A method for preventing banding in gradient printing

Abstract

The present application provides a method for preventing the appearance of a fault in a gradient color print, comprising the following steps: copying a print image as an initial repair image; using image processing software to locate a gradient fault area with a step value of 70-85% on the repair image; performing a repair gradient in the gradient fault area, saving it as a final repair image, and gradually reducing the step value from the middle to both sides; and engraving a print image on a plate roller first, and then engraving the final repair image on the plate roller to complete the production of a fault-free plate roller. The present application solves the problem of the appearance of a fault in the middle tone area when a gradient image is printed on an existing electrographic plate roller.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of intaglio printing technology, in particular to a method for preventing the appearance of faults in gradient color printing. BACKGROUND

[0002] At present, the printing of packaging paper with gradient color is carried out by first drawing a gradient format tiff format image by Photoshop and the like image processing, then importing the image into the software of an electrographic machine, and then engraving the gradient size dots (meshes) on the plate roller according to the image by the electrographic machine, and then printing on the printing paper by using the plate roller with engraved dots. Since the electrographic technology can only use amplitude modulation dots, the amplitude modulation dots have the feature that the number of dots corresponding to different unit areas of gradient color is the same, the dots corresponding to the area with deeper printing color are larger, and the width of the mesh wall is smaller, while the dots corresponding to the area with shallower printing color are smaller, and the width of the mesh wall is larger. Under normal circumstances, with the gradient of the color, the ratio of the dots and the mesh wall engraved by the electrographic machine will not have a jump change. During printing, the ink will be transferred from the dots on the surface of the plate roller to the surrounding mesh wall through a certain pressure, and when the expansion reaches a certain amplitude, the ink between the dots will be connected, and the ink will be merged. However, in the middle tone area with a gradient of 70-85% of the tone value, the ink in the dots of part of the area with the middle tone will be completely merged after being transferred, while the ink in some dots cannot be merged due to uneven pressure and insufficient expansion amplitude, and the ratio of the corresponding dots and the mesh wall will suddenly change, resulting in a large change. In addition, the different ink viscosity and printing materials of different manufacturers result in a jump change in the merged and unmerged areas, and the printed color has a relatively obvious fault, especially in the case of transparent white packaging paper, the fault will be more obvious, which affects the printing quality. SUMMARY

[0003] The purpose of the present application is to provide a method for preventing the appearance of faults in gradient color printing, and to solve the problem that the existing electrographic plate roller has a obvious fault in the middle tone area when printing a gradient image.

[0004] The technical scheme adopted by the present application to solve the technical problem is as follows:

[0005] A method for preventing the appearance of faults in gradient color printing, comprising the following steps:

[0006] copying a printing image to obtain an initial repair image;

[0007] positioning to the gradient fault area with a tone value of 70-85% on the repair image by using an image processing software;

[0008] performing a repair gradient in the gradient fault area, and saving the repair gradient as a final repair image, wherein the tone value of the repair gradient gradually decreases from the middle to both sides.

[0009] In the engraving of the plate roller, the printing image is first engraved on the plate roller, and then the final repair image is engraved on the plate roller to complete the production of the seamless plate roller.

[0010] Further, the image processing software is Photoshop.

[0011] Further, the color mode of the printing image and the repair image is CMYK color.

[0012] Further, in positioning the gradual transition layer area, the corresponding color image is selected in the channel according to the color of the layer to perform the repair transition.

[0013] Further, in positioning the gradual transition layer area, a set of color anchor points are set at positions with 70% and 85% of the tone value, and the area between the two sets of color anchor points is the gradual transition layer area.

[0014] Further, the repair transition gradually decreases from the highest 40-45% tone value in the middle to both sides.

[0015] Further, the repair transition is adjusted by the "curve" function.

[0016] The beneficial effects of the present application: using the method provided by the present application to make a repair image according to a printing image and perform repair engraving, can supplement the screen dots on the screen wall with gradual transition in the middle tone area. When printing, the ink can fill more screen dots in this area, and the ink merging is not easy to appear layer, which can well guarantee the color quality of the printed product.

[0017] The present application will be described in more detail below with reference to the accompanying drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is the initial repair image pattern in the present application which has not been processed by gradual transition.

[0019] Figure 2 It is the final repair image pattern processed by gradual transition in the present application.

[0020] Figure 3 It is the screen dot screen wall structure engraved on the plate roller surface corresponding to the gradual transition layer area.

[0021] Figure 4 It is the screen dot screen wall structure for repairing the gradual transition layer area.

