A pre-press image trapping method, system and storage medium

Abstract

The application relates to a pre-printing image trapping processing method, a system and a storage medium, and the method comprises the following steps: acquiring a real object electric separation image of an image to be printed, the real object electric separation image comprising four-color channels and special-color channels, the four-color channels comprising a yellow channel, a red channel, a blue channel and a black channel in sequence from light to dark; selecting a partition needing trapping in the real object electric separation image as a region to be processed; performing trapping among the four-color channels in the region to be processed according to an expansion and contraction direction from light to dark; performing trapping among the special-color channels in the region to be processed after the trapping among the four-color channels is completed, according to the expansion and contraction direction from light to dark; and performing trapping from the four-color channels to the special-color channels in the region to be processed after the trapping among the special-color channels is completed, so as to acquire a processed image. Compared with the prior art, the application can make the trapping effect more obvious and natural.

Description

Technical Field

[0001] This invention relates to the field of image trapping technology, and in particular to an image trapping processing method, system and storage medium before printing. Background Technology

[0002] Image trapping, also known as misregistration or misalignment, is a crucial pre-printing process. Ideally, in multi-color printing, the printing plates for different colors should be perfectly aligned. However, in reality, paper expansion and contraction, machine precision, and vibrations during high-speed printing make slight misregistration unavoidable. When implementing trapping, the principle of "trapping lighter colors, not darker colors" is primarily followed. This is because darker colors have greater visual weight, and the expansion of lighter colors into darker areas has the least visual impact.

[0003] The common trapping methods are as follows: Single-color line overprinting: Add a light-colored line to the edge of a color and set it to overprint; Layering: Shrinking or expanding graphic elements on different layers; Shifting method: Moving the inflection point of a color block, often used in gradient design. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art by providing a method, system and storage medium for image trapping before printing, thereby improving the naturalness and aesthetics of the image after trapping.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for image trapping before printing includes the following steps: Obtain the physical color separation image of the image to be printed. The physical color separation image includes four color channels and spot color channels. The four color channels include yellow channel, red channel, blue channel and black channel from light to dark. Select the areas to be trapped in the physical electrical analysis diagram as the areas to be processed; Trapping is performed between the four color channels in the area to be processed, following a direction of expansion and contraction from light to dark. After trapping between the four color channels, trapping between the spot color channels is performed in a direction of expansion and contraction from light to dark. For the area to be processed after trapping between spot color channels, trapping is performed from the four color channels to the spot color channels to obtain the trapped image.

[0006] Furthermore, the trapping process between the four color channels includes: Select the channel that needs to be expanded or contracted from the four color channels, open the channel to be expanded, and perform trapping to expand the selected channel into the opened channel.

[0007] Furthermore, the trapping process between the spot color channels includes: Close the four color channels, select the channel that needs to be expanded or contracted from the spot color channels, open the channel to be expanded, and perform trapping to expand the selected spot color channel into the opened spot color channel.

[0008] Furthermore, the process of trapping from the four color channels to the spot color channels includes: Select the channel that needs to be expanded or contracted from the four color channels, open the spot color channel with opaque ink, and expand the selected channel into the opened channel.

[0009] Furthermore, during the trapping process, the method determines the scaling amount of the image based on the resolution of the area to be processed.

[0010] Furthermore, determining the image scaling amount based on the resolution of the region to be processed specifically involves: If the resolution of the area to be processed is within the range of 250-350, then the scaling factor of the image is 3 pixels. If the area to be processed contains fine lines or text, the scaling of the image shall be within 2 pixels.

[0011] Furthermore, if the desired processing effect cannot be achieved when trapping with one pixel, the method will perform trapping multiple times consecutively.

[0012] Furthermore, before trapping, the method determines whether the corresponding area to be processed contains coffee beans, fruit, animal hair, water splashes, rice, salt, or sesame seeds; if so, the images before and after trapping are compared to determine whether the color change is too large or details are missing; if so, the trapping scaling amount is adjusted.

