Moire suppression method, moire suppression device, and moire suppression system

Abstract

To provide means which can more effectively suppress the occurrence of moire by breaking the cycle of dots.SOLUTION: A moire suppression method comprises the steps of: generating a grid that sections a plurality of dots constituted by one or more first pixels (blackening pixels or whitening pixels) into individual regions in a first region where moire occurs with respect to an input image expressed by dots, converting the first pixels contacting the grid in the dots sectioned by the grid into second pixels (whitening pixels when the first pixels are the blackening pixels, blackening pixels when the first pixels are the whitening pixels), and selecting a candidate to be converted into the first pixels among the second pixels contacting the first pixels of the dots sectioned by the grid on the basis of the number of converted pixels to perform conversion.SELECTED DRAWING: Figure 14

Description

[Technical Field]

[0001] The present invention relates to a moire suppression method, a moire suppression device, and a moire suppression system. [Background technology]

[0002] Moiré (or moire) is a visual interference pattern that occurs when multiple periodic patterns or structures are superimposed. In physical terms, moiré can be described as a beat phenomenon of two spatial frequencies. Although there are cases where this moiré is actively utilized as a useful phenomenon, if it occurs unintentionally, it can ruin the design of the image and lead to a deterioration in the quality of the printed material, so methods for suppressing moiré have also been proposed.

[0003] For example, the image processing system in Patent Document 1 describes a technology for eliminating or mitigating single-plate moire, which is stripes caused by interference between output resolution and screen ruling. The technology determines the positions of black pixels that should be non-contact points among the contact points of halftone dots with a halftone percentage of around 50±5% and the positions of white pixels that should be contact points among the non-contact points of halftone dots, and swaps them to eliminate or mitigate the moire. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-143405 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the image processing system of Patent Document 1 is used to represent a pattern by overlaying multiple plates, it is believed to be insufficient as a countermeasure against so-called overlay moire, which occurs when the original pattern information to be represented by halftone dots on one plate, particularly the structural information contained in the original pattern information itself, such as thin lines that are barely visible and arranged periodically, interferes with the periodicity of the halftone dots on another plate. Therefore, there is a need for a means to more effectively suppress moire.

[0006] SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a means for more effectively suppressing the occurrence of moire by breaking up the periodicity of halftone dots. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, one representative moiré suppression method of the present invention includes a grid generation step of generating a grid for an input image represented by halftone dots, the grid dividing a plurality of halftone dots, each of which is made up of one or more first pixels (blackened pixels or whitened pixels) in a first region where moiré occurs, into individual cells; a conversion step of converting first pixels of the halftone dots separated by the grid, the first pixels being in contact with the grid, into second pixels (if the first pixels are black pixels, they are white pixels; if the first pixels are white pixels, they are black pixels); a first filling step of selecting a candidate to be converted into a first pixel from among second pixels adjacent to the first pixel of the halftone dot divided by the grid based on the number of converted pixels, and converting the selected candidate into the first pixel; The method includes a halftone dot processing step including:

[0008] Furthermore, one of the representative moire suppression devices of the present invention is a halftone dot area extraction unit that extracts halftone dot areas by forming a grid that separates the halftone dots included in the platemaking data into individual areas; The method includes a halftone dot processing unit that performs a conversion step of converting a first pixel of the halftone dot area that is adjacent to the grid into a second pixel (a whitening pixel if the first pixel is a blackening pixel, or a blackening pixel if the first pixel is a whitening pixel), and a first filling step of selecting a candidate to be converted into a first pixel from among the second pixels that are adjacent to the first pixel of the halftone dot divided by the grid based on the number of converted pixels. [Effects of the Invention]

[0009] According to the present invention, by changing the arrangement of pixels in contact with the grid, it is possible to provide a means for breaking up the periodic structure of halftone dots and more effectively suppressing the occurrence of moire. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing an example of moire. [Figure 2] FIG. 2 is a diagram showing another example of moire occurrence. [Figure 3] FIG. 3 is a diagram for explaining halftone representation using halftone dots. [Figure 4] FIG. 4 is a diagram for explaining the screen angle of the halftone dots. [Figure 5] FIG. 5 is a diagram for explaining the inclination angle of the inclination pattern. [Figure 6] FIG. 6 shows an example of print image data and moire patterns. [Figure 7] FIG. 7 illustrates a computer system for implementing an embodiment of the present invention. [Figure 8] FIG. 8 is a diagram illustrating an example of the configuration of a moire suppression system according to an embodiment. [Figure 9] FIG. 9 is a flowchart illustrating a moire suppression method according to an embodiment. [Figure 10] FIG. 10 is a flowchart illustrating the details of the processing in the grid processing unit. [Figure 11] FIG. 11 is a diagram illustrating an example of a grid. [Figure 12] FIG. 12 shows halftone dots with a density value of 50% or less and halftone dots obtained by inverting the halftone dots and shifting the grid period by half a period. [Figure 13] FIG. 13 is a diagram showing an example of the initial state of the halftone dots to be processed. [Figure 14] FIG. 14 is a diagram showing an example of a pixel area to be converted and a pixel area to be filled in for a halftone dot. [Figure 15] FIG. 15 is a diagram for explaining the area to be subjected to the first filling step and the area to be subjected to the second filling step. [Figure 16] FIG. 16 is a diagram showing whitened halftone dots. [Figure 17] FIG. 17 is a diagram showing the flow of processing for extracting a contour region according to an embodiment of the present invention. [Figure 18] FIG. 18 is a diagram showing the flow of processing for extracting a contour region according to an embodiment of the present invention. [Figure 19] FIG. 19 is a diagram showing a specific example of contour extraction performed according to the procedure shown in FIGS. [Figure 20] FIG. 20 is a diagram showing a specific example of contour extraction performed according to the procedure shown in FIGS. [Figure 21] FIG. 21 shows the print image data shown in FIG. 20 after smoothing processing but before halftoning, and the results of extracting a contour area from the print image data. [Figure 22] FIG. 22 is a diagram showing an example of a contour image extracted by binarizing the image shown in FIG. [Figure 23] FIG. 23 is a diagram showing an overlapping image in which the contour image shown in FIG. 22 is displayed overlapping with the contour image shown in FIG. [Figure 24] FIG. 24 is a schematic diagram of a printing machine 50 for printing a design on the printing surface of a printing body 52. [Figure 25] FIG. 25 is a schematic diagram of the inside of the ink application units 53 to 56. [Figure 26] FIG. 26 is a diagram for explaining the printing plate. [Figure 27] FIG. 27 is a schematic diagram showing the process up to the development of a printing plate. [Figure 28] FIG. 28 is a schematic diagram showing the process up to when the dampening solution is attached to the printing plate. [Figure 29] FIG. 29 is a schematic diagram showing the process of ink being applied to a printing plate. [Figure 30] FIG. 30 is a diagram showing the suppression effect obtained by this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] First, examples of halftone dot generation and moire in commercial printing will be described with reference to FIGS. <Halftone dots in commercial printing> In the field of commercial printing, RIP (Raster Image Processor) processing (hereafter referred to as "halftone processing") is applied to print image data at the time of submission, and the image is expressed as monochrome binary halftone dots for each printing element color, that is, blocks of blackened or whitened pixels. RIP processing involves rasterizing digital data created on a general-purpose computer into a data format that can be output by a printing press, and expressing the image as halftone dots of a certain size. Image data that has been expressed as halftone dots using RIP processing is sometimes called "RIPped data," "platemaking data," or "drawing data."

[0012] Generally, colors expressed using halftone dots are expressed using subtractive mixing of four colors (called R4C): C (cyan), M (magenta), Y (yellow), and K (ink). For each of the C, M, Y, and K colors, a separate plate is created to print the image, and the shade information and colors are reproduced by overlaying the ink on the paper.

