Self-adaptive linear dot generation method and system for flexographic printing

Abstract

The invention discloses a self-adaptive linear dot generation method and system for flexographic printing, and belongs to the technical field of printing, and the method comprises the steps: obtaining a gray value of an image pixel needing flexographic printing; assuming that the width of the linear dot is a preset minimum length and width limit value of the dot, and calculating to obtain the length of the linear dot according to a preset printing line number and a formula; if the length, obtained through calculation in the above step, of the linear dot is smaller than a preset dot minimum length and width limit value, it is assumed that the width and the length of the linear dot are both the preset dot minimum length and width limit value again, and the self-adaptive printing line number is obtained through calculation according to a formula so that flexographic printing can be conducted through the self-adaptive printing line number. Therefore, the situation of dot loss at the highlight position is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of printing, and in particular to a method and system for generating self-adaptive linear dots for flexographic printing. Background Art

[0002] Flexographic printing technology requires converting multi-valued digital images into binary images with dots before printing through flexographic printing equipment. Generally, amplitude modulation or frequency modulation screening technology is used to generate dots. At present, the mainstream technology of flexographic printing is amplitude modulation technology. When flexographic printing uses amplitude modulation technology to generate dots, the most commonly used dot shape is circular.

[0003] Compared with other commonly used printing technologies, flexographic printing is more prone to dot loss in highlight areas, and in dark tones, dots tend to become solid too early due to tone jumps. Therefore, many scholars and experts have conducted relevant research to control the dot problem. Some have improved it from the perspective of hardware and consumables such as printing plates, ink viscosity and anilox rollers, while others have achieved optimization from the perspective of process such as plate making, printing pressure and dot generation methods.

[0004] At present, there are some research results on the dot generation method of flexographic printing technology, but it has not been widely used. In my country, the amplitude modulation technology using circular dots still occupies the mainstream position in the market. This is mainly because the new dot generation method is often more complicated and the cost of use is higher. Therefore, compared with other types of printing technologies, the current flexographic printing technology still generally has the problem of easy loss of highlight dots and premature conversion of dark dots into solid. Summary of the invention

[0005] In view of the problem in the prior art that flexographic highlight dots are easily lost and thus lead to mesh failure, the purpose of the present invention is to provide an adaptive linear dot generation method and system for flexographic printing, so as to at least partially solve the above problem.

[0006] To achieve the above object, the technical solution of the present invention is: In a first aspect, the present invention provides a method for generating adaptive linear dots for flexographic printing, the method comprising the following steps: S1. Obtaining the grayscale value k of the image pixel to be printed by flexographic printing; S2. Assume that the width e of the linear dot is the preset minimum length and width limit a of the dot, and according to the formula Calculate the length f of the linear dots, where g is the spacing between the printed dots, g=25.4 / b, and b is the preset number of printing screen lines; S3. If the length f of the linear dot calculated in step S2 is less than the preset minimum length and width limit a of the dot, then re-assume that the width e and length f of the linear dot are both the preset minimum length and width limit a of the dot, and calculate the length according to the formula The adaptive printing screen count z is calculated to facilitate flexographic printing by using the adaptive printing screen count z and the parameter e=f=a.

[0007] In some preferred embodiments, the method further comprises the following steps: S4. If the length f of the linear dots calculated in step S2 is greater than the spacing g of the printed dots, it is assumed that the length f of the linear dots is equal to the spacing g of the printed dots, and according to the formula The actual width of the linear dots is calculated, and the number of adaptive printing screen lines z is the preset number of printing screen lines b, so that the preset number of printing screen lines b and , f=g parameters for flexographic printing.

[0008] In some preferred embodiments, the method further comprises the following steps: S5. If the length f of the linear dots calculated in step S2 is between the preset minimum length and width limit a of the dots and the spacing g of the printed dots, flexographic printing is performed using the preset screen line number b, e=a and the length f of the linear dots calculated in step S2.

[0009] In some preferred embodiments, the preset minimum length and width limit a of the dot is 50 microns, and the preset printing screen count b is 150 lpi.

[0010] In some preferred embodiments, a screening angle d for flexographic printing is also included.

[0011] In some preferred embodiments, the screening angle d is 37.5°.

[0012] In some preferred embodiments, in step S1 , the grayscale values ​​k of a plurality of image pixels to be flexographically printed are simultaneously acquired.

[0013] In a second aspect, the present invention also provides an adaptive linear dot generation system for flexographic printing, comprising an acquisition module, a processing module and a storage module, wherein the processing module is electrically connected to the acquisition module and the storage module; the storage module is used to store executable computer program codes; the acquisition module is used to acquire the grayscale values ​​of image pixels to be flexographically printed and transmit them to the processing module; the processing module is used to call the executable computer program code in the storage module and execute the method as described above.

