CN112848727A - Screening method, printing method, system and device for image halftone color generation - Google Patents
Screening method, printing method, system and device for image halftone color generation Download PDFInfo
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Abstract
The embodiment of the application provides a screening method, a printing method, a system and a device for displaying the color of the halftone of an image, wherein the method comprises the steps of dividing each pixel in the image to be screened into a plurality of grids, and forming a grid which corresponds to the pixel and is composed of the grids; respectively calculating thresholds of the grids according to a mesh point function to obtain a grid threshold matrix, wherein the mesh point function comprises a first function and a second function, the area of the mesh point expanded to a grid central point in a four-corner part is determined through the first function, and the area of the central mesh point expanded to a grid vertex is determined through the second function; according to the grid threshold matrix, carrying out normalization processing on the image to be screened to obtain a screened image; and printing the screened image to obtain a printed image, so that dot lapping angles can be avoided, and the gradation level of the printed image is uniformly changed.
Description
Technical Field
The embodiment of the application relates to the field of printing, in particular to a screening method, a printing method, a system and a device for image halftone color generation.
Background
In the prior art, the color generation mode of the circular screen dots corresponding to one grid is centered on the center of the grid, and the radius of the screen dots is gradually increased along with the increase of the area rate of the screen dots. The dot function is: z is 1- (x)2+y2)。
Therefore, in the printing process, when the area of a circular dot is larger than a certain value, a certain part of the outline of the circular dot is connected with the grid boundary where another circular dot is located, so that a 'lap angle' occurs, the printed color is changed suddenly, the area rate is increased more or less suddenly, the increase destroys the uniform change of the tone, and the tone reproduction of the image is not favorable.
Therefore, how to improve the tone uniformity variation of the circular dots in the printing process becomes an urgent problem to be solved.
Disclosure of Invention
The embodiment of the application provides a screening method, a printing method, a system and a device for the color generation of an image halftone, and at least the influences of density jump and severe color change caused by circular dot expansion can be avoided through some embodiments of the application, so that the color reproduction gradation and the color reproduction precision are better ensured.
In a first aspect, an embodiment of the present application provides a screening method for displaying halftone of an image, where the method includes: dividing each pixel in an image to be screened into a plurality of grids to form a grid which is corresponding to the pixel and consists of the grids; respectively calculating thresholds of the grids according to a mesh point function to obtain a grid threshold matrix, wherein the mesh point function comprises a first function and a second function, the area of the mesh point expanded to a grid central point in a four-corner part is determined through the first function, and the area of the central mesh point expanded to a grid vertex is determined through the second function; and normalizing the image to be screened according to the grid threshold matrix to obtain a screened image.
Therefore, the dot area expansion is simultaneously carried out through the two dot functions, the four-corner partial dots in the grid can be expanded to the grid central point, and the grid central dots are expanded to the grid top points, so that the influences of density jump and severe color change caused by dot expansion can be avoided, the color reproduction gradation and the color reproduction precision can be better ensured, and the defect that the color printing transition of amplitude modulation halftone is not soft can be solved.
With reference to the first aspect, in one embodiment, the halftone dot function is obtained by: constructing a circular boundary by taking the vertex of the grid as a circle center, wherein the part between the circular boundary and the vertex of the grid is a first area, and the part between the circular boundary and the center point of the grid is a second area; and according to the extreme value of the threshold, constructing the first function in the first area and constructing the second function in the second area.
With reference to the first aspect, in an embodiment, the constructing the first function in the first region and the constructing the second function in the second region according to the extreme value of the threshold includes: defining a threshold on the circular boundary as a minimum of the threshold; defining the sum of the thresholds at the center point of the mesh and the thresholds at the vertices of the mesh as maxima of the thresholds; and constructing the first function in the first area and constructing the second function in the second area according to the maximum value and the minimum value.
Therefore, the accuracy of calculating the threshold matrix can be guaranteed by constructing the dot function, and the dot function is divided into the first function and the second function, so that the dot function can be bounded by the circular boundary, the first area and the second area can be expanded to different directions simultaneously in the printing process, the density jump and the color intensity of dots are avoided, and the defect that the color printing transition of amplitude modulation halftone is not soft is overcome.