[0013] When creating the data to be drawn for each of the above-mentioned plates, a color conversion table called a profile is arbitrarily selected and color matching is performed to match the color space of the original data (e.g., RGB color system) with the color space of the printing machine (CMYK color system). The profile is configured in the form of a lookup table (LUT) and is created by dividing the RGB space, CMYK space, or L*a*b space into each component and determining a representative value. Then, during color matching processing, the input image data is approximated to the representative value and the corresponding output value is calculated by referring to the lookup table.

[0014] Typical methods for expressing gradation (shade expression) using halftone dots include AM screening (Amplitude Modulation Screening), which varies the size of the dots, and FM screening (Frequency Modulation Screening), which keeps the dot size constant and varies the density. FM screening theoretically does not produce moiré because the arrangement of the dots is irregular, but it is technically difficult to perfectly reproduce minute dots without misalignment or dot gain (spreading of the dots). AM screening is resistant to plate misalignment and is technically easy, so it is commonly used in commercial printing, where stable quality and mass production are essential.

[0015] To reproduce colors, AM screening does not overlap halftone dots in the same position and mix the inks, but instead uses an optical illusion (called an optical illusion) to make a collection of dots appear as any desired pattern or color when viewed from a distance.

[0016] <Example of moiré> FIG. 1 is a diagram showing an example of moiré. In FIG. 1, four patterns 21, 22, 23, and 24 are shown, each represented by halftone dots. The halftone dots in these patterns 21, 22, 23, and 24 are spaced at equal intervals, but the inclinations of the dots are different, resulting in different halftone dot periods. Furthermore, pattern 25 is formed by overlapping patterns 21, 22, 23, and 24, centered on each other. As shown in FIG. 1, circular and linear patterns that did not exist in patterns 21, 22, 23, and 24 before the overlapping have appeared as moiré in pattern 25.

[0017] Fig. 2 shows another example of moiré. Fig. 2 shows a pattern 26 in which halftone dots are regularly arranged, and a pattern 27 in which lines are regularly arranged. Furthermore, pattern 28 is obtained by overlapping pattern 26 and pattern 27. Figure 2 As shown in FIG. 1, a regular pattern of oblique straight lines that did not exist in either pattern 26 or pattern 27 appears as moire in pattern 28.

[0018] <By halftone dots Gradation Expression> Next, referring to FIG. 3, Gradation Explain the expression. Figure 3 is a halftone dot image. Gradation 3 is a diagram for explaining the representation. Gradation Pattern 31 and Gradation The enlarged areas 32, 33, and 34 are obtained by extracting and enlarging a part of the pattern 31. As shown in the enlarged areas 32, 33, and 34, the size of halftone dots that are too large to be seen with the naked eye is changed. Gradation The density of the pattern 31 can be expressed appropriately.

[0019] <Screen angle> Next, the screen angle of the halftone dots will be described with reference to FIGS. 4 is a diagram for explaining the screen angle of halftone dots, showing a tilted pattern 36 in which the arrangement of halftone dots is tilted.

[0020] Furthermore, the halftone dots of each color are arranged at an arbitrary angle (called the screen angle) as shown in Figure 4, with a constant distance between the centers of the halftone dots (hereafter referred to as the "halftone dot generation interval"). If the dots are arranged at a constant period and angle, the halftone dots of each color will interfere with each other, causing moiré.

[0021] Figure 5 shows the inclination angle of the inclination pattern 36 shown in Figure 4, where different angles are set for each of the R4C color plates, for example. As mentioned above, if the inclination angle is set to a constant period and angle, the halftone dots of each color will interfere with each other, causing moire. Therefore, to prevent moire, it is desirable to set different inclination angles for each color plate, as shown in Figure 5, so that the halftone dots do not overlap. Furthermore, moire is most noticeable when the difference in screen angle between each plate is small. For example, if Y (yellow) 40 is set as the reference (0°), C41 may be set as 15°, K42 as 45°, and M43 as 75°. Also, the amount of movement of the halftone dots for Y (yellow) 40 may be set to 0, and the amount of movement of the halftone dots for the other colors may be set to a value other than 0. In this way, the angle formed by each color plate (from the reference) is an angle of 5° or more and less than 30°. In this way, by setting different angles for each color plate, it is possible to prevent moiré outside the printing area where moiré is likely to occur. This also makes it possible to limit the area where halftone dots are moved to suppress moiré. This allows for maintaining print quality and improving the efficiency of halftone image generation.

[0022] As will be described later, the color plates whose halftone dots are moved can be all color plates or some of the color plates. When moving the halftone dots in all color plates, the amount of halftone dot movement or the proportion of halftone dots moved can be different for each color plate. In this case, the amount of halftone dot movement, the proportion of halftone dots moved, or both can be made larger for cyan, which has low sensitivity to spatial frequencies, than for the other color plates. The same can be done when moving halftone dots in some color plates. The color plate whose halftone dots are not moved can be yellow, which has the lowest visibility.

[0023] <Moiré caused by the periodicity of image data for printing> As described above, moire is a phenomenon in which, when patterns with different periods are superimposed on each other, a new pattern that is not included in the other patterns is generated. However, moire that occurs in the field of commercial printing is not only caused by interference between halftone dots, but can also be caused by interference between the period of the input print image data and the period of the halftone dots in the data that is output after halftone processing of that data.

[0024] For example, if the print image data submitted for commercial printing contains a periodic pattern such as a striped pattern, when this pattern is represented using halftone dots, the period of the pattern and the period of the halftone dots may interfere with each other, and a new pattern that does not exist in the original image data may appear as a moire. A specific example will be described with reference to Fig. 6. Fig. 6(a) shows a photographic image of the original design before plate-making, that is, the print image data at the time of submission. "Before plate-making" means data before halftoning processing is performed.

[0025] In Figure 6(a), the fiber pattern in the fabric appears periodically, but no moiré appears in the image at this point. On the other hand, FIG. 6(b) shows an example in which moire occurs when the image in FIG. 6(a) is printed after being subjected to halftone processing. The image in Figure 6(b) is a moire pattern created by overlaying an image of one plate (Figure 6(c)) from the platemaking data, which has been subjected to halftone processing on the same area as Figure 6(a), with a screen tone image (Figure 6(d)) from a different plate, which has also been subjected to halftone processing on the same area as Figure 6(a). In this way, when an image containing a periodic pattern is expressed as halftone dots, the period of the pattern and the period of the halftone dots interfere with each other, and new patterns that do not exist in the original image data may appear as moire.

[0026] In this disclosure, a "halftone dot" is a group of at least one blackened or whitened pixel (also called a "pixel"), and is the smallest unit for expressing the gradation of an object to be drawn. Furthermore, a "grid" is a line segment on the data that separates halftone dots provided on the drawing data, and an area separated by a "grid" is called a "cell" or a "halftone dot area." Furthermore, "pixels in contact with the grid" refers to pixels whose coordinate positions partially overlap with the grid.

[0027] In the field of commercial printing, if a printed product is visually inspected and moiré is found, the original image data before the RIP process is applied is returned to and modified to suppress the moiré. The data is modified by an operator. The RIP process is then used again to create halftone data for printing, and the resulting printed product is visually inspected again.

[0028] However, printing and visual inspection every time a correction is made is a time-consuming and costly process. Furthermore, even though visual evaluation requires time and money, it is difficult to completely prevent accidents that would otherwise require printing to be stopped or reprinted. Therefore, there is a need for a method to suppress moiré by processing and correcting halftone data, rather than returning to the original image data and making corrections.

[0029] As mentioned above, there are known methods for reducing moiré by uniformly shifting the halftone dots that make up an image that has been RIP-processed, or by correcting their shape, but these methods do not completely destroy the structure created by multiple halftone dots, and therefore cannot completely suppress moiré.

