阅读说明：本技术 一种快速调幅加网的方法、系统、计算机设备、终端 (Method and system for rapidly amplitude-modulating and screening, computer equipment and terminal ) 是由 李广鑫 任翔 刘佳来 王超 孙熙蒙 于 2021-07-21 设计创作，主要内容包括：本发明属于数字加网技术领域,公开了一种快速调幅加网的方法、系统、计算机设备、终端,所述调幅加网的方法包括：设定矩阵转换参数,即最小阈值矩阵转换为单元格阈值矩阵的相关参数；根据参数将最小阈值矩阵转换为单元格阈值矩阵；记录单元格阈值矩阵的分布规则,确保单元格阈值矩阵与最小阈值矩阵的等效性；单元格图像预生成及预存储,根据单元格阈值矩阵生成网点生长趋势图,并保存在Map结构中；基于单元格阈值矩阵的调幅加网。本发明采用单元格阈值矩阵代替最小阈值矩阵的等效思想,使得调幅加网能够避免大量单元格图像的重复计算；利用Map数据结构快速访问特性,能够很好的满足RIP对页面的解释速度跟上照排机曝光速度的需求。(The invention belongs to the technical field of digital screening, and discloses a method, a system, computer equipment and a terminal for rapid amplitude modulation screening, wherein the method for amplitude modulation screening comprises the following steps: setting matrix conversion parameters, namely, converting the minimum threshold matrix into relevant parameters of the cell threshold matrix; converting the minimum threshold matrix into a cell threshold matrix according to the parameters; recording the distribution rule of the cell threshold matrix, and ensuring the equivalence of the cell threshold matrix and the minimum threshold matrix; pre-generating and pre-storing a cell image, generating a net point growth trend graph according to a cell threshold matrix, and storing the net point growth trend graph in a Map structure; amplitude modulation screening based on a cell threshold matrix. The equivalent idea of replacing the minimum threshold matrix with the cell threshold matrix is adopted, so that amplitude modulation and screening can avoid repeated calculation of a large number of cell images; by utilizing the quick access characteristic of the Map data structure, the requirement that the interpretation speed of the RIP to the page is kept up with the exposure speed of the photo setter can be well met.)

1. A method of amplitude modulated screening, the method comprising:

setting matrix conversion parameters: converting the minimum threshold matrix into relevant parameters of the cell threshold matrix;

matrix conversion: converting the minimum threshold matrix into a cell threshold matrix according to the parameters;

matrix distribution rule: recording the distribution rule of the cell threshold matrix, and ensuring the equivalence of the cell threshold matrix and the minimum threshold matrix;

cell image pre-generation and pre-storage: generating a dot growth trend graph according to the cell threshold matrix, and storing the dot growth trend graph in a Map structure;

amplitude modulation screening: amplitude modulation screening based on a cell threshold matrix.

2. The method of amplitude modulation screening according to claim 1, wherein said setting matrix switching parameters comprises:

(1) setting the amplitude modulation screening order I, wherein the amplitude modulation screening order depends on the resolution of the phototypesetter and is in dpi, and the amplitude modulation screening line number is in lpi; obtaining the screening order I according to the following formula:

(2) setting the width and height of a minimum threshold matrix as KxL, wherein the screening angles on four color plates of CMYK are different, the minimum threshold matrix used for screening on each color plate is also different, and the width and height of the minimum threshold matrix KxL finally depends on the screening angle of the color plates and the screening order I;

(3) the width and height of the cell threshold matrix are equal to the amplitude modulation screening order number, which is represented as I multiplied by I, and the number num of a group of cell threshold matrixes equivalent to the minimum threshold matrix is obtained by calculating the least common multiple through the following formula₂：

The function Lcm represents the least common multiple, Lcm (K, I) represents the least common multiple of the minimum threshold matrix width K and the cell threshold matrix width I, Lcm (L, I) represents the least common multiple of the minimum threshold matrix length L and the cell threshold matrix length I, and Lcm (K, I) × Lcm (L, I) is the width and height of a rectangular area obtained according to the principle of the least common multiple, and the area is called a large threshold matrix area.

3. The method of amplitude modulation screening as claimed in claim 1, wherein said matrix converting comprises:

(1) obtaining the width and height of the large threshold matrix area as Lcm (K, I) multiplied by Lcm (L, I) according to the least common multiple;

(2) according to the distribution rule of the minimum threshold matrix in the halftone image space during amplitude modulation screening, filling a large threshold matrix with the width of Lcm (K, I) multiplied by Lcm (L, I) by using the minimum threshold matrix with the width of Kmultiplied by L;

(3) dividing a large threshold matrix into num according to a cell threshold matrix with the width of I multiplied by I₂Number of different cell threshold matrices, num₂The variable is comprehensively determined by the width and height K multiplied by L of the minimum threshold matrix and the width and height I multiplied by I of the cell threshold matrix.