With reference to the first aspect, in one embodiment, the first function is characterized by the following formula:
wherein Z represents a threshold value of the plurality of grids, x represents an abscissa corresponding to each of the plurality of grids, y represents an ordinate corresponding to each of the plurality of grids, and r represents a radius of a mesh point where each of the plurality of grids is located.
Therefore, the coordinates of the grids in the first area are substituted into a formula for calculation, so that the threshold values of the grids corresponding to the four corners of the grids can be obtained, the threshold value matrix of the grids is obtained, whether each grid in the first area is colored or not is judged, the accuracy of ink jet is improved, and the overlapping of circular mesh points in two adjacent grids caused by the fact that only the mesh points in the center of the grids are expanded towards the periphery in the related technology is effectively avoided.
With reference to the first aspect, in one embodiment, the second function is characterized by the following formula:
wherein Z represents a threshold value of the plurality of grids, x represents an abscissa corresponding to each of the plurality of grids, y represents an ordinate corresponding to each of the plurality of grids, and r represents a radius of a mesh point where each of the plurality of grids is located.
Therefore, the area increasing mode that the mesh points at the center of the grid simultaneously expand towards the periphery is different from the area increasing mode that the mesh points at the center of the grid simultaneously expand towards the periphery in the related technology, the growing image of the mesh points at the center of the grid in the embodiment of the application is a section of circular arc, and the circular arc is tangent to the horizontal line and the vertical line at the center of the grid, so that the defect that the color printing transition of the amplitude modulation halftone is not soft is overcome, and meanwhile, the influence of density jump and severe color change caused by the enlargement of the mesh points can be avoided, and the color reproduction gradation and the color reproduction precision are better guaranteed.
With reference to the first aspect, in an implementation manner, the screening the image to be screened according to the grid threshold matrix to obtain a screened image includes: carrying out normalization calculation on each threshold value of the grid threshold value matrix to obtain a normalized threshold value; respectively comparing the normalized threshold with the area ratio of the dots to obtain comparison results; and screening the image to be screened according to the comparison result to obtain a screened image.
Therefore, the grid threshold matrix and the dot area rate value can be conveniently compared through normalized calculation, and calculation is simplified.
In a second aspect, embodiments of the present application provide a method of image printing, the method comprising: screening each ink channel for printing color by adopting the method in the first aspect to obtain a screened image; and printing the screened image of each ink channel to obtain a printed image.
In a third aspect, an embodiment of the present application provides a system for image printing, including: a processing apparatus and a printing press; the processing device is configured to implement the method for image screening according to the first aspect and all embodiments thereof; the printer for carrying out the method of image printing according to the second aspect.
In a fourth aspect, an embodiment of the present application provides a screening apparatus for halftone color generation of image screening, the apparatus including: the dividing module is configured to divide each pixel in the image to be screened into a plurality of grids to form a grid which corresponds to the pixel and is composed of the grids; a calculating module configured to calculate thresholds of the plurality of grids respectively according to a mesh point function to obtain a grid threshold matrix, wherein the mesh point function includes a first function and a second function, an area of a quadrangle partial mesh point expanding to a mesh center point is determined through the first function, and an area of a central mesh point expanding to the mesh vertex is determined through the second function; and the screening module is configured to perform normalization processing on the image to be screened according to the grid threshold matrix to obtain a screened image.
With reference to the fourth aspect, in one embodiment, the halftone dot function is obtained by: constructing a circular boundary by taking the vertex of the grid as a circle center, wherein the part between the circular boundary and the vertex of the grid is a first area, and the part between the circular boundary and the center point of the grid is a second area; and according to the extreme value of the threshold, constructing the first function in the first area and constructing the second function in the second area.