[0022] Figure 5 It is the screen dot screen wall structure after two times of engraving on the plate roller surface corresponding to the gradual transition layer area. DETAILED DESCRIPTION

[0023] A method for preventing layering defects in gradient color printing includes the following steps:

[0024] First, make a copy of the printed image as the initial repair image 11 to repair the gradient; it should be noted that the color mode of both the printed image and the initial repair image 11 is CMYK.

[0025] Open the initial repair image 11 using Photoshop image processing software, and open the "Channels" panel. Based on the color of the fault, you can see the corresponding CMYK color image in the channel, and select only one color (such as cyan) to locate the gradient fault area 4 and perform the repair gradient.

[0026] Open and refer to the "Info" panel under the "Window" menu. Use the color sampling tool to move and select the gradient fault area 4, as shown below. Figure 1 As shown, color anchor points 2 and 3 are set at positions with a tonal value of 70% and 85% respectively, and the area between the two sets of color anchor points is a gradient fault area 4 with a tonal value of 70-85%.

[0027] In the "Image" - "Adjustments" menu, open the "Curves" dialog box. Perform a repair gradient within the gradient fault area 4. Drag the curve to adjust the gradient, making the tonal values ​​of the repair gradient gradually decrease from the highest 40-45% in the middle towards both sides. Try to avoid letting the gradient colors cover the normal color areas. Then delete other color images (such as magenta, yellow, and black), keeping only the processed color image (such as cyan). The image will automatically be converted to grayscale mode. Alternatively, select the processed color image (such as cyan), then select the "Image" - "Mode" menu and choose the "Grayscale" option. Merge the layers and discard the other channels. Finally, save as follows: Figure 2 The final repaired image 12 shown is in TIFF format;

[0028] When engraving the printing roller, the original printed image is first imported into the engraving software and engraved onto the roller, forming a shape like... Figure 3 The dotted mesh wall structure shown is then used to construct the mesh wall structure as shown in the diagram. Figure 2 The final repaired image 12 shown is imported into the electro-engraving software and engraved onto the printing roller, as shown. Figure 3 The image shows a dotted mesh wall structure used for repair, which is formed after two carvings. Figure 4 The dot wall structure shown can be used to create a non-discontinuous printing roller and can be used for non-gradient color discontinuous printing.

[0029] By performing second engraving on the plate roller, the screen dot corresponding to the final repair image is engraved to the gradual fault area, the screen wall is partially supplemented with screen dots, the gradual fault area can fill more ink, the ink is transferred from the screen dots during roller pressing, and the ink is not easy to appear fault when the ink overcomes the screen wall and merges with each other, effectively avoiding the problem that the printed color appears fault, and ensuring the color quality of the printed product.

[0030] The method for preventing gradual color printing from appearing fault is exemplarily described above in combination with the drawings. Apparently, the specific implementation of the present application is not limited by the above manner, and various improvements using the method concept and technical solution of the present application or direct application to other occasions without improvement all fall within the protection scope of the present application.

Claims

1. A method of preventing banding in a gradient print, characterized by, It comprises the following steps: Copy one print image as an initial repair image (11) for repairing the gradient; Open the initial repair image (11), and perform the repair gradient on the corresponding color image in the channel according to the color of the fault when locating the fault area (4); Locate the fault area (4) with an image processing software on the initial repair image (11) when the step value is 70-85%; Set a group of color anchors at the two end points of the step value when locating the fault area (4), and the area between the two groups of color anchors is the fault area (4); Perform the repair gradient in the fault area (4), and adjust the gradient so that the step value of the repair gradient gradually decreases from the highest 40-45% step value in the middle to both sides; Delete other color images and only keep the processed color image, and automatically convert the image to grayscale mode and save it as a final repair image (12); or select the processed color image, select the "grayscale" option, combine the layers and discard other channels, and save it as a final repair image (12); When engraving the plate roller, first engrave the print image on the plate roller, and then engrave the final repair image (12) on the plate roller, engrave the corresponding screen holes of the final repair image (12) to the fault area (4), and supplement the screen holes to part of the screen wall to make the fault area (4) fill more ink, and complete the production of the fault-free plate roller.

2. The method of preventing banding in gradient printing according to claim 1, wherein The image processing software is Photoshop.

3. The method of preventing banding in gradient printing according to claim 1, wherein The color mode of the print image and the repair image is CMYK color.

4. The method of preventing banding in gradient printing according to claim 1, wherein When performing the repair gradient, try not to cover the normal color area with the gradient color.

5. The method of preventing banding in gradient printing according to claim 1, wherein The repair gradient is adjusted by the "curve" function.

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