JP2023021779A - Moire suppression method, moire suppression device and moire suppression system - Google Patents

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

The present invention relates to a moire suppression method, a moire suppression device, and a moire suppression system.

"Moire (or Moire)" is interference fringes visually generated when multiple periodic patterns or structures are superimposed. In terms of physics, moiré can be said to be a beat phenomenon of two spatial frequencies.
Although there are cases where this moire is useful and positively utilized, when unintended moire occurs, it can impair the design of the image and lead to deterioration of the quality of the printed matter. Means are also proposed.

For example, in the image processing system of Patent Document 1, regarding fringes and single-plate moire generated by interference between output resolution and screen ruling, non- There is a technique for eliminating or alleviating moire by determining the positions of black pixels to be contacts and the positions of white pixels to be contacts among the non-contact positions of halftone dots and replacing them. Are listed.

Japanese Patent Application Laid-Open No. 2003-143405

However, in the image processing system of Patent Document 1, for example, when a pattern is expressed by superimposing a plurality of plates, the original pattern information to be expressed by the halftone dots on a certain plate, especially the thin lines that are almost invisible, is periodic. It is insufficient as a countermeasure against so-called superposition moiré, which is a fringe that occurs due to interference between the structural information of the original pattern information itself, which is arranged in a regular pattern, and the periodicity of halftone dots on another plate. I believe that.
Therefore, means for more effectively suppressing moiré are desired.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide means for more effectively suppressing the occurrence of moire by breaking the periodicity of halftone dots.

In order to solve the above problems, one of the representative moiré suppression methods of the present invention is to reduce the moiré by one or more points in a first region where moiré occurs in an input image represented by halftone dots. a grid generation step of generating a grid that divides a plurality of halftone dots each composed of a first pixel (blackened pixel or whitened pixel) into individual cells;
Of halftone dots separated by the grid, a first pixel in contact with the grid is a second pixel (when the first pixel is a blackened pixel, a whitened pixel; when the first pixel is a whitened pixel, a conversion step of converting to a blackened pixel);
selecting a candidate to be converted into a first pixel from among second pixels contacting the first pixel of the halftone dot divided by the grid based on the number of the converted pixels; and a halftone dot processing step including a filling step.

Also, one of the representative moire suppression devices of the present invention is
a halftone dot area extracting unit that extracts a halftone dot area by forming a grid that separates the halftone dots included in the platemaking data into individual areas;
Of the halftone dots in the halftone dot area, the first pixel in contact with the grid is the second pixel (when the first pixel is a black pixel, it is a white pixel; when the first pixel is a white pixel, it is a black pixel). and converting from second pixels contacting the first pixel of the grid delimited halftone dots to the first pixel based on the number of the converted pixels. a halftone dot processor for performing a first filling step of selecting and transforming candidates;

According to the present invention, by changing the arrangement of pixels in contact with the grid, it is possible to break down the periodic structure of halftone dots and provide means for more effectively suppressing the occurrence of moire.

FIG. 1 is a diagram showing an example in which moire occurs. FIG. 2 is a diagram showing another example in which moire occurs. FIG. 3 is a diagram for explaining gradation representation by halftone dots. FIG. 4 is a diagram for explaining screen angles of halftone dots. FIG. 5 is a diagram for explaining the tilt angle of the tilt pattern. FIG. 6 is a diagram showing an example of print image data and moire. FIG. 7 illustrates a computer system for implementing embodiments of the present invention. FIG. 8 is a diagram illustrating an example of a configuration of a moiré suppression system according to the embodiment; FIG. 9 is a flowchart for explaining a moiré suppression method according to the embodiment. FIG. 10 is a flowchart for explaining details of processing in the grid processing unit. FIG. 11 is a diagram showing an example of a grid. FIG. 12 shows halftone dots having a density value of 50% or less and halftone dots obtained by reversing this and shifting the grid period by half the period. FIG. 13 is a diagram showing an example of the initial state of halftone dots to be processed. FIG. 14 is a diagram showing an example of a region of pixels to be converted and a region of pixels to be interpolated for halftone dots. FIG. 15 is a diagram for explaining the target area of the first filling process and the target area of the second filling process. FIG. 16 is a diagram showing whitening halftone dots. FIG. 17 is a diagram showing the flow of processing for extracting a contour region according to the embodiment of the present invention. FIG. 18 is a diagram showing the flow of processing for extracting a contour region according to the embodiment of the present invention. FIG. 19 is a diagram showing a specific example of contour extraction in the procedure shown in FIGS. 17-18. FIG. 20 is a diagram showing a specific example of contour extraction according to the procedure shown in FIGS. FIG. 21 is a diagram showing the result of extracting a contour region from the image data for printing after smoothing processing and before halftone processing and the image data for printing shown in FIG. FIG. 22 is a diagram showing an example of a contour image obtained by binarizing the image shown in FIG. 21 and extracting it. FIG. 23 is a diagram showing a superimposed image in which the contour images shown in FIG. 22 are superimposed and displayed. FIG. 24 is a schematic diagram of a printing press 50 for printing a design on the printing surface of a printing body 52. As shown in FIG. FIG. 25 is a schematic view of the inside of the ink applicator units 53-56. FIG. 26 is a diagram for explaining the printing plate. FIG. 27 is a schematic diagram showing the flow up to development of the printing plate. FIG. 28 is a schematic diagram showing dampening water adhering to the printing plate. FIG. 29 is a schematic diagram showing how ink adheres to the printing plate. FIG. 30 is a diagram showing the suppression effect obtained by this embodiment.

First, examples of halftone dot generation and moire in commercial printing will be described with reference to FIGS. 1 to 6. FIG.
<Halftone dots in commercial printing>
In the field of commercial printing, RIP (Raster Image Processor) processing (hereinafter also referred to as “halftone processing”) is performed on image data for printing at the time of submission, and the image is converted to monochrome for each printing element color. A method of expressing with binary halftone dots, that is, a mass of blackened pixels or whitened pixels is adopted. RIP processing means rasterizing digital data created by a general-purpose computer into a data format that can be output by a printing machine, and expresses an image with halftone dots of a certain size. Image data obtained by rendering image data for printing with halftone dots by RIP processing is sometimes referred to as "RIP-completed data", "prepress data", and "drawing data".

Color expression using halftone dots is generally done by subtractive color mixture using four colors of C (cyan), M (magenta), Y (yellow), and K (black) (this is called R4C). Then, for each color of C, M, Y, and K, a plate for expressing the drawing content by printing is prepared, and the gradation information and color are reproduced by superimposing the ink on the paper.

When creating the data to be drawn for each plate described above, a color conversion called a profile is used to match the color space of the original data (for example, the RGB color system) and the color space of the printing machine (the CMYK color system). Arbitrarily select a table and perform color matching. A profile is configured in a lookup table (LUT) format, and is created by dividing an RGB space, a CMYK space, or an L*a*b space for each component and determining a representative value. 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.

Typical methods of gradation expression (shading expression) by halftone dots include AM screening (Amplitude Modulation Screening) in which the size of halftone dots is changed, and FM screening in which the size of halftone dots is kept constant and the density is changed. (Frequency Modulation Screening). FM screening does not generate moire in principle because the arrangement of halftone dots is irregular. difficult to AM screening is resistant to misregistration and has a low level of technical difficulty, so it is generally used in commercial printing where mass production is essential while stabilizing quality.

