order to switch the definition of the dense area AR3 in the print control process shown in Figure 3, the printing device 1 can display the dense area specification screen 540, as exemplified in Figure 6C, on at least one of the output unit 25 of the operation panel 24 and the display device DU1 of the host device HO1. Figure 6C schematically shows an example of the display of the dense area specification screen 540. The dark area specification screen 540 shown in Figure 6C includes multiple options 240 to be applied to the dark area AR3, such as the "black only" option 241 and the "other than white" option 242. The "black only" option 241 is an option to apply black (R,G,B)=(0,0,0) as an example of a predetermined color to the dark area AR3. The "other than white" option 242 is an option to apply a color other than white as an example of a predetermined color range to the dark area AR3. For example, the controller 10 displays the dark area specification screen 540 on the output unit 25 and accepts the selection of one of the multiple options (241,242) at the input unit 26 of the operation panel 24. If the controller 10 accepts the selection of the "black only" option 241, it applies black (R,G,B)=(0,0,0) to the dark area AR3 of the images (IM1~IM3) and reference pattern P0 and performs the print control processing shown in Figure 3. When the controller 10 receives a "non-white" item 242, it applies all colors whose pixel values ​​(R,G,B) are not (255,255,255) to the images (IM1~IM3) and the dark region AR3 of the reference pattern P0, and performs the print control processing shown in Figure 3. Of course, the host device HO1 may display the dark region specification screen 540 on the display device DU1 and accept the specification of one of the multiple options 240 at an input unit not shown. In either case, a color specification process ST6 is performed to accept the specification of an option to be applied to the dark region AR3 from among the multiple options 240, including the "black only" item 241 and the "non-white" item 242.

[0061] When item 241, "black only," is specified, the printer 1 treats pixel PX0 with (R,G,B)=(0,0,0) as the image (IM1~IM3) and the dark region AR3 of reference pattern P0, and performs the print control processing shown in Figure 3. For example, the controller 10 detects a pixel PX1 of interest in the image IM1, where the arrangement of the surrounding region AR2 with (R,G,B)=(255,255,255) and the dark region AR3 with (R,G,B)=(0,0,0) matches the arrangement of any of the reference patterns P1~P5, as the first processing target edge portion E1. When a predetermined color is specified, the control unit U1 can be said to detect at least one of the following as the first processing target edge portion E1: the first edge portion E11 located on one side of the dark region AR3 of the predetermined color in the first direction D1, and the second edge portion E12 located on one side of the dark region AR3 of the predetermined color in the second direction D2.

[0062] If item 242, "other than white," is specified, the printing device 1 treats pixel PX0, whose pixel value (R,G,B) is other than (255,255,255), as a dark region AR3 and performs the printing control processing shown in Figure 3. For example, the controller 10 detects a pixel PX1 of interest in the image IM1 as the first processing target edge E1, where the arrangement of the surrounding region AR2 with (R,G,B)=(255,255,255) and the dark region AR3 that is not (R,G,B)=(255,255,255) matches the arrangement of any of the reference patterns P1 to P5. When a predetermined color range is specified, the control unit U1 can be said to detect at least one of the edges E0 present in the detection target area AR1 as the first processing target edge portion E1, which is located on one side of the dark area AR3 in the predetermined color range in the first direction D1, and the second edge portion E12 located on one side of the dark area AR3 in the predetermined color range in the second direction D2.

[0063] For example, if an object such as text or a barcode is black and the "black only" item 241 is specified, a high-quality printed image IM5 can be obtained by reducing the amount of ink in the processed edge areas (E1, E2) of the black object. For example, consider a case where you want to reduce the amount of ink in the edge areas of text, but it is difficult to add information such as "text" to the image IM1. In this case, by targeting only black, which is commonly used for text, to reduce the amount of ink, complex processing is not required to generate dot data DA2, and the pixels PX0 whose ink amount you want to reduce can be extracted from the original image IM1 and the ink amount of those pixels PX0 can be reduced. Also, if an object is a color other than white and the "other than white" item 242 is specified, a high-quality printed image IM5 can be obtained by reducing the amount of ink in the processed edge areas (E1, E2) of objects of colors other than black, even if the object is not black. Therefore, a high-quality printed image IM5 can be obtained according to the color of the object, such as text or a barcode. Furthermore, even if objects such as text or barcodes are colors other than black, such as blue or red, the print control process shown in Figure 3 may be performed using a predetermined color included in the multiple options 240.

