Mixed screening method for color newspaper printing
By using the phase automatic modulation and screening method of pentagonal grid in color newspaper printing, the visual discontinuity and moiré problems in traditional hybrid screening technology are solved, and higher precision dot control and color management are achieved. Improve the quality of color prints.
Patent Information
- Application Number
- CN202411441211.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-16
- Publication Date
- 2025-01-14
AI Technical Summary
Traditional hybrid screening technology has problems of visual discontinuity, moiré and uneven color transitions in color newspaper printing, especially in high-speed printing, dot expansion and rose patterns are difficult to avoid.
Using the tiling method of pentagonal mesh, the phase automatic modulation grid is constructed to form a hybrid grid technology with double amplitude modulation mutual embedding. The threshold matrix is constructed through pure circle dots and four-color preset grid angles to realize the CMYK Color mode mixing and screening processing.
It effectively reduces the formation of moiré and rose patterns in traditional AMM screens, achieves a demoiré effect equivalent to FM screens, and improves the image clarity and color performance of color prints.
Smart Images
Figure CN119316528A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of printing screening, in particular to a mixed screening method for color newspaper printing. Background Art
[0002] The hybrid screening technology used in color newspaper printing is a key method to improve the quality of printed images and color performance. Traditional screening technologies usually have two forms: amplitude modulation screening (AM) and frequency modulation screening (FM), which respectively make different adjustments in dot size and dot distribution. In recent years, with the development of color printing technology, the hybrid screening method combines AM and FM screening technologies to improve the quality of color prints, especially in the field of color newspaper printing. The hybrid screening method can better control color, restore details, improve image clarity, and reduce printing defects such as moiré.
[0003] The core idea of hybrid screening technology is to utilize the stability and operability of AM screening while giving full play to the advantages of FM screening in highlight and shadow levels. Specifically, hybrid screening technology can achieve high-line-count fine reproduction while maintaining good printability by combining AM and FM dots in the same image. However, despite the obvious advantages of hybrid screening technology in color newspaper printing, there are still some problems and challenges. For example, when traditional AM screening and traditional FM screening are combined into hybrid screening, there will be obvious visual discontinuity and obvious moiré at the junction of the two. In addition, due to the high printing speed of color newspapers and the relatively low paper quality, it is difficult for hybrid screening technology to completely avoid the problems of uneven color transition and dot enlargement in high-speed printing.
[0004] The current research status shows that the application of hybrid screening technology has achieved certain success in commercial printing. For example, Agfa's Sublima screening technology and Screen's Spekta screening technology are both successful application cases of hybrid screening technology. Among them, Sublima screening technology uses AM screening in the middle tone of 10%-90%, and FM screening in 0-10% and 90%-100%, that is, the smallest dot that can be expressed by printing is used as the dividing point, and the dots above the dividing point are AM dots, and the dot size below the dividing point is kept unchanged, and the position corresponds to the AM dots. The distribution of the FM dots is precisely calculated, and the number of dots is changed by reducing the dots at the original AM dot position to express the FM level, thereby achieving a perfect mixture of FM and AM and eliminating obvious boundaries; Spekta screening technology also uses FM screening in the 0-10% and 90-99% replication areas, and AM circular dot screening in the range of 10-90%. The difference is that all dots within the total dot range are randomly distributed, so there is no restriction on the screening angle between different colors, which can eliminate obvious rose spots and moire.
[0005] Therefore, with the advancement of digital technology, it is urgent to develop a new hybrid screening algorithm and digital preprocessing technology to achieve higher-precision dot control and color management, so as to further improve the application effect of hybrid screening technology in color newspaper printing. Summary of the invention
[0006] The object of the present invention is to provide a hybrid screening method for color newspaper printing, which obtains a phase automatic modulation screening method based on traditional amplitude modulation screening by establishing a pentagonal grid tile, forming a hybrid screening method with double amplitude modulation interlocking, thereby reducing the formation of moiré and rose patterns in traditional amplitude modulation screening in an orderly manner, achieving an effect equivalent to that of frequency modulation screening, and solving the problems raised in the above-mentioned background technology.