With reference to the fourth aspect, in one embodiment, the calculation module is configured to define the threshold on the circular dividing line as a minimum value of the threshold; defining the sum of the thresholds at the center point of the mesh and the thresholds at the vertices of the mesh as maxima of the thresholds; and constructing the first function in the first area and constructing the second function in the second area according to the maximum value and the minimum value.
With reference to the fourth aspect, in one embodiment, the first function is characterized by the following formula:
wherein Z represents a threshold value of the plurality of grids, x represents an abscissa corresponding to each of the plurality of grids, y represents an ordinate corresponding to each of the plurality of grids, and r represents a radius of a mesh point where each of the plurality of grids is located.
With reference to the fourth aspect, in one embodiment, the second function is characterized by the following formula:
wherein Z represents a threshold value of the plurality of grids, x represents an abscissa corresponding to each of the plurality of grids, y represents an ordinate corresponding to each of the plurality of grids, and r represents a radius of a mesh point where each of the plurality of grids is located.
With reference to the fourth aspect, in an embodiment, the screening module is configured to perform normalization calculation on each threshold in the grid threshold matrix to obtain a normalized threshold; respectively comparing the normalized threshold with the area ratio of the dots to obtain comparison results; and screening the image to be screened according to the comparison result to obtain a screened image.
In a fifth aspect, an embodiment of the present application provides an apparatus for image printing, the apparatus including: an image screening module configured to screen each ink channel of the printing color by the method according to the first aspect to obtain a screened image; and the image printing module is configured to print the screened image of each ink channel to obtain a printing image.
In a sixth aspect, an embodiment of the present application provides an electronic device, including: a processor, a memory and a bus, the processor being connected to the memory via the bus, the memory storing computer readable instructions for implementing the method according to any one of the first and second aspects when the computer readable instructions are executed by the processor.
In a seventh aspect, an embodiment of the present application provides a computer-readable storage medium, where a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a server, the computer program implements the method according to any one of the first aspect.
Drawings
FIG. 1 is a system for image printing, shown in an embodiment of the present application;
fig. 2 is a flowchart illustrating a screening method for halftone rendering of an image according to an embodiment of the present application;
FIG. 3 is a graph showing the printing effect of 90% dot area ratio in the embodiment of the present application;
FIG. 4 is a schematic diagram of a dot function structure shown in the embodiment of the present application;
FIG. 5 is a block diagram of an internal part of a screening device for halftone color generation of an image according to an embodiment of the present application;
FIG. 6 is a block diagram of an alternative screening device for halftone rendering of an image according to an embodiment of the present application;
fig. 7 is an internal module of an electronic device according to an embodiment of the present disclosure.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all the embodiments. The components of the embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present application, as presented in the figures, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present application without making any creative effort, shall fall within the protection scope of the present application.
The method steps in the embodiments of the present application are described in detail below with reference to the accompanying drawings.
The present embodiment can be applied to a system for generating an image halftone, as shown in fig. 1, the system for generating an image halftone includes: the printing system comprises a processing device 110 and a printing machine 120, wherein the processing device 110 is used for screening the image to be printed, and the printing machine 120 is used for finishing printing based on the screened image output by the processing device 110. Under the condition that the printing technology is improved day by day, the printing precision and the printing definition are improved day by day, but when the printing area of the dots reaches a certain degree, the dot enlargement is inevitably generated by the traditional amplitude modulation halftone color generation printing method, and the density is gradually changed, so that the printing precision is reduced. In order to solve these problems, the inventors of the present application have designed new dot functions (i.e., a first function and a second function), and when the area of the grid is expanded by the new dot functions, the new dot functions can be bounded by circular boundaries, so that four first regions and one second region, which are located in the same grid and divided by the boundaries, can be simultaneously expanded in different directions during the screening process, which is significant in effectively avoiding dot density jump and intense color, and solving the defect that the color printing transition is not soft in the amplitude modulation halftone.