4. The method of amplitude modulation screening according to claim 1, wherein the matrix distribution rule comprises:

(1) for the num obtained₂The cell threshold matrixes are numbered, and the minimum threshold matrix with the width of KxL can be converted into num according to the least common multiple at each screening angle₂The cell threshold value matrixes are different from one another, so that the matrixes are numbered and distinguished;

(2) determining a distribution rule of the cell threshold matrix in a halftone image space; when amplitude modulation is used for screening, the distribution of the minimum threshold matrix in a halftone image space is regular and is used as an equivalent matrix of the minimum threshold matrix, num₂The threshold matrix of each cell in the halftone image space must meet certain regularity to realize equivalence with the minimum threshold matrix; on the premise of realizing matrix equivalence, sum and record num₂Distribution rules of the cell threshold value matrixes;

the number of pixel points in the original image is completely the same as the number of cells in the halftone image space, and the pixel coordinates (x, y) of the original image correspond to the cells with the coordinates (x, y) in the halftone image space; according to a distribution rule equivalent to the minimum threshold matrix, each original image pixel coordinate (x, y) can uniquely determine a cell threshold matrix m; therefore, the matrix distribution rule is determined, that is, the pixel coordinate and num of each original image are determined₂Mapping relation of the threshold matrix of each cell.

5. The method of amplitude modulation screening according to claim 1, wherein the pre-generating and pre-storing of the cell image comprises:

(1) generating a cell image according to a gray value v of a pixel of an original, wherein each pixel coordinate (x, y) in the original image space can uniquely determine a cell threshold matrix m in a halftone image space, the gray value v of the pixel acts on the cell threshold matrix m to obtain a cell image, and each cell image comprises 144 recording grids;

(2) setting pixel gray value v of the original image to be gradually reduced from 255 to 0, calculating a cell image for all cell threshold matrixes every time the pixel gray value is changed, and recording a cell image in a Map data structure every time a cell image is generated in the process, wherein the mapping relation of the cell threshold matrixes m & gt → the cell image is that the pixel gray value v is less than the pixel gray value m & gt; after the traversal is finished, each cell threshold matrix is necessarily corresponding to 256 cell images, and the cell image information is called a net point growth trend graph;

the pre-generation is a process of generating a dot growth trend graph containing a cell image, and the pre-storage is a process of recording a mapping relation related to the cell image in a Map data structure; the pre-generation stage aims at exhausting all the cell images possibly encountered in the amplitude modulation screening process, and according to the second step, four minimum threshold matrixes are needed when four color plates of CMYK are subjected to amplitude modulation screening, so that the total number of the four groups of cell threshold matrixes is set to be num, and the number of the cell images is 256 multiplied by num;

when the order I of amplitude modulation screening is 12, the minimum threshold matrix shapes of 0 °, 15 °, 45 °, and 75 ° are 12 × 12, 3 × 51, 8 × 16, and 3 × 51, respectively, and the equivalent four sets of cell threshold matrix numbers num are set to be equal to each other₂1, 17, 8 and 17, so num is 1+17+8+17 is 43, and the number of unit grid images is 256 × 43 is 11008; when the 12-level tone width is screened, no matter how large the resolution of the original image is, and no matter how many cell images are contained in the halftone image, wherein the number of the different cell images is certainly not more than 11008, obviously, the calculation amount of the cell images is limited to a constant level;

recording that the resolution of the color original image is W × H, the color halftone image generated after amplitude modulation screening is composed of 4 × W × H cell images, when W is 1000 and H is 1000, the number of the cell images is 4000000 and is much larger than 11008, and the repetition calculation rate of the cell images is as high as (4000000-11008)/4000000-99.7%; the page interpretation time of amplitude modulation screening based on the minimum threshold matrix is in direct proportion to the number of cell images, namely O (W multiplied by H), and inevitably increases sharply with the increase of the resolution of the original image; however, amplitude modulation and screening based on the cell threshold matrix limit the number of cell images within 11008 by utilizing the internal principle of screening, and the improvement on the page interpretation speed of RIP is very obvious; and the pre-storing stage is used for storing all the cell images generated in the pre-generating stage and mapping relations between the cell images and the cell threshold matrix m and the pixel gray value v of the original image, so as to exert the advantages of a Map data structure, and make the time complexity for acquiring the cell images be O (1).

6. The method of amplitude modulation screening according to claim 1, wherein the amplitude modulation screening based on a cell threshold matrix comprises:

(1) respectively determining screening angles for all color plates of CMYK, and if the original image is a gray image, selecting the screening angle for only one color plate; if the original image is a color image, selecting screening angles for four color plates of CMYK;

(2) determining a corresponding cell threshold matrix m according to pixel coordinates (x, y) of the original image based on the three established matrix distribution rules; in the Map data structure, according to the mapping relation, namely < pixel gray value v, cell threshold matrix m > → cell image, taking out the pre-stored cell image, and filling the cell image to the halftone image space;

(3) and (2) executing in a traversal mode, calculating a corresponding cell image for the gray value of each pixel in the original image in each channel, and finally storing the obtained halftone image as a tif file.