[0030] Therefore, the inventor came up with the idea that the periodicity of halftone dots can be more effectively broken by cutting off the contact points between halftone dots while maintaining the density values ​​of each halftone dot. Furthermore, simply cutting off the contact points between all halftone dots may result in blurring of the entire image. Therefore, rather than correcting all halftone dots at once, the inventor first targeted only the halftone dots in the area where moiré occurs in an image excluding the outlines, setting an arbitrary ratio (e.g., 60-80%), and controlling whether or not to process each halftone dot based on this ratio. This effectively suppresses moiré while suppressing blurring caused by processing, thereby successfully obtaining a clearer image in which the structure of the object is maintained.

[0031] As described above, according to the present invention, it is possible to provide a moiré suppression method that suppresses deterioration of the quality of a printed matter due to deformation of the halftone dot shape without changing the color of the printed matter. In other words, because the halftone dot structure itself, which is the cause of moiré in a printed matter, is destroyed, it is possible to obtain an image in which the appearance of moiré is not visible regardless of the direction from which the printed matter is viewed.

[0032] The following describes the background of the present invention and embodiments of the present invention with reference to the drawings. Note that the present invention is not limited to these embodiments. In addition, in the description of the drawings, the same parts are denoted by the same reference numerals.

[0033] <Hardware configuration> First, referring to Figure 7, a computer system 300 for implementing embodiments of the present disclosure will be described. The mechanisms and devices of various embodiments disclosed herein may be applied to any suitable computing system. The main components of the computer system 300 include one or more processors 302, memory 304, a terminal interface 312, a storage interface 314, an I / O (input / output) device interface 316, and a network interface 318. These components may be interconnected via a memory bus 306, an I / O bus 308, a bus interface unit 309, and an I / O bus interface unit 310.

[0034] Computer system 300 may include one or more general-purpose programmable central processing units (CPUs) 302A and 302B, collectively referred to as processors 302. In some embodiments, computer system 300 may include multiple processors, while in other embodiments, computer system 300 may be a single CPU system. Each processor 302 executes instructions stored in memory 304 and may include an on-board cache.

[0035] In some embodiments, memory 304 may include random-access semiconductor memory, storage devices, or storage media (either volatile or non-volatile) for storing data and programs. Memory 304 may store all or part of the programs, modules, and data structures that implement the functions described herein. For example, memory 304 may store a moiré suppression application 350. In some embodiments, moiré suppression application 350 may include instructions or descriptions that execute the functions described below on processor 302.

[0036] In some embodiments, moiré suppression application 350 may be implemented in hardware via semiconductor devices, chips, logic gates, circuits, circuit cards, and / or other physical hardware devices instead of or in addition to a processor-based system. In some embodiments, moiré suppression application 350 may include data other than instructions or descriptions. In some embodiments, cameras, sensors, or other data input devices (not shown) may be provided to communicate directly with bus interface unit 309, processor 302, or other hardware in computer system 300.

[0037] Computer system 300 may include a bus interface unit 309 that provides communication between processor 302, memory 304, display system 324, and I / O bus interface unit 310. I / O bus interface unit 310 may couple to an I / O bus 308 for transferring data to and from various I / O units. I / O bus interface unit 310 may communicate via I / O bus 308 with multiple I / O interface units 312, 314, 316, and 318, also known as I / O processors (IOPs) or I / O adapters (IOAs).

[0038] Display system 324 may include a display controller, a display memory, or both. The display controller may provide video, audio, or both data to display device 326. Computer system 300 may also include one or more sensors or other devices configured to collect data and provide the data to processor 302.

[0039] For example, computer system 300 may include biometric sensors that collect heart rate data, stress level data, etc., environmental sensors that collect humidity data, temperature data, pressure data, etc., and motion sensors that collect acceleration data, movement data, etc. Other types of sensors may also be used. Display system 324 may be connected to a display device 326, such as a standalone display screen, a television, a tablet, or a handheld device.

[0040] The I / O interface unit provides functionality for communicating with various storage or I / O devices. For example, the terminal interface unit 312 may be attached to user I / O devices 320, such as user output devices such as a video display, a television with speakers, and user input devices such as a keyboard, a mouse, a keypad, a touchpad, a trackball, buttons, a light pen, or other pointing device. A user may use a user interface to enter input data or instructions into the user I / O devices 320 and the computer system 300, and receive output data from the computer system 300, by operating the user input devices. The user interface may be displayed on a display, played through speakers, or printed via a printer via the user I / O devices 320, for example.

[0041] Storage interface 314 may accept one or more disk drives or direct access storage devices 322 (typically magnetic disk drive storage devices, but may also be an array of disk drives or other storage devices configured to appear as a single disk drive). In some embodiments, storage device 322 may be implemented as any secondary storage device. Contents of memory 304 may be stored in storage device 322 and retrieved as needed from storage device 322. I / O device interface 316 may provide an interface to other I / O devices, such as printers, fax machines, etc. Network interface 318 may provide a communications path that allows computer system 300 and other devices to communicate with each other. This communications path may be, for example, network 330.

[0042] In some embodiments, computer system 300 may be a device that receives requests from other computer systems (clients) without a direct user interface, such as a multi-user mainframe computer system, a single-user system, or a server computer. In other embodiments, computer system 300 may be a desktop computer, a portable computer, a laptop, a tablet computer, a pocket computer, a telephone, a smartphone, or any other suitable electronic device.

[0043] <Moiré suppression system> Next, the configuration of a moire suppression system according to an embodiment of the present invention will be described with reference to FIG.

[0044] Fig. 8 is a diagram showing an example of the configuration of a moiré suppression system 360 according to an embodiment of the present invention. As shown in Fig. 8, the moiré suppression system 360 mainly includes a client terminal 365, a communication network 370, a printing unit 375, and a moiré suppression device 380. The client terminal 365, the printing unit 375, and the moiré suppression device 380 are connected to each other via the communication network 370. The communication network 370 may include, for example, a local area network (LAN), a wide area network (WAN), a satellite network, a cable network, a Wi-Fi network, or any combination thereof. Also, the connections between the client terminal 365, the printing unit 375, and the moiré suppression device may be wired or wireless.

[0045] The client terminal 365 is a terminal that transmits input data, which is to be processed by a moiré suppression method described below, to the moiré suppression device via the communication network 370. This client terminal 365 may be a terminal used by an individual, or may be a shared terminal within an organization such as a private company. Furthermore, this client terminal 365 may be any device, such as a desktop computer, a laptop computer, a tablet, or a smartphone.

[0046] Data storage unit 372 is a storage unit for storing image data (hereinafter referred to as "input data") expressed by halftone dots and to be processed by the moiré suppression method, which is transmitted from client terminal 365 via communication network 370. This data storage unit may be, for example, a local storage such as an HDD (Hard Disk Drive) or SSD (Solid State Drive), or may be a cloud-based storage area accessible to moiré suppression device 380.

[0047] The halftone dot generation condition input unit 374 is a functional unit for inputting halftone dot generation conditions for the input data stored in the data storage unit 372. These halftone dot generation conditions include, for example, screen ruling, screen angle, etc. The halftone dot generation condition input unit may also be a user I / O interface capable of receiving input from a user, such as a touch screen, a mouse, a keyboard, or a voice recognition device.

[0048] <Moire suppression device> The moiré suppression device 380 is a device for performing processing in the moiré suppression method according to an embodiment of the present invention. The moiré suppression device 380 receives input data stored in the data storage unit 372 and halftone dot generation conditions input via the halftone dot generation condition input unit 374.

[0049] Also, as shown in FIG. 8, the moire suppression device 380 may include a blackening halftone dot area extraction unit 382, ​​a blackening halftone dot processing unit 384, a whitening halftone dot area extraction unit 386, a whitening halftone dot processing unit 388, and an image output unit 390 to implement the moire suppression method according to an embodiment of the present invention. In the following explanation, the moiré suppression device will be described as including all of the blackened halftone dot area extraction unit 382, ​​blackened halftone dot processing unit 384, and whitened halftone dot area extraction unit 386, and whitened halftone dot processing unit 388. However, if moiré can be suppressed by blackened halftone dot processing alone, the device may be provided with the blackened halftone dot area extraction unit 382 and blackened halftone dot processing unit 384, but may not be provided with the whitened halftone dot area extraction unit 386 and whitened halftone dot processing unit 388.