[0014] In a third aspect, the present invention further provides an electronic device, comprising a memory storing executable program code and a processor coupled to the memory; wherein the processor calls the executable program code stored in the memory to execute the method as described above.

[0015] In a fourth aspect, the present invention further provides a computer-readable storage medium storing a computer program, wherein the computer program executes the method described above when executed by a processor.

[0016] By adopting the above technical scheme, the beneficial effect of the present invention is that: compared with the prior art, the present invention sets the minimum length and width limit of the linear dots and calculates the adaptive printing screen count through an adaptive formula, and uses it as the actual screen count for printing, thereby effectively avoiding the situation where the dots in the highlights are too small and cause loss. In areas other than the highlights, the preset printing screen count is used for screening, so that the actual screen count of most areas of the printed image except the highlights is the preset printing screen count that is desired to be used in the printing process, and the operator is almost not required to have high skills, and the printing screen count and dot size required for actual printing can be adaptively and automatically calculated. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The flowchart of the method for generating adaptive linear dots for flexographic printing in the present invention.

[0018] Figure 2 This is a linear dot effect diagram in a uniform color block when the grayscale value of the image pixel in the present invention is 2%K.

[0019] Figure 3 This is a linear dot effect diagram in a uniform color block when the grayscale value of the image pixel in the present invention is 30%K.

[0020] Figure 4 This is a linear dot effect diagram in a uniform color block when the grayscale value of the image pixel in the present invention is 15%K. DETAILED DESCRIPTION

[0021] The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0022] Example 1 An adaptive linear dot generation method for flexographic printing, such as Figure 1 As shown, the method comprises the following steps: S1. Obtaining the grayscale value k of the image pixel to be printed by flexographic printing; S2. Assume that the width e of the linear dot is the preset minimum length and width limit a of the dot, and according to formula (1) Calculate the length f of the linear dots, where g is the spacing between the printed dots, g=25.4 / b, and b is the preset number of printing screen lines; S3. If the length f of the linear dot calculated in step S2 is less than the preset minimum length and width limit a of the dot, then re-assume that the width e and length f of the linear dot are both the preset minimum length and width limit a of the dot, and according to formula (2): The adaptive printing screen count z is calculated to facilitate flexographic printing by using the adaptive printing screen count z and the parameter e=f=a.

[0023] In step S1, the gray value k of the image pixel is expressed as a percentage of K, where K refers to black, for example, 2% K represents 2% black. Typically, in step S1, the gray values ​​k of multiple image pixels that need to be printed on a flexographic plate can be obtained simultaneously for calculation.

[0024] In step S2, it is necessary to determine in advance the preset minimum length and width limit a of the dots, which is generally 50 microns. When taking the value of the minimum length and width limit a of the dots, the value should be set as small as possible under the premise that the dots in the highlights on the printing plate are not lost. This is mainly due to the fact that flexographic printing technology at the current level may cause too small dots to be easily lost. However, when the dots in the highlights of the printing plate are still seriously lost, a larger preset value may be set according to the actual situation. This value is usually an empirical value, and different models of printing plates and printing equipment have different empirical values.

[0025] The preset printing screen count b is the screen count that is desired to be used in printing according to the general AM screen technology, for example, 150 lpi. However, if the same screen count is used for all the different brightness levels of the entire image, it is easy to cause the problem of highlight screen failure. Therefore, this embodiment further sets step S3 to solve this problem.

[0026] According to the assumption in step S2 that the width e of the linear dot is equal to the preset minimum length and width limit a of the dot and formula (1), the length f of the linear dot can be calculated. According to the common sense that the length of the linear dot cannot be less than the preset minimum length and width limit a of the dot, it is necessary to verify whether the length f of the linear dot calculated in step S2 is less than the preset minimum length and width limit a of the dot. If it is less than, it means that the content of step S2 is incorrect.

[0027] At this time, it is re-assumed that the length f of the linear dot is the preset minimum length and width limit a of the dot. On this basis, the adaptive printing screen count z can be calculated according to formula (2).

[0028] For example, when the gray value k of the image pixel is 2%K, the preset minimum length and width limit of the dot a is 50 microns, and the preset printing screen count b is 150 lpi. The length f of the linear dot calculated in step S2 is 11.5 microns, which is obviously less than the preset minimum length and width limit of the dot a, i.e., 50 microns. Therefore, in step S3, it is re-assumed that the width e and length f of the linear dot are both 50 microns, i.e., the linear dot is set to the minimum size, and then the adaptive printing screen count z can be calculated as 71.8 lpi according to the formula.

[0029] Thus, after the above three steps, the method provided by the embodiment of the present invention can adaptively adjust the screen count at the highlight, thereby ensuring that the dots are not lost due to being too small.