7. An am screening system for implementing the am screening method of any one of claims 1 to 6, the am screening system comprising:

the matrix conversion parameter setting module is used for setting matrix conversion parameters, wherein the minimum threshold matrix is converted into relevant parameters of the cell threshold matrix;

the matrix conversion module is used for converting the minimum threshold matrix into a cell threshold matrix according to the parameters;

the matrix distribution rule determining module is used for recording the distribution rule of the cell threshold matrix and ensuring the equivalence of the cell threshold matrix and the minimum threshold matrix;

the cell image processing module is used for pre-generating and pre-storing cell images, generating a dot growth trend graph according to the cell threshold matrix and storing the graph in a Map structure;

and the amplitude modulation screening module is used for realizing amplitude modulation screening based on the cell threshold matrix.

8. A computer device, characterized in that the computer device comprises a memory and a processor, the memory storing a computer program which, when executed by the processor, causes the processor to carry out the steps of:

setting matrix conversion parameters, wherein the minimum threshold matrix is converted into relevant parameters of the cell threshold matrix; converting the minimum threshold matrix into a cell threshold matrix according to the parameters; recording the distribution rule of the cell threshold matrix, and ensuring the equivalence of the cell threshold matrix and the minimum threshold matrix; pre-generating and pre-storing a cell image, generating a dot growth trend graph according to a cell threshold matrix, and storing the graph in a Map structure; and amplitude modulation screening based on the cell threshold matrix is carried out.

9. A computer-readable storage medium storing a computer program which, when executed by a processor, causes the processor to perform the steps of:

setting matrix conversion parameters, wherein the minimum threshold matrix is converted into relevant parameters of the cell threshold matrix; converting the minimum threshold matrix into a cell threshold matrix according to the parameters; recording the distribution rule of the cell threshold matrix, and ensuring the equivalence of the cell threshold matrix and the minimum threshold matrix; pre-generating and pre-storing a cell image, generating a dot growth trend graph according to a cell threshold matrix, and storing the graph in a Map structure; and amplitude modulation screening based on the cell threshold matrix is carried out.

10. An information data processing terminal characterized by being used for implementing the amplitude modulation screening system as claimed in claim 7.

Technical Field

The invention belongs to the technical field of digital screening, and particularly relates to a method, a system, computer equipment and a terminal for rapid amplitude modulation screening.

Background

At present, screening techniques have been developed on the basis of printing techniques, also known as halftone techniques. When the printer prints the dots, only ink spraying and ink non-spraying are selected, so that the printer can only print binary images and cannot directly print continuous tone images. In order to convert a continuous tone image into a binary image, a technology of approximately replacing continuous color change by ink area ratio change is proposed, the technology is a compromise of continuous tone and binarization, and a halftone technology is named for this reason.

The Amplitude Modulation Screening (AMS) halftone technique is an earlier halftone technique, and is characterized in that the Screening frequency is unchanged, and the change of continuous tone is simulated by changing the area rate of a color part sprayed in a dot. Taking black and white as an example, the darker the tone corresponding to the dot, the larger the area of the black portion in the dot. The amplitude modulation screening technology comprises three types: first, Rational Tangent Screening (RTS): as the name implies, the tangent of the screening angle is a rational number, and the technique is fast in generating halftone images and is the basis of the other two techniques, but the screening angle is too coarse to approach 15 ° and 75 ° in the conventional screening method. Second, Irrational Tangent Screening (ITS): the method is closer to the traditional screening angle technology on the basis of RTS, can better solve the angle error caused by screening of the RTS, and reduces the possibility of rose spots of the halftone image. Thirdly, Super Cell Screening Technology (SCST): this technology was proposed at the end of the 20 th century, and the use of the ultra-microcell concept enabled it to approach 15 ° and 75 ° more closely than RTS and ITS technologies, enabling the effect of digital screening to reach and even exceed that achievable by traditional four-color separation processes.

However, the above three techniques focus more on improving the accuracy of the screening angle, rather than increasing the screening speed. The speed of amplitude modulated screening is not only related to the hardware configuration but also to the selection of the screening algorithm. The main problem of increasing the screening speed is the speed matching between the photo-setter and the raster graphics processor (RIP), i.e. the interpretation speed of the RIP to the page is to keep up with the exposure speed of the photo-setter; similarly, the exposure speed of the photocopier can be kept up to the RIP interpretation speed of the page. In the usual case, the interpretation speed of the RIP tends to lag behind the exposure speed of the phototypesetter. Therefore, only a phototypter with a high exposure speed is not sufficient, and high-performance RIP support is also required. And the RIP performance depends on an efficient algorithm. The core of the algorithm lies in the generation of an amplitude modulation screening threshold matrix, and the research is very important for improving the existing digital screening technology. Although a lot of networking software is published at present, the networking algorithm and the technical problem are secret for each enterprise technology, the quality of the networking image is good and uneven, most of the networking image is foreign software, and the networking image is in a monopoly status all the time, which is not beneficial to the development of the industry to a great extent.

At present, most of amplitude modulation screening in China realizes rational and irrational tangent screening through a minimum threshold matrix, the shape of the matrix needs to be adjusted according to a screening angle by the threshold matrix, and the amplitude modulation screening mode based on the minimum threshold matrix has a large amount of repeated calculation, so that the page interpretation speed of RIP is not favorably improved. Therefore, a new method, system, computer device, and terminal for fast am screening are needed.