[0050] Conversely, if the moire suppression device can suppress moire by processing only the whitening halftone dots, it may be equipped with a whitening halftone dot area extraction unit 386 and a whitening halftone dot processing unit 388, and may not be equipped with a blackening halftone dot area extraction unit 382 and a blackening halftone dot processing unit 384. Furthermore, since the blackening halftone dot area extraction unit 382 and the whitening halftone dot area extraction unit 386 essentially have the same function, they may be integrated into one unit and configured as a halftone dot area extraction unit. In addition, the moire suppression device may be composed of only a halftone dot area extraction unit for a first pixel (a blackened pixel or a whitened pixel) and a first halftone dot processing unit, or may additionally include a halftone dot area extraction unit for a second pixel (a pixel of a different color from the first pixel) and a second halftone dot processing unit. Furthermore, the first halftone dot processing section and the second halftone dot processing section may be integrated into one halftone dot processing section.

[0051] The blackened halftone dot area extraction unit 382 and the whitened halftone dot area extraction unit 386 are functional units that extract halftone dot areas by generating grids into which each blackened halftone dot and each whitened halftone dot of the input data input from the data storage unit 372 fits, based on the halftone dot generation conditions input via the halftone dot generation condition input unit 374, and forming grid areas.

[0052] The blackened halftone dot processing unit 384 processes an arbitrary proportion of the blackened halftone dots that fit within the grid in the blackened halftone dot area extracted by the blackened halftone dot area extraction unit 382, ​​determines the specific blackened halftone dots to be processed, and when processing, converts the blackened pixels that contact the grid among the blackened pixels that make up the blackened halftone dot into whitened pixels (conversion step), and converts the whitened pixels that do not contact the grid in the periphery of the blackened halftone dot into blackened pixels by the number of converted pixels (filling step).

[0053] Similarly, the whitening halftone dot processing unit 388 has a function of processing an arbitrary proportion of the whitening halftone dots that fit within the grid in the whitening halftone dot area extracted by the whitening halftone dot area extraction unit 386, determining the specific whitening halftone dots to be processed, and when performing processing, converting the whitening pixels that contact the grid among the whitening pixels that make up the whitening halftone dot into blackening pixels (conversion step), and converting the blackening pixels that do not contact the grid in the periphery of the whitening halftone dot into whitening pixels by the number of converted pixels (filling step).

[0054] The image output unit 390 is a functional unit that outputs image data after moire has been suppressed by processing in the functional units from the blackening halftone dot region extraction unit 382 to the whitening halftone dot processing unit 388 . The printing unit and printing method will be described in detail later.

[0055] A moire suppression method according to an embodiment of the present invention will be described below. <Moiré suppression method> As described above, in the embodiment of the present application, for an input image represented by halftone dots, a grid is generated for a region (first region) where moire occurs, based on a predetermined halftone dot generation interval, dividing blackened halftone dots or whitened halftone dots into individual cells. For pixels of the halftone dots included in the grid that are adjacent to the grid, if they are blackened halftone dots, the blackened pixels are converted to whitened pixels (conversion process), and whitened pixels around the blackened halftone dots are converted to blackened pixels to match the original density values ​​within the grid (filling process). Furthermore, if the pixels adjacent to the grid are whitened halftone dots, the whitened pixels are converted to blackened pixels (conversion process), and blackened pixels around the whitened halftone dots are converted to whitened pixels to match the original density values ​​within the grid (filling process), thereby disrupting the periodicity of the halftone dots and suppressing the occurrence of moire.

[0056] Next, a moire suppression method according to an embodiment of the present invention will be described with reference to FIG. 9 is a diagram illustrating a moiré suppression method 800 according to an embodiment of the present invention. The moiré suppression method 800 may be implemented by, for example, the respective functional units included in the moiré suppression device 380 described with reference to FIG. <Determining whether moiré occurs> First, in step S801, the platemaking data containing the area where moiré occurs is selected and input. The platemaking data selected here is preferably at least one of the four platemaking data for each printing element color. The platemaking data is binary image data in which the pattern is expressed as halftone dots using RIP processing. The determination of whether moiré occurs can be performed by a human user projecting the input image onto a display or printing the input image using an inkjet printer and then visually checking for moiré, or by using a means (such as a neural network) that automatically detects the presence or absence of moiré based on the period, pitch, etc. of the pattern in the platemaking data. To reduce printing costs, a method for determining whether moiré occurs based on the data is desirable.

[0057] <Extracting contour areas> In step S802, the outline area is extracted using moiré suppression processing, and the outline area of ​​the platemaking data is removed in advance before the moiré suppression processing is performed. This is because if the halftone dots included in the outline area are moved by the moiré suppression processing, noise may be generated, and the outline of the object may become blurred.

[0058] For platemaking data that contains moiré, if the print image data before halftoning is available (either on hand or received), it is even more desirable to perform a process to extract the contour areas of objects appearing in the print image data before halftoning. The contour area extraction process uses a smoothing process, as described below, but in the case of platemaking data after RIP processing, a stronger smoothing process is required than in the case of print image data before RIP processing. Therefore, in the case of platemaking data after RIP processing, there is a high possibility that the contour position will be shifted. For this reason, it is more desirable to perform the contour extraction process on the print image data at the time of submission. By performing this outline region extraction process, halftone dots contained within the outline region can be excluded from the halftone dot processing that is performed in the steps following this step. The outline region extraction process will be described in detail later.

[0059] <Grid generation> Next, in step S803, areas determined to require moiré suppression are extracted from the image input in step S801, and a grid is generated in which each blackened halftone dot is divided into individual cells. This grid is generated according to the AM screen type set for each plate, particularly the distance between the centers of the halftone dot to be processed and the adjacent halftone dot (halftone dot generation interval), in accordance with the information input from the halftone dot generation condition input unit 374 in Fig. 8. Here, this grid is not a line drawn on the actual data as pixel information, but an index generated to visualize the halftone dot processing.

[0060] An example of a grid is shown in FIG. 11, which uses as an example plate data in which halftone dots are arranged in the direction of an angle θ116 (called the "screen angle") formed between indicator lines 117. As shown in FIG. 11, the grid 111 includes a plurality of cells 113. Here, it is desirable that the grid 111 is generated so that each cell 113 contains one or less halftone dot. Also, x114 shown in FIG. 11 represents the spacing between the grid 111 in the horizontal direction, and similarly, y115 represents the spacing between the grid 111 in the vertical direction. These x114 and y115 are the "halftone dot generation spacing." These halftone dot generation spacings are calculated by the following mathematical formula: x ≒ y ≒ halftone image resolution [dpi] / halftone image frequency [lpi]

[0061] Here, we will describe an example of a method for generating grid lines. When generating a grid from platemaking data, if the image before halftoning by RIP processing has an area where there is almost no change in density value (almost no structure), the halftone dots in the AM screen are usually arranged at regular intervals as shown in Figure 11. Therefore, all halftone dots will exist in an area (halftone dot area) surrounded by a grid that will be set in a later process.

[0062] Figure 12 shows halftone dots (a) with a density value of 50% or less, and an image of halftone dots (b) that is the inverse of the halftone dots with the grid period shifted by half a period. In other words, the positions of the blackened halftone dots in (a) and the whitened halftone dots in (b) are not on the same grid, but are shifted by half a half period.