As can be seen from the above description, in the related art, the am halftone color printing related to image printing uses a grid formed by multiple grids as a basic unit for color presentation, and in the related art of current circular halftone dot color presentation, the color presentation manner of the circular halftone dots corresponding to one grid is centered on the center of the grid, and the halftone dot radius gradually increases as the halftone dot area ratio increases. The dot function is: z is 1- (x)2+y2) Therefore, in the printing process, when the area of a circular dot is larger than a certain value, a certain part of the outline of the circular dot is connected with the grid boundary where another circular dot is located, so that a 'lap angle' occurs, the printed color is changed suddenly, the area rate is increased more or less suddenly, the increase destroys the uniform change of the tone, and the tone reproduction of the image is not favorable. Therefore, how to improve the tone uniformity variation of the circular dots in the printing process becomes an urgent problem to be solved.
In view of the above problems, the embodiments of the present application provide a screening method, a printing method, a system and a device for halftone color generation of an image, the method includes dividing each pixel in an image to be screened into a plurality of grids, and forming a grid composed of the grids corresponding to the pixels; respectively calculating thresholds of the grids according to a mesh point function to obtain a grid threshold matrix, wherein the mesh point function comprises a first function and a second function, the area of the mesh point expanded to a grid central point in a four-corner part is determined through the first function, and the area of the central mesh point expanded to a grid vertex is determined through the second function; according to the grid threshold matrix, carrying out normalization processing on the image to be screened to obtain a screened image; and printing the screened image to obtain a printed image, wherein the tone in the printing process can be uniformly changed.
The following describes in detail, with reference to fig. 2, implementation steps of a screening method for halftone color rendering of an image, as shown in fig. 2, including:
s210, dividing each pixel in the image to be screened into a plurality of grids.
In one embodiment, each pixel in the image to be screened is divided into a plurality of grids, and a grid composed of the plurality of grids corresponding to the pixels is formed.
The processing device divides each pixel in the image to be screened into a plurality of grids, in other words, one grid is composed of at least one pixel, and each pixel of the at least one pixel is composed of a plurality of grids.
It should be noted that the number of pixels of each mesh may be determined according to actual conditions such as printing precision requirements and printing capability of a printing machine, for example, each mesh in an image to be screened may be divided into 4 pixels as shown in the embodiment of the present application, or each mesh may be divided into 8 pixels or 16 pixels, and similarly, each mesh may be regarded as one pixel, and then each mesh may be divided into 100 grids, each grid representing a dot area ratio of 1%, which is not limited in the embodiment of the present application.
And S220, respectively calculating the thresholds of the grids according to the mesh point functions to obtain a grid threshold matrix.
In one embodiment, the mesh point functions include a first function by which an area of a corner partial mesh point extending toward a mesh center point is determined, and a second function by which an area of a center mesh point extending toward the mesh vertex is determined.
In the embodiment of the application, in order to avoid the jump of printing caused by the contact of the dot outline and the grid boundary, a boundary is constructed in a square grid, and a central dot in the boundary and four corner partial dots outside the boundary are expanded simultaneously, so that the expansion of the central dot is limited in a circular area formed by the boundary, and the area between the dot vertex and the boundary is not blank, in other words, the dot coverage is still left in the part between the boundary and the grid vertex, the four corner partial dots are expanded along with the expansion of the central dot area, but the outline of the four corner partial dots is kept circular, and finally, the central dot and the four corner partial dots are attached to each other to achieve the solid. As shown in fig. 3, fig. 3 shows that when the dot area ratio is 90%, the printing result of one dot shows that the vertex 330 is the center of the circular boundary, the middle part represents the central dot 320, the black part covered around the central dot 320 is the area needing ink ejection, the four-corner part dots 310 are distributed on the four corners of the grid, and the black area covered on the vertex represents the ink ejection area determined by the first function.
Therefore, according to the screening method for the color generation of the image halftone, the four-corner part dots in the grid can be expanded towards the grid center point in the printing process, and the center dots are expanded towards the grid vertexes, so that the influences of density jump and severe color change caused by dot expansion can be avoided, the color reproduction gradation and the color reproduction precision can be better ensured, and the defect that the transition of the color generation printing of the amplitude modulation halftone is not soft can be overcome.