Through the above analysis, the problems and defects of the prior art are as follows:

(1) the existing amplitude modulation screening technology focuses more on the improvement of the accuracy of the screening angle, but not on the improvement of the screening speed, and only a phototypesetter with a high exposure speed is not enough, and high-performance RIP support is required.

(2) The existing networking algorithm and the technical problem are all secret technologies of enterprises, the quality of the networking images is not uniform, most of the networking images are foreign software, and the networking images are monopolized, so that the networking algorithms are not beneficial to the development of the industry.

(3) At present, most of amplitude modulation screening in China realizes rational and irrational tangent screening through a minimum threshold matrix, the shape of the matrix needs to be adjusted according to a screening angle by the threshold matrix, and the amplitude modulation screening mode based on the minimum threshold matrix has a large amount of repeated calculation, so that the speed of the RIP for explaining the page is not improved.

The difficulty in solving the above problems and defects is: the amplitude modulation screening based on the minimum threshold matrix at the present stage is analyzed from the screening mechanism at the bottom layer, and the result of each exposure point of the halftone image depends on the gray value of the pixel of the original image and the threshold value of the minimum threshold matrix. Each calculation is very mechanically repeated, and the operation is not regular at the pixel level. Through a large amount of observation and theoretical analysis, the regularity of operation is finally found at the level of the cell, and a formula is given as a basis.

The significance of solving the problems and the defects is as follows: the method is beneficial to breaking the bad situation of monopoly in the field of digital screen adding needles, and makes the related technology in the field develop more benign. The problems that the minimum threshold matrix shape is not fixed and the repeated calculation is excessive in the amplitude modulation screening technology based on the minimum threshold matrix are solved, and the interpretation speed of the RIP to the page cannot keep up with the exposure speed of the photo setter. By adopting the equivalent idea that the cell threshold matrix replaces the minimum threshold matrix, the amplitude modulation screening based on the cell threshold matrix can avoid repeated calculation of a large number of cell images, and the calculated number of the cell images is kept at a constant level; by means of the characteristic of quick access of the Map data structure, the time complexity of acquiring each unit grid image is O (1), and the requirement that the interpretation speed of the RIP to the page is required to be kept up to the exposure speed of the photo-setter can be well met. Compared with amplitude modulation screening based on a minimum threshold matrix, the amplitude modulation screening method has the advantages that the working efficiency of amplitude modulation screening is greatly improved, and the method is very suitable for amplitude modulation screening processing of high-resolution original images and large-batch original images.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a method, a system, computer equipment and a terminal for rapid amplitude modulation screening, in particular to an amplitude modulation screening method and a system based on a cell threshold matrix, aiming at solving the problems that the cell image is repeatedly calculated in the existing amplitude modulation screening algorithm based on the minimum threshold matrix and the interpretation speed of a RIP (raster image processor) on a page is difficult to match the exposure speed of a phototypesetter.

The invention is realized in such a way that an amplitude modulation screening method comprises the following steps:

step one, setting matrix conversion parameters: the minimum threshold matrix is converted to the relevant parameters of the cell threshold matrix. The positive effect of the first step is to provide a formulated quantitative analysis and theoretical basis for the subsequent matrix conversion;

step two, matrix conversion: the minimum threshold matrix is converted to a cell threshold matrix according to the parameters. The positive effect of the step two is that the design of a novel threshold matrix, namely a cell threshold matrix, provides possibility for the optimization of subsequent amplitude modulation screening;

step three, matrix distribution rule: and recording the distribution rule of the cell threshold matrix, and ensuring the equivalence of the cell threshold matrix and the minimum threshold matrix. The third step has the positive effects that the width and the height of the novel threshold matrix designed through equivalence are always kept stable and do not change along with the change of the screening angle;

step four, pre-generating and pre-storing a cell image: and generating a dot growth trend graph according to the cell threshold matrix, and storing the dot growth trend graph in a Map structure. The positive effect of the step four is that the pre-generation and pre-storage can be in a space time-switching mode, so that the amplitude modulation screening avoids a large amount of repeated calculation.

Step five, amplitude modulation and screening: amplitude modulation screening based on a cell threshold matrix.

Further, in the first step, the setting of the matrix conversion parameters includes:

(1) setting the amplitude modulation screening order I, wherein the amplitude modulation screening order depends on the resolution of the phototypesetter and is in dpi, and the amplitude modulation screening line number is in lpi; obtaining the screening order I according to the following formula:

(2) setting the width and height of a minimum threshold matrix as KxL, wherein the screening angles on four color plates of CMYK are different, the minimum threshold matrix used for screening on each color plate is also different, and the width and height of the minimum threshold matrix KxL finally depends on the screening angle of the color plates and the screening order I;

(3) the width and height of the cell threshold matrix are equal to the amplitude modulation screening order number, which is represented as I multiplied by I, and the number num of a group of cell threshold matrixes equivalent to the minimum threshold matrix is obtained by calculating the least common multiple through the following formula₂：

The function Lcm represents the least common multiple, Lcm (K, I) represents the least common multiple of the minimum threshold matrix width K and the cell threshold matrix width I, Lcm (L, I) represents the least common multiple of the minimum threshold matrix length L and the cell threshold matrix length I, and Lcm (K, I) × Lcm (L, I) is the width and height of a rectangular area obtained according to the principle of the least common multiple, and the area is called a large threshold matrix area.