[0013] The present invention also provides an image trapping processing system for implementing the image trapping processing method described above before printing, comprising: The image acquisition module is used to acquire the physical color separation image of the image to be printed. The physical color separation image includes four color channels and spot color channels. The four color channels include yellow channel, red channel, blue channel and black channel from light to dark. The selection module is used to select the partitions that need to be trapped in the physical electrical analysis diagram as the areas to be processed; The four-color channel trapping module is used to trap the area to be processed between four color channels in an expansion and contraction direction from light to dark. The spot color channel trapping module is used to trap the area to be processed after the trapping between the four color channels is completed, according to the expansion and contraction direction from light to dark. The inter-channel trapping module is used to trap the area to be processed after trapping between spot color channels using four color channels to the spot color channels, thereby obtaining the trapped image.

[0014] The present invention also provides a computer-readable storage medium on which a computer program is stored, the computer program being executed by a processor using the method described above.

[0015] Compared with the prior art, the present invention has the following advantages: (1) Compared with traditional image trapping methods with random or fixed order, this invention decomposes complex multi-channel trapping into three clear and fixed sequential stages: first process the interior of the four color channels, then process the interior of the spot color channels, and finally process the boundary between the two; and all are processed in the direction of expansion and contraction from light to dark, avoiding the trapping defects caused by disordered order or incorrect direction in traditional methods, making the trapping effect more obvious and natural.

[0016] (2) The present invention determines the scaling amount of trapping processing based on the resolution and makes targeted judgments on the items in the image, reflecting the anticipation of possible trapping defects, ensuring that the details of the image are not easily lost and the color transition is smoother.

[0017] (3) This invention proposes trapping of the four color channels sequentially and expansion / contraction trapping between spot color channels for the area to be processed. It clarifies the expansion / contraction method of opacity inks and establishes a standardized operating procedure with opacity as the judgment criterion, upgrading trapping processing from a skill relying on subjective experience to a process based on objective data. This not only ensures the visual hierarchy and outline stability but also conforms to the actual printing effect. More importantly, it provides clear and unified instructions for prepress software and operators, ensuring the stability and consistency of output effects on different devices and materials, and restoring the expected visual performance of the original design. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating an image trapping process before printing provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of an image trapping processing system provided in an embodiment of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0021] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0022] Example 1 like Figure 1 As shown, this embodiment provides an image trapping processing method before printing, including the following steps: S1: Obtain the physical color separation image of the image to be printed. The physical color separation image includes four color channels and spot color channels. The four color channels, from light to dark, include yellow channel, red channel, blue channel and black channel. Generally, for four-color electrochromatograms, the yellow (Y) channel changes the most after trapping, followed by the red (M) channel, then the blue (C) channel changes little, and the black (K) channel remains unchanged. S2: Select the area to be trapped in the physical electrical analysis map as the area to be processed; Before trapping, you need to make a selection area; for flat halftone, you don't need to make a selection area. Without selection trapping, the overall effect of the electrical discharge map changes significantly; with selection, only the selected area changes, while the rest remains unchanged. Trapping treatment follows these principles: light colors show greater variation, dark colors show less variation, and the darkest colors show no variation. S3: Trapping between the four color channels in the area to be processed, following the expansion and contraction direction from light to dark; The trapping process between the four color channels includes: Select the channel that needs to be expanded or contracted from the four color channels, open the channel to be expanded, and perform trapping to expand the selected channel into the opened channel.

[0023] The trapping process between the four color channels mainly involves selecting the CMYK channel, trapping the four colors without considering halftone, expanding from light to dark colors, and following the expansion and contraction direction from light (Y) to dark (K). Specifically, select the channel that needs to be expanded or contracted, and expand or contract the selected channel from light to dark. Open the channel you want to expand into, but don't select it. After trapping, the selected channel will expand into the open channel. For example, if you select channel M, open channel C, and close other channels, after trapping, channel M will expand into channel C, and the other channels will not participate in the expansion or contraction.

