CN108391030A - A kind of the colorless fluorescent halftone color image screening method and device arranged side by side based on site - Google Patents

Abstract

The invention discloses a colorless fluorescent half-tone color image screening method and device based on dot juxtaposition. The method comprises: forming a threshold value matrix used for parallel AM screening with regular triangular network points, and using the threshold value matrix to perform amplitude modulation screening on the R, G, and B three-color chips of the color image, so that the color separation chips form halftones image. The device includes: a matrix module, which is used for the threshold value matrix of the side-by-side AM screening of the dots formed by regular triangular dots. The parallel AM screening method of equilateral triangular dots proposed by the present invention makes the gradation effect of the colorless fluorescent halftone color image better, can well show the gradation level of the image, and has good reproduction performance, which overcomes the existing technology to achieve no Problems with fluorescent color images.

Description

A colorless fluorescent halftone color image screening method based on dot juxtaposition and its device

technical field

The invention relates to the field of colorless fluorescent printing, in particular to a colorless fluorescent halftone color image screening method and device based on dot juxtaposition.

Background technique

In recent years, with the continuous maturity of printing anti-counterfeiting technology, more and more printing suppliers are pursuing unique and safe anti-counterfeiting artistic effects. Colorless fluorescent ink is more and more popular because of its simple implementation, bright colors, good concealment, low cost, and convenient inspection. Colorless fluorescent prints can emit visible light with a longer wavelength under the excitation of short-wave ultraviolet rays, so they have a certain anti-counterfeiting effect and are widely used in packaging printing and anti-counterfeiting printing. At present, colorless fluorescent inks are limited to printing monochrome patterns. The technology of using colorless fluorescent inks to print true-color anti-counterfeiting images is not yet mature. The research of printing color pattern technology is particularly important.

In the prior art, attempts have been made to use colorless fluorescent inks to reproduce true-color images, so that colorful images with rich tones can be observed under fluorescent lamps. Chinese patent CN102241208A discloses a colorless fluorescent anti-counterfeiting method, which aims to color the same image multiple times with three fluorescent colors of red, blue and yellow to achieve the image effect of color superimposition, and through super-line FM anti-counterfeiting pattern and personalized manual signature to achieve the purpose of improving the anti-counterfeiting effect. According to the context of this patent, this color overprinting method cannot well restore color images with rich tones.

Chinese patent CN102514408A also discloses a method of printing color anti-counterfeiting images using colorless fluorescent ink. The method uses image processing software to separate the printed anti-counterfeiting images according to red, green and blue colors, and then distributes dots according to the pictures. Processing, making red, green and blue three-color printing plates, and then printing on the machine with corresponding red, green and blue colorless fluorescent inks. Through the context of this patent, no specific dot distribution processing method or algorithm is proposed, and it is difficult to judge the specific effect of colorless fluorescent ink printing color anti-counterfeiting images realized by it.

Chinese patent CN102490507A also discloses a method for making anti-counterfeit printed matter with colorless fluorescent ink. The method described in this patent is basically consistent with the method described in Chinese patent CN102514408A, and there is no substantial improvement plan.

Chinese patent CN106515241A discloses a fluorescent color image screening method and device, which proposes to arrange at least three dots into a regular triangle or regular hexagonal grid unit, and arrange the grid units into a grid array, which has a common The angle between the grid center point line of the side and the horizontal reference line includes X°, X+60° or X+120°, where X is between 0°-360°, and then the UV-excited colorless fluorescent RGB ink is used as a grid Array method for screen processing. This method changes the arrangement of dots to reduce the probability of overprinting of RGB three-color inks, and solves the problem of paleness of colorless fluorescent inks under the excitation state of ultraviolet light. However, this method reduces the overprinting probability of RGB three-color inks. The restored image is generally dark, and the color reproduction of bright parts is not good.