[0007] In order to solve the above technical problems, the technical solutions provided by the present invention are as follows: A hybrid screening method for color newspaper printing, by establishing a pentagonal seamless tile grid, using pure circular dots as the grid shape, to form a threshold matrix for hybrid screening, specifically comprising the following steps: S1. Obtaining the minimum tiling unit: seamlessly tiling with a pentagon as the grid shape, and obtaining the minimum tiling unit when the grid is seamlessly tiled; S2. Obtaining a threshold matrix: Based on the minimum tile unit obtained in S1, a different threshold matrix for mixed screening of C, M, Y, K four-color separation sheets is constructed by combining the pure circular dot grid set in the pentagonal grid and the preset screening angles of C, M, Y, and K four-color separation sheets; S3. Obtaining a halftone image: Using the threshold matrix corresponding to the C, M, Y, and K four-color separation obtained in S2, a color image in the CMYK color mode is subjected to mixed screening to obtain a halftone color image after screening; S4. Plate making and output printing: The halftone color image obtained in S3 is combined with other text plates to form a plate making file, and the plate making and output printing plates are used for color newspaper printing.
[0008] Furthermore, the pentagonal mesh in step S1 is a convex pentagon, and its specific shape is: the two end points of the base are respectively connected to one of the end points of the second side and the third side, the other end point of the second side is connected to one of the end points of the fourth side, the other end point of the third side is connected to one of the end points of the fifth side, and the other end points of the fourth side and the fifth side are connected to form the vertices of the pentagon, wherein the lengths of the second, third, fourth and fifth sides are equal and are times the length of the base. times, the included angles between the bottom side and the second side, between the bottom side and the third side, between the fourth side and the fifth side are all 120°, and the included angles between the second side and the fourth side, between the third side and the fifth side are all 90°.
[0009] Furthermore, the method for seamlessly tiling the pentagonal grid in step S1 is: S11. With the base of the first pentagon as the axis of symmetry, a second pentagon is arranged at its mirror image position, and the bases of the two pentagons completely overlap; S12. The vertex of the third pentagon coincides with one endpoint of the base of the first pentagon in step S11 and the fourth side of the third pentagon completely coincides with the second side of the first pentagon, the vertex of the fourth pentagon coincides with the other endpoint of the base of the first pentagon in step S11 and the fifth side of the fourth pentagon completely coincides with the third side of the first pentagon; S13. Using the new hexagon formed by the four pentagons tiled together in steps S11 and S12 as the basic unit, perform seamless tiling until the required seamless tiling size is obtained; S14. Divide the seamlessly tiled grid into a plurality of seamlessly tiled minimum tiling units, wherein the boundary of the minimum tiling unit is a rectangle, and each minimum tiling unit comprises: a hexagon, which is a hexagonal basic unit composed of four pentagons in step S13, and eight 1 / 2 pentagons, wherein four 1 / 2 pentagons are located above the hexagon, and the other four 1 / 2 pentagons are located below the hexagon, wherein the pentagonal grid is divided into two equal parts using the height on the bottom side of the pentagon as a cutting line.
[0010] Furthermore, the specific method of obtaining the threshold matrix in step S2 is: S21. Using the minimum tiling unit obtained in S14 as the minimum tiling threshold matrix, setting pure circular dots in the pentagonal grid in the minimum tiling threshold matrix; S22. The threshold change contour line is formed by radiating outward from the center of the pure circular grid point, and the radiation boundary of the threshold change contour line is a pentagonal grid; S23. Starting from the center of the circle, the thresholds of each pixel are set outward from the starting point along the threshold change contour line, and the threshold value at the starting point is the smallest; S24. After setting the thresholds of each pixel in each pentagonal grid part in the minimum tile threshold matrix, a minimum tile threshold matrix is formed; S25. The minimum tiling threshold matrix obtained in step S24 is tiled in an array, and the large threshold matrix obtained by tiling is rotated according to the preset screening angles of the C, M, Y, and K four-color separations, and is cropped according to the size of the image to be halftoned to obtain different threshold matrices for mixed screening of the C, M, Y, and K four-color separations.