[0030] At this time, the length f and width e of the linear dots are both 50 microns, and the number of adaptive printing screen lines z is 71.8 lpi for flexographic printing. Usually, the printing also includes a screen angle d for flexographic printing, for example, the screen angle d is 37.5°. The printing effect obtained after printing is as follows Figure 2 shown.

[0031] In some preferred embodiments, the method provided by the embodiment of the present invention further includes the following steps: S4. If the length f of the linear dots calculated in step S2 is greater than the spacing g of the printed dots, it is assumed that the length f of the linear dots is equal to the spacing g of the printed dots, and according to formula (3): The actual width of the linear dots is calculated, and the adaptive printing screen count z is configured as the preset printing screen count b, so that the preset printing screen count b and , f=g parameters for flexographic printing.

[0032] It is easy to understand that, according to formula (1), the length f of the linear dots calculated in step S2 is proportional to the grayscale value k of the image pixel. Therefore, when the grayscale value k of the image pixel is greater than a certain value, the length f of the linear dots calculated in step S2 will be greater than the spacing g of the printed dots. When the preset printing screen count b is determined to be 150 lpi, according to the formula g=25.4 / b, it can be known that the g value is 169.3 microns.

[0033] For example, when the grayscale value k of the image pixel in step S1 is 30%K, the length f of the linear dots calculated in step S2 is 172 microns, which is greater than the spacing g of the printed dots. This will cause two adjacent linear dots to overlap along their length direction. In this case, it is only necessary to configure the upper limit of the length f of the linear dots to be equal to the spacing g of the printed dots. On this basis, according to the formula By calculating the actual width of the linear dots, it can be seen that the actual width of the linear dots e=gk, that is, the actual width of the linear dots is always less than or equal to the spacing g of the printed dots.

[0034] Therefore, in step S4, the maximum length f of the linear dots in this embodiment can only be the spacing g of the printed dots, that is, 169.3 microns. When the length f of the linear dots calculated in step S2 exceeds this value, the length f of the linear dots is limited to g. According to formula (3), the actual width e of the linear dots can be calculated to be 50.8 microns, which is greater than the preset minimum length and width limit a of the dots. It is easy to understand that because the spacing g of the printed dots is obtained by the preset printing screen count b, the adaptive printing screen count z is directly taken as the preset printing screen count b, that is, 150 lpi.

[0035] At this time, the flexographic printing is performed according to the length f of the linear dots of 169.3 microns, the width e of 50.8 microns, the number of adaptive printing screen lines z of 150 lpi, and the screen angle d of 37.5°. The printing effect obtained after printing is as follows: Figure 3 shown.

[0036] In some preferred embodiments, the method provided by the embodiment of the present invention further includes the following steps: S5. If the length f of the linear dots calculated in step S2 is between the preset minimum length and width limit a of the dots and the spacing g of the printed dots, flexographic printing is performed using the preset screen line number b, e=a and the length f of the linear dots calculated in step S2.

[0037] It is easy to understand that when the length f of the linear dots calculated in step S2 is between the preset minimum length and width limit a of the dots and the spacing g of the printed dots, it means that under the guidance of the dimensions a and b, the printing plate will not have missing dots in the highlights because the linear dots are too small, and therefore will not cause the phenomenon of missing dots. This means that the length f of the linear dots calculated in step S2 is reasonable and usable.

[0038] For example, when the gray value k of the image pixel in step S1 is 15%K, the length f of the linear dot calculated in step S2 is 86 microns, which is between a and g. At this time, according to the linear dot length f of 86 microns, width e of 50 microns, adaptive printing screen number z of 150lpi, and screen angle d of 37.5°, flexographic printing is performed, and the printing effect obtained after printing is as follows: Figure 4 shown.

[0039] From the above content, it can be seen that in the highlight (when the grayscale value k of the image pixel is small), by appropriately reducing the screen count (that is, the adaptive printing screen count z calculated in step S3, whose value is smaller than the preset printing screen parameter b), and increasing the size of the linear dots (compared to the length f of the linear dots calculated in step S2, the minimum length and width of the linear dots used in actual printing are equal to the minimum length and width limit a), the printing plate will not be missing dots in the highlight due to the dot size being too small, thereby avoiding the occurrence of the screen break phenomenon.

[0040] As the grayscale value k of the image pixel read in step S1 increases, the value of the adaptive printing screen line number z calculated in step S3 will also increase until the adaptive printing screen line number z increases to a level equal to the preset printing screen line number b. At this time, the grayscale value k of the image pixel and the larger image pixel grayscale value k are actually printed using the preset printing screen line number b, and the corresponding dot size is calculated using the preset printing screen line number b.