In one embodiment, the dot function is obtained by: constructing a circular boundary by taking the vertex of the grid as a circle center, wherein the part between the circular boundary and the vertex of the grid is a first area, and the part between the circular boundary and the center point of the grid is a second area; and according to the extreme value of the threshold, constructing the first function in the first area and constructing the second function in the second area.
Since the dots are centrosymmetric, and the coordinates are taken as absolute values during the calculation process, taking the first quadrant as an example, a dot function is constructed, as shown in fig. 4, a coordinate axis is established with the central point (0,0) of the grid as an origin, the vertex (1,1) of the grid as a center, the side length of the grid as a diameter to establish a circular boundary 410, an area between the circular boundary 410 and the vertex of the grid as a first area 420, and an area between the circular boundary 410 and the central point of the grid as a second area 430.
Therefore, the accuracy of calculating the threshold matrix can be guaranteed by constructing the dot function, and the dot function is divided into the first function and the second function, so that the dot function can be bounded by the circular boundary, the first area and the second area can be expanded to different directions simultaneously in the printing process, the density jump and the color intensity of dots are avoided, and the defect that the color printing transition of amplitude modulation halftone is not soft is overcome.
In one embodiment, the threshold on the circular dividing line is defined as the minimum of the threshold; defining the sum of the thresholds at the center point of the mesh and the thresholds at the vertices of the mesh as maxima of the thresholds; and constructing the first function in the first area and constructing the second function in the second area according to the maximum value and the minimum value.
In order to construct the first function and the second function, the threshold value on the circular boundary is set to be the minimum value-1 of the threshold value, and the grid center point and the grid vertex are set to be the maximum value +1 of the threshold value, that is, in the first region, the threshold value is decreased from +1 to-1 along with the expansion of the central dot radius, and in the second region, the threshold value is decreased from-1 to +1 along with the expansion of the dot radius, so that different dot functions need to be respectively established. At any point P (x, y) in the coordinate system, in a gridThe vertex (1,1) is used as the center of a circle, and the radius of the circle taking the distance from the vertex to the point P as the radius is used as the radius
In the first region, when r is 0, the threshold value z is 1, and when r is 1, the threshold value z is-1, and thus, the straight-line equation z is-2 × r +1 is obtained; in the second area when
When the threshold value z is 1 and r is 1, the threshold value z is-1, and therefore, a linear equation is obtained
In one embodiment, the first function is characterized by the following equation:
wherein Z represents a threshold value of the plurality of grids, x represents an abscissa corresponding to each of the plurality of grids, y represents an ordinate corresponding to each of the plurality of grids, and r represents a radius of a mesh point where each of the plurality of grids is located.
Therefore, the coordinates of the grids in the first area are substituted into the formula for calculation, the threshold values of the grids can be obtained, the threshold value matrix of the grids is obtained, whether each grid in the first area is colored or not is judged, and therefore the accuracy of ink jetting is improved.
In one embodiment, the second function is characterized by the following equation:
wherein Z represents a threshold value of the plurality of grids, x represents an abscissa corresponding to each of the plurality of grids, y represents an ordinate corresponding to each of the plurality of grids, and r represents a radius of a mesh point where each of the plurality of grids is located.
Therefore, the coordinates of the second area grids are substituted into a formula for calculation, and whether each grid of the second area should be colored can be judged through the obtained grid threshold value, so that the second area can be subjected to ink jet coloring in the color printing of the amplitude modulation halftone, the defect that the transition of the color printing of the amplitude modulation halftone is not soft is overcome, meanwhile, the influence of density jump and severe color change caused by dot expansion can be avoided, and the color reproduction gradation and the color reproduction precision are better ensured.
After the dot function including the first function and the second function is constructed and completed through the method, the grid coordinates are brought into the dot function by taking the pixel center point as the origin, and the threshold matrixes of the grids are obtained.
S130, according to the grid threshold matrix, normalization processing is carried out on the image to be screened, and a screened image is obtained.