[0064] Furthermore, the surrounding region AR2 is not limited to the white region where (R,G,B)=(255,255,255). For example, if GR is an integer value greater than 128 and less than 255, the surrounding region AR2 may also be the region of light-colored pixels PX0 satisfying R≧GR, G≧GR, and B≧GR. In this case, the dark region AR3 will be a dark-colored region satisfying R≦GR-1, or G≦GR-1, or B≦GR-1. The predetermined color range included in the multiple options 240 may also be a color range satisfying R≦GR-1, or G≦GR-1, or B≦GR-1.

[0065] Furthermore, in order to switch the width of the processing target edge portions (E1, E2) in the print control process shown in Figure 3, the printing device 1 can display the edge width specification screen 560, as exemplified in Figure 7A, on at least one of the output unit 25 of the operation panel 24 and the display device DU1 of the host device HO1. Figure 7A schematically shows an example of the display of the edge width specification screen 560. Figure 7B schematically illustrates a 5x5 pixel reference pattern P10. For convenience, the pixel of interest PX1, the surrounding area AR2, and the dark area AR3 are attached to the reference pattern P10.

[0066] The edge width specification screen 560 shown in Figure 7A includes multiple options for specifying the width of the first processing target edge E1, such as the "1-dot width" item 261 and the "2-dot width" item 262. The "1-dot width" item 261 is an option to set the width of the first processing target edge E1 to 1 dot. The "2-dot width" item 262 is an option to set the width of the first processing target edge E1 to 2 dots. For example, the controller 10 displays the edge width specification screen 560 on the output unit 25 and accepts the selection of one of the multiple options (261, 262) at the input unit 26 of the operation panel 24. If the controller 10 accepts the selection of the "1-dot width" item 261, in the first detection process S102 shown in Figure 3, the controller 10 detects the first processing target edge E1 from the image IM1 by pattern matching using the 3x3 pixel reference pattern P0 shown in Figure 4. When the controller 10 receives the "2-dot width" item 262 specification, in the first detection process S102 shown in Figure 3, it detects the first processing target edge portion E1 from the image IM1 by pattern matching using the 5x5 pixel reference pattern P10 shown in Figure 7B. Of course, the host device HO1 may also display the edge width specification screen 560 on the display device DU1 and accept the specification of one of the multiple options (261, 262) at an input unit not shown. In either case, the edge width specification process ST7 is performed to accept the specification of the width of the first processing target edge portion E1. The controller 10 or the host device HO1 performs a first detection process to detect the first processing target edge portion E1 so that it has the specified width.

[0067] The 5x5 pixel reference pattern P10 shown in Figure 7B is a collective term for multiple individual reference patterns with different arrangements of light and dark pixels. For example, the controller 10 can sequentially set a target pixel PX1 from the image IM1 and perform pattern matching by applying the reference pattern P10 to a 5x5 pixel determination area AD0 centered on the target pixel PX1. With the 5x5 pixel reference pattern P10, not only pixels adjacent to the surrounding area AR2 in the dark area AR3, but also pixels one pixel away from the surrounding area AR2 in the first direction D1 or second direction D2 can become the first processing target edge part E1.

[0068] Therefore, the width of the detected first processing target edge E1 can be adjusted to the user's intent. Consequently, the print image quality is improved according to the user's intent. Furthermore, for the second processing target edge portion E2, it is possible to accept width specification by displaying a screen similar to the edge width specification screen 560. In this case, the controller 10 or host device HO1 only needs to perform a second detection process to detect the second processing target edge portion E2 so that it has the specified width.

[0069] Furthermore, in order to switch the detection target area AR1 in the print control process shown in Figure 3, the printing device 1 can display the object specification screen 580, exemplified in Figure 8A, on at least one of the output unit 25 of the operation panel 24 and the display device DU1 of the host device HO1. Figure 8A schematically shows an example of the display of the object specification screen 580. Figure 8B schematically illustrates the detection target area AR1 included in the image IM1.