In order to reproduce colors, in AM screening, instead of overlapping halftone dots at the same position and mixing ink, an optical illusion (this is called optical illusion) is used to see a set of dots from a distance. Sometimes it's showing up in any pattern or color.

<Example of Moire>
FIG. 1 is a diagram showing an example of moiré. FIG. 1 shows four patterns 21, 22, 23 and 24 represented by halftone dots. The halftone dots of these patterns 21, 22, 23, and 24 are arranged at the same intervals, but have different inclinations, so that the halftone dot periods are also different. A pattern 25 is obtained by stacking the patterns 21, 22, 23, and 24 on the center. As shown in FIG. 1, a pattern of circles and a pattern of straight lines, which did not exist in any of the patterns 21, 22, 23 and 24 before being superimposed, are generated in the pattern 25 as moire.

FIG. 2 is a diagram showing another example of moire. FIG. 2 shows a pattern 26 in which halftone dots are regularly arranged and a pattern 27 in which lines are regularly arranged. Also, the pattern 28 is obtained by overlapping the pattern 26 and the pattern 27 . As shown in FIG. 4, a pattern of regular oblique straight lines, which did not exist in either pattern 26 or pattern 27, occurs in pattern 28 as moire.

<Gradation representation by halftone dots>
Next, with reference to FIG. 3, gradation representation by halftone dots will be described.
FIG. 3 is a diagram for explaining gradation representation by halftone dots. FIG. 3 shows a gradation pattern 31 whose brightness changes smoothly, and enlarged areas 32, 33, and 34 obtained by extracting and enlarging a part of the gradation pattern 31. FIG. As indicated by the enlarged areas 32, 33, and 34, the density of the gradation pattern 31 is appropriately expressed by changing the size of halftone dots (dots) that are too large to be recognized by the naked eye. be able to.

<Screen angle>
Next, screen angles of halftone dots will be described with reference to FIGS. 4 and 5. FIG.
FIG. 4 is a diagram for explaining screen angles of halftone dots. FIG. 4 shows a slanted pattern 36 with a slanted line of halftone dots.

Furthermore, the halftone dots of each color are given an arbitrary angle (this is called a screen angle) as shown in FIG. ”). When given a certain period and angle, halftone dots of each color interfere with each other, causing moire.

FIG. 5 is a diagram showing that the tilt angles of the tilt pattern 36 shown in FIG. 4 are different for each R4C color plate, for example. As described above, if a certain period and angle are given, the halftone dots of each color interfere with each other, causing moiré. It is desirable to provide a different tilt angle for each color plate so that halftone dots do not overlap. Moire is also strongly visible when the screen angle difference between the plates is small.
For example, if Y (yellow) 40 is the reference (0°), C41 may be 15°, K42 may be 45°, and M43 may be 75°. Also, for Y (yellow) 40, the amount of movement of halftone dots can be set to 0, and the amount of movement of halftone dots of other colors can be set to non-zero. Thus, the angle formed by each color plate (from the reference) is 5° or more and less than 30°.
In this way, by setting the angles of the respective color plates to different values, it is possible to prevent moire outside the printing area where moire tends to occur. In addition, by doing so, it is possible to limit the region where halftone dots are moved for suppressing moire. As a result, it is possible to maintain the print quality and improve the efficiency of halftone dot image generation.

Further, as will be described later, the color plates to which halftone dots are moved can be all color plates or some color plates. When halftone dots are moved for all color plates, the amount of halftone dot movement or the proportion of the halftone dots to be moved may be different for each color plate. At this time, for cyan, which has low spatial frequency sensitivity, the moving amount of halftone dots, the moving halftone dot ratio, or both can be made larger than those of the other color plates. Also, the case of moving halftone dots in some color plates may be handled in the same way. A color plate that does not move halftone dots may be yellow, which is the least visible.

<Moire due to cycle of image data for printing>
As described above, moire is a phenomenon in which when patterns having different periods are overlapped, a new pattern that is not included in each pattern is generated.
However, moiré that occurs in the field of commercial printing is not only caused by interference between halftone dots, but also due to the period of input image data for printing and the data that is output after halftone processing is performed on the data. However, there are cases where halftone dot periods interfere with each other.

For example, if there is a periodic pattern such as a striped pattern in the image data for printing at the time of submission in commercial printing, if this pattern is represented by halftone dots, the period of the pattern and the period of halftone dots will interfere. However, new patterns that do not exist in the original image data may appear as moire.
A specific example will be described with reference to FIG. FIG. 6(a) is a photographic image of the original design before plate making, that is, image data for printing at the time of manuscript submission. "Before platemaking" means data before halftone processing.

In FIG. 6(a), the pattern of the fibers in the fabric is periodically generated, but no moiré is generated in the image at this time.
On the other hand, FIG. 6B shows an example in which moiré occurs as a result of printing the image in FIG. 6A after halftone processing.
The image in FIG. 6(b) is the image of the first plate in the plate making data (FIG. 6(c)) in which halftone processing is performed on the same area as in FIG. 6(a). Moire is generated by superimposing a screen tone image (FIG. 6(d)) of a different version from the above-described version on which halftone processing has been performed on the same area.
In this way, when an image in which a periodic pattern exists is represented by halftone dots, the period of the pattern interferes with the period of the halftone dot, and a new pattern that does not exist in the original image data is generated. May appear as moire.

In the present disclosure, a “halftone dot” is a cluster of at least one or more blackened pixels or whitened pixels (also referred to as “pixels”), and is the minimum unit for expressing the gradation of a drawing target. be.
A "grid" is a line segment on the data for separating halftone dots provided on drawing data, and the area separated by the "grid" is called a "cell" or a "halftone dot area".
In addition, “pixels in contact with the grid” means pixels whose coordinate positions partly overlap with the grid.

In the field of commercial printing, when a printed matter is visually inspected and it is confirmed that moiré has occurred, in order to suppress moiré, the original image data before halftone dot processing by RIP processing is restored and the moiré is removed. Add a fix to suppress it. Data corrections are made by the operator. After that, halftone dot data for printing is created again by RIP processing, and the printed matter is visually inspected again.

However, it takes a lot of time and effort and costs to print and visually inspect each time a correction is made. Moreover, although visual evaluation takes time and effort, it is difficult to completely prevent accidents such as stopping printing and reprinting. Therefore, there is a demand for means for suppressing moire by processing and correcting halftone data instead of returning and correcting the original image data.

Further, as described above, means for alleviating moiré by uniformly moving halftone dots constituting an image subjected to RIP processing or by correcting the shape are known. The structure made up of halftone dots cannot be destroyed, and moire cannot be completely suppressed.

Therefore, the inventor of the present invention came up with the idea that the halftone dot period can be broken more effectively by disconnecting the contact portions between the halftone dots while ensuring the density values of the individual halftone dots. Furthermore, if all the halftone dots are simply cut off from each other, there is a risk that blurring will occur in the entire pattern. Therefore, instead of correcting all the halftone dots all at once, the present inventor first corrected halftone dots in an area where moire occurs in an image excluding the contour portion of the image, and corrected an arbitrary ratio (for example, , 60 to 80%, etc.), and by controlling whether or not to process each halftone dot at this ratio, it is possible to effectively suppress moire, suppress blurring due to processing, and maintain the structure of the object. Succeeded in obtaining a clear image.