[0011] Furthermore, in step S21, the pure circular dots are arranged in the pentagonal grid, and the centers of the pure circular dots are located at the height on the bottom edge of the pentagonal grid.
[0012] Furthermore, the center of the pure circular dots set in the pentagonal grid in step S21 can be moved at the height on the bottom edge of the pentagonal grid.
[0013] The beneficial effects of the present invention are: The present invention obtains a phase automatic modulation screening method based on traditional amplitude modulation screening by establishing a tiling of pentagonal grids, and forms a hybrid screening method of double amplitude modulation interlocking, thereby reducing the formation of moiré and rose patterns of traditional amplitude modulation screening in an orderly manner, and achieving the effect of removing moiré patterns equivalent to that of frequency modulation screening. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 A schematic diagram of a pentagonal grid and pure circular dots in the grid according to the present invention; Figure 2 A schematic diagram of a new hexagonal tiling unit composed of four pentagons of the present invention; Figure 3 A schematic diagram of a minimum tiling unit with a rectangular boundary when a pentagonal grid is seamlessly tiled according to the present invention; Figure 4 It is a schematic diagram of the threshold value change contour lines in the minimum tiling threshold value matrix of the present invention; Figure 5 A schematic diagram of the distribution of hybrid screening dots of the present invention; Figure 6 It is a schematic diagram of a pattern of connecting the centers of dots in adjacent pentagonal grids in the hybrid screening of the present invention; Figure 7 It is a schematic diagram of the dot distribution and shape when the mixed screening has different gradations according to the present invention; Figure 8 It is a schematic diagram of the effect of the hybrid screening of the present invention and the traditional amplitude modulation screening when four colors are superimposed.
[0015] In the figure: 1. pentagon, 11. base, 12. second side, 13. third side, 14. fourth side, 15. fifth side, 16. vertex, 17. height; 2. Pure circular dots, 21. Center of circle, 3. Hexagon, 4. Minimum tiling unit, 5. Primary periodic line, 6. Secondary primary periodic line, 7. Secondary secondary periodic line. DETAILED DESCRIPTION
[0016] In order to make the technical problems solved by the present invention, the technical solutions adopted and the technical effects achieved clearer, the technical solutions of the present invention are further described below in conjunction with the accompanying drawings and through specific implementation methods. It is understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for the convenience of description, only the parts related to the present invention are shown in the accompanying drawings, not all.
[0017] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
[0018] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.
[0019] In the description of this embodiment, the terms "upper", "lower", "right", etc., directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.
[0020] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.
[0021] like Figure 1-Figure 8 As shown, this embodiment discloses a hybrid screening method for color newspaper printing, by establishing a seamless tiled grid of pentagons 1 and using pure circular dots 2 as a mesh shape to form a threshold matrix for hybrid screening, specifically including the following steps: S1. Obtaining a minimum tiling unit 4: seamlessly tiling the pentagon 1 as the grid shape, and obtaining a minimum tiling unit 4 when the grid is seamlessly tiled; S2. Obtaining a threshold matrix: Based on the minimum tile unit 4 obtained in S1, combined with the pure circular dot 2 mesh set in the pentagonal grid 1 and the preset screening angles of the C, M, Y, and K four-color separations, different threshold matrices for mixed screening of the C, M, Y, and K four-color separations are formed; S3. Obtaining a halftone image: Using the threshold matrix corresponding to the C, M, Y, and K four-color separation obtained in S2, a color image in the CMYK color mode is subjected to mixed screening to obtain a halftone color image after screening; S4. Plate making and output printing: The halftone color image obtained in S3 is combined with other text plates to form a plate making file, and the plate making and output printing plates are used for color newspaper printing.