In one embodiment, each threshold in the grid threshold matrix is subjected to normalization calculation to obtain a normalized threshold; respectively comparing the normalized threshold with the area ratio of the dots to obtain comparison results; and screening the image to be screened according to the comparison result to obtain a screened image.
The calculation of the threshold matrix needs to be compared with a preset mesh point area rate, normalization calculation needs to be carried out on all threshold values in the threshold matrix for convenient comparison, a normalization threshold value corresponding to each threshold value is obtained, each normalization threshold value is compared with the mesh point area rate respectively, a comparison result is obtained, the comparison result comprises the threshold value which is larger than or equal to the mesh point area rate and the threshold value which is smaller than the mesh point area rate, the threshold value which is larger than or equal to the mesh point area rate is selected for color presentation, the screening process of the image to be screened is achieved, and the screened image is obtained.
Therefore, the grid threshold matrix and the dot area rate value can be conveniently compared through normalized calculation, and calculation is simplified.
The processing device obtains a screened image by the screening method for the halftone coloration of the image, and then prints the screened image by using a printer to obtain a printed image.
The implementation steps of the screening method for image halftone color generation are described in detail above, and the screening method for screening and printing the corresponding image halftone color generation by using two functions of the embodiments of the present application is exemplarily described below by taking a dot area ratio of C ═ 70 as an example.
Assuming that the image to be screened needs to be subjected to color rendering of amplitude modulation halftone according to the halftone dot area rate of C-70, the processing device divides the image to be screened into a plurality of halftone dots. In the example, each mesh point is divided into 4 pixels, then each pixel is subjected to rasterization processing, the pixels are divided into grids of 6 rows and 6 columns, and the coordinates of each grid are determined.
Carrying out normalization processing on the coordinates of the grid, and bringing the normalized coordinates into the following formula:
wherein x represents an abscissa corresponding to each of the plurality of grids, y represents an ordinate corresponding to each of the plurality of grids, and r represents a radius of a mesh point where each of the plurality of grids is located.
When the value of r is in the range of 0 to 1, the first function is substituted.
Z＝1-2×r (1.0≥r≥0)
Wherein Z represents a threshold value of the plurality of grids, and r represents a radius of a mesh point where each of the plurality of grids is located.
When r is greater than 1 and less than
Equal to, is substituted into the second function.
Wherein Z represents a threshold value of the plurality of grids, and r represents a radius of a mesh point where each of the plurality of grids is located.
The completed dot threshold matrix is calculated as shown in table 1:
TABLE 1 dot threshold matrix
| 5 | 10 | 26 | 29 | 31 | 33 |
| 11 | 4 | 9 | 21 | 28 | 32 |
| 16 | 8 | 1 | 2 | 20 | 24 |
| 25 | 22 | 3 | 1 | 12 | 18 |
| 34 | 27 | 19 | 14 | 6 | 15 |
| 35 | 30 | 23 | 17 | 13 | 7 |
The threshold matrix in table 1 was normalized to 1-100 as shown in table 2:
TABLE 2 dot normalization threshold matrix
And printing ink dots on grids corresponding to the threshold values which are greater than or equal to 70 in the dot normalization threshold value matrix in the table 2, and not printing ink dots on grids corresponding to the threshold values which are less than 70.
The foregoing describes in detail a specific embodiment of a screening method for rendering an image halftone, and the following describes an apparatus for rendering an image halftone with reference to fig. 5 and 6, and an internal module of an electronic device with reference to fig. 7.
As shown in fig. 5, an apparatus for halftone rendering of an image includes a dividing module 510, a calculating module 520, and a screening module 530.
In one embodiment, an apparatus for halftone rendering of an image includes: the dividing module is configured to divide each pixel in the image to be screened into a plurality of grids to form a grid which corresponds to the pixel and is composed of the grids; a calculating module configured to calculate thresholds of the plurality of grids respectively according to a mesh point function to obtain a grid threshold matrix, wherein the mesh point function includes a first function and a second function, an area of a quadrangle partial mesh point expanding to a mesh center point is determined through the first function, and an area of a central mesh point expanding to the mesh vertex is determined through the second function; and the screening module is configured to perform normalization processing on the image to be screened according to the grid threshold matrix to obtain a screened image.
