Image processing apparatus, image processing method, program, method for manufacturing a sleeve printing plate, and method for manufacturing a can.

Abstract

To provide a technique capable of suitably thinning out a dot of a gradation image.SOLUTION: An image processing device comprises: an acquisition unit which acquires thinning-out image data indicating a thinning-out image constituted of dots for thinning out a dot in a thinning-out target region in a gradation image; and a generation unit which generates thinned-out image data indicating a thinned-out image obtained by thinning out an overlapping region where the dot in the thinning-out target region and the dot in the thinning-out image overlap each other from the thinning-out target region when the thinning-out region and the thinning-out image are made to overlap each other.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to an image processing apparatus, an image processing method, a program, a method for manufacturing a sleeve printing plate, and a method for manufacturing a can.

Background Art

[0002] When a gradation image is printed on a printing target such as a can, dot gain may occur in each of the halftone dots constituting the image. Therefore, for example, FM screening may be performed by software to thin out the halftone dots for an area where halftone dots with a density within a predetermined range, such as 0% to 10%, are drawn.

[0003] FIG. 18 is a diagram showing a gradation image before thinning out. FIG. 18 shows a target area for FM screening and a halftone area. FIG. 19 is a diagram showing a thinned-out image in which the halftone dots in the target area of FIG. 18 are thinned out by performing FM screening so that the tone in the halftone area does not change.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As shown in FIG. 19, when FM screening is performed so that the tone in the halftone area does not change, the thinning effect becomes weak. Therefore, in order to obtain a thinning effect without causing a change in the tone in the halftone area, when the original gradation image is adjusted and FM screening is performed on the target area, the image shown in FIG. 20 is obtained. The image shown in FIG. 20 becomes a brighter image compared to the image in FIG. 18 and is different from the original gradation image. There has been a problem that even when such adjustment is performed, suitable thinning cannot be performed.

[0006] In view of the above circumstances, the present invention aims to provide a technique that can suitably thin out the halftone dots in a gradient image. [Means for solving the problem]

[0007] One aspect of the present invention is an image processing apparatus comprising: an acquisition unit that acquires thinned image data showing a thinned image consisting of halftone dots for thinning out halftone dots in a thinned-out area within a gradient image; and a generation unit that generates a thinned-out image showing a thinned-out image showing an overlapping area where halftone dots in the thinned-out area and halftone dots in the thinned-out image overlap when the thinned-out area and the thinned-out image are superimposed.

[0008] One aspect of the present invention is an image processing method comprising: an acquisition step of acquiring thinned image data showing a thinned image consisting of halftone dots for thinning out halftone dots in a thinned-out area within a gradient image; and a generation step of generating a post-thinned image showing a post-thinned image in which, when the thinned-out area and the thinned-out image are superimposed, the superimposed area where the halftone dots in the thinned-out area and the halftone dots in the thinned-out image overlap is thinned out from the thinned-out area.

[0009] One aspect of the present invention is a program that causes a computer to function as an image processing apparatus, characterized in that the computer functions as an acquisition unit that acquires thinned image data showing a thinned image consisting of halftone dots for thinning out halftone dots in a thinned-out area within a gradient image, and a generation unit that generates a thinned-out image showing a thinned-out image showing an overlapping area where the halftone dots in the thinned-out area and the halftone dots in the thinned-out image overlap when the thinned-out area and the thinned-out image are superimposed.

[0010] One aspect of the present invention is a method for manufacturing a sleeve printing plate, comprising an image pattern forming step of forming an image pattern on a cylindrical sleeve body, and using a laser processing machine equipped with a rotating drum on which the sleeve body can be mounted on its outer circumference, and a laser beam irradiation unit for irradiating the sleeve body mounted on the rotating drum with laser light, wherein the image pattern forming step is performed with the sleeve body mounted on the same rotating drum, the image pattern is based on downsampled image data generated by the image processing device, and the method for manufacturing a sleeve printing plate is to perform the image pattern forming step based on the downsampled image data.