As described above, according to the present invention, it is possible to provide a moire suppressing means that does not change the color of the printed matter and suppresses deterioration of the quality of the printed matter due to deformation of the halftone dot shape. In other words, since the halftone dot structure itself, which causes moire in the printed matter, is destroyed, an image in which the occurrence of moire is not visually recognized can be obtained regardless of which direction the printed matter is viewed.

The background underlying the present invention and embodiments of the present invention will be described below with reference to the drawings. It should be noted that the present invention is not limited by this embodiment. Moreover, in the description of the drawings, the same parts are denoted by the same reference numerals.

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

Computer system 300 may include one or more general-purpose programmable central processing units (CPUs) 302A and 302B, collectively referred to as processors 302. As shown in FIG. In some embodiments, computer system 300 may include multiple processors, and 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.

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 Moiré suppression application 350 . In some embodiments, Moiré suppression application 350 may include instructions or descriptions that perform the functions described below on processor 302 .

In some embodiments, Moiré suppression application 350 may be implemented in semiconductor devices, chips, logic gates, circuits, circuit cards, and/or other physical hardware devices instead of or in addition to processor-based systems. may be implemented in hardware via In some embodiments, the Moiré suppression application 350 may include data other than instructions or descriptions. In some embodiments, a camera, sensor, or other data input device (not shown) may be provided in direct communication with bus interface unit 309, processor 302, or other hardware of computer system 300. .

Computer system 300 may include 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 be coupled to I/O bus 308 for transferring data to and from various I/O units. I/O bus interface unit 310 communicates via I/O bus 308 a plurality of I/O interface units 312, 314, 316, also known as I/O processors (IOPs) or I/O adapters (IOAs); and 318.

Display system 324 may include a display controller, display memory, or both. The display controller can 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 such data to processor 302 .

For example, the computer system 300 may include a biometric sensor that collects heart rate data, stress level data, etc., an environmental sensor that collects humidity data, temperature data, pressure data, etc., and a motion sensor that collects acceleration data, motion data, etc. may include Other types of sensors can also be used. The display system 324 may be connected to a display device 326 such as a single display screen, television, tablet, or handheld device.

The I/O interface unit provides the ability to communicate with various storage or I/O devices. For example, the terminal interface unit 312 may be used for user output devices such as video displays, speaker televisions, etc., and user input devices such as keyboards, mice, keypads, touch pads, trackballs, buttons, light pens, or other pointing devices. Such user I/O devices 320 can be attached. A user inputs input data and instructions to the user I/O device 320 and the computer system 300 by operating the user input device using the user interface, and receives output data from the computer system 300. good too. The user interface may be displayed on a display device, played by a speaker, or printed via a printer, for example, via user I/O device 320 .

Storage interface 314 connects to one or more disk drives or direct access storage device 322 (typically a magnetic disk drive storage device, but an array of disk drives or other storage device configured to appear as a single disk drive). ) can be attached. In some embodiments, storage device 322 may be implemented as any secondary storage device. The contents of memory 304 may be stored in storage device 322 and read from storage device 322 as needed. I/O device interface 316 may provide an interface to other I/O devices such as printers, fax machines, and the like. Network interface 318 may provide a communication pathway to allow computer system 300 and other devices to communicate with each other. This communication path may be, for example, network 330 .

In some embodiments, computer system 300 is a device that receives requests from other computer systems (clients) that do not have a direct user interface, such as multi-user mainframe computer systems, single-user systems, or server computers. There may be. In other embodiments, computer system 300 may be a desktop computer, handheld computer, laptop, tablet computer, pocket computer, phone, smart phone, or any other suitable electronic device.

<Moire suppression system>
Next, the configuration of the moiré suppression system according to the embodiment of the present invention will be described with reference to FIG.

FIG. 8 is a diagram showing an example 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 consists of 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 .
Communication network 370 may include, for example, a local area network (LAN), a wide area network (WAN), a satellite network, a cable network, a WiFi network, or any combination thereof. Also, the connection between the client terminal 365, the printing unit 375, and the moiré suppression device may be wired or wireless.

The client terminal 365 is a terminal that transmits input data to be processed by a moire suppression method, which will be described later, to the moire suppression device via the communication network 370 . This client terminal 365 may be a terminal used by an individual, or may be a terminal shared by an organization such as a private company. Also, the client terminal 365 may be any device such as a desktop computer, a notebook computer, a tablet, a smart phone, or the like.

The data storage unit 372 is for storing image data represented by halftone dots (hereinafter referred to as “input data”) to be processed by the moiré suppression method, which is transmitted from the client terminal 365 via the communication network 370. is the storage part of This data storage unit may be, for example, a local storage such as a HDD (Hard Disk Drive) or an SSD (Solid State Drive), or may be a cloud-type storage area accessible to the moiré suppression device 380 .

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

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

Further, as shown in FIG. 8, the moiré suppression device 380 includes a blackened halftone dot area extraction unit 382, a blackened halftone dot processing unit 384, a whitened halftone dot region extracting unit 382, a blackened halftone dot processing unit 384, and a whitening mesh. A point area extractor 386 , a whitening dot processor 388 and an image output unit 390 may be included.
In the following description, the moire suppression device is assumed to include all of the blackened halftone dot region extraction unit 382, blackened halftone dot processing unit 384, whitening halftone dot region extraction unit 386, and whitening halftone dot processing unit 388. However, if the moire can be suppressed only by processing the blackened halftone dots, a blackened halftone dot region extraction unit 382 and a blackened halftone dot processing unit 384 are provided, and a whitened halftone dot region extraction unit 386 and a whitened halftone dot region extraction unit 386 are provided. The point processing unit 388 may not be provided.

On the contrary, if the moiré suppression device can suppress moiré only by processing the whitening halftone dots, the whitening halftone dot region extracting unit 386 and the whitening halftone dot processing unit 388 are provided. The extraction unit 382 and the blackened halftone dot processing unit 384 may not be provided.
Furthermore, since the blackened halftone dot area extractor 382 and the whitened halftone dot area extractor 386 essentially have the same function, they may be made common and configured as a halftone dot area extractor.
Further, the moiré suppression device may be composed only of the halftone dot area extraction unit for the first pixel (blackened pixel or whitened pixel) and the first halftone dot processing unit. A halftone dot area extractor for pixels (pixels of a different color from the first pixels) and a second halftone dot processor may be provided.
Further, the first halftone dot processing section and the second halftone dot processing section may be shared and configured as a halftone dot processing section.

The blackened halftone dot area extracting section 382 and the whitened halftone dot area extracting section 386 extract the input data input from the data storage section 372 based on the halftone dot generation conditions input via the halftone dot generation condition input section 374 . , generates a grid in which each blackened halftone dot and each whitened halftone dot is accommodated, and forms a grid area, thereby extracting a halftone dot area.

In the blackened halftone dot area extracted by the blackened halftone dot area extracting part 382, the blackened halftone dot processing unit 384 processes an arbitrary proportion of the blackened halftone dots within the grid. When a blackened halftone dot to be specifically processed is determined and the processing is performed, among the blackened pixels forming the blackened halftone dot, the blackened pixels that are in contact with the grid are converted into whitened pixels (conversion process ), and has a function of converting the whitened pixels not in contact with the grid around the blackened halftone dot into blackened pixels by the number of converted pixels (filling step).