[0063] When processing platemaking data with such significantly different density values, after processing by the blackening halftone dot processing unit in Figure 8 is completed, a grid is generated by focusing on the whitening halftone dot shown in Figure 12(b) with a density value of 50% or more, which is located half a period away from the blackening halftone dot shown in Figure 12(a) with a density value of 50% or less. Specifically, attention is paid to one arbitrary blackened halftone dot in Fig. 12(a), and the blackened halftone dots existing in its eight neighbors are extracted. Then, the center points of the blackened halftone dot of interest and the eight neighboring blackened halftone dots are calculated. The calculated center points are then connected to generate a grid 111. If the grid 111 is generated in the x 114 direction and y 115 direction from the target halftone dot at halftone dot periodic intervals, each blackened halftone dot area on the platemaking data will be enclosed. If the platemaking data to be processed has a density value of 50% or more, as described above, a single whitened halftone dot in FIG. 12(b) is selected and the eight blackened halftone dots in its vicinity are extracted. Then, the center points of the whitened halftone dot of interest and the eight neighboring whitened halftone dots are calculated. A grid is then obtained by connecting the calculated center points.

[0064] Various methods for calculating the halftone dot center have been proposed, and one example is a method in which white pixels adjacent to a white pixel of interest are scanned until there are no adjacent points without overlapping, and the centroid coordinates of the coordinate set of the obtained pixels are calculated. However, this method is not limited to this, and any method that reduces the processing load may be used instead. This method is not limited to this, and any grid generation method that reduces the processing load may be used instead.

[0065] For example, in platemaking data with a density value of 50% or more, if the blackened halftone dots and the whitened halftone dots are positioned such that the halftone dot generation cycle is shifted by half, first focus on the blackened halftone dots, calculate the centers of the blackened halftone dots, and create a line segment connecting these center points, which can then become a grid surrounding the whitened halftone dots. Conversely, for platemaking data with a density value of 50% or less, the whitened halftone dots are focused on, the centers of the whitened halftone dots are calculated, and a line segment connecting these center points is formed, which can then become a grid surrounding the blackened halftone dots.

[0066] Note that x114 and y116 may be the same value, or deviation may be permitted within a range of x:y=0.9:1.1 to x:y=1.1:0.9. Ideally, the grid inclination (screen angle θ116) should match the halftone dot generation condition input section 374 in Figure 2, but a deviation of θ±1 degree may be permitted.

[0067] In the AM screen according to the embodiment of the present invention, the screen ruling may be in the range of 60 lines or more. The shape of the halftone dots may be selected from square, elliptical, round, chain, TH net, and the like.

[0068] <Determining whether black halftone processing is possible> In S804 of Fig. 9, a determination is made as to whether or not to process blackened halftone dots present within the halftone dot area surrounded by the grid 111. Generally, as shown in Fig. 12, halftone dots should be generated in sizes that fit within the area surrounded by the grid, with blackened halftone dots being generated if the density value is 50% or less, and whitened halftone dots being generated if the density value is 50% or more. In S804, a determination is made as to whether or not processing is possible when focusing on the blackened halftone dots as shown in Fig. 12(a), and if processing is to be performed, the process proceeds to S804, and if not, the process proceeds to S806.

[0069] In S804, for the blackened halftone dot region generated in S803, a processing ratio for the blackened halftone dots to be processed is first determined, and specific blackened halftone dots to be processed are selected based on this processing ratio using pseudo-random numbers. Here, the processing ratio can be set to any value between 0% and 100%. It has been confirmed that increasing the processing ratio gradually increases the moiré suppression effect and the blur effect. Approximately 70 types of moiré-producing samples were processed at various processing ratios, and printed materials were compared in moiré suppression effect and blur visibility. Approximately 10 subjects evaluated a processing ratio between 60% and 80% as providing a balanced effect of moiré suppression while minimizing the visibility of blur.

[0070] Furthermore, when processing is performed narrowly to the moiré-occurring area, if the visibility of the blur becomes dominant due to the emphasis on the moiré suppression effect, it is possible to reduce the visibility of the partial blur by processing the halftone dot area present in any area excluding the outline around the moiré area at an arbitrarily lower ratio from the set ratio in stages. Furthermore, the above-mentioned stepped ratio can be set to a value greater than 0% and less than the value set in the moiré-occurring area, and it is desirable that the number of steps for change be 0 or more. If the number of steps for change is set to 2 or more, it is desirable that the ratio be lowered as the area becomes farther away from the moiré-occurring area.

[0071] The halftone dot areas selected at the above ratio are processed based on the grid processing internal 810 in FIG. FIG. 10 is a flowchart illustrating the details of the processing in steps S804 and S805 in FIG. In step S811 of Fig. 10, an image in which only the halftone dot area has been extracted is input. Fig. 11 shows an example of an arbitrary blackened halftone dot, which is the input data. Fig. 11 shows an input image in which a blackened halftone dot 112 is stored inside a cell 113, which is a halftone dot area surrounded by a grid 111.

[0072] <Extraction of candidate black pixels to be removed> 10, among the black pixels constituting the black halftone dot, those present in a pixel region inscribed in the grid 111 are extracted as black pixels to be removed, and their coordinates are acquired. Here, removing black pixels means converting the black pixels into white pixels (conversion step). Furthermore, in the subsequent processing, any white pixels will be converted to black pixels (filling step) in accordance with the rules described below, equal to the number of black pixels converted to white here.

[0073] Pixel conversion and filling will be described below with reference to FIGS. 13 is a diagram showing an example of the initial state of a halftone dot to be processed. In this example, a black halftone dot 212 is shown partially in contact with a grid 211. It also shows that white pixels 213 exist around the black halftone dot 212. FIG. 14 is a diagram showing an example of a pixel area to be converted and a pixel area to be filled for the halftone dot shown in FIG. 14 shows blackened pixels 218 (area surrounded by thick lines) that constitute blackened halftone dots present in pixel area 217 (area surrounded by dotted lines) inscribed in the grid. In other words, these blackened pixels 218 are candidates for conversion to whitened pixels. Whitened pixels in pixel area 219 (area shown by diagonal lines) are targets for filling in blackened pixels. In other words, the pixel area to be filled in is the area of ​​halftone dot area 213 in FIG. 13 , excluding blackened halftone dots 212 and pixel area 217 that contacts the grid.

[0074] <Verification of white pixels that can be converted to black pixels> In step S813, the black pixels extracted in step S812 are removed (converted to white pixels), and it is determined whether or not the same number of white pixels extracted in step S812 can be converted to black pixels (filled in). The method of determination will be described with reference to FIG. 15. FIG. 15 shows white pixel regions to be filled, classified into two types: a region 221 to be subjected to a first filling process, and a region 222 to be subjected to a second filling process. When processing the halftone dot 212 in Fig. 15, the same number of white pixels in the pixel area 219 in Fig. 14 are converted to black pixels as the number of black pixels 218 converted to white pixels in Fig. 14. In other words, the white pixels are converted to black pixels and the black pixels are filled in.

[0075] However, as conversion candidates, white pixels adjacent to the halftone dot 212 are preferentially selected. For example, in the example of Fig. 15, any pixel existing in the white pixel area 221 (pixel area indicated by horizontal diagonal lines) adjacent to the halftone dot 212 is set as a conversion candidate (candidate for the first filling step). If all pixels in the white pixel area 221 have been converted to black pixels and there are still pixels that need to be converted to black pixels, any pixel in the white pixel area 222 (pixel area indicated by vertical diagonal lines) adjacent to the white pixel area 221 is selected as the next conversion candidate (candidate for the second filling process). In other words, if the number of pixels to be converted in the conversion process is greater than the number of white pixels adjacent to the halftone dot 212, first the white pixels adjacent to the halftone dot 212 are used as candidates for filling (candidates for the first filling process), and then the white pixel area 222 adjacent to the white pixel area 221 (pixels after filling) is selected as a candidate for filling (candidate for the second filling process).