[0011] One aspect of the present invention is a method for manufacturing a can, comprising a printing step of printing on the outer surface of a cylindrical body, wherein the printing step is performed using a printing apparatus that uses a sleeve printing plate manufactured by the above manufacturing method. [Brief explanation of the drawing]

[0012] [Figure 1] This is a functional block diagram showing the functional configuration of an image processing device. [Figure 2] This figure shows an example of an image before thinning and the area to be thinned. [Figure 3] This is a diagram showing thinned-out images. [Figure 4] This figure shows the image after thinning. [Figure 5] This is a diagram showing the image before thinning. [Figure 6] This is a diagram showing thinned-out images. [Figure 7] This figure shows the image after thinning. [Figure 8] This flowchart shows the process of thinning out the plants. [Figure 9] This is a diagram showing thinned-out images. [Figure 10] This figure shows the image after thinning. [Figure 11] This is a perspective view diagram of the sleeve printing plate. [Figure 12] This is an explanatory diagram of the sleeve printing plate viewed from the axial direction. [Figure 13] It is a schematic diagram of a laser processing apparatus for implementing a method of manufacturing a sleeve printing plate. [Figure 14] It is a schematic diagram of a printing apparatus in which a sleeve printing plate is used. [Figure 15] It is a schematic diagram of a cylinder to which a sleeve printing plate is attached. [Figure 16] It is an explanatory diagram showing a state in which a sleeve printing plate is attached. [Figure 17] It is an explanatory diagram showing a state in which a sleeve printing plate is attached. [Figure 18] It is a diagram for explaining the prior art. [Figure 19] It is a diagram for explaining the prior art. [Figure 20] It is a diagram for explaining the prior art.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, specific configuration examples of the present invention will be described with reference to the drawings. FIG. 1 is a functional block diagram showing the functional configuration of an image processing apparatus 100 according to the present embodiment. The image processing apparatus 100 includes a storage device such as a CPU (Central Processing Unit) and a memory connected by a bus, an auxiliary storage device, etc., and functions as a device including a communication unit 110, an operation display unit 115, a control unit 120, and an image data storage unit 140 by executing an image processing program. Note that all or part of the functions of the communication unit 110, the operation display unit 115, the control unit 120, and the image data storage unit 140 may be realized using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array).

[0014] The image processing program may be recorded on a computer-readable recording medium. Computer-readable recording media include, for example, portable media such as flexible disks, magneto-optical disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks and SSDs (Solid State Drives) built into computer systems. The image processing program may also be transmitted via a telecommunications line.

[0015] The communication unit 110 is a network interface. The communication unit 110 communicates with other devices via a LAN (Local Area Network) or the Internet. For example, the communication unit 110 receives image data from other devices or transmits processed image data to other devices. The operation display unit 115 accepts operation input from the operator of the image processing device 100 and displays various information to the operator. The display of various information is performed, for example, by an LCD (Liquid Crystal Display) or an organic EL (Electro-Luminescence).

[0016] The image data storage unit 140 is configured using a storage device such as a magnetic hard disk drive or a semiconductor storage device. The image data storage unit 140 stores image data to be downsampled and image data that has been downsampled.

[0017] In Figure 1, the control unit 120 controls the operation of each part of the image processing device 100. The control unit 120 is executed by a device equipped with a processor such as a CPU and RAM. By executing an image processing program, the control unit 120 functions as an acquisition unit 121, a generation unit 122, a parameter detection unit 123, a change parameter specification unit 124, a reverse gradient image generation unit 125, and a decimation region specification unit 126.

[0018] The acquisition unit 121 acquires downsampling image data that shows a downsampling image composed of halftone dots for downsampling dots in the downsampling target area within the gradient image. The generation unit 122, when the downsampling area and the downsampling image are superimposed, downsamples the superimposed area from the downsampling target area where the halftone dots in the downsampling target area and the halftone dots in the downsampling image overlap. In the following description, the gradient image to be downsampled will be referred to as the "image before downsampling". The image after downsampling, in which the superimposed area where the halftone dots in the downsampling target area and the halftone dots in the downsampling image overlap has been downsampled from the downsampling target area, will be referred to as the "image after downsampling".

[0019] Figure 2 shows an example of the pre-thinning image and the region to be thinned. In Figure 2, the region to be thinned is the lower part of the pre-thinning image, but this is just an example; the region to be thinned can be any region of the pre-thinning image, or it can be the entire region of the pre-thinning image. Figure 3 shows an example of a thinned image. As shown in Figure 3, the thinned image is a gradient image with a gradient in the opposite direction to the gradient direction in the region to be thinned.

[0020] Here, the direction of the gradient is defined as the direction in which the proportion of halftone dots increases in the image. Therefore, the direction of the gradient in the pre-thinning image shown in Figure 2 is upward. On the other hand, the direction of the gradient in the thinned image is downward, so it is the opposite direction. Alternatively, the direction of the gradient may be defined as the direction in which the proportion of halftone dots decreases in the image. In this case, the direction of the gradient in the pre-thinning image shown in Figure 2 is downward. On the other hand, the direction of the gradient in the thinned image is upward. Therefore, even when the direction of the gradient in the thinned image is defined as the direction in which the proportion of halftone dots decreases in the image, the thinned image is a gradient image with a direction opposite to the gradient in the thinned area.