[0022] like Figure 1 As shown, the pentagon 1 mesh in step S1 is a convex pentagon, and its specific shape is: the two end points of the base 11 are respectively connected to one of the end points of the second side 12 and the third side 13, the other end point of the second side 12 is connected to one of the end points of the fourth side 14, the other end point of the third side 13 is connected to one of the end points of the fifth side 15, and the other end points of the fourth side 14 and the fifth side 15 are connected to form the vertex 16 of the pentagon 1, wherein the side lengths of the second side 12, the third side 13, the fourth side 14 and the fifth side 15 are equal and are 1 / 2 of the length of the base 11. times, the included angles between the bottom side 11 and the second side 12, the included angles between the bottom side 11 and the third side 13, the fourth side 14 and the fifth side 15 are all 120°, and the included angles between the second side 12 and the fourth side 14, and between the third side 13 and the fifth side 15 are all 90°.
[0023] In order to obtain the minimum tile unit 4, the method for seamless tiling of the pentagon 1 grid in step S1 is: S11. With the base of the first pentagon 1 as the axis of symmetry, a second pentagon 1 is arranged at its mirror image position, and the bases 11 of the two pentagons 1 completely overlap; S12. The vertex 16 of the third pentagon 1 coincides with one endpoint of the base 16 of the first pentagon 1 in step S11 and the fourth side 14 of the third pentagon 1 completely coincides with the second side 12 of the first pentagon 1, the vertex 16 of the fourth pentagon 1 coincides with the other endpoint of the base 11 of the first pentagon 1 in step S11 and the fifth side 15 of the fourth pentagon 1 completely coincides with the third side 13 of the first pentagon 1; S13. A new hexagon 3 composed of four pentagons 1 tiled together in steps S11 and S12 is used as a basic unit for seamless tiling. The hexagon 3 basic unit is as follows: Figure 2 as shown, until the desired seamless tiling size is obtained; S14. Divide the seamlessly tiled grid into a plurality of seamlessly tiled minimum tile units 4, wherein the boundary of the minimum tile unit 4 is a rectangle, and each minimum tile unit 4 comprises: a hexagon 3, wherein the hexagon 3 is a hexagonal basic unit composed of four pentagons 1 in step S13, and eight 1 / 2 pentagons 1, wherein four 1 / 2 pentagons 1 are located above the hexagon 3, and the other four 1 / 2 pentagons 1 are located below the hexagon 3, wherein the height 17 on the bottom edge 11 of the pentagon 1 is used as a cutting line to divide the pentagon 1 grid into two equal parts, as shown in the following example. Figure 3 shown.
[0024] Furthermore, the specific method of obtaining the threshold matrix in step S2 is: S21. Taking the minimum tiling unit 4 obtained in S14 as the minimum tiling threshold matrix, setting a pure circular dot 2 in the pentagonal grid 1 in the minimum tiling threshold matrix; S22. The threshold change contour line is formed by radiating outward from the center 21 of the pure circular grid point 2. The radiation boundary of the threshold change contour line is a pentagonal grid 1. Specifically, Figure 4 As shown; S23. Starting from the center of the circle 21, the threshold of each pixel is set outward from the starting point along the threshold change contour line, and the threshold value at the starting point is the smallest; S24. After setting the thresholds of each pixel in each pentagonal 1 grid part in the minimum tile threshold matrix, a minimum tile threshold matrix is formed; S25. The minimum tiling threshold matrix obtained in step S24 is tiled in an array, and the large threshold matrix obtained by tiling is rotated according to the preset screening angles of the C, M, Y, and K four-color separations, and is cropped according to the size of the image to be halftoned to obtain different threshold matrices for mixed screening of the C, M, Y, and K four-color separations.