Further, in step two, the matrix transformation includes:

(1) obtaining the width and height of the large threshold matrix area as Lcm (K, I) multiplied by Lcm (L, I) according to the least common multiple;

(2) according to the distribution rule of the minimum threshold matrix in the halftone image space during amplitude modulation screening, filling a large threshold matrix with the width of Lcm (K, I) multiplied by Lcm (L, I) by using the minimum threshold matrix with the width of Kmultiplied by L;

(3) dividing a large threshold matrix into num according to a cell threshold matrix with the width of I multiplied by I₂Number of different cell threshold matrices, num₂The variable is comprehensively determined by the width and height K multiplied by L of the minimum threshold matrix and the width and height I multiplied by I of the cell threshold matrix.

Further, in step three, the matrix distribution rule includes:

(1) for num obtained in the second step₂The cell threshold matrixes are numbered, and the minimum threshold matrix with the width of KxL can be converted into num according to the least common multiple at each screening angle₂The cell threshold value matrixes are different from one another, so that the matrixes are numbered and distinguished;

(2) determining a distribution rule of the cell threshold matrix in a halftone image space; when amplitude modulation is used for screening, the distribution of the minimum threshold matrix in a halftone image space is regular and is used as an equivalent matrix of the minimum threshold matrix, num₂The threshold matrix of each cell in the halftone image space must meet certain regularity to realize equivalence with the minimum threshold matrix; on the premise of realizing matrix equivalence, sum and record num₂Distribution rules of the cell threshold value matrixes;

the number of pixel points in the original image is completely the same as the number of cells in the halftone image space, and the pixel coordinates (x, y) of the original image correspond to the cells with the coordinates (x, y) in the halftone image space; according to a distribution rule equivalent to the minimum threshold matrix, each original image pixel coordinate (x, y) can uniquely determine a cell threshold matrix m; therefore, the matrix distribution rule is determined, that is, the pixel coordinate and num of each original image are determined₂Mapping relation of the threshold matrix of each cell.

Further, in the fourth step, the pre-generating and pre-storing of the cell image includes:

(1) generating a cell image according to a gray value v of a pixel of an original, wherein each pixel coordinate (x, y) in the original image space can uniquely determine a cell threshold matrix m in a halftone image space, the gray value v of the pixel acts on the cell threshold matrix m to obtain a cell image, and each cell image comprises 144 recording grids;

(2) setting pixel gray value v of the original image to be gradually reduced from 255 to 0, calculating a cell image for all cell threshold matrixes every time the pixel gray value is changed, and recording the cell image in a Map data structure every time a cell image is generated in the process, namely, the mapping relation of the pixel gray value v, the cell threshold matrix m > → the cell image; after the traversal is finished, each cell threshold matrix is necessarily corresponding to 256 cell images, and the cell image information is called a net point growth trend graph;

the pre-generation is a process of generating a dot growth trend graph containing a cell image, and the pre-storage is a process of recording a mapping relation related to the cell image in a Map data structure; the pre-generation stage aims at exhausting all the cell images possibly encountered in the amplitude modulation screening process, and according to the second step, four minimum threshold matrixes are needed when four color plates of CMYK are subjected to amplitude modulation screening, so that the total number of the four groups of cell threshold matrixes is set to be num, and the number of the cell images is 256 multiplied by num;

when the order I of amplitude modulation screening is 12, the minimum threshold matrix shapes of 0 °, 15 °, 45 °, and 75 ° are 12 × 12, 3 × 51, 8 × 16, and 3 × 51, respectively, and the equivalent four sets of cell threshold matrix numbers num are set to be equal to each other₂1, 17, 8 and 17, so num is 1+17+8+17 is 43, and the number of unit grid images is 256 × 43 is 11008; when the 12-level tone width is screened, no matter how large the resolution of the original image is, and no matter how many cell images are contained in the halftone image, wherein the number of the different cell images is certainly not more than 11008, obviously, the calculation amount of the cell images is limited to a constant level;

recording that the resolution of the color original image is W × H, the color halftone image generated after amplitude modulation screening is composed of 4 × W × H cell images, when W is 1000 and H is 1000, the number of the cell images is 4000000 and is much larger than 11008, and the repetition calculation rate of the cell images is as high as (4000000-11008)/4000000-99.7%; the page interpretation time of amplitude modulation screening based on the minimum threshold matrix is in direct proportion to the number of cell images, namely O (W multiplied by H), and inevitably increases sharply with the increase of the resolution of the original image; however, amplitude modulation and screening based on the cell threshold matrix limit the number of cell images within 11008 by utilizing the internal principle of screening, and the improvement on the page interpretation speed of RIP is very obvious; and the pre-storing stage is used for storing all the cell images generated in the pre-generating stage and mapping relations between the cell images and the cell threshold matrix m and the pixel gray value v of the original image, so as to exert the advantages of a Map data structure, and make the time complexity for acquiring the cell images be O (1).