[0021] Figure 4 shows the image after thinning. As shown in Figure 4, it can be seen that some of the halftone dots have been thinned out. This type of thinning method, in which only some of the halftone dots are thinned out rather than the entire dots, cannot be achieved by FM screening or AM screening. Therefore, according to this embodiment, it is possible to generate images with halftone dots that cannot be obtained by FM screening or AM screening.

[0022] Returning to the explanation of Figure 1, the thinning area designation unit 126 receives the thinning area specified by the operator. The thinning area may be specified, for example, by displaying the pre-thinning image and a UI (User Interface) that allows the operator to specify the thinning area on the operation input unit 115. Alternatively, the thinning area designation unit 126 may specify the thinning area according to a predetermined thinning area. Information indicating the thinning area (for example, the coordinates of the four corners of the thinning area) is stored in the storage device.

[0023] The parameter detection unit 123 detects various parameters from the pre-decimation image stored in the image data storage unit 140. In this embodiment, the parameter types include the screen angle in the area to be deciphered, the number of lines per inch of the halftone dots, and the dot shape of the halftone dots. The parameters detected by the parameter detection unit 123 are output to the inverse gradient image generation unit 125, which generates the deciphered image.

[0024] The parameter change specification unit 124, when generating the downsampled image produced by the inverse gradient image generation unit 125, allows the operator to specify which parameter types from the above parameter types should be different from the parameters detected from the downsampled area. The operator can specify any parameter type. The parameter types specified by the operator in the parameter change specification unit 124 are output to the inverse gradient image generation unit 125.

[0025] Furthermore, among the parameters of the downsampled image, only the screen angle needs to differ from the screen angle of the downsampled area; the screen line count and dot shape of the halftone dots may be the same as those of the downsampled area. Therefore, the operator can specify the following combinations of parameter types to be different from those detected from the downsampled area. Combination 1: Screen angle, halftone screen count Combination 2: Screen angle, dot shape Combination 3: Screen angle, halftone screen count, dot shape Note that combinations that do not include the screen angle may also be used, in which case the following combinations will be added as alternative combinations. Combination 4: Number of lines per halftone, dot shape

[0026] The reverse gradient image generation unit 125 generates a gradient image as a downsampled image that is in the opposite direction to the gradient direction in the downsampled region. At this time, the downsampled image is generated such that the parameter of the parameter type specified by the operator is different from the parameter of the same type detected by the parameter detection unit 123.

[0027] Next, to clearly explain the thinning process in this embodiment, we will use larger halftone dots for explanation. Figure 5 shows the image before thinning. The entire image before thinning is considered the thinning target area. The direction of the gradient in the thinning target area is upward. Now, suppose the operator specifies the screen angle, the number of lines per halftone dots, and the dot shape of the halftone dots in the change parameter specification unit 124. As a result, a thinned image is generated that differs from the thinning target area in terms of screen angle, number of lines per halftone dots, and dot shape of the halftone dots.

[0028] Figure 6 shows a thinned image generated by the inverse gradient image generation unit 125. The screen angle of the halftone dots in the thinned image shown in Figure 6 is different from the screen angle of the halftone dots in the thinned area. Also, the number of lines of the halftone dots in the thinned image is different from the number of lines of the halftone dots in the thinned area. Furthermore, the dot shape of the halftone dots in the thinned image is different from the dot shape of the halftone dots in the thinned area. Moreover, the thinned image is a gradient image with the opposite direction to the gradient direction in the thinned area. The acquisition unit 121 acquires the thinned image generated by the inverse gradient image generation unit 125 in this way. Note that the outlines of each dot in the thinned image shown in Figure 6 are black, but this is to make the shape easier to understand, and the color of the dot outline is the same as the color inside the dot.

[0029] The generation unit 122 generates a post-downsampled image data that shows the downsampled image obtained by downsampling the overlapping region where the halftone dots in the downsampled region and the halftone dots in the downsampled image overlap when the downsampled region and the downsampled image are superimposed. Figure 7 shows the post-downsampled image. As shown in Figure 7, it can be seen that the region where the dots overlap has been downsampled.

[0030] The downsampled image shown in Figure 7 is an image that cannot be obtained even when FM screening and AM screening are performed. Therefore, the downsampled process shown in this embodiment yields images that could not be obtained with conventional downsampled processes.

[0031] The decimation process described above will now be explained using a flowchart. Figure 8 is a flowchart showing the decimation process performed by the image processing device 100. In Figure 8, the image processing device 100 acquires pre-decimation image data that shows the image before decimation (step S101). This pre-decimation image data may be acquired via a network or by reading data recorded on a recording medium. The acquired pre-decimation image data is stored in the image data storage unit 140. The decimation area designation unit 126 is used to designate a decimation area by the operator (step S102). Information indicating the designated decimation area is stored in the storage device.