[0070] The object specification screen 580 shown in Figure 8A includes multiple options for specifying the detection target area AR1, such as the "Text and Lines" item 281 and the "Entire Image" item 282. The "Text and Lines" item 281 is an option to make the detection target area AR1 consist of text and lines (including barcodes). Text and lines are examples of objects contained in image IM1. The "Entire Image" item 282 is an option to make the detection target area AR1 consist of the entire image IM1. For example, the controller 10 displays the object specification screen 580 on the output unit 25 and accepts the selection of one of the multiple options (281, 282) at the input unit 26 of the operation panel 24. If the selection of the "Text and Lines" item 281 is accepted, the controller 10 extracts the text area AR1c and the line area AR1b from image IM1 as the detection target area AR1, as shown in Figure 8B. Image IM1 often has information indicating the position of text and lines associated with it. For example, if image IM1 originates from an image file containing information indicating the attributes of characters and lines, the controller 10 can obtain information indicating the positions of the characters and lines originating from the image file from the host device HO1 or the like. When the controller 10 receives a specification for the "whole" item 282, it treats the entire image IM1 as the detection target area AR1. Of course, the host device HO1 may also display the object specification screen 580 on the display device DU1 and accept the specification of one of the multiple options (281, 282) at an input unit not shown. In either case, the object specification step ST8, in which objects included in image IM1 are specified, is performed. The controller 10 or host device HO1 performs a first detection process to detect the first processing target edge portion E1 with the specified object regions (AR1c, AR1b) as the detection target area AR1.

[0071] Therefore, the detection target area AR1 can be adjusted to the user's intent. Consequently, the print image quality is improved according to the user's intent. In particular, the effect of reducing the amount of ink used in the processing target edges (E1, E2) is significant for characters and lines (including barcodes). Furthermore, the object can consist of text only, or lines only.

[0072] (4) Variations: Various modifications of this invention are conceivable. For example, the combination of ink colors is not limited to C, M, Y, and K, and may include orange, green, light cyan at a lower concentration than C, light magenta at a lower concentration than M, dark yellow at a higher concentration than Y, light black at a lower concentration than K, etc. Of course, the embodiments of this application can also be applied when the printing apparatus 1 does not use any of the C, M, Y, and K inks.

[0073] The detection of the first processing target edge E1 is not limited to pattern matching. For example, the printing device 1 may detect a pixel of interest in the dark region AR3 whose filter calculation value using a horizontal Sobel filter is greater than or less than a predetermined threshold as the first edge E11. The printing device 1 may also detect a pixel of interest in the dark region AR3 whose filter calculation value using a vertical Sobel filter is greater than or less than a predetermined threshold as the second edge E12. Furthermore, the printing device 1 may detect the entire edge E0 in the dark region AR3 by filtering using a Laplacian filter, and then detect the first processing target edge E1 based on the position of a light pixel adjacent to the dark pixel at edge E0.

[0074] In the specific example described above, the processing target edge was detected from an RGB image and the amount of ink in the processing target edge was reduced, but the method is not limited to this. For example, the control unit may detect the processing target edge from a CMYK image represented by ink amount data and reduce the amount of ink in the processing target edge. Alternatively, the control unit may detect the processing target edge from a dot image represented by uncorrected dot data and generate corrected dot data by downsampling or reducing the size of the dots in the processing target edge.

[0075] (5) Conclusion: As described above, according to the present invention, in various embodiments, it is possible to provide a configuration that can suppress the deterioration of fine lines due to insufficient ink discharge across the entire edge, while also suppressing the reduction in print quality due to ink bleeding. Of course, even in embodiments consisting only of the constituent elements of the independent claims, the basic functions and effects described above can be obtained. Furthermore, configurations obtained by substituting or changing the combinations of each configuration disclosed in the above-mentioned examples, configurations obtained by substituting or changing the combinations of each configuration disclosed in the prior art and the above-mentioned examples, etc., are also possible. The present invention also includes these configurations, etc. [Explanation of Symbols]