[0025] Furthermore, in step S21, the pure circular dots 2 are arranged in the pentagonal grid 1, and the center 21 of the pure circular dots 2 is located on the height 17 on the bottom 11 of the pentagonal grid 1. Specifically, the center 21 coincides with the midpoint of the height 17. Figure 1 shown.
[0026] like Figure 5As shown in the figure, it is a schematic diagram of the hybrid screening dot distribution of the present invention. The pentagon 1 grid is not shown in this figure. It can be seen from the figure that the distribution of the hybrid screening dots of the present invention is different from the distribution law of the traditional amplitude modulation screening dots, but still presents a certain amplitude modulation screening law. The distribution of the main period line 5 shown in the T period in the figure is a relatively macroscopic amplitude modulation screening distribution law. Although the main period line 5 is a distribution period established based on the midline of the secondary one-period line 6 of the T1 period and the secondary two-period line 7 of the T2 period, the center 21 of the first pure circular dot 2 in the first row from top to bottom in the figure is located at the intersection of the two secondary one-period lines 6; the center 21 of the second pure circular dot 2 in the first row is located at the intersection of a secondary one-period line 6 and a secondary two-period line 7; the center 21 of the first pure circular dot 2 in the second row is located at the intersection of a secondary one-period line 6 and a secondary two-period line 7; the center 21 of the second pure circular dot 2 in the second row is located at the intersection of two secondary two-period lines 7; the positions of these four pure circular dots 2 constitute the smallest unit of a repeated array.
[0027] like Figure 6 As shown, the centers 21 of the pure circular dots 2 in the grids of two adjacent pentagons 1 are connected together, and each center 21 has five connecting lines radiating to the periphery. The two adjacent pentagons 1 here refer to two pentagons 1 with common sides, and two pentagons 1 without common sides are considered to be non-adjacent. As can be seen from the figure, the pattern formed by connecting the centers 21 of the pure circular dots 2 is a seamless tile pattern composed of regular triangles and regular quadrilaterals, and the side lengths of the regular triangles and regular quadrilaterals are the same.
[0028] like Figure 7 The figure is a schematic diagram of the dot distribution and shape when the mixed screening has different gradations according to the present invention; Figure 8 The effect comparison of the hybrid screening of the present invention and the traditional amplitude modulation screening when four colors are superimposed is shown in the figure, wherein the left half is the dot distribution effect diagram after the hybrid screening of the present invention is superimposed with four colors, and the right half is the dot distribution effect diagram after the traditional amplitude modulation screening is superimposed with four colors, wherein the screening angles in the two screening methods are: C screening angle 22°, M screening angle 68°, Y screening angle 0°, K screening angle 45°. Obviously, the dot distribution after the four colors are superimposed in the hybrid screening method of the present invention presents a frequency modulation screening dot distribution effect, which significantly reduces the generation of moiré and rose patterns in the traditional amplitude modulation screening.
[0029] The above embodiments are only to illustrate the basic principles and characteristics of the present invention. The present invention is not limited by the above embodiments. Without departing from the spirit and scope of the present invention, the present invention may be subject to various changes and modifications, which are within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.
Claims
1. A hybrid screening method for color newspaper printing, by establishing a pentagonal seamless tiled grid, with pure circular dots as the mesh shape, to form a threshold matrix for hybrid screening, characterized in that: The specific steps include: S1. Obtaining the minimum tiling unit: seamlessly tiling with a pentagon as the grid shape, and obtaining the minimum tiling unit when the grid is seamlessly tiled; S2. Obtaining a threshold matrix: Based on the minimum tile unit obtained in S1, a different threshold matrix for mixed screening of C, M, Y, K four-color separation sheets is constructed by combining the pure circular dot grid set in the pentagonal grid and the preset screening angles of C, M, Y, and K four-color separation sheets; S3. Obtaining a halftone image: Using the threshold matrix corresponding to the C, M, Y, and K four-color separation obtained in S2, a color image in the CMYK color mode is subjected to mixed screening to obtain a halftone color image after screening; S4. Plate making and output printing: The halftone color image obtained in S3 is combined with other text plates to form a plate making file, and the plate making and output printing plates are used for color newspaper printing.