[0032] Next, the parameter detection unit 123 detects the screen angle from the pre-decimation image (step S103) and stores the detected screen angle in the memory device. The parameter detection unit 123 detects the line count from the pre-decimation image (step S104) and stores the detected line count in the memory device. The parameter detection unit 123 detects the size (diameter) of the dots from the pre-decimation image (step S105) and stores the detected size (diameter) in the memory device. Here, the parameter detection unit 123 detects the maximum and minimum diameters of the dots and stores them in the memory device. The parameter detection unit 123 detects the dot shape from the pre-decimation image (step S106) and stores the detected dot shape in the memory device. Here, the dot shape may be information indicating the shape of a figure, such as a circle or a square, or if it is not a circle, information indicating the vertex coordinates of the dot.

[0033] The parameter change specification unit 124 allows the operator to specify, from among the parameter types, the parameter types to be different from those detected in the area to be downsampled (step S108). The reverse gradient image generation unit 125 generates a gradient image in the opposite direction to the gradient direction in the area to be downsampled as the downsampled image (step S109). At this time, the downsampled image is generated such that the parameter of the parameter type specified by the operator in step S107 is different from the parameter of the same type detected by the parameter detection unit 123. Alternatively, the maximum dot diameter of the dots in the generated downsampled image may be set to the maximum dot diameter detected from the pre-downsampled image, and the minimum dot diameter of the dots in the downsampled image may be set to the minimum dot diameter detected from the pre-downsampled image. The downsampled image data showing the generated downsampled image is stored in the image data storage unit 140.

[0034] The acquisition unit 121 acquires downsampled image data from the image data storage unit 140. The generation unit 122, when the downsampled region and the downsampled image are superimposed, downsamples the superimposed region from the downsampled region where the halftone dots in the downsampled region and the halftone dots in the downsampled image overlap (step S110).

[0035] The generation unit 122, for example, when the pre-decimation image data is binary image data, performs a process of subtracting the pixel value of the pixel in the decimation image superimposed on that pixel if the pixel value of the pixel in the pre-decimation image is 1. Specifically, if the pixel value of the pre-decimation image is 0, the pixel value of the post-decimation image remains 0. If the pixel value of the pre-decimation image is 1, the pixel value of the decimation image is subtracted from 1, and the result of this subtraction is used as the pixel value of the post-decimation image. Even with multi-level image data greater than binary, if the result of the subtraction is 1 or greater, the result of the subtraction is used as the pixel value of the post-decimation image. If the result of the subtraction is 0 or less, the pixel value of the post-decimation image is set to 0.

[0036] The thinning processing unit 122 outputs thinned image data showing the thinned image generated by the thinning process (step S111). Possible output destinations include, for example, the image data storage unit 140 or the laser processing device described later.

[0037] When printing in multiple colors, if dot reduction is performed for each color, the reduced image data is output for each color. Then, a sleeve printing plate is manufactured for each color using a laser processing machine.

[0038] In the embodiments described above, as shown in Figure 2, the area to be downsampled was a part of the image, and as shown in Figure 3, the downsampled image was a gradient image, but the embodiments are not limited to these. For example, the area to be downsampled may be the entire image, and the downsampled image may be a flat screen image.

[0039] Let's explain this using diagrams. First, the area to be thinned is the entire image shown in Figure 2. The screen angle of the flat screen image is different from the screen angle of the image shown in Figure 2. Figure 9 shows an example of a flat screen image thinned out. Figure 10 shows the image after thinning out the flat screen image shown in Figure 9 from the image shown in Figure 2. As shown in Figure 10, because the area to be thinned out is the entire image, the shape of the halftone dots in the image shown in Figure 2 becomes a shape where halftone dots are missing overall, and the tone also changes. As a result, gaps are created between the halftone dots in the midtones, which reduces tone jumps.

[0040] Thus, even if the area to be thinned is the entire image and the thinned image is a flat halftone image, it is possible to suitably thin the halftone dots of the gradient image, provided that at least the screen angles are different.

[0041] Next, the laser processing device 50 will be described. The downsampled image data output by the image processing device 100 is used as the second image data, which will be described later, in the laser processing device 50. Before describing the laser processing device 50, the sleeve printing plate 30 processed by the laser processing device 50 will be described first.

[0042] As shown in Figures 11 and 12, the sleeve printing plate 30 comprises a cylindrical sleeve body 31 extending along the axis O, and a printing plate material 32 disposed on the outer circumference of the sleeve body 31.