[0076] 15 is less than the total number of black pixels 218 to be replaced with white pixels, it is not possible to replace all of the black pixels 218 with white pixels. In this case, only the black pixels 218, the number of which is equal to the total number of pixels in the white pixel regions 221 and 222, may be set as the black pixels to be removed. Alternatively, it may be determined that the halftone dot cannot be processed, and removal of the black pixels may be abandoned. If the number of black pixels inscribed in the grid that are removed, i.e., the number that are converted to white pixels, is not the same as the number of white pixels that are converted to black pixels within the grid, the internal density value will differ from the density value within the halftone dot area before processing. Therefore, in principle, it is desirable that the number of black pixels to be removed and the number of white pixels that are converted to black pixels be the same.

[0077] In step S813, if it is determined that all (or some) of the blackened pixels inscribed in the grid can be removed, the process proceeds to step S814. If it is determined that processing is not possible, the process proceeds to step S812 if there is a halftone dot area to be considered next, or to step S816 if there is not.

[0078] In step S814 of Fig. 10, the black halftone dots determined to be removable in step S813 are converted to white pixels. Then, candidates for conversion to black pixels are selected from the white pixel region 221 adjacent to the black halftone dot 212, and the conversion is performed (first filling step). In this case, the selection of the pixels to be converted may be performed by randomly extracting and converting from the candidate pixels to be converted based on pseudo-random numbers, or the method of selecting the conversion candidates may have any regularity. However, if the selection method is particularly random, periodicity is less likely to occur between the halftone dot regions after processing, and moiré suppression efficiency is further improved. Step S814 is repeated for each pixel until it is determined in step S815 (described later) that the filling is complete. Therefore, as already explained in step S813, if the number of black halftone dots that can be removed is smaller than the number of pixels in the white pixel region 221, candidates for conversion to black pixels are extracted from the white pixel region 221. In other words, the white pixels to be converted to black pixels are preferentially selected in order of proximity to the black halftone dots.

[0079] Then, when all the white pixels in the white pixel region 221 have been converted to black pixels and the total number of black pixels 218 does not satisfy the conversion number, the white pixel region 222 is next targeted for conversion to black pixels. Then, when all the white pixel region 222 has been converted and the total number of black pixels 218 does not satisfy the conversion number, if there are any white pixels outside the white pixel region 222 that do not contact the grid, the white pixel region is finally converted to black pixels. In the manner described above, the white pixels are converted stepwise one after another to black pixels. As described above, when selecting white pixels to be converted into black pixels from a plurality of white pixel regions with the same priority for conversion into black pixels, the selection is made using pseudo-random numbers or the like.

[0080] In step S815, the total number of black pixels 218 to be removed is compared with the number of white pixels converted to black pixels. If the number of white pixels converted to black pixels is less than the total number of black pixels 218 to be removed, the process proceeds to step S814. If the total number of white pixels converted to black pixels is equal to the total number of black pixels 118, the process proceeds to step S816.

[0081] In step S816, it is determined whether or not all blackened halftone dots determined to be removable in step S813 have been processed. If there are any blackened halftone dot areas for which processing has not been completed, the process proceeds to step S812. If processing has been completed for all blackened halftone dots selected in step S803, the process proceeds to step S817.

[0082] In S817, the platemaking data in the state where the blackened halftone dots in the moire extraction region have been processed is output, and similarly becomes the output data of S804.

[0083] Returning to FIG. 9 again, the subsequent steps will be described. In S805, it is determined whether or not to process the blackened halftone dot processed platemaking data output from S804 or the blackened halftone dot unprocessed platemaking data output from S803, focusing on the whitened halftone dots present within the halftone dot area surrounded by grid 111, as in S803.

[0084] The processing in S805 and S806 is the same as the processing in S803 and S804 described above, except that the processing performed on blackened halftone dots is entirely replaced with whitened halftone dots, and therefore a description thereof will be omitted. As described above, the positions of the whitened halftone dots are shifted by a half period from the positions of the blackened halftone dots, as shown in an example in Fig. 16. Furthermore, unlike grid generation for blackened halftone dots in a moiré extraction region, grid generation for whitened halftone dots should be performed by replacing blackening in the grid generation procedure described above with whitening, targeting regions with a density value of 50% or more.

[0085] In S807, the whitened halftone dot processed platemaking data output from S806 or the whitened halftone dot unprocessed platemaking data output from S805 is output.

[0086] As described above, the reason for performing processing that focuses on blackened halftone dots or whitened halftone dots is that moiré-generating areas can be caused not only by blackened halftone dots but also by whitened halftone dots. Also, although it has been confirmed that a sufficient effect can be obtained by performing each of the blackened halftone dot processing S803 and S804 and the whitened halftone dot processing S805 and S806 once, if the output result is considered to be insufficient, the order of the steps may be reversed, or each step may be performed multiple times.

[0087] <Details of contour extraction processing> As mentioned above, it is desirable not to apply moiré suppression to areas of cells that overlap with the periphery of a contour extracted by any method. This is because processing the halftone dots contained within the contour area may blur the contours of objects that are particularly highly visible, which corresponds to high-frequency components, and may result in a deterioration in quality. Furthermore, the above-mentioned outline peripheral area may be extracted using any method, and then the area may be enlarged or reduced as necessary. This is because if the extracted outline is too wide, the suppression effect may be weak, or if the extracted outline is too narrow, the deterioration of the outline peripheral area caused by the suppression process may be significant. By preventing the deterioration caused by the above-mentioned suppression process of the outline peripheral area, it is possible to prevent deterioration of the entire output (i.e., object).

[0088] The outline region extraction process will be described in detail below. FIG. 17 shows the flow of processing for extracting a contour area when the print image data before halftoning is usable. When the print image data before halftoning is input, a smoothing process is first performed to suppress noise in the image. Then, a filter that digitizes the brightness change in the image is used to extract the brightness change value. Then, a specific threshold value is used to binarize the brightness change value. This allows the extracted contour area to be output.

[0089] The smoothing process described above may be freely selected by the user, but it is particularly desirable to use a Gaussian filter. The filter that quantifies the luminance change may be freely selected by the user, but it is particularly desirable to use a Sobel filter. Contour extraction may not be performed automatically, but may be manually specified by the user.

[0090] Figure 18 shows the process flow for extracting contour areas when print image data, which is data before halftoning, is not available. The process order is the same as in the case shown in Figure 17, but the difference from the process shown in Figure 17 is that the input image, the platemaking data, already contains halftone dots, so there is a high possibility that the halftone dots will remain if smoothing processing is performed at a normal strength. For this reason, smoothing must be performed at a strength that does not leave the halftone dots. However, the smoothing process may be freely selected by the user, but it is particularly desirable to use a Gaussian filter. The filter that quantifies the luminance change may be freely selected by the user, but it is particularly desirable to use a Sobel filter. Contour extraction may not be performed automatically, but may be manually specified by the user. This is the same as in the case of FIG. 17.

[0091] Figures 19 and 20 are diagrams showing a specific example of contour extraction performed according to the procedures shown in Figures 17 and 18. Figure 19 shows print image data 1910 before halftoning and platemaking data 1920 after halftoning. As shown in Figure 19, print image data 1910 before halftoning is a normal image that is not expressed using halftone dots, while platemaking data 1920 is expressed using halftone dots.

[0092] Figure 20 shows image 1911 after smoothing processing has been applied to the printing image data 1910 before halftoning shown in Figure 19, and image 1921 after smoothing processing has been applied to the platemaking data 1920 after halftoning. As shown in Figure 20, it is desirable that the smoothing processing applied to the platemaking data 1920 be stronger than the smoothing processing applied to the printing image data 1910 before halftoning. This is because care must be taken to ensure that the shapes of the halftone dots in the platemaking data 1920 do not remain. For this reason, the smoothing processing applied to the platemaking data is naturally stronger than the smoothing applied to the printing image data 1910 before halftoning for the simple purpose of noise suppression.

[0093] Fig. 21 shows the results of extracting contour areas from the printing image data 1910 before halftoning and the platemaking data 1920 after smoothing processing shown in Fig. 20. Fig. 21 shows an image 2110 in which the contour area of ​​the printing image data 1910 before halftoning has been extracted, and an image 2120 in which the contour area of ​​the platemaking data 1920 has been extracted.