Similarly, the whitening halftone dot processing unit 388 processes an arbitrary ratio of halftone dots within the grid in the whitening halftone dot region extracted by the whitening halftone dot region extraction unit 386 . When the whitening halftone dots to be processed are determined, and the whitening pixels constituting the whitening halftone dots are processed, whitening pixels in contact with the grid are converted into blackening pixels (conversion step). It has a function of converting blackened pixels that are not in contact with the grid in the peripheral portion of the whitened halftone dot into whitened pixels by the number of pixels (filling step).

The image output unit 390 is a functional unit that outputs image data after moire is suppressed by the processing of the functional units from the blackened halftone dot region extraction unit 382 to the whitened halftone dot processing unit 388 .
Details of the printing unit and the printing method will be described later.

A moire suppression method according to an embodiment of the present invention will be described below.
<Moire suppression method>
As described above, in the embodiment of the present application, in an input image represented by halftone dots, a region (first region) in which moire occurs is blackened based on a predetermined halftone dot generation interval. Generate a grid that separates each halftone dot or whitening halftone dot into individual cells, and among the halftone dots included in the grid, for a pixel that touches the grid, if this is a blackening halftone dot, this blackening pixel is Convert to whitening pixels (conversion step), and convert whitening pixels around blackened halftone dots to blackened pixels according to the original density values inside the grid (filling step). If the pixels in contact with the grid are white halftone dots, the white pixels are converted to black pixels (conversion process), and the black pixels around the white halftone dots are converted to white pixels in accordance with the original density values inside the grid. (compensation step), the periodicity of halftone dots can be destroyed, and the occurrence of moire can be suppressed.

Next, a moire suppression method according to an embodiment of the present invention will be described with reference to FIG.
FIG. 9 is a diagram illustrating a moiré suppression method 800 according to an embodiment of the invention. This moire suppression method 800 may be implemented by respective functional units included in the moire suppression device 380 described with reference to FIG. 8, for example.
<Determination of Moire Occurrence>
First, in step S801, plate-making data including a moiré area is selected and input. The prepress data selected here is desirably at least one prepress data among the four prepress data for each printing element color.
Further, the plate-making data is binary image data in which a pattern is represented by halftone dots by RIP processing. In addition, the determination of whether or not moire occurs is performed by a method in which a human user projects an input image onto a display or the like or prints the input image using an inkjet machine or the like, and then confirms the moire with the naked eye. Alternatively, it may be performed by means (neural network, etc.) for automatically detecting the presence or absence of moire based on the period, pitch, etc. of the pattern in the platemaking data. In order to reduce the cost of printing, it is desirable to use a method for determining the occurrence of moire on data.

<Extraction of contour area>
In step S802, a contour area is extracted by moiré suppression processing, and processing for removing the contour region of the platemaking data is performed in advance before moiré suppression processing is performed. This is because if the halftone dots included in the contour area are moved by the moiré suppression process, noise may occur and the contour of the object may become blurred.

For plate making data with moire, if the image data for printing before halftone dot conversion is available (either at hand or received), the printing before halftone dot conversion is possible. It is further desirable that processing for extracting the contour area of an object appearing in the image is performed on the image data for the object. As will be described later, the contour area extraction process uses smoothing processing. In the case of prepress data after RIP processing, stronger smoothing processing is performed than in the case of printing image data before RIP processing. There is a need to do. Therefore, in the case of prepress 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 printing image data at the time of manuscript submission.
With such contour area extraction processing, halftone dots included in the contour area can be excluded from the halftone dot processing performed in steps subsequent to this step.
The details of the contour area extraction process will be described later.

<Grid generation>
Next, in step S803, first, in the image input from step S801, regions determined to require moire suppression are extracted, and a grid is generated in which each black halftone dot is divided into individual cells. . This grid determines the halftone dot to be processed and the adjacent halftone dots according to the AM screen halftone type set in each version, particularly the information input from the halftone dot generation condition input section 374 in FIG. generated according to the distance between the centers of the dots (halftone dot generation interval). Here, this grid is not a line drawn on the actual data as pixel information, but an index generated to visualize halftone dot processing.

An example of the grid is shown in FIG. 11, taking as an example the plane data in which the halftone dots are arranged in the direction of the angle θ 116 (this is called the “screen angle”) formed between the pointing lines 117 . As shown in FIG. 11, grid 111 includes multiple cells 113 . Here, the grid 111 is desirably generated so that each cell 113 can accommodate one halftone dot or less. Also, x114 shown in FIG. 11 is the interval of the grid 111 in the horizontal direction, and similarly, y115 represents the interval of the grid 111 in the vertical direction. These x114 and y115 are the "halftone dot generation interval". These halftone dot generation intervals are calculated by the following formulas.
x≈y≈resolution of halftone dot image [dpi]/number of lines of halftone dot image [lpi]

An example of a grid line generation method will now be described. When a grid is generated from plate making data, in an image before halftone dot processing by RIP processing, halftone dots in an AM screen are usually generated in an area where there is almost no change in density value (almost no structure exists). They are arranged at regular intervals as indicated by 11 . Therefore, all the halftone dots exist in the area (halftone dot area) surrounded by the grid set in the later process.

FIG. 12 shows a halftone dot image (a) with a density value of 50% or less and an image (b) of a halftone dot image obtained by reversing this and shifting the grid period by half the period. That is, in FIG. 12, the position of the blackened halftone dot in (a) and the position of the whitened halftone dot in (b) do not exist on the same grid, but are shifted by half a halftone dot period.

When processing such prepress data with greatly different density values, after the processing by the black halftone dot processing unit in FIG. A grid is generated by paying attention to the whitening halftone dots shown in FIG.
Specifically, attention is paid to an arbitrary blackened halftone dot in FIG. 12(a), and blackened halftone dots existing in the vicinity of the blackened halftone dot are extracted. Then, the central points of the target blackened halftone dot and the eight neighboring blackened halftone dots are calculated.
After that, the grid 111 is generated by connecting the calculated center points. If the grid 111 is generated from the halftone dot of interest in the x114 direction and the y115 direction at halftone dot period intervals, each blackened halftone dot area on the platemaking data is surrounded.
When the stencil data to be processed has a density value of 50% or higher, similarly to the above, focus on an arbitrary white halftone dot in FIG. to extract Then, each center point of the target whitening halftone dot and the eight neighboring whitening halftone dots is calculated. A grid can then be obtained by connecting the calculated center points.

Various methods for calculating the halftone dot center described above have been proposed. As an example, whitening pixels adjacent to a whitening pixel of interest are scanned without overlapping until there are no adjacent points, and the barycentric coordinates of the obtained pixel coordinate set are calculated as follows: There is a method of asking. However, the method is not limited to this method, and may be replaced with any method that reduces the processing load. Any grid generation method that reduces the processing load may be used instead of this method.

For example, in plate-making data with a density value of 50% or more, when the black halftone dot and the white halftone dot are in a positional relationship in which the halftone dot generation period is shifted from each other, the black halftone dot is first focused on, and the black halftone dot is By calculating the centers of the halftone dots and forming a line segment connecting these center points, this line segment can form a grid surrounding the whitening halftone dots.
Contrary to this, in the platemaking data with a density value of 50% or less, attention is focused on the whitening halftone dot, the center of the whitening halftone dot is calculated, and a line segment connecting these center points is formed. The minute can be a grid surrounding the blackened halftone dots.

Note that x114 and y116 may have the same value, and even if deviation is allowed within the range of the ratio of x: y = 0.9: 1.1 to x: y = 1.1: 0.9 good. Ideally, the inclination of the grid (screen angle θ116) should match the halftone dot generation condition input section 374 in FIG. 2, but a deviation of θ±1 degree may be allowed.