[0041] Compared with the prior art, the present invention calculates the adaptive printing screen count z through an adaptive formula, and uses it as the actual screen count during printing for screening, thereby effectively avoiding the situation where the dots in the highlights are too small and cause loss. In areas other than the highlights, the preset printing screen count b is used for screening, so that the actual screen count in most areas of the printed image is the preset printing screen count b that is desired to be used in the printing process, and the operating workers are almost not required to have high skills, and the printing screen count and dot size required for actual printing can be adaptively and automatically calculated.

[0042] Example 2 This embodiment also provides an adaptive linear dot generation system for flexographic printing, which includes an acquisition module, a processing module and a storage module, wherein the processing module is electrically connected to the acquisition module and the storage module.

[0043] The storage module is used to store executable computer program codes; the acquisition module is used to acquire the grayscale values ​​of the image pixels to be flexographically printed and transmit them to the processing module; the processing module is used to call the executable computer program codes in the storage module and execute the method provided in the above embodiment.

[0044] Example 3 An electronic device includes a memory storing executable program code and a processor coupled to the memory; wherein the processor calls the executable program code stored in the memory to execute the method steps disclosed in the above embodiment.

[0045] Example 4 A computer storage medium stores a computer program, and when the computer program is executed by a processor, the method steps disclosed in the above embodiment are executed.

[0046] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0047] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0048] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0049] It should be noted that, in the description of the present invention, the directions or positional relationships indicated by the terms "up", "down", "left", "right", "front", "back", etc. are descriptions of the structure of the present invention based on the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0050] The "first" and "second" in this technical solution are only used to distinguish the names of the same or similar structures, or corresponding structures with similar functions, and are not an arrangement of the importance of these structures, nor do they have a ranking, comparison of size, or other meanings.

[0051] In addition, unless otherwise clearly specified and limited, the terms "installation" and "connection" should be understood in a broad sense. For example, the connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be a connection between the two structures. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood based on the overall idea of ​​the present invention and the specific context of the present solution.

[0052] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the scope of protection of the present invention.

Claims

1. A method for generating adaptive linear dots for flexographic printing, characterized in that: The method comprises the following steps: S1. Obtaining the grayscale value k of the image pixel to be printed by flexographic printing; S2. Assume that the width e of the linear dot is the preset minimum length and width limit a of the dot, and according to the formula Calculate the length f of the linear dots, where g is the spacing between the printed dots, g=25.4 / b, and b is the preset number of printing screen lines; S3. If the length f of the linear dot calculated in step S2 is less than the preset minimum length and width limit a of the dot, then re-assume that the width e and length f of the linear dot are both the preset minimum length and width limit a of the dot, and calculate the length according to the formula The adaptive printing screen count z is calculated to facilitate flexographic printing by using the adaptive printing screen count z and the parameter e=f=a.

2. The method according to claim 1, characterized in that: The method further comprises the following steps: S4. If the length f of the linear dots calculated in step S2 is greater than the spacing g of the printed dots, it is assumed that the length f of the linear dots is equal to the spacing g of the printed dots, and according to the formula The actual width of the linear dots is calculated, and the number of adaptive printing screen lines z is the preset number of printing screen lines b, so that the preset number of printing screen lines b and , f=g parameters for flexographic printing.

3. The method according to claim 1, characterized in that: The method further comprises the following steps: S5. If the length f of the linear dots calculated in step S2 is between the preset minimum length and width limit a of the dots and the spacing g of the printed dots, flexographic printing is performed using the preset screen line number b, e=a and the length f of the linear dots calculated in step S2.

4. The method according to claim 1, characterized in that: The preset minimum length and width limit a of the dot is 50 microns, and the preset printing screen count b is 150 lpi.

5. The method according to claim 1, characterized in that: Also included is the screen angle d for flexographic printing.

6. The method according to claim 5, characterized in that: The screen angle d is 37.5°.

7. The method according to claim 1, characterized in that: In step S1 , the grayscale values ​​k of a plurality of image pixels to be flexographically printed are simultaneously acquired.

8. An adaptive linear dot generation system for flexographic printing, characterized in that: It comprises an acquisition module, a processing module and a storage module, wherein the processing module is electrically connected to the acquisition module and the storage module; the storage module is used to store executable computer program codes; the acquisition module is used to acquire the grayscale values ​​of image pixels to be flexographically printed and transmit them to the processing module; the processing module is used to call the executable computer program code in the storage module and execute the method as described in any one of claims 1 to 7.

9. An electronic device, characterized in that: It comprises a memory storing executable program code and a processor coupled to the memory; wherein the processor calls the executable program code stored in the memory to execute the method according to any one of claims 1-7.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 7 is performed.

Images