In one embodiment, the halftone dot function is obtained by: constructing a circular boundary by taking the vertex of the grid as a circle center, wherein the part between the circular boundary and the vertex of the grid is a first area, and the part between the circular boundary and the center point of the grid is a second area; and according to the extreme value of the threshold, constructing the first function in the first area and constructing the second function in the second area.
In one embodiment, the calculation module is configured to define a threshold on the circular dividing line as a minimum of the threshold; defining the sum of the thresholds at the center point of the mesh and the thresholds at the vertices of the mesh as maxima of the thresholds; and constructing the first function in the first area and constructing the second function in the second area according to the maximum value and the minimum value.
In one embodiment, the first function is characterized by the following equation:
wherein Z represents a threshold value of the plurality of grids, x represents an abscissa corresponding to each of the plurality of grids, y represents an ordinate corresponding to each of the plurality of grids, and r represents a radius of a mesh point where each of the plurality of grids is located.
In one embodiment, the second function is characterized by the following equation:
wherein Z represents a threshold value of the plurality of grids, x represents an abscissa corresponding to each of the plurality of grids, y represents an ordinate corresponding to each of the plurality of grids, and r represents a radius of a mesh point where each of the plurality of grids is located.
In one embodiment, the screening module is configured to perform a normalization calculation on each threshold in the grid threshold matrix to obtain a normalized threshold; respectively comparing the normalized threshold with the area ratio of the dots to obtain comparison results; and screening the image to be screened according to the comparison result to obtain a screened image.
In the embodiment of the present application, the module shown in fig. 5 can implement each process in the method embodiments of fig. 1 to 4. The operations and/or functions of the respective modules in fig. 5 are respectively for implementing the corresponding flows in the method embodiments in fig. 1 to 4. Reference may be made specifically to the description of the above method embodiments, and a detailed description is appropriately omitted herein to avoid redundancy.
As shown in fig. 6, an apparatus for halftone rendering of an image, includes: an image screening module 610 and an image printing module 620.
In one embodiment, the present application provides an apparatus for halftone rendering of an image, the apparatus comprising: the image screening module is configured to screen each ink channel for printing color by adopting the method to obtain a screened image; and the image printing module is configured to print the screened image of each ink channel to obtain a printing image.
In the embodiment of the present application, the module shown in fig. 6 can implement each process in the printing method embodiment of the halftone color generation of the image. The operations and/or functions of the respective modules in fig. 6 are respectively for realizing the corresponding flows in the method embodiment of image printing. Reference may be made specifically to the description of the above method embodiments, and a detailed description is appropriately omitted herein to avoid redundancy.
As shown in fig. 7, an embodiment of the present application provides an electronic device, including: a processor 710, a memory 720 and a bus 730, wherein the processor is connected to the memory through the bus, the memory stores computer readable instructions, when the computer readable instructions are executed by the processor, the computer readable instructions are used for implementing the method of any one of the above-mentioned all embodiments, and the detailed description can be referred to the description of the above-mentioned method embodiments, and is omitted here appropriately for avoiding repetition.
Wherein the bus is used for realizing direct connection communication of the components. The processor in the embodiment of the present application may be an integrated circuit chip having signal processing capability. The Processor may be a general-purpose Processor, and includes a Central Processing Unit (CPU), a Network Processor (NP), and the like; but may also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components. The various methods, steps, and logic blocks disclosed in the embodiments of the present application may be implemented or performed. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
The Memory may be, but is not limited to, a Random Access Memory (RAM), a Read Only Memory (ROM), a Programmable Read Only Memory (PROM), an Erasable Read Only Memory (EPROM), an electrically Erasable Read Only Memory (EEPROM), and the like. The memory stores computer readable instructions that, when executed by the processor, perform the methods described in the embodiments above.
It will be appreciated that the configuration shown in fig. 7 is merely illustrative and may include more or fewer components than shown in fig. 7 or have a different configuration than shown in fig. 7. The components shown in fig. 7 may be implemented in hardware, software, or a combination thereof.