[0043] The sleeve body 31 is made of polyethylene terephthalate (PET) resin, with an outer diameter of 100 mm to 300 mm, an axial length in the O direction of 50 mm to 600 mm, and a wall thickness of 0.1 mm to 1.0 mm. The printing plate material 32 is made of, for example, a photosensitive resin that can be engraved with laser light, and is cylindrical in shape with a thickness of 0.5 mm to 1.0 mm. A relief plate 33 having an image pattern is engraved on the outer surface of this printing plate material 32. In this embodiment, as shown in Figures 11 and 12, two relief plates 33 are formed at 180° opposing positions.

[0044] Furthermore, a positioning notch 34 is formed at one end of the sleeve printing plate 30 in the direction of axis O (left side in Figure 11), which engages with a guide pin 24 erected on the cylinder 21 of the offset printing apparatus 80 (described later) to guide the circumferential relative position and the axial relative position in the direction of axis O relative to the cylinder 21. In this embodiment, as shown in Figures 11 and 12, four positioning notches 34a, 34b, 34c, and 34d are formed at 90° intervals in the circumferential direction.

[0045] The positioning notches 34a and 34c are formed at intermediate positions in the non-image area where the relief plate 33 is not formed, and are arranged at positions 180° opposite to each other. The positioning notches 34b and 34d are formed at intermediate positions in the image area where the relief plate 33 is formed, and are positioned 180° opposite to each other. In addition, a bridge portion 35 is formed at the open end (one end in the direction of axis O) of the positioning notches 34B and 34. In other words, the positioning notches 34a, 34b, 34c, and 34d are arranged axially symmetrically at 90° intervals.

[0046] Next, the laser processing apparatus 50 used in manufacturing the sleeve printing plate 30 of this embodiment will be described with reference to Figure 13.

[0047] As shown in Figure 13, the laser processing apparatus 50 includes a rotating drum 51 having a cylindrical surface 51A on which a cylindrical sleeve body 40 is mounted, a sleeve body support part 53 having a pivot support part 52 that rotatably supports the rotating drum 51, a rotation drive part 55 that rotates the rotating drum 51 about an axis N, a laser beam irradiation part 60 that irradiates the sleeve body 40 mounted on the rotating drum 51 with laser light, a linear motion part 65 that moves the laser beam irradiation part 60 in a direction parallel to the axis N of the rotating drum 51, and a control unit 70 that controls the operation of the rotating drum 51, the linear motion part 65, and the laser beam irradiation part 60.

[0048] The linear motion unit 65 includes a guide bar 66 extending in a direction parallel to the axis N of the rotating drum 51, a support member 67 that moves along the guide bar 66, and an axial position sensor 68 that obtains position information (axis N direction position information Z) of the support member 67. The laser beam irradiation unit 60 is supported by a support member 67 of the linear motion unit 65 and is configured to be movable in a direction parallel to the axis N. The laser beam irradiation unit 60 is also provided with an output regulator 61 for adjusting the laser beam output. In this embodiment, the laser beam irradiation unit 60 is composed of a carbon dioxide laser.

[0049] The control unit 70 includes a storage means 71 for storing first image data indicating the position and shape of the positioning notch and the cutting position and shape, and second image data indicating the position and shape of the image pattern of the relief plate 33, and an energy density adjustment unit 72 for adjusting the energy density of the laser light when cutting and forming the positioning notch based on the first image data and the energy density of the laser light when forming the image pattern of the relief plate 33 based on the second image data, respectively. Then, based on the first and second image data, the operation of the rotating drum 51, the linear motion unit 65, and the laser beam irradiation unit 60 is controlled to cut the sleeve body 40, form the positioning notch 34, and form the relief plate 33. As described above, the second image data is the thinned image data output from the image processing device 100. As a method for acquiring the second image data, for example, a communication means is provided in the laser processing device 50, and this communication means is configured to enable communication with the image processing device 100 so that the laser processing device 50 can acquire the thinned image data.

[0050] Next, a method for manufacturing a sleeve printing plate 30 using a laser processing apparatus 50 configured in this way will be described. First, the sleeve body 40 is attached to the cylindrical surface 51A of the rotating drum 51. At this time, one end of the sleeve body 40 is fitted into the rotating drum 51, and in this state, air is ejected from the air hole by the air ejection mechanism. As a result, the sleeve body 40 expands in diameter due to this air, and the sleeve body 40 is attached to the rotating drum 51. At this time, the axis O of the sleeve body 40 and the axis N of the rotating drum 51 coincide.