[0094] Fig. 22 is a diagram showing examples of contour images 2210 and 2220 extracted by binarizing the image 2110 and the image 2120 shown in Fig. 21. Fig. 23 is a diagram showing an overlapping image in which the contour images 2210 and 2220 shown in Fig. 22 are displayed superimposed on each other. As shown in Figure 23, when comparing the contour area 2310 (the core part) output from the printing image data before halftoning with the contour area 2320 (the part sandwiching the core) output from the platemaking data, it can be seen that the contour area 2310 output from the printing image data before halftoning has been extracted with higher accuracy (it is an area closer to the center than the contour area 2320 and is extracted as a thinner line).

[0095] <Printing unit> Next, the printing unit and printing method will be described in detail. The printing unit 375 is a printing unit for printing image data expressed by halftone dots after moire suppression, which has been generated by the moire suppression device 380 . In addition, this printing unit 375 may print the image output from the image output section 390 of the moire suppression device 380, or may print in response to a request from the client terminal 365 after the image output from the image output section 390 is returned to the client terminal 365.

[0096] Each functional unit included in the moiré suppression system 360 may be a software module constituting the moiré suppression application 350 shown in FIG. 7, or may be an independent dedicated hardware device. The functional units may be implemented in the same computing environment or in a distributed computing environment. For example, the halftone dot generation condition input unit 374 may be implemented in a remote server or client terminal 365, and the other functional units may be implemented in the moiré suppression device 380.

[0097] Furthermore, embodiments of the present invention are not limited to the configuration of the moiré suppression system 360 described with reference to Fig. 8. For example, any configuration is possible, such as a configuration in which the moiré suppression device 380 is directly connected to the client terminal 365, or a configuration in which the moiré suppression device 380 and the client terminal 365 are integrated together.

[0098] <Printing method> Next, a printing method that is the premise of the present invention will be described with reference to FIGS. 24 is a schematic diagram of a printing press 50 for printing a design on the printing surface of a printing body 52. ​​The printing body 52 is supplied from a conveying port 51, and inside each of the ink application units 53 to 56, the inks set in the ink application units 53 to 56 are applied to the printing surface of the printing body 52 so as to depict the content to be printed. In this way, the ink application units depict the content to be depicted on the printing surface of the printing body 52, and the printed matter is conveyed to a discharge port 57.

[0099] The printing speed of the printing press 50 is preferably set to a value within the range of 200 m / min to 700 m / min. Printing at a speed higher than this may cause machine vibrations to affect the ink transfer. In this case, halftone dot reproducibility may decrease, and color misalignment and moire may occur more easily due to the printing press.

[0100] Each of the ink application units 53 to 56 is set with a different ink. The ink application units 53 to 56 according to the embodiment of the present invention can be at least one unit, i.e., at least one color, and preferably four colors: CMYK (referred to as R4C). In one example of ink application using these four colors, K can be applied to ink application unit 53, C to ink application unit 54, M to ink application unit 55, and Y to ink application unit 56. Printing in this order begins with K, which is most susceptible to moiré, preventing irregular moiré patterns from occurring. If moiré occurs irregularly, it can be difficult to identify the area where the halftone dots should be moved. In other words, printing from K, which is more susceptible to moiré, makes it easier to identify the area where moiré will occur.

[0101] The inks set in the ink application units 53 to 56 according to the embodiment of the present invention include, for example, general ink, process ink, gold ink, silver ink, carton ink, fluorescent ink, web offset ink, ultraviolet curing (UV) ink, infrared drying (IR) ink, etc. Furthermore, the general inks may be those sold by ink manufacturers as a series of 20 to 50 colors.

[0102] The inks set in the ink application units 53 to 56 according to the embodiment of the present invention may be compositions. These compositions may contain, for example, a colorant component, a vehicle (varnish) component, and the like as their essence. These compositions may also contain auxiliary components. The colorant component may be either an organic pigment or an inorganic pigment. The vehicle component may contain a resin or a solvent. The auxiliary component may be added to enhance the abrasion resistance of the ink, and may be, for example, a wax, a surfactant, a gelling agent, or the like.

[0103] Furthermore, the inks described above may thicken dots depending on the fluidity of the ink used during printing. However, since it is difficult to uniformly define this fluidity for each ink, adjustments may be made each time based on the behavior of the printing ink during the printing process in commercial printing. Furthermore, in a halftone dot image, the dots may be made smaller by the amount of thickening of the print. Since the degree of thickening of the dots also varies depending on the amount of movement of the dots, when the dots are moved significantly, the amount of adjustment of the dot size may be made larger compared to areas where the dots are not moved.

[0104] The printing method in the present invention may be either a plate-based method or a plateless method. However, as an embodiment of the present invention, plate-based printing is particularly desirable. Here, plate-based methods may include lithographic printing, relief printing, intaglio printing, stencil printing, etc. Furthermore, lithographic printing is often called offset printing, relief printing is often called letterpress printing, intaglio printing is often called gravure printing, and stencil printing is often called screen printing. The moire suppression means of the present invention may be applied to any printing method, but is particularly effective for lithographic printing.

[0105] The printing medium 52 is a printing information paper. The printing information paper here may be, for example, uncoated printing paper, lightly coated printing paper, coated printing paper, special printing paper, or information paper. However, it is preferable that the printing medium 52 be either uncoated printing paper or coated printing paper.

[0106] Uncoated printing paper may include, for example, printing paper A, printing paper B, printing paper C, and printing paper D. Printing paper A is paper made using 100% bleached chemical pulp as raw material and is a high-quality paper. Printing paper B is paper made using 70% or more bleached chemical pulp as raw material and is a medium-quality paper with a brightness of 70%. Printing paper C is paper made using 40% to less than 70% bleached chemical pulp as raw material and has a brightness of approximately 65%. Printing paper D is paper made using less than 40% bleached chemical pulp as raw material and has a brightness of approximately 55%. Printing papers C and D are collectively low-quality papers.

[0107] Pulp is a fiber extracted from raw materials, and its main component is cellulose. These raw materials may include, for example, wood, non-wood, waste paper, synthetic fibers, etc. Wood pulp is made by pulping softwoods, hardwoods, etc. Non-wood pulp is made by pulping plants, particularly linters, kenaf, bagasse, bamboo, etc. Waste paper pulp is made by deinking paper and repulping it. Synthetic fiber pulp is made by pulping chemically synthesized fibers (rayon, vinylon, etc.). Pulp includes mechanical pulp and chemical pulp. Mechanical pulp is made by mechanically grinding raw materials. Chemical pulp is made by chemically extracting fibers. Bleached pulp is mechanical pulp or chemical pulp that has been bleached.

[0108] Coated printing paper may include, for example, art paper, coated paper, lightly coated paper, lightly coated paper, etc. Art paper is a type of paper that can be printed on a sheet of paper up to 1 m 2 The coated paper is either wood-free or medium-quality paper with 40g of coating agent applied on both sides per 1m. 2 The coated paper is either wood-free or medium-weight paper with 20g of coating agent applied on both sides per 1m. 2It is a fine or medium-quality paper with 15g of coating agent applied on both sides per 1m. 2 It is high-quality or medium-quality paper with a coating weight of 12g or less on both sides.

[0109] Regarding printing paper, halftone dots are more likely to thicken on uncoated printing paper than on coated printing paper. Among uncoated printing papers, the likelihood of dot gain decreasing in the order of Printing Paper D, Printing Paper C, Printing Paper B, and Printing Paper A. Among coated printing papers, the likelihood of halftone dots thickening decreasing in the order of Lightly Coated Paper, Lightly Coated Paper, Coated Paper, and Art Paper.