Note that the screen ruling of the AM screen in the embodiment of the present invention can be in the range of 60 lines or more. The halftone dot shape may be selected from square, elliptical, round, chain, TH mesh, and the like.

<Determining Whether Blackened Halftone Dot Processing is Possible>
In S804 of FIG. 9, it is determined whether or not to focus on the blackened halftone dots existing inside the halftone dot area surrounded by the grid 111 and perform processing. In general, as shown in FIG. 12, if the density value is 50% or less, the halftone dot is blackened, and if the density value is 50% or more, the whitened halftone dot. should be generated in size. In S804, it is determined whether or not processing is possible when the focus is placed on the black halftone dot as shown in FIG. 12A.

In S804, for the blackened halftone dot area generated in S803, first, the processing ratio of the blackened halftone dots to be processed is determined, and based on this processing ratio, the blackened halftone dots to be specifically processed are set to pseudorandom numbers. choose based on Here, the processing ratio can be set to any value within the range of greater than 0% and less than or equal to 100%. In addition, it has been confirmed that as the processing ratio is increased, the effect of suppressing moiré is gradually increased, and the feeling of blurring is also gradually increased. About 70 types of moiré samples were processed at varying ratios, and output printed matter was referenced. % or more and 80% or less, about 10 subjects evaluated that it was a well-balanced processing ratio in which a moire suppressing effect was obtained and the visibility of blurring was low.

In addition, regarding the above ratio, when processing is performed by narrowing down to the moire generation area, if the visibility of the blur feeling becomes dominant due to the emphasis on the moire suppression effect, for example, the contour part around the moire area is excluded. It is possible to soften the visibility of partial blurring by performing processing on a halftone dot area existing in an arbitrary area at an arbitrarily low ratio in stages from a set ratio. Further, the stepwise ratio described above can be set to a value greater than 0% and less than the value set in the moire occurrence area, and the number of steps to be changed is preferably 0 or more. When the number of stages to be changed is set to 2 or more, it is desirable to decrease the ratio as the region moves away from the moire generation area.

The halftone dot area selected at the above ratio is processed based on the grid processing internal 810 in FIG.
FIG. 10 is a flowchart for explaining the details of the processing in steps S804 and S805 of FIG.
At step S811 in FIG. 10, an image from which only halftone dot areas are extracted is input. FIG. 11 exemplifies an arbitrary blackened halftone dot as 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 enclosed by a grid 111 .

<Extraction of Blackened Pixel Candidates to be Removed>
In step S812 of FIG. 10, of the blackened pixels forming the blackened halftone dot, the blackened pixels existing in the pixel area inscribed in the grid 111 are extracted as the blackened pixels to be removed, and the coordinates of the blackened pixels are obtained. Here, removing a blackened pixel means converting the blackened pixel into a whitened pixel (conversion step).
Also, in the subsequent processing, any of the whitened pixels corresponding to the number of blackened pixels subjected to whitening conversion will be converted to blackened pixels according to the rules described below (filling step).

Transformation and interpolation of pixels will be described below with reference to FIGS. 13 and 15 as well.
FIG. 13 is a diagram showing an example of the initial state of halftone dots to be processed. In this example, a portion of the black halftone dot 212 is in contact with the grid 211 . Also, it is shown that whitened pixels 213 exist around the blackened halftone dots 212 .
FIG. 14 is a diagram showing an example of a region of pixels to be converted and a region of pixels to be interpolated for the halftone dots shown in FIG.
In FIG. 14, a blackened pixel 218 (area surrounded by thick lines) forming a blackened halftone dot existing in a pixel area 217 (area surrounded by dotted lines) inscribed in the grid is shown. That is, these blackened pixels 218 are candidates for conversion to whitened pixels. Then, the whitened pixels in the pixel area 219 (the shaded area) are the target of the blackened pixels. In other words, the pixel area to be interpolated is the halftone dot area 213 in FIG. 13 excluding the blackened halftone dot 212 and the pixel area 217 in contact with the grid.

<Verification of whitened pixels that can be converted to blackened pixels>
In step S813, the blackened pixels extracted in step S812 are removed (converted to whitened pixels), and it is determined whether or not the same number of converted whitened pixels can be converted (filled in) to blackened pixels. The determination method will be described with reference to FIG.
FIG. 15 shows the whitened pixel regions to be filled in by classifying them into two types, 221 for the first filling process and 222 for the second filling process.
When processing the halftone dot 212 in FIG. 15, whitening pixels in the pixel region 219 in FIG. 14 are converted into blackening pixels by the same number as the number of blackening pixels 218 to be converted into whitening pixels in FIG. That is, the whitened pixels are converted into blackened pixels to compensate for the blackened pixels.

However, whitening pixels adjacent to the halftone dot 212 are preferentially selected as conversion candidates. For example, in the example of FIG. 15, arbitrary pixels existing in a whitened pixel area 221 (pixel area indicated by horizontal hatching) adjacent to the halftone dot 212 are set as conversion candidates (candidates for the first filling process).
If all of the whitened pixel regions 221 have been converted to blackened pixels and there are still a number of pixels that need to be converted to blackened pixels, whitened pixel regions 222 adjacent to the whitened pixel region 221 (indicated by vertical hatching) Any pixel existing in the pixel region) is set as the next conversion candidate (candidate for the second filling step).
That is, when the number of pixels to be converted in the conversion process is larger than the number of whitening pixels adjacent to the halftone dot 212, first, the whitening pixels adjacent to the halftone dot 212 are used as filling candidates (first filling process ), and then a whitened pixel region 222 adjacent to the whitened pixel region 221 (pixel after filling) is selected as a filling candidate (candidate for the second filling step).

At this time, if the total number of pixels in the whitened pixel regions 221 and 222 illustrated in FIG. 15 is less than the total number of blackened pixels 218 to be replaced with whitened pixels, all of the blackened pixels 218 cannot be replaced with whitened pixels. It will happen. In that case, only blackened pixels 218 of the same number as the total number of pixels in the whitened pixel regions 221 and 222 may be blackened pixels to be removed. Alternatively, it may be determined that the halftone dot cannot be processed, and the removal of blackened pixels may be abandoned.
If the number of removed blackened pixels inscribed in the grid, i.e., the number of conversions to whitening pixels, is not the same as the number of whitening pixels converted to blackened pixels inside the grid, the internal density value will be within the halftone dot area before processing. In principle, it is desirable that the number of blackened pixels to be removed and the number of whitened pixels to be converted into blackened pixels be the same.

If it is determined in step S813 that all (or some) of the blackened pixels inscribed in the grid can be removed, the process proceeds to step S814. On the other hand, if it is determined that processing is impossible, the process proceeds to step S812 if there is a halftone dot area to be examined next, and to step S816 if there is not.

In step S814 of FIG. 10, the conversion of the blackened halftone dots made removable in step 813 into whitened pixels is performed. Then, a candidate for conversion to a black pixel is selected from the white pixel region 221 in contact with the black halftone dot 212 and conversion is executed (first filling step). In this case, the pixels to be converted may be randomly extracted based on pseudo-random numbers from among the pixel candidates to be converted, and the conversion candidates may be selected with any regularity. good too. However, if the method of selection is particularly random, it is difficult for periodicity to occur between halftone dot areas after processing, and moire suppression efficiency is improved.
Step S814 is repeatedly performed for each pixel, and is performed until step S815, which will be described later, determines that the filling is completed. Therefore, as already described in step S813, if the number of blackened halftone dots that can be removed is smaller than the number of pixels in the whitened pixel region 221, the pixels in the whitened pixel region 221 are converted into blackened pixels. Extract candidates for That is, whitening pixels to be converted to blackening pixels are preferentially selected in order of proximity to the blackening halftone dot.