[0051] Next, the storage means 71 stores first image data showing the position and shape of the positioning notch and the cutting position and shape, and second image data showing the position and shape of the image pattern of the relief plate 33. Then, the control unit 70 controls the operation of the rotating drum 51, the linear motion unit 65, and the laser beam irradiation unit 60 based on these first and second image data.

[0052] While irradiating the sleeve body 40 with laser light from the laser beam irradiation unit 60, the rotating drum 51 is rotated by the rotation drive unit 55 and moved in the axial direction N by the linear motion unit 65, thereby scanning the entire outer surface of the sleeve body 40 with the laser beam irradiation unit 60.

[0053] In this section, corresponding to the first image data, a command signal is transmitted from the energy density adjustment unit 72 to the output adjuster 61, setting the laser beam output to a higher level, and the entire thickness of the sleeve body 40 is removed. This results in the cutting of the sleeve body 40 and the formation of the positioning notch 34. On the other hand, in the area corresponding to the second image data, a command signal is transmitted from the energy density adjustment unit 72 to the output adjuster 61, setting the laser beam output to a lower level, and a portion of the thickness of the sleeve body 40 is removed. As a result, the image pattern of the relief plate 33 is formed on the sleeve body 40.

[0054] In this way, by adjusting the output of the laser beam, the energy density of the laser beam is adjusted, and by scanning the entire outer surface of the sleeve body 40 once with the laser beam irradiation unit 60, the sleeve body 40 is cut, the positioning notches 34 are formed, and the image pattern of the relief plate 33 is formed. As described above, the sleeve printing plate 30 according to this embodiment is manufactured.

[0055] Next, an offset printing apparatus 80 using the sleeve printing plate 30 of this embodiment will be described. A schematic of the offset printing apparatus 80 is shown in Figure 14. This offset printing apparatus 80 is a can printing apparatus that prints on the outer surface of a cylindrical can. The offset printing apparatus 80 is generally composed of multiple ink application mechanisms 81 and a can moving mechanism 91.

[0056] The ink adhesion mechanism 81 consists of an inker unit 84 that supplies ink, and a blanket wheel 82 which has multiple blankets 83 that come into contact with the inker unit 84 to transfer the ink, and then come into contact with the outer surface of the can cylinder 90 to print (adhere) the ink. The inker unit 84 consists of an ink source 85, a ducting roll 86 that contacts the ink source 85 to receive ink, an ink mixing roll 87 made up of multiple rollers connected to the ducting roll 86, an inking roll 88 connected to the ink mixing roll 87, and a plate cylinder 20 connected to the inking roll 88. A sleeve printing plate 30 with an image pattern to be transferred to the can cylinder 90 is disposed on the outer circumferential surface of the plate cylinder 20. Multiple blankets 83 are provided on the outer circumferential surface of the blanket wheel 82. These blankets 83 are configured to contact the relief plate 33 of the sleeve printing plate 30 disposed on the outer circumferential surface of the plate cylinder 20, as well as the can cylinder 90.

[0057] The can moving mechanism 91 consists of a can chute 92 for taking in the can body 90, a mandrel 93 for rotatably holding the can body 90 supplied from the can chute 92, and a mandrel turret 94 for sequentially rotating the can body 90 mounted on the mandrel 93 toward the ink adhesion mechanism 81.

[0058] As shown in Figures 16 and 17, the printing cylinder 20 is cylindrical and has a cylinder 21 that is cantileverably supported on the shaft portion 95 of the printing device 80. The sleeve printing plate 30, which is the subject of this embodiment, is fitted onto the outer circumference of this cylinder 21. Here, the inner diameter of the sleeve printing plate 30 and the outer diameter of the cylinder 21 are set to be approximately the same. Multiple air holes 22 are formed on the outer circumference of the cylinder 21, and by supplying air from an introduction hole 23 formed on the end face of the cylinder 21 and ejecting it from the air holes 22, the inner diameter of the sleeve printing plate 30 is expanded, allowing it to be attached to and detached from the cylinder 21. In other words, the sleeve printing plate 30 is fixed to the cylinder 21 by the contraction force of the sleeve printing plate 30 trying to return to its original inner diameter, which causes the sleeve printing plate 30 to adhere tightly to the outer circumference of the cylinder 21.

[0059] Furthermore, the cylinder 21 is provided with a guide pin 24 that protrudes radially outward on the shaft portion 95 side of its outer circumferential surface. A positioning notch 34 of the sleeve printing plate 30 engages with the guide pin 24, thereby determining the circumferential position and axial position O of the sleeve printing plate 30 and the cylinder 21. In this embodiment, as shown in Figure 15, the guide pin 24 is detachably mounted in a pin hole 25 drilled on the outer circumferential surface of the cylinder 21. The cylinder 21 has two pin holes 25a and 25b formed at 90° intervals in the circumferential direction, and the guide pin 24 is configured to be selectively mounted in these two pin holes 25a and 25b.