[0110] The type of printing paper mentioned above affects the degree of ink absorption, making halftone dots more likely to thicken. Therefore, the screen ruling used in commercial printing is considered and set appropriately depending on the object being printed. For example, when printing on low-grade paper, the screen ruling may be 10 lines or more but less than 110 lines. When printing on medium-grade paper, the screen ruling may be 110 lines or more but less than 210 lines. When printing on high-quality paper, the screen ruling may be 210 lines or more but less than 2000 lines.

[0111] Figure 25 is a schematic diagram of the inside of the ink application units 53 to 56 in Figure 24. First, a dampening water roller 63 applies dampening water 64 to a printing plate 62 set on a plate cylinder 61. Then, an ink roller 65 applies ink 66 to the printing plate 62. Next, the ink 66 is transferred (washed off) from the printing plate 62 to which the ink 66 has been applied to a rubber blanket 67. Furthermore, an impression cylinder 68 presses the printing body 52 against the rubber blanket 67 to which the ink 66 has been transferred, thereby transferring (setting) the ink 66 to the printing body 52. ​​In this way, the content to be expressed by printing is printed on the printing body 52.

[0112] <Printing using printing plates> FIG. 26 is a diagram illustrating a printing plate 62. The printing plate 62 may be, for example, a PS plate, a CTP plate, or a wipe-on plate, with a PS plate being particularly desirable. The PS plate may also be made of aluminum, stainless steel, or chrome, which are metals with strong hydrophilicity (the contact angle between the surface of the material and water is close to 0 degrees), with aluminum being particularly desirable. The printing plate 62 may also be a metal surface coated with ultraviolet-curable resin. FIG. 26 shows the surface of the printing plate 62 after development, and is composed of a lipophilic area 71 representing the image content and a hydrophilic area 72 other than that.

[0113] FIG. 27 is a schematic diagram showing the process up to development of a printing plate 62. First, a platemaking film 76, consisting of an area 74 representing the image content and an area 75 not representing the image content, is placed on the printing plate 62, the surface of which is coated with a UV-curable resin 73, and vacuum-sealed. The surface of the printing plate is then exposed to UV light from a light source lamp 77, rendering the photosensitive area on the surface of the UV-curable resin 73 alkali-soluble. This light source lamp 77 may be, for example, a mercury lamp. Furthermore, if the photosensitive area of ​​the exposed PS plate is dissolved in a strongly alkaline developer, the remaining area becomes a lipophilic area 71, while the dissolved area exposes the metal surface and becomes a hydrophilic area 72. In this manner, the printing plate 62 is made.

[0114] 28 is a schematic diagram of the process up to when dampening solution 64 is applied to a printing plate 62. The dampening solution roller 63 applies dampening solution 64 to hydrophilic regions 72 on the surface of the printing plate 62. At this time, the dampening solution 64 does not adhere to lipophilic regions 71 because these regions have a low affinity for water.

[0115] 29 is a schematic diagram of the process up to when ink 66 is applied to a printing plate 62. Ink roller 65 applies ink 66 to lipophilic areas 71 on the surface of printing plate 62. At this time, ink 66 does not adhere to areas 72 to which dampening water 64 is applied, because ink 66 is repelled by dampening water 64.

[0116] The above describes an embodiment of the present invention. The suppression effect obtained by this embodiment is illustrated in Fig. 30. It should be possible to confirm that the diagonal stripes visible in Fig. 30(a) (an image similar to Fig. 6(b)) are almost invisible as shown in Fig. 30(b).

[0117] The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the gist of the present invention.

[0118] The pseudorandom numbers according to embodiments of the present invention (e.g., a first pseudorandom number for determining the rate at which the halftone dots are moved, a second pseudorandom number for determining the direction at which the halftone dots are moved, and a third pseudorandom number for determining the amount at which the halftone dots are moved) may be values ​​generated by any of the following methods: square root extraction, linear congruential algorithm, linear feedback shift register, Mersenne Twister, multiplication with carry, Xorshift, Lagged Fibonacci algorithm, RANLUX, Permuted congruential generator, Blum-Blum-Shub, and Fortuna.

[0119] When the moiré suppression process according to the embodiment of the present invention is implemented as a program, a random number table can be created and used from pseudo-random numbers generated by the above-described method in order to control the process so that equivalent performance is obtained for any given platemaking data. This random number table lists multiple predetermined random number values. Therefore, each time the process according to the embodiment of the present invention is performed, the same suppression performance can be obtained by using random number values ​​extracted from the same random number table. Furthermore, this random number table may be created and used with a capacity appropriate for the specifications of each user's computer used to execute the process according to the embodiment of the present invention. [Explanation of symbols]

[0120] 111 Grid 112 Blackened halftone dots 113 cells 360 Moire suppression measures 365 client terminal 370 Communication Networks 372 Data Storage Unit 374 Halftone dot generation condition input section 375 printing units 380 Moire suppression device 382 Blackening halftone area extraction part 386 Whitening halftone area extraction part 390 Image Output Unit

Claims

1. For an input image represented by halftone dots, a grid generating step of generating a grid that divides a plurality of halftone dots, each of which is composed of one or more first pixels (blackened pixels or whitened pixels) in a first region where moiré occurs, into individual regions based on a predetermined halftone dot generation interval; a conversion step of converting first pixels of the halftone dots separated by the grid, the first pixels being in contact with the grid, into second pixels (if the first pixels are black pixels, they are white pixels; if the first pixels are white pixels, they are black pixels); a first filling step of selecting a candidate to be converted into a first pixel from among second pixels adjacent to the first pixel of the halftone dot divided by the grid based on the number of converted pixels, and converting the selected candidate into the first pixel; halftone processing process including A moire suppression method comprising:

2. 2. The moire suppression method according to claim 1, If the number of first pixels converted by the conversion step is greater than the number of second pixels adjacent to the first pixels inside the grid, a second padding step is provided after the first padding step, in which a candidate to be converted is selected from second pixels adjacent to the padded pixels that have been converted from second pixels to first pixels and become the first pixels, and the candidate is converted. A moire suppression method comprising:

3. 3. The moire suppression method according to claim 1, the converting step and the first filling step are performed on an arbitrary proportion of halftone dots in the first region where moire occurs, The first pixel to be subjected to the conversion process is selected by a pseudo-random number based on a given ratio. A moire suppression method comprising:

4. 4. The moire suppression method according to claim 1, The halftone dot processing step includes a contour excluding step of excluding halftone dots included in a contour area of ​​the image from the moire suppression processing. A moire suppression method comprising:

5. a halftone dot area extraction unit that extracts halftone dot areas by forming a grid that divides the halftone dots included in the platemaking data into individual areas based on a predetermined halftone dot generation interval; a conversion step of converting a first pixel of the halftone dot area that contacts the grid into a second pixel (a white pixel if the first pixel is a black pixel, or a black pixel if the first pixel is a white pixel); a halftone dot processing unit that performs a first filling step of selecting a candidate to be converted into a first pixel from among second pixels that are adjacent to the first pixel of the halftone dot divided by the grid based on the number of converted pixels, and converting the selected candidate into the first pixel; A moire suppression device comprising:

6. 6. The moire suppression device according to claim 5, If the number of first pixels converted by the conversion step is greater than the number of second pixels adjacent to the first pixels inside the grid, after the first filling step, the halftone dot processing unit performs a second filling step of selecting candidates to be converted from second pixels adjacent to the filled pixels that have been converted from second pixels to first pixels and have become the first pixels. A moire suppression device comprising:

7. 7. The moire suppression device according to claim 5, performing the conversion step and the first filling step on an arbitrary proportion of halftone dots in a first region where moire occurs; The first pixel to be subjected to the conversion process is selected by a pseudo-random number based on an arbitrary ratio. A moire suppression device comprising:

8. 8. The moire suppression device according to claim 5, A contour area extraction unit extracts a contour area from an input image. A moire suppression device comprising:

9. A moire suppression device according to any one of claims 5 to 8; a halftone dot generation condition input unit; a data storage unit; Printing Unit A moire suppression system comprising:

Images