Further, in step five, the amplitude modulation screening based on the cell threshold matrix includes:

(1) respectively determining screening angles for all color plates of CMYK, and if the original image is a gray image, selecting the screening angle for only one color plate; if the original image is a color image, selecting screening angles for four color plates of CMYK;

(2) determining a corresponding cell threshold matrix m according to pixel coordinates (x, y) of the original image based on the three established matrix distribution rules; in the Map data structure, according to the mapping relationship, namely < pixel gray value v, > cell threshold matrix m > → cell image, taking out a pre-stored cell image, and filling the cell image onto a halftone image space;

(3) and (2) executing in a traversal mode, calculating a corresponding cell image for the gray value of each pixel in the original image in each channel, and finally storing the obtained halftone image as a tif file.

Another object of the present invention is to provide an am screening system applying the am screening method, the am screening system comprising:

the matrix conversion parameter setting module is used for setting matrix conversion parameters, wherein the minimum threshold matrix is converted into relevant parameters of the cell threshold matrix;

the matrix conversion module is used for converting the minimum threshold matrix into a cell threshold matrix according to the parameters;

the matrix distribution rule determining module is used for recording the distribution rule of the cell threshold matrix and ensuring the equivalence of the cell threshold matrix and the minimum threshold matrix;

the cell image processing module is used for pre-generating and pre-storing cell images, generating a dot growth trend graph according to the cell threshold matrix and storing the graph in a Map structure;

and the amplitude modulation screening module is used for realizing amplitude modulation screening based on the cell threshold matrix.

It is a further object of the invention to provide a computer device comprising a memory and a processor, the memory storing a computer program which, when executed by the processor, causes the processor to perform the steps of:

setting matrix conversion parameters, wherein the minimum threshold matrix is converted into relevant parameters of the cell threshold matrix; converting the minimum threshold matrix into a cell threshold matrix according to the parameters; recording the distribution rule of the cell threshold matrix, and ensuring the equivalence of the cell threshold matrix and the minimum threshold matrix; pre-generating and pre-storing a cell image, generating a dot growth trend graph according to a cell threshold matrix, and storing the graph in a Map structure; and amplitude modulation screening based on the cell threshold matrix is carried out.

It is another object of the present invention to provide a computer-readable storage medium storing a computer program which, when executed by a processor, causes the processor to perform the steps of:

setting matrix conversion parameters, wherein the minimum threshold matrix is converted into relevant parameters of the cell threshold matrix; converting the minimum threshold matrix into a cell threshold matrix according to the parameters; recording the distribution rule of the cell threshold matrix, and ensuring the equivalence of the cell threshold matrix and the minimum threshold matrix; pre-generating and pre-storing a cell image, generating a dot growth trend graph according to a cell threshold matrix, and storing the graph in a Map structure; and amplitude modulation screening based on the cell threshold matrix is carried out.

Another object of the present invention is to provide an information data processing terminal for implementing the amplitude modulation screening system.

By combining all the technical schemes, the invention has the advantages and positive effects that: the amplitude modulation screening method provided by the invention standardizes the shape of the threshold matrix, the width and the height of the cell threshold matrix are always kept I multiplied by I no matter any amplitude modulation screening angle, and the cell threshold matrix has a very good corresponding relation with the pixels of the original image, the cells in the halftone image space and the cell image.

The invention effectively reduces the repeated calculation of the cell image, greatly improves the working efficiency of amplitude modulation screening compared with the amplitude modulation screening based on the minimum threshold matrix, reduces the time complexity of the cell image calculation from O (W multiplied by H) to O (1), can avoid 90 percent of repeated calculation when the resolution of the gray manuscript image is more than 314 multiplied by 314 or the resolution of the color manuscript image is more than 157 multiplied by 157, can avoid 99 percent of repeated calculation when the resolution of the gray manuscript image is more than 1044 multiplied by 1044 or the resolution of the color manuscript image is more than 522 multiplied by 522, and the larger the resolution of the manuscript image is, the avoided repeated calculation is closer to 100 percent.

The amplitude modulation screening process of the invention uses the Map data structure, and the characteristic of quick access of the Map data structure ensures that the time complexity of obtaining each cell image is O (1), thereby being capable of well meeting the requirement that the interpretation speed of RIP to the page is required to keep up with the exposure speed of a photo-setter, and further improving the efficiency of amplitude modulation screening.

Therefore, the method is very suitable for amplitude modulation screening processing of high-resolution original images and large-batch original images, when the original images are large enough, the interpretation speed of the RIP to the page tends to be stable, and compared with the minimum threshold matrix amplitude modulation screening, the speed is improved by 6.9 times.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments of the present invention will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a flowchart of an amplitude modulation screening method according to an embodiment of the present invention.