[0060] Here, when using the positioning notches 34a and 34c formed at the intermediate position of the non-image portion of the sleeve printing plate 30, the guide pin 24 mounted in the pin hole 25a is used, as shown in Figure 16. On the other hand, when using the positioning notches 34b and 34d formed in the middle of the image portion of the sleeve printing plate 30, the guide pin 24 mounted in the pin hole 25b is used, as shown in Figure 17. In other words, the circumferential position of the guide pin 24 can be changed to correspond to the multiple positioning notches 34a, 34b, 34c, and 34d formed in the sleeve printing plate 30.

[0061] In this offset printing apparatus 80, where the sleeve printing plate 30 is arranged, inks of different colors are applied from the ink sources 85 of each inker unit 84 to the relief plate 33 arranged on the outer surface of the plate cylinder 20 via the ducting roll 86, ink mixing roll 87, and inking roll 88. These inks of each color are then placed as a pattern on the blanket 83 on the rotating blanket wheel 82, and this pattern is printed while in contact with the can cylinder 90 held by the mandrel 93.

[0062] As described above, this embodiment provides a technique that can suitably thin out the halftone dots in a gradient image.

[0063] According to this embodiment, the occurrence of dot gain can also be suppressed, so this embodiment is particularly effective when printing on surfaces that do not absorb ink or absorb ink poorly (for example, cans).

[0064] Furthermore, as mentioned above, it is possible to generate images with halftone dots that cannot be obtained by conventional FM screening or AM screening, which are used for thinning. In other words, this embodiment can provide a thinning process that was not available in the past, and can therefore contribute to the development of the printing industry.

[0065] In the embodiments described above, an example of performing relief printing using raster data generated by the image processing device 100 was explained, but this embodiment can be applied to any printing device that performs printing using raster data. For example, this embodiment can be applied to lithographic printing devices that use flat plates with almost no irregularities on the plate, as well as inkjet printers and electrophotographic printers.

[0066] Furthermore, in this embodiment, a sleeve printing plate 30 was used which was provided with four positioning notches 34a, 34b, 34c, and 34d. However, the positioning notches are not limited to four; one or more are sufficient.

[0067] The functions of the image processing apparatus 100 in the above-described embodiment may be implemented using a computer. In that case, the functions may be implemented by recording a program for implementing these functions on a computer-readable recording medium, loading the program recorded on this recording medium into a computer system, and executing it. Here, "computer system" includes hardware such as an OS and peripheral devices. Furthermore, "computer-readable recording medium" refers to portable media such as flexible disks, magneto-optical disks, ROMs, CD-ROMs, and storage devices such as hard disks built into a computer system. Moreover, "computer-readable recording medium" may also include those that dynamically hold programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or communication lines such as telephone lines, and those that hold programs for a certain period of time, such as volatile memory inside a computer system that acts as a server or client in such cases. Furthermore, the above-mentioned program may only implement a part of the functions described above, and may also be able to implement the above-mentioned functions in combination with programs already recorded in the computer system.

[0068] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0069] 30-sleeve print version 31 sleeves 32 Plate material 33 Toppan Printing 50 Laser processing equipment 60 Laser beam irradiation area 61 Output regulator 70 Control Unit 71 Memory means 80 Offset printing press 90 can body 100 Image Processing Devices 110 Communications Department 115 Operation display section 120 Control Unit 121 Acquisition Department 122 Thinning Processing Unit 123 Parameter detection unit 124 Change parameter specification section 125 Reverse Gradient Image Generation Unit 126 Thinning area designation section 140 Image data storage unit

Claims

1. An acquisition unit that acquires downsampling image data, which shows a downsampling image consisting of halftone dots for downsampling halftone dots in the area to be downsampled within a gradient image, A generation unit generates a reduced image data that shows a reduced image obtained by superimposing the reduced area and the reduced image, where the superimposed Equipped with, An image processing apparatus in which the screen angle of the halftone dots in the thinned image is different from the screen angle of the halftone dots in the area to be thinned.

2. An acquisition unit that acquires downsampling image data, which shows a downsampling image consisting of halftone dots for downsampling halftone dots in the area to be downsampled within a gradient image, A generation unit generates a reduced image data that shows a reduced image obtained by superimposing the reduced area and the reduced image, where the superimposed Equipped with, An image processing device in which the number of lines per second of halftone dots in the thinned image is different from the number of lines per second of halftone dots in the area to be thinned.