Embodiments of the present application further provide a computer-readable storage medium, where a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a server, the method in any of the above-mentioned all embodiments is implemented, which may specifically refer to the description in the above-mentioned method embodiments, and in order to avoid repetition, detailed description is appropriately omitted here.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (10)
1. A method for screening halftone images, the method comprising:
dividing each pixel in an image to be screened into a plurality of grids to form a grid which is corresponding to the pixel and consists of the grids;
respectively calculating thresholds of the grids according to a mesh point function to obtain a grid threshold matrix, wherein the mesh point function comprises a first function and a second function, the area of the mesh point expanded to the central point of the grid in a four-corner part is determined through the first function, and the area of the central mesh point expanded to the vertex of the grid is determined through the second function;
and normalizing the image to be screened according to the grid threshold matrix to obtain a screened image.
2. The method of claim 1, wherein the halftone dot function is obtained by:
constructing a circular boundary by taking the vertex of the grid as a circle center, wherein the part between the circular boundary and the vertex of the grid is a first area, and the part between the circular boundary and the center point of the grid is a second area;
and according to the extreme value of the threshold, constructing the first function in the first area and constructing the second function in the second area.
3. The method of claim 2, wherein said constructing the first function in the first region and the second function in the second region according to the threshold extremum comprises:
defining a threshold on the circular boundary as a minimum of the threshold;
defining the sum of the thresholds at the center point of the mesh and the thresholds at the vertices of the mesh as maxima of the thresholds;
and constructing the first function in the first area and constructing the second function in the second area according to the maximum value and the minimum value.
4. The method of claim 3, wherein the first function is characterized by the formula:
wherein Z represents a threshold value of the plurality of grids, x represents an abscissa corresponding to each of the plurality of grids, y represents an ordinate corresponding to each of the plurality of grids, and r represents a radius of a mesh point where each of the plurality of grids is located.
5. The method of claim 3, wherein the second function is characterized by the formula:
wherein Z represents a threshold value of the plurality of grids, x represents an abscissa corresponding to each of the plurality of grids, y represents an ordinate corresponding to each of the plurality of grids, and r represents a radius of a mesh point where each of the plurality of grids is located.
6. The method according to claim 1, wherein the screening the image to be screened according to the grid threshold matrix to obtain a screened image comprises:
carrying out normalization calculation on each threshold value in the grid threshold value matrix to obtain a normalized threshold value;
respectively comparing the normalized threshold with the area ratio of the dots to obtain comparison results;
and according to the comparison result, carrying out normalization processing on the image to be screened so as to represent the non-inking/inking state of the ink, and obtaining the screened image.
7. A method of printing in halftone images, said method comprising:
screening each ink channel of the printing color by the method as claimed in claims 1-6 to obtain a screened image;
and printing the screened image of each ink channel to obtain a printed image.
8. A system for halftone rendering of an image, the system comprising: a processing apparatus and a printing press;
the processing device for implementing the method according to any one of claims 1 to 6, resulting in a screened image;
the printer is configured to complete image printing based on the screened image.
9. An apparatus for halftone rendering of an image, the apparatus comprising:
the dividing module is configured to divide each pixel in the image to be screened into a plurality of grids to form a grid which corresponds to the pixel and is composed of the grids;
a calculating module configured to calculate thresholds of the plurality of grids respectively according to a mesh point function to obtain a grid threshold matrix, wherein the mesh point function includes a first function and a second function, an area of a quadrangle partial mesh point expanding to a mesh center point is determined through the first function, and an area of a central mesh point expanding to a vertex of the grid is determined through the second function;
and the screening module is configured to perform normalization processing on the image to be screened according to the grid threshold matrix to obtain a screened image.
10. An apparatus for halftone rendering of an image, the apparatus comprising:
an image screening module configured to screen each ink channel of a print color using the method of claims 1-6 to obtain a screened image;
and the image printing module is configured to print the screened image of each ink channel to obtain a printing image.
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