FIG. 2 is a block diagram of an AM screening system according to an embodiment of the present invention;

in the figure: 1. a matrix conversion parameter setting module; 2. a matrix conversion module; 3. a matrix distribution rule determining module; 4. a cell image processing module; 5. and the amplitude modulation screening module.

Fig. 3 is a schematic diagram of a parameter relationship between a minimum threshold matrix and a cell threshold matrix according to an embodiment of the present invention.

Fig. 4 is a schematic diagram of converting a minimum threshold matrix into a cell threshold matrix according to an embodiment of the present invention.

Fig. 5 is a schematic diagram illustrating a distribution rule of a cell threshold matrix in a halftone image space according to an embodiment of the present invention.

Fig. 6 is a schematic diagram of generating a dot growth trend graph according to a cell threshold matrix according to an embodiment of the present invention.

Fig. 7 is a schematic diagram of amplitude modulation screening based on a cell threshold matrix according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In view of the problems in the prior art, the present invention provides a method, a system, a computer device, and a terminal for fast amplitude modulation screening, and the present invention is described in detail below with reference to the accompanying drawings.

As shown in fig. 1, the amplitude modulation screening method provided by the embodiment of the present invention includes the following steps:

s101, setting matrix conversion parameters: converting the minimum threshold matrix into relevant parameters of the cell threshold matrix;

s102, matrix conversion: converting the minimum threshold matrix into a cell threshold matrix according to the parameters;

s103, matrix distribution rule: recording the distribution rule of the cell threshold matrix, and ensuring the equivalence of the cell threshold matrix and the minimum threshold matrix;

s104, cell image pre-generation and pre-storage: generating a dot growth trend graph according to the cell threshold matrix, and storing the dot growth trend graph in a Map structure;

s105, amplitude modulation screening: amplitude modulation screening based on a cell threshold matrix.

As shown in fig. 2, the amplitude modulation screening system provided in the embodiment of the present invention includes:

a matrix conversion parameter setting module 1, configured to set matrix conversion parameters, where a minimum threshold matrix is converted into related parameters of a cell threshold matrix;

the matrix conversion module 2 is used for converting the minimum threshold matrix into a cell threshold matrix according to the parameters;

the matrix distribution rule determining module 3 is used for recording the distribution rule of the cell threshold matrix and ensuring the equivalence of the cell threshold matrix and the minimum threshold matrix;

the cell image processing module 4 is used for pre-generating and pre-storing cell images, generating a dot growth trend graph according to the cell threshold matrix and storing the graph in a Map structure;

and the amplitude modulation screening module 5 is used for realizing amplitude modulation screening based on the cell threshold matrix.

The technical solution of the present invention will be further described with reference to the following examples.

The invention is realized in this way, an amplitude modulation screening method and system based on cell threshold matrix, the method transforms the minimum threshold matrix into the cell threshold matrix, exhausts all cell images in the amplitude modulation screening process by means of the cell threshold matrix, avoids repeated calculation by pre-generating and pre-storing the cell images, the amplitude modulation screening method based on cell threshold matrix includes the following steps:

(1) setting matrix conversion parameters: converting the minimum threshold matrix into relevant parameters of the cell threshold matrix;

(2) matrix conversion: converting the minimum threshold matrix into a cell threshold matrix according to the parameters;

(3) matrix distribution rule: recording the distribution rule of the cell threshold matrix, and ensuring the equivalence of the cell threshold matrix and the minimum threshold matrix;

(4) pre-generating and pre-storing a cell image: before the step five of amplitude modulation screening, firstly, generating a mesh point growth trend graph (the mesh point growth trend graph is composed of a plurality of cell images) in advance according to the cell threshold matrix, and then pre-storing the cell images in a Map data structure;

(5) amplitude modulation screening: amplitude modulation screening based on a cell threshold matrix.

As shown in fig. 3, the width and height of the minimum threshold matrix is K × L, the width and height of the cell threshold matrix is I × I, the shapes of the two threshold matrices are different from each other, and if the two threshold matrices are equivalent, a corresponding relationship between the two threshold matrices needs to be established. In a rectangular area with a width Lcm (K, I) × Lcm (L, I), this matrix area is called a large threshold matrix, and it can be known from formula 2 that num is included therein₁A minimum threshold matrix, num₂The individual cell threshold matrix, function Lcm, represents the least common multiple. It is apparent that num is analyzed by least common multiple₂The width and height of the cell threshold matrix are I × I, and the cell threshold matrix can be equivalent to the minimum threshold matrix with the width and height of K × L. I is the am screening order, which is determined by the phototypesetter resolution and the am screening line number as shown in equation 1. If the resolution of the film setter is 2400dpi, when the number of the screened lines is 150lpi, I is 16; when the number of the screened lines is 200lpi, I is 12. The shape of the minimum threshold matrix is determined by the order I of am screening and the screening angle, and when I is 12, K × L is 12 × 12, num when the screening angle is 0 °₂1 is ═ 1; when the screening angle is 15 degrees, K multiplied by L is 3 multiplied by 51, num₂17; when the screening angle is 45 degrees, K multiplied by L is 8 multiplied by 16, num₂8. Therefore, under different parameter conditions, the corresponding relationship between the minimum threshold matrix and the cell threshold matrix is different, so that parameters need to be specified for conversion between the matrices in the step one.