3. An acquisition unit that acquires downsampling image data, which shows a downsampling image consisting of halftone dots for downsampling halftone dots in the area to be downsampled within a gradient image, A generation unit generates a reduced image data that shows a reduced image obtained by superimposing the reduced area and the reduced image, where the superimposed Equipped with, The aforementioned downsampled image is an image processing apparatus in which the gradient image is in the opposite direction to the gradient direction in the region to be downsampled.

4. The image processing apparatus according to any one of claims 1 to 3, wherein the dot shape of the halftone dots in the thinned image is different from the dot shape of the halftone dots in the thinned region.

5. Acquisition step of acquiring downsampled image data that shows a downsampled image consisting of halftone dots for downsampling halftone dots in the area to be downsampled within a gradient image, A generation step of generating a reduced image data that shows a reduced image obtained by removing from the reduced area the halftone dots in the reduced area and the halftone dots in the reduced image overlap when the reduced area and the reduced image are superimposed. Equipped with, An image processing method in which the screen angle of the halftone dots in the thinned image is different from the screen angle of the halftone dots in the area to be thinned.

6. Acquisition step of acquiring downsampled image data that shows a downsampled image consisting of halftone dots for downsampling halftone dots in the area to be downsampled within a gradient image, A generation step of generating a reduced image data that shows a reduced image obtained by removing from the reduced area the halftone dots in the reduced area and the halftone dots in the reduced image overlap when the reduced area and the reduced image are superimposed. Equipped with, An image processing method in which the number of lines of halftone dots in the thinned image is different from the number of lines of halftone dots in the area to be thinned.

7. Acquisition step of acquiring downsampled image data that shows a downsampled image consisting of halftone dots for downsampling halftone dots in the area to be downsampled within a gradient image, A generation step of generating a reduced image data that shows a reduced image obtained by removing from the reduced area the halftone dots in the reduced area and the halftone dots in the reduced image overlap when the reduced area and the reduced image are superimposed. Equipped with, An image processing method wherein the thinned image is a gradient image with a gradient direction opposite to the direction of the gradient in the thinned region.

8. The image processing method according to any one of claims 5 to 7, wherein the dot shape of the halftone dots in the thinned image is different from the dot shape of the halftone dots in the thinned region.

9. A program that makes a computer function as an image processing device, The aforementioned computer, An acquisition unit that acquires downsampling image data, which shows a downsampling image consisting of halftone dots for downsampling halftone dots in the area to be downsampled within a gradient image, A generation unit generates a reduced image data that shows a reduced image obtained by superimposing the reduced area and the reduced image, where the superimposed and make it work A program characterized in that the screen angle of the halftone dots in the thinned image is different from the screen angle of the halftone dots in the area to be thinned.

10. A program that makes a computer function as an image processing device, The aforementioned computer, An acquisition unit that acquires downsampling image data, which shows a downsampling image consisting of halftone dots for downsampling halftone dots in the area to be downsampled within a gradient image, A generation unit generates a reduced image data that shows a reduced image obtained by superimposing the reduced area and the reduced image, where the superimposed and make it work A program characterized in that the number of lines per second of halftone dots in the thinned image is different from the number of lines per second of halftone dots in the area to be thinned.

11. A program that makes a computer function as an image processing device, The aforementioned computer, An acquisition unit that acquires downsampling image data, which shows a downsampling image consisting of halftone dots for downsampling halftone dots in the area to be downsampled within a gradient image, A generation unit generates a reduced image data that shows a reduced image obtained by superimposing the reduced area and the reduced image, where the superimposed and make it work The program is characterized in that the thinned image is a gradient image with a gradient direction opposite to the direction of the gradient in the thinned region.

12. The program according to any one of claims 9 to 11, wherein the dot shape of the halftone dots in the thinned image is different from the dot shape of the halftone dots in the thinned region.

13. A method for manufacturing a sleeve printing plate, The process includes an image pattern forming step in which an image pattern is formed on a cylindrical sleeve body. Using a laser processing machine equipped with a rotating drum on which the sleeve body can be attached to its outer circumference, and a laser beam irradiation unit that irradiates laser light onto the sleeve body attached to the rotating drum, the image pattern formation process is performed with the sleeve body attached to the same rotating drum. The image pattern is based on downsampled image data generated by an image processing apparatus according to any one of claims 1 to 4, and the method for manufacturing a sleeve printing plate is to carry out the image pattern formation step based on the downsampled image data.

14. A method for manufacturing cans, It includes a printing process for printing on the outer surface of a cylindrical body, A method for manufacturing cans, wherein the printing step is performed using a printing apparatus that uses a sleeve printing plate manufactured by the manufacturing method described in claim 13.

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