2. The hybrid screening method for color newspaper printing according to claim 1, characterized in that: The pentagonal mesh in step S1 is a convex pentagon, and its specific shape is: the two end points of the base are respectively connected to one of the end points of the second side and the third side, the other end point of the second side is connected to one of the end points of the fourth side, the other end point of the third side is connected to one of the end points of the fifth side, and the other end points of the fourth side and the fifth side are connected to form the vertices of the pentagon, wherein the side lengths of the second, third, fourth and fifth sides are equal and are the length of the base side. times, the included angles between the bottom side and the second side, between the bottom side and the third side, between the fourth side and the fifth side are all 120°, and the included angles between the second side and the fourth side, between the third side and the fifth side are all 90°.
3. The hybrid screening method for color newspaper printing according to claim 1, characterized in that: The method for seamless tiling of the pentagonal grid in step S1 is: S11. With the base of the first pentagon as the axis of symmetry, a second pentagon is arranged at its mirror image position, and the bases of the two pentagons completely overlap; S12. The vertex of the third pentagon coincides with one endpoint of the base of the first pentagon in step S11 and the fourth side of the third pentagon completely coincides with the second side of the first pentagon, the vertex of the fourth pentagon coincides with the other endpoint of the base of the first pentagon in step S11 and the fifth side of the fourth pentagon completely coincides with the third side of the first pentagon; S13. Using the new hexagon formed by the four pentagons tiled together in steps S11 and S12 as the basic unit, perform seamless tiling until the required seamless tiling size is obtained; S14. Divide the seamlessly tiled grid into a plurality of seamlessly tiled minimum tiling units, wherein the boundary of the minimum tiling unit is a rectangle, and each minimum tiling unit comprises: a hexagon, which is a hexagonal basic unit composed of four pentagons in step S13, and eight 1 / 2 pentagons, wherein four 1 / 2 pentagons are located above the hexagon, and the other four 1 / 2 pentagons are located below the hexagon, wherein the pentagonal grid is divided into two equal parts using the height on the bottom side of the pentagon as a cutting line.
4. The hybrid screening method for color newspaper printing according to claim 1, characterized in that: The specific method of obtaining the threshold matrix in step S2 is: S21. Using the minimum tiling unit obtained in S14 as the minimum tiling threshold matrix, setting pure circular dots in the pentagonal grid in the minimum tiling threshold matrix; S22. The threshold change contour line is formed by radiating outward from the center of the pure circular grid point, and the radiation boundary of the threshold change contour line is a pentagonal grid; S23. Starting from the center of the circle, the thresholds of each pixel are set outward from the starting point along the threshold change contour line, and the threshold value at the starting point is the smallest; S24. After setting the thresholds of each pixel in each pentagonal grid part in the minimum tile threshold matrix, a minimum tile threshold matrix is formed; S25. The minimum tiling threshold matrix obtained in step S24 is tiled in an array, and the large threshold matrix obtained by tiling is rotated according to the preset screening angles of the C, M, Y, and K four-color separations, and is cropped according to the size of the image to be halftoned to obtain different threshold matrices for mixed screening of the C, M, Y, and K four-color separations.
5. The hybrid screening method for color newspaper printing according to claim 1, characterized in that: In step S21, the pure circular dots are arranged in the pentagonal grid, and the centers of the pure circular dots are located at the height on the bottom edge of the pentagonal grid.
6. The hybrid screening method for color newspaper printing according to claim 1, characterized in that: In step S21, the pure circular dots are arranged in the pentagonal grid, and the center of the pure circular dots can move on the height on the bottom side of the pentagonal grid.