If all the whitened pixels in the whitened pixel region 221 are converted to blackened pixels and the total number of blackened pixels 218 is less than the number of conversions, the whitened pixel region 222 is next converted to blackened pixels. Then, when the whitened pixel region 222 is all converted and the total number of blackened pixels 218 is less than the number of conversions, if there is a whitened pixel outside the whitened pixel region 222 that does not touch the grid, the whitened pixel is finally converted. Convert the region to blackened pixels. Whitening pixels are converted to blackening pixels in stages in the manner described above.
As described above, when selecting whitening pixels to be converted into blackening pixels from among a plurality of whitening pixel regions having the same priority for conversion to blackening pixels, pseudorandom numbers or the like are used for selection. is.

In step S815, the total number of blackened pixels 218 to be removed and the number of whitened pixels converted to blackened pixels are compared. If the number of whitened pixels converted to blackened pixels is less than the total number of blackened pixels 218 to be removed, the process proceeds to step S814. If the sum of the whitened pixels converted to blackened pixels is equal to the sum of the blackened pixels 118, the process proceeds to step S816.

In step S816, it is determined whether or not all of the blackened halftone dots determined to be removable in S813 have been processed. If there is a blackened halftone dot area for which processing has not been completed, the process proceeds to S812, and if all of the blackened halftone dots selected in S803 have been processed, the process proceeds to S817.

At S817, the prepress data in which the black halftone dots in the moire extraction region have been processed is output, and similarly becomes the output data of S804.

Returning to FIG. 9 again, the subsequent steps will be described.
In S805, the blackened halftone dot-processed platemaking data output from S804 or the blackened halftone dot unprocessed platemaking data output from S803 are plotted inside the halftone dot area surrounded by the grid 111 as in S803. It is determined whether or not to perform processing by paying attention to existing whitening halftone dots.

The processes of S805 and S806 are the same as the process of replacing all the black halftone dots with the white halftone dots in S803 and S804 described above, so description thereof will be omitted.
As described above, the positions of the white halftone dots are shifted from the black halftone dots by half a period, an example of which is shown in FIG. Grid generation for whitening halftone dots in a moiré extraction region is different from grid generation for black halftone dots. It is good to replace and generate.

In S807, the whitening halftone dot processed plate making data output from S806 or the whitening halftone unprocessed plate making data output from S805 is output.

As described above, the reason why the process focusing on the blackened halftone dots or the whitened halftone dots is performed is that the moiré area can be generated not only from the blackened halftone dots but also from the whitened halftone dots. is. In addition, although it has been confirmed that the black halftone dot processing S803 and S804 and the white halftone dot processing S805 and S806 are basically performed once, a sufficient effect can be obtained, but the output result is not sufficient. If possible, the order may be changed and each process may be performed multiple times.

<Details of outline extraction processing>
In addition, as described above, it is desirable not to perform moiré suppression on the area of the cell that overlaps with the outline peripheral portion extracted by an arbitrary method. This is because if the halftone dots included in the outline area are processed, the outline of the object, which is worthy of the high-frequency component with particularly high visibility, will be blurred, which may lead to quality deterioration.
In addition, after extracting the outline peripheral portion described above by an arbitrary method, the region may be subjected to enlargement/reduction processing as necessary. This is because if the extracted contour is too wide, the suppression effect may be weak, or if the extracted contour is too narrow, the deterioration of the periphery of the contour caused by suppression processing may become noticeable. be. By preventing the deterioration due to the above-described suppression processing of the periphery of the contour, it is possible to prevent the deterioration of the entire output (that is, the object).

In the following, the details of the contour region extraction processing will be described.
FIG. 17 is a diagram showing the flow of processing for extracting a contour area when print image data before halftone dotization is available. When printing image data before halftone dot processing is input, first, smoothing processing is performed to suppress noise in the image in advance. After that, a process of extracting a luminance change value is performed by a filter that quantifies the luminance change in the image. Then, a process of binarizing the luminance change value is performed by using a specific threshold value. As a result, the extracted contour area can be output.

The smoothing process described above may be freely selected by the user, but it is particularly desirable to use a Gaussian filter. A user may freely select a filter for quantifying luminance changes, but it is particularly desirable to use a sobel filter. Alternatively, the user may manually specify the outline without automatically extracting the outline.

FIG. 18 is a diagram showing a flow of processing for extracting a contour area when printing image data, which is data before halftone dot conversion, cannot be used. The order of processing is the same as in the case shown in FIG. 17, but the difference from the flow shown in FIG. In the smoothing process, there is a high possibility that halftone dot shapes remain. For this reason, it is necessary to perform smoothing at a strength that does not leave halftone dot shapes.
However, the smoothing process may be freely selected by the user, but it is particularly desirable to use a Gaussian filter. A user may freely select a filter for quantifying luminance changes, but it is particularly desirable to use a sobel filter. Alternatively, the user may manually specify the contour extraction without performing automatic processing. This point is the same as in the case of FIG.

19 and 20 are diagrams showing a specific example of contour extraction in the procedure shown in FIGS. 17 and 18. FIG. FIG. 19 shows printing image data 1910 before halftoning and prepress data 1920 after halftoning. As shown in FIG. 19, printing image data 1910 before halftone dot conversion is not represented by halftone dots, but is a normal image, and platemaking data 1920 is represented by halftone dots. there is

FIG. 20 shows an image 1911 after smoothing the printing image data 1910 before halftone dots shown in FIG. is a diagram showing an image 1921 of . As shown in FIG. 20, the smoothing process performed on the prepress data 1920 is stronger than the smoothing process performed on the printing image data 1910 before halftone processing. is desirable. This is because it is necessary to ensure that the halftone dot shape of the platemaking data 1920 does not remain. Therefore, the smoothing process for the prepress data is naturally stronger than the simple smoothing for the purpose of noise suppression performed on the printing image data 1910 before halftone dot conversion.

FIG. 21 is a diagram showing the result of extracting a contour area from the printing image data 1910 after smoothing and before halftone processing and the prepress data 1920 shown in FIG. . FIG. 21 shows an image 2110 obtained by extracting the contour area of the printing image data 1910 before halftone processing, and an image 2120 obtained by extracting the contour area of the prepress data 1920 .

FIG. 22 is a diagram showing an example of contour images 2210 and 2220 obtained by binarizing and extracting the image 2110 and the image 2120 shown in FIG. 21, respectively. Also, FIG. 23 is a diagram showing an overlapping image in which the contour images 2210 and 2220 shown in FIG. 22 are overlapped and displayed.
As shown in FIG. 23, a contour region 2310 (core portion) output from printing image data before halftone dotization and a contour region 2320 (portion sandwiching the core) output from platemaking data. , the contour region 2310 output from the printing image data before halftone dotization is extracted with higher accuracy (it is closer to the center than the contour region 2320 and is extracted as a thin line). ).