As shown in fig. 4, the minimum threshold matrix is filled into a rectangular area with a width Lcm (K, I) × Lcm (L, I), so as to obtain a large threshold matrix, and the parameter num obtained in the step one is used₂Num can be obtained by dividing the large threshold matrix₂The width and height are I multiplied by I unit cell threshold value matrixes. Num is known according to the principle of least common multiple₂Threshold moment of unit cell with width and height of I multiplied by IThe matrix can describe the distribution of the minimum threshold matrix with the width of K multiplied by I in the halftone image space, and num₂The cell threshold matrices with width and height I × I are different from each other.

As shown in FIG. 5, for num₂And numbering the different cell threshold matrixes, and further obtaining the distribution condition of the cell threshold matrixes in the halftone image space. Each minimum threshold matrix may be spatially regularly distributed by its equivalent num₂The regular distribution of the individual cell threshold matrices is reproduced in order to ensure that the amplitude modulation screening based on the minimum threshold matrix is equivalent to the amplitude modulation screening based on the cell threshold matrix.

As shown in fig. 6, when the gray value v of the pixels of the original image is set to be gradually decreased from 255 to 0, a dot growth trend graph is obtained by applying the gray value v to a cell threshold matrix m. One cell threshold matrix m corresponds to a dot growth trend graph, and one growth trend graph comprises 256 cell images, and each cell image comprises exposure conditions of 144 recording grids.

As shown in fig. 7, each halftone image can be subdivided into cell images, so that the process of generating a cell image according to the gray-scale value of each pixel of the original document image is the process of generating a halftone image. Since the cell image pre-generated in step S104 has exhausted all the cell images that may be encountered during the amplitude modulation screening, a large amount of repeated calculation is avoided during the amplitude modulation screening, and it is only necessary to determine the cell threshold matrix m according to the pixel coordinates (x, y) of the original image, then acquire the cell image from the Map data structure according to the mapping relationship (< pixel gray value v, cell threshold matrix m > → cell image), and then fill the cell image onto the halftone image. After each pixel of the original image is successfully converted into a cell image, the cell images are gathered together to form a halftone image, which is an amplitude modulation screening principle based on a cell threshold matrix.

Aiming at the problems that the shape of a minimum threshold matrix is not fixed and the repeated calculation is excessive and the interpretation speed of a page by RIP cannot follow the exposure speed of a photo setter in the amplitude modulation screening technology based on the minimum threshold matrix in the field of digital screening at present, the invention provides a screening method based on a cell threshold matrix, which adopts the equivalent idea that the cell threshold matrix replaces the minimum threshold matrix, so that the amplitude modulation screening based on the cell threshold matrix can avoid the repeated calculation of a large number of cell images and keep the number of the cell images in a constant level; the method utilizes the characteristic of quick access of the Map data structure to ensure that the time complexity of acquiring each cell image is O (1), and can well meet the requirement that the interpretation speed of the RIP to the page is required to be kept up with the exposure speed of a photo-setter. The invention has wide application range, greatly improves the working efficiency of amplitude modulation screening compared with amplitude modulation screening based on a minimum threshold matrix, reduces the time complexity of cell image calculation from O (W multiplied by H) to O (1), can avoid repeated calculation of 90 percent when the resolution of a gray-scale original document image is more than 314 multiplied by 314 or the resolution of a color original document image is more than 157 multiplied by 157, can avoid repeated calculation of 99 percent when the resolution of the gray-scale original document image is more than 1044 multiplied by 1044 or the resolution of the color original document image is more than 522 multiplied by 522, and the larger the resolution of the original document image, the more the avoided repeated calculation approaches 100 percent. Therefore, the method is very suitable for amplitude modulation screening processing of high-resolution original images and large-batch original images, when the original images are large enough, the interpretation speed of the RIP to the page tends to be stable, and compared with the minimum threshold matrix amplitude modulation screening, the speed is improved by 6.9 times.

In the above embodiments, the implementation may be wholly or partially realized by software, hardware, firmware, or any combination thereof. When used in whole or in part, can be implemented in a computer program product that includes one or more computer instructions. When loaded or executed on a computer, cause the flow or functions according to embodiments of the invention to occur, in whole or in part. The computer may be a general purpose computer, a special purpose computer, a network of computers, or other programmable device. The computer instructions may be stored in a computer readable storage medium or transmitted from one computer readable storage medium to another, for example, the computer instructions may be transmitted from one website site, computer, server, or data center to another website site, computer, server, or data center via wire (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL), or wireless (e.g., infrared, wireless, microwave, etc.)). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device, such as a server, a data center, etc., that includes one or more of the available media. The usable medium may be a magnetic medium (e.g., floppy Disk, hard Disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., Solid State Disk (SSD)), among others.

The above description is only for the purpose of illustrating the present invention and the appended claims are not to be construed as limiting the scope of the invention, which is intended to cover all modifications, equivalents and improvements that are within the spirit and scope of the invention as defined by the appended claims.