[0024] S4: For the area to be processed after trapping between the four color channels, trapping between the spot color channels is performed in the direction of expansion and contraction from light to dark. The trapping process for spot color channels is only related to density and hue. Higher density means a darker color, while hue is determined automatically by Lab.

[0025] When the density of all spot color channels is 0, the depth is automatically determined based on the hue.

[0026] When the density of a spot color channel is 100, it means that this spot color is the darkest, and other colors are diffused into it.

[0027] Density is used to simulate the covering power of spot color inks in actual printing, i.e., opacity. It only changes the display in the software to predict the printing effect and does not change the actual output color data.

[0028] 0 represents transparent, and 100 represents opaque with the strongest coverage, completely obscuring the text and images underneath. Higher opacity values ​​indicate a darker color. Generally, black, gold, and silver are opaque colors.

[0029] A spot color density of 100 indicates that this spot color is the darkest, and other colors expand into it.

[0030] During processing, all spot color channels are selected and processed in an expansion / contraction direction from light to dark, with black being the darkest color and no trapping applied by default.

[0031] Specifically, select the spot color channel, turn off the four color channels, trap between spot colors, and do not trap between color separations; Open the channel that needs to be expanded, and expand the opened channel with a special color.

[0032] S5: For the area to be processed after trapping between spot color channels, trap the four color channels into the spot color channels to obtain the trapped image.

[0033] When trapping a spot color channel from a four-color channel, the spot color density is 100.

[0034] During processing, select all channels, use four-color trapping to spot color, and the default spot color is opaque ink; Specifically, select a single channel and open the channel that needs to be expanded; after trapping, expand the selected channel into the opened channel; The spot color channel uses opaque inks, and by default, the bottom spot color is the darkest color and is not trapped.

[0035] Preferably, before trapping, it is determined whether the corresponding area to be processed contains coffee beans, fruit, animal hair, water splashes, rice, salt, or sesame seeds; if so, the images before and after trapping are compared to determine whether the color change is too large or the details are missing; if so, the trapping expansion and contraction amount is adjusted.

[0036] Specifically, the color depth of an electrical discharge map is rich and dense, and the color becomes darker after scaling; the opposite color becomes black after scaling, with a large contrast between the bright and dark areas and few midtones; such as coffee beans, fruits, etc. After trapping in an electrostatically separated layer, the color of highlights changes significantly; for example, in animal fur. Details are easily lost once they are captured; such as water droplets, rice, salt, sesame seeds, etc.

[0037] Preferably, during the trapping process, the scaling factor of the image is determined based on the resolution of the area to be processed.

[0038] Specifically: If the resolution of the area to be processed is within the range of 250-350, then the image scaling factor is 3 pixels. If the area to be processed contains fine lines or text, the image scaling will be within 2 pixels.

[0039] If the desired processing effect cannot be achieved when trapping with 1 pixel, multiple trapping processes are performed consecutively, such as trapping 2-3 times consecutively.

[0040] In addition, the aesthetics of trapping must also be considered during the trapping process. Specifically: When applying a background color to an electrical separation pattern with varying shades, it is important to ensure that the main body of the pattern is not affected after scaling. The primary principle for expansion and contraction is to maintain aesthetics. Shadows can be appropriately lightened to create a smooth transition between expansion and contraction.

[0041] When expanding or shrinking, pay attention to the hue of the spot color. Based on the hue of the spot color, hues that do not show color will expand or shrink normally, while hues that change color will shrink less.