<Print unit>
Next, details of the printing unit and printing method will be described.
The printing unit 375 is a printing unit for printing the image data represented by halftone dots after the moire suppression generated by the moire suppression device 380 .
The printing unit 375 may print the image output from the image output unit 390 of the moiré suppression device 380, and after the image output from the image output unit 390 is returned to the client terminal 365, the client terminal Printing may be performed in response to H.365 requests.

Note that each functional unit included in the moiré suppression system 360 may be a software module that configures the moiré suppression application 350 shown in FIG. 7, or may be an independent dedicated hardware device. Also, the functional units described above may be implemented in the same computing environment or in distributed computing environments. For example, the halftone dot generation condition input unit 374 may be implemented in a remote server or client terminal 365, and other functional units may be implemented in the moiré suppression device 380. FIG.

Also, embodiments of the present invention are not limited to the configuration of the moire suppression system 360 described with reference to FIG. For example, any configuration is possible, such as a configuration in which the moire suppression device 380 is directly connected to the client terminal 365, or a configuration in which the moire suppression device 380 and the client terminal 365 are integrated.

<Printing method>
Next, with reference to FIGS. 24 to 29, a printing method that is a premise of the present invention will be described.
FIG. 24 is a schematic diagram of a printing press 50 for printing a design on the printing surface of a printing body 52. As shown in FIG. The printed body 52 is supplied from the transport port 51, and each ink set in the ink coating units 53 to 56 is applied to the printing surface of the printed body 52 inside each of the ink coating units 53 to 56. It is applied so that it is drawn according to the content to be expressed by printing. In this way, the printed matter on which the content to be expressed by printing is drawn on the printing surface of the printed body 52 by the ink applicator unit is conveyed to the discharge port 57 .

It is desirable to set the printing speed of the printer 50 to a value within the range of 200 m/min to 700 m/min. When printing at a speed higher than that, the transfer of ink may be affected by vibration of the machine or the like. In this case, halftone dot reproducibility is reduced, and color shift and moire are likely to occur with a printing machine.

Different inks are set for each of the ink applying units 53 to 56 . At least one or more ink applicator units 53 to 56 according to the embodiment of the present invention can be used, that is, at least one or more colors, and in particular, four colors of CMYK (referred to as R4C) are desirable. With regard to the application of ink using these four colors as an example, the ink application unit 53 may be K, the ink application unit 54 may be C, the ink application unit 55 may be M, and the ink application unit 56 may be Y. When printing is performed in this order, since K, which is most likely to affect moire, is printed first, it is possible to prevent occurrence of irregular moire.
It should be noted that if moire occurs irregularly, it may be difficult to specify the region where halftone dots are to be moved. In other words, printing from K, which tends to affect moire, makes it easier to identify the area where moire occurs.

The inks set in the ink application units 53 to 56 according to the embodiment of the present invention include, for example, general inks, process inks, gold inks, silver inks, Calton inks, fluorescent inks, offset inks, ultraviolet curable (UV ) inks, infrared drying (IR) inks, and the like. Further, the general ink may be a series of 20 to 50 colors provided by an ink manufacturer.

Also, the ink set in the ink applicator units 53 to 56 according to the embodiment of the present invention may be a composition. This composition may have, for example, a colorant component, a vehicle (varnish) component, or the like as an essence. The composition may also contain additional adjuvant ingredients. Also, the colorant component may be either an organic pigment or an inorganic pigment. The vehicle component may also contain resins and solvents. The adjuvant component may be added to enhance the friction resistance of the ink, and may be, for example, a wax, a surfactant, a gelling agent, or the like.

In addition, with the above-mentioned ink, there is a possibility that halftone dots become thick due to the fluidity of the ink used at the time of printing. The behavior of the printing ink may be adjusted each time. Also, in the halftone dot image, the halftone dots may be made smaller by the thickness of the print. Since the thickness of the halftone dot also varies depending on the amount of movement of the halftone dot, when moving the halftone dot by a large amount, the adjustment amount of the size of the halftone dot should be increased compared to the portion where the halftone dot is not moved. good too.

The printing method in the present invention may be a plate type or a plateless type. However, as an embodiment of the present invention, it is particularly desirable to use a plate type printing. The plate-type here may include lithographic printing, letterpress printing, intaglio printing, stencil printing, and the like. Lithographic printing is often called offset printing, letterpress printing is letterpress printing, intaglio printing is gravure printing, and stencil printing is screen printing. The moire suppressing means of the present invention may be applied to any printing method, but is particularly effective for lithographic printing.

The printed material 52 is a printed information sheet. 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 desirable that the printed material 52 be either uncoated printing paper or coated printing paper.

The uncoated printing paper may include, for example, printing paper A, printing paper B, printing paper C, D, and the like. The printing paper A is paper made from 100% bleached chemical pulp as a raw material, and is fine paper. The printing paper B is paper made by using bleached chemical pulp as a raw material in an amount of 70% or more, and is medium quality paper with a whiteness of 70%. The printing paper C is paper made by using 40% or more and less than 70% bleached chemical pulp as a raw material, and has a whiteness of about 65%. Printing paper D is paper made using less than 40% bleached chemical pulp as raw material and has a brightness of about 55%. The printing papers C and D are collectively low-grade papers.

Pulp is a fiber extracted from a raw material, and the main component is cellulose. The raw material may include, for example, wood, non-wood, waste paper, synthetic fibers, and the like. Wood pulp is obtained by pulping coniferous trees, broad-leaved trees, or the like. Non-wood pulp is pulped from plants, especially linters, kenaf, bagasse, bamboo and the like. Waste paper pulp is paper that has been deinked and repulped. Synthetic fiber pulp is obtained by pulping chemical synthetic fibers (rayon, vinylon, etc.). Pulp also includes mechanical pulp and chemical pulp. Mechanical pulp is pulp produced by mechanically grinding raw materials. Chemical pulp is pulp from which fibers have been chemically extracted. Bleached pulp is mechanical pulp or chemical pulp that has been bleached.

Coated printing papers may include, for example, art papers, coated papers, lightweight coated papers, lightly coated papers, and the like. Art paper is fine or medium quality paper coated with 40 g of coating agent ^per square meter on both sides. Coated paper is fine or medium quality paper coated with 20 g of coating agent ^per square meter on both sides. Lightweight coated paper is fine or medium quality paper with 15 g of coating agent ^per square meter on both sides. Lightly coated papers are fine or medium quality papers coated with up to 12 g of coating agent per square meter on ^both sides.

As for the printing paper, halftone dots tend to be thicker on uncoated printing paper than on coated printing paper. Among the uncoated printing papers, the possibility of dot gain occurring decreases in the order of printing paper D, printing paper C, printing paper B, and printing paper A. Among the coated printing papers, the possibility of the halftone dots becoming thicker decreases in the order of lightly coated paper, lightweight coated paper, coated paper, and art paper.

Depending on the type of printing paper described above, the degree of absorption of ink changes, and halftone dots tend to become thicker. Therefore, the number of screen lines to be used is taken into account and appropriately set depending on the object to be printed in commercial printing. The screen ruling may be 10 lines or more and less than 110 lines, for example, in the case of printing on low-grade paper. Also, in the case of printing on medium-quality paper, the number of screen lines may be 110 lines or more and less than 210 lines. Further, in the case of printing on high-quality paper, the number of screen lines may be 210 lines or more and less than 2000 lines.