[0076] 1...Printing device, 2...Printer, 10...Controller, 12...Edge correction unit, 30...Print head, 33...Nozzle row, 34...Nozzle, 36...Ink, 37...Ink droplet, 38...Dot, 50...Drive unit, 201..."Once only" item, 202..."Two-stage processing" item, 220...Type, 221...First type, 222...Second type, 240...Option, 241..."Black only" item, 242..."Other than white" item, 261..."1 dot width" item, 262..."2 dot width" item, 281..."Characters and lines" item, 282..."Overall" item, 500...Edge detection processing specification screen, 520...Media type specification screen, 540...Dark area specification screen, 560...Edge width specification screen, 580...Object specification screen, AD0...Judgment area, AR1...Detection target area, AR1b...Line Area, AR1c... Character area, AR2... Surrounding area, AR3... Dark area, D1... First direction, D2... Second direction, DA1... Ink amount data, DA2... Dot data, DU1... Display device, E0... Edge, E1... First processing target edge part, E2... Second processing target edge part, E11... First edge part, E12... Second edge part, HO1... Host device, IM1... Image, IM2... Extracted image, IM3... Corrected image, IM5... Printed image, ME0... Printing medium, P0, P1~P5, P10... Reference pattern, PX0... Pixel, PX1... Pixel of interest, ST1... First detection process, ST2... Second detection process, ST3... Generation process, ST4... Printing process, ST5... Medium type specification process, ST6... Color specification process, ST7... Edge width specification process, ST8... Object specification process, U1... Control unit.

Claims

1. A method for generating dot data that generates dot data indicating the position of dots formed by ink from a print head, A first detection step in which, among the edges in a detection target area of ​​an image having a plurality of pixels arranged in a first direction and a second direction intersecting the first direction, at least one of a first edge portion located on one side of a region that is darker than the surrounding area in the first direction and a second edge portion located on one side of a region that is darker than the surrounding area in the second direction is detected as a first processing target edge portion; A method for generating dot data, comprising a generation step of generating dot data from an image such that the amount of ink ejected from the print head to the first processing target edge portion is reduced.

2. The process further includes a second detection step of detecting at least a portion of the edges present in the extracted image representing the portion of the detection target area other than the first processing target edge portion as a second processing target edge portion. The dot data generation method according to claim 1, wherein in the generation step, the dot data is generated from the image such that no ink is ejected from the print head to the first processing target edge, and the amount of ink ejected from the print head to the second processing target edge is reduced to a range that is not zero.

3. A printing process in which ink is ejected from the print head onto a printing medium based on the dot data, A media type designation step that accepts the designation of the type to be used from among a plurality of types of printing media that can be used as the printing medium, including a first type and a second type that is more prone to ink bleeding than the first type, When the second type is specified, the method further includes a second detection step of detecting edges present in the extracted image representing the portion of the detection target area other than the first processing target edge portion as the second processing target edge portion, In the above generation process, When the first type is specified, the dot data is generated from the image so that the ink is not ejected from the print head to the first processing target edge. The dot data generation method according to claim 1, wherein, when the second type is specified, the dot data is generated from the image such that the ink is not ejected from the print head to the first processing target edge, and the amount of ink ejected from the print head to the second processing target edge is reduced to a degree that is not zero.

4. The process further includes a color specification step of receiving a selection of options, including a predetermined color and a predetermined color range, to be applied to the dark area. In the first detection step, When the predetermined color is specified, at least one of the edges in the detection target area, which is located on one side of the dark area of ​​the predetermined color in the first direction, and which is located on one side of the dark area of ​​the predetermined color in the second direction, is detected as the first processing target edge. A dot data generation method according to any one of claims 1 to 3, wherein, when the predetermined color range is specified, at least one of the edges present in the detection target area, which is located on one side of the dark area in the predetermined color range in the first direction, and which is located on one side of the dark area in the predetermined color range in the second direction, is detected as the first processing target edge.

5. The process further includes an edge width specification step for receiving a specification of the width of the first target edge portion, The dot data generation method according to any one of claims 1 to 3, wherein the first detection step involves detecting the first processing target edge portion so that it has the specified width.

6. The process further includes an object specification step of specifying the objects included in the aforementioned image, The dot data generation method according to any one of claims 1 to 3, wherein in the first detection step, the first processing target edge portion is detected with the region of the specified object as the detection target region.

7. A printing apparatus that forms a printed image on a printing medium using ink, A print head capable of ejecting the aforementioned ink, The system includes a control unit that controls the ejection of ink from the print head to the printing medium so that dots constituting the printed image are formed on the printing medium, The control unit, A first detection process that detects, as a first processing target edge portion, at least one of the edges in a detection target region of an image having a plurality of pixels arranged in a first direction and a second direction intersecting the first direction, a first edge portion located on one side of a region that is darker than the surrounding area in the first direction, and a second edge portion located on one side of a region that is darker than the surrounding area in the second direction. A printing apparatus that performs an ejection control process that controls the ejection of the ink from the print head to the printing medium so that the amount of ink ejected to the first target edge portion is reduced.

Images