[0042] Example 2 like Figure 2 As shown, this embodiment provides an image trapping processing system that implements the image trapping processing method before printing as described in Embodiment 1, comprising: The image acquisition module is used to acquire the physical color separation image of the image to be printed. The physical color separation image includes four color channels and spot color channels. The four color channels, from light to dark, include yellow channel, red channel, blue channel and black channel. The selection module is used to select the areas that need to be trapped in the physical electrical analysis diagram as the areas to be processed; The four-color channel trapping module is used to trap the area to be processed between four color channels in an expansion and contraction direction from light to dark. The spot color channel trapping module is used to trap the area to be processed after the trapping between the four color channels is completed, according to the expansion and contraction direction from light to dark. The inter-channel trapping module is used to trap the area to be processed after trapping between spot color channels using four color channels to the spot color channels, thereby obtaining the trapped image.

[0043] This embodiment also provides a computer-readable storage medium storing a computer program, which is executed by a processor as the image trapping processing method before printing as described in Embodiment 1.

[0044] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for image trapping processing before printing, characterized in that, Includes the following steps: Obtain the physical color separation image of the image to be printed. The physical color separation image includes four color channels and spot color channels. The four color channels include yellow channel, red channel, blue channel and black channel from light to dark. Select the areas to be trapped in the physical electrical analysis diagram as the areas to be processed; Trapping is performed between the four color channels in the area to be processed, following a direction of expansion and contraction from light to dark. After trapping between the four color channels, trapping between the spot color channels is performed in a direction of expansion and contraction from light to dark. For the area to be processed after trapping between spot color channels, trapping is performed from the four color channels to the spot color channels to obtain the trapped image.

2. The image trapping processing method before printing according to claim 1, characterized in that, The trapping process between the four color channels includes: Select the channel that needs to be expanded or contracted from the four color channels, open the channel to be expanded, and perform trapping to expand the selected channel into the opened channel.

3. The image trapping processing method before printing according to claim 1, characterized in that, The trapping process between the spot color channels includes: Close the four color channels, select the channel that needs to be expanded or contracted from the spot color channels, open the channel to be expanded, and perform trapping to expand the selected spot color channel into the opened spot color channel.

4. The image trapping processing method before printing according to claim 1, characterized in that, The process of trapping from the four color channels to the spot color channels includes: Select the channel that needs to be expanded or contracted from the four color channels, open the spot color channel with opaque ink, and expand the selected channel into the opened channel.

5. The image trapping processing method before printing according to claim 1, characterized in that, During the trapping process, the method determines the scaling factor of the image based on the resolution of the area to be processed.

6. The image trapping processing method before printing according to claim 5, characterized in that, The process of determining the image scaling based on the resolution of the region to be processed is as follows: If the resolution of the area to be processed is within the range of 250-350, then the scaling factor of the image is 3 pixels. If the area to be processed contains fine lines or text, the scaling of the image shall be within 2 pixels.

7. The image trapping processing method before printing according to claim 6, characterized in that, If the method fails to achieve the desired processing effect when trapping with a single pixel, it will perform trapping multiple times consecutively.

8. The image trapping processing method before printing according to claim 1, characterized in that, Before trapping, the method determines whether the corresponding area to be processed contains coffee beans, fruit, animal hair, water splashes, rice, salt, or sesame seeds. If so, the images before and after trapping are compared to determine whether the color change is too large or details are missing. If so, the trapping scaling amount is adjusted.

9. An image trapping processing system that implements the image trapping processing method before printing as described in any one of claims 1-8, characterized in that, include: The image acquisition module is used to acquire the physical color separation image of the image to be printed. The physical color separation image includes four color channels and spot color channels. The four color channels include yellow channel, red channel, blue channel and black channel from light to dark. The selection module is used to select the partitions that need to be trapped in the physical electrical analysis diagram as the areas to be processed; The four-color channel trapping module is used to trap the area to be processed between four color channels in an expansion and contraction direction from light to dark. The spot color channel trapping module is used to trap the area to be processed after the trapping between the four color channels is completed, according to the expansion and contraction direction from light to dark. The inter-channel trapping module is used to trap the area to be processed after trapping between spot color channels using four color channels to the spot color channels, thereby obtaining the trapped image.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, which is executed by a processor according to any one of claims 1 to 8.

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