25 is a schematic view of the interior of the inking units 53 to 56 of FIG. 24. FIG. First, the dampening water roller 63 causes the dampening water 64 to adhere to the printing plate 62 set on the plate cylinder 61 . Ink roller 65 then applies ink 66 to printing plate 62 . Next, the ink 66 is transferred (off) from the printing plate 62 with the ink 66 to the rubber blanket 67 . Further, the ink 66 is transferred (set) to the printed body 52 by pressing the printed body 52 against the rubber blanket 67 to which the ink 66 has been transferred by the impression cylinder 68 . As a result, the content to be expressed by printing is printed on the printed body 52 .

<Printing with a printing plate>
FIG. 26 is a diagram for explaining the printing plate 62. FIG. The printing plate 62 may be, for example, a PS plate, a CTP plate, or a wipe-on plate, but the PS plate is particularly desirable. In addition, the PS plate may be any of aluminum, stainless steel, and chromium, which are highly hydrophilic metals (a property in which the contact angle between the surface of the substance and water is close to 0 degrees), but aluminum is particularly desirable. . Moreover, the printing plate 62 may have a metal surface coated with an ultraviolet curable resin. FIG. 26 shows the developed surface of the printing plate 62, which is composed of a lipophilic area 71 representing the drawing content and a hydrophilic area 72 other than the lipophilic area.

FIG. 27 is a schematic diagram showing the flow up to development of the printing plate 62. As shown in FIG. First, on the printing plate 62 whose surface is coated with the ultraviolet curable resin 73, a plate-making film 76 composed of an area 74 representing the content of drawing and an area 75 not representing the drawing content is placed and vacuum-bonded. After that, the surface of the printing plate is exposed to ultraviolet rays by the light source lamp 77, so that the photosensitive portions on the surface of the ultraviolet curable resin 73 are rendered alkali-soluble. This light source lamp 77 may be, for example, a mercury lamp. In addition, when the photosensitive area of the PS plate after exposure is dissolved with a strong alkaline developer, the remaining area becomes the lipophilic area 71, and the dissolved area has the exposed metal surface and is hydrophilic. becomes a region 72 with . Thus, the printing plate 62 is plate-made.

28A and 28B are schematic diagrams until the dampening water 64 adheres to the printing plate 62. FIG. A dampening solution roller 63 applies dampening solution 64 to hydrophilic areas 72 on the surface of printing plate 62 . At this time, the dampening water 64 does not adhere to the oleophilic region 71 because of its low affinity for water.

FIG. 29 is a schematic diagram showing how the ink 66 adheres to the printing plate 62 . Ink roller 65 applies ink 66 to oleophilic areas 71 on the surface of printing plate 62 . At this time, since the ink 66 is repelled by the dampening water 64, the ink 66 does not adhere to the area 72 where the dampening water 64 is adhered.

The embodiments of the present invention have been described above. FIG. 30 illustrates the suppression effect obtained by this embodiment. It should be possible to confirm that the oblique striped pattern visible in FIG. 30(a) (image similar to FIG. 6(b)) is almost invisible as shown in FIG. 30(b).

The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the gist of the present invention.

Pseudorandom numbers according to the embodiment of the present invention (for example, a first pseudorandom number for determining the moving rate of halftone dots, a second pseudorandom number for determining the moving direction of halftone dots, and a moving amount of halftone dots) A third pseudo-random number for determining ) is the square picking method, the linear congruential method, the linear feedback shift register, the Mersenne twister, the multiplication with carry, the Xorshift, the Lagged Fibonacci method, the RANLUX, the Permuted congruential generator, Blum- It may be a value generated from either the Blum-Shub or Fortuna method.

When the moire suppression processing according to the embodiment of the present invention is implemented by a program, in order to control so that the same performance can be obtained for any prepress data, the pseudo-random numbers generated by the above-described method must be: Can create and operate random number tables. This random number table lists a plurality of predetermined random numbers. Therefore, by using random numbers extracted from the same random number table each time the processing of the embodiment of the present invention is performed, the same suppression performance can be obtained. Also, this random number table may be created and operated with a capacity suitable for the specifications of the computer owned by each user, for example, for executing the processing according to the embodiment of the present invention.

111 Grid 112 Blackened halftone dot 113 Cell 360 Moire suppression measure 365 Client terminal 370 Communication network 372 Data storage unit 374 Halftone dot generation condition input unit 375 Printing unit 380 Moiré suppression device 382 Blackened halftone dot area extraction unit 386 Whitened halftone dot area Extraction unit 390 Image output unit

Claims (9)

For an input image represented by halftone dots,
A grid generation step of generating a grid dividing a plurality of halftone dots each composed of one or more first pixels (blackened pixels or whitened pixels) into individual regions in the first region where moire occurs. and,
Of halftone dots separated by the grid, a first pixel in contact with the grid is a second pixel (when the first pixel is a blackened pixel, a whitened pixel; when the first pixel is a whitened pixel, a conversion step of converting to a blackened pixel);
selecting a candidate to be converted into a first pixel from among second pixels contacting the first pixel of the halftone dot divided by the grid based on the number of the converted pixels; A moire suppression method including a halftone dot processing step including a filling step. In the moire suppression method according to claim 1,
If the number of first pixels transformed by the transformation step is greater than the number of second pixels bordering the first pixels inside the grid, after the first filling step, a second Moire suppression, characterized by comprising a second filling step of selecting and converting a candidate to be converted from a second pixel contacting a post-filling pixel that has been converted from a pixel to a first pixel and has become a first pixel. Method. In the moire suppression method according to claim 1 or 2,
The converting step and the filling step are performed on an arbitrary ratio of halftone dots in the first region where the moiré occurs,
A moiré suppression method, wherein the first pixels to be subjected to the conversion step are selected by pseudo-random numbers based on an arbitrary ratio. In the moire suppression method according to any one of claims 1 to 3,
A moire suppression method, wherein the halftone dot processing step includes a contour exclusion step of excluding halftone dots included in a contour region of an image from targets of moire suppression processing. a halftone dot area extracting unit that extracts a halftone dot area by forming a grid that separates the halftone dots included in the platemaking data into individual areas;
Of the halftone dots in the halftone dot area, the first pixel in contact with the grid is the second pixel (when the first pixel is a black pixel, it is a white pixel; when the first pixel is a white pixel, it is a black pixel). converting second pixels contacting the first pixel of the grid-delimited halftone dot to the first pixel based on the number of the converted pixels; and a halftone dot processor for performing a first filling step of selecting and converting candidates. In the moire suppression device according to claim 5,
If the number of first pixels transformed by the transformation step is greater than the number of second pixels bordering the first pixels inside the grid, after the first filling step, a second A halftone dot processing unit that performs a second filling step of selecting and converting a candidate to be converted from a second pixel that is in contact with a post-filling pixel that has been converted from a pixel to a first pixel and that has become the first pixel. A moire suppressing device characterized by: In the moire suppression device according to claim 5 or 6,
performing the converting step and the filling step on an arbitrary ratio of halftone dots in the first region where the moire occurs;
A moire suppression apparatus, wherein the first pixels to be subjected to the conversion step are selected by a pseudo-random number based on an arbitrary ratio. In the moire suppression device according to any one of claims 5 to 7,
A moire suppression device, comprising: a contour region extracting unit that extracts a contour region from an input image. A moire suppression device according to any one of claims 5 to 8;
a halftone dot generation condition input unit;
a data storage unit;
A moire suppression system comprising a printing unit.

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