Improvement method of grating anti-counterfeiting phase modulation based on color values

Abstract

The invention discloses an improvement method of grating anti-counterfeiting phase modulation based on color values. The method comprises the following steps: step 1: selecting and decomposing a hostimage; step 2: determining a hidden area of the host image and anti-counterfeiting information: at least one color channel of the host image has a hidden area where the anti-counterfeiting informationcan be set, the hidden area has s*s pixel points, the color channel where the hidden area is located is recorded as a mother set, the color values of all pixel points of the hidden area on the motherset are the same and are recorded as alpha, and the rest color channels are 3 secondary versions; step 3, performing halftone processing on the host image; and step 4: hiding the anti-counterfeitinginformation: selecting the anti-counterfeiting information that needs to be hidden, establishing a lattice point selection area in the hidden area corresponding to the contour of the anti-counterfeiting information in image processing software, recording lattice points in the lattice point selection area as a set A, and performing phase modulation on the lattice points in the set A. By adoption ofthe improvement method disclosed by the invention, the modulable angle range of the lattice points is expanded.

Description

technical field [0001] The invention belongs to the technical field of grating anti-counterfeiting, and in particular relates to an improved method for phase modulation of grating anti-counterfeiting based on color values. Background technique [0002] The limit resolution ability of normal human vision is limited. When the size and pitch of dots in the digitally screened image are smaller than the limit resolution ability of human vision, the human eye cannot distinguish the dots. Therefore, in fact, the discretized binary image is discontinuous, but due to the visual characteristics of the human eye, if you look at it at a certain viewing distance, you cannot distinguish the dots at all, that is, you cannot distinguish the image details, and finally give people a continuous tone. image effects for print reproduction of continuous tone originals. [0003] Grating anti-counterfeiting is the anti-counterfeiting technology produced by the combination of halftone screening tec...

AI Technical Summary

Problems solved by technology

[0007] 1. There is a far-reaching technical bias in the principle of optimal outlets: Existing studies all believe that the displacement setting of outlets must meet the principle of optimal outlets. Only when the outlets that make up the anti-counterfeiting information are at the optimal location, when the digital grating detects the anti-counterfeiting information, The reproduction of anti-counterfeiting information is the most obvious and clear, but there has been a habitual technical bias in the prior art for many years, and it is believed that the best point is only to move D / 2 along the direction of the screen angle or the direction perpendicular to the screen angle, resulting in theoretical Guidance angle The angle and distance that can be adjusted by the net point are very limited;

[0008] 2. The research on the overlap of dots is not in place: In order to realize the moiré effect, all the dots in the dot selection area are considered to have the same displacement. The displacement direction is along the direction of the screen angle or the direction perpendicular to the screen angle. The displacement distance It is D / 2. At the same time, since the screening parameters will be set in the early halftone processing, the number of screen lines is a known number, and the number of screen lines determines D and the side length D of a single halftone adjustment unit. 2 , D=D 2 , therefore, D / 2 is a fixed value; however, for some of the dots located on the border of the dot selection area, the actual movable distance is the distance between the closest points of the two dots, which is recorded as D 1 , with the increase of dot percentage, D 1 will gradually decrease, therefore, D 1 is a variable; when D 1 When it is less than D / 2, if the phase modulation is still carried out according to the method of the prior art, it will cause overlapping between the network points on the boundary, cause strong visual perception, and make the anti-counterfeiting invalid. The actual distance between the network points has not been considered in the prior art Synergistic impact on concealment and extraction performance

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