Foreign patent US8085438B2 discloses a method for printing color images visible under fluorescent lamps on anti-counterfeiting documents and securities. The method uses linearly arranged dots to perform parallel screen processing of R, G, and B three colors, that is, R The dots of the three colors of , G, and B are arranged in a staggered order in a straight line, and then printed with the corresponding three-color colorless fluorescent ink of R, G, and B. This method can avoid the whitening of the color caused by excessive overlapping of RGB three colors, but because the dots are arranged in a straight line, the gap between adjacent dots will reveal the paper color, and when observed under the purple light , The natural color paper without the addition of fluorescent whitening agent is black or grayish black, which makes the color image realized by this method darker overall.

Contents of the invention

In order to overcome at least one defect of the above-mentioned prior art, the present invention proposes a colorless fluorescent halftone color image screening method and device based on dot juxtaposition, which can well display the image's gradation level and good reproduction performance .

In order to solve the problems of the technologies described above, the technical solution of the present invention is as follows:

A colorless fluorescent halftone color image screening method based on dot juxtaposition is provided, comprising the following steps:

S1. Constitute the threshold value matrix used for the parallel AM screening of network points with equilateral triangle network points;

S2. Set different threshold matrixes for the three color separations of R, G, and B. When performing threshold processing on the image, it is satisfied that the dot coverage area of the bright tone part of the image increases with the increase of the bright tone, so as to meet the requirements of the three color separations of R, G, and B. The color screen dots form the effect of dot overlap in the bright tone part, so that the restored bright tone part is consistent with the original image; the dot coverage area of the dark tone part of the image decreases with the increase of the dark tone, so as to meet the three-color dots of R, G, and B. The juxtaposition of dots is formed in the dark part, so that the restored dark part is consistent with the original image;

S3. Use the threshold value matrix corresponding to the R, G, and B three color separations to perform amplitude modulation screening on the R, G, and B three color separations of the color image, so that the color separations form a halftone image;

After the color separation screen is completed, the color separation printing plate is output, and the corresponding R, G, B color colorless fluorescent ink is used for printing, and the colorless fluorescent halftone color image with the same color and tone as the original image is reproduced.

Further, step S1 specifically includes:

Step S11, tiling regular triangular network points in the threshold matrix;

Step S12, setting different threshold matrixes for the three color separations of R, G, and B;

Step S13, mapping each pixel of the corresponding threshold value matrix to each regular triangular mesh point of the corresponding R, G, and B trichromatic colors;

Step S14 , for each regular triangle dot on the three color separations of R, G, and B, a threshold is set for each pixel therein.

Further, step S11 specifically includes:

dividing the threshold matrix into a plurality of tiled feature rectangles;

Set each feature rectangle to include: two regular triangle dots D01 and D02, in the middle, and four 1/2 regular triangle dots D1, D2, D3, D4, respectively located at the four corners of the feature rectangle, and similar to D01 and D02 adjacent. Wherein, take the horizontal line of the tiling direction as the cutting line, pass through the midline of the regular triangle, and divide the regular triangle dots into two parts.

Further, in step S11, the method for dividing the threshold matrix into a plurality of tiled characteristic rectangles includes: setting the length s and width t of the characteristic rectangles to be relatively prime, and satisfying

Set the tiling direction θ, where tgθ=a/b, and a and b are also relatively prime;

Set the length M and width N of the threshold matrix, where:

Among them, Min{,} means the operation of taking the minimum value, <,> means the operation of taking the greatest common divisor, the symbol int() means the operation of taking positive numbers, res is the printing output resolution, and freq is the number of printing screen lines.

Further, step S12 specifically includes:

The threshold setting of the R color separation chip starts from the left vertex of the regular triangle, follows the direction indicated by the arrow in the figure, and ends at the upper vertex of the regular triangle to complete the threshold setting;

The threshold setting of the G color separation chip starts from the right vertex of the equilateral triangle, follows the direction indicated by the arrow in the figure, and ends at the left vertex of the equilateral triangle to complete the threshold setting;

The threshold setting of the color separation chip of B starts from the upper vertex of the equilateral triangle, follows the direction indicated by the arrow in the figure, and ends at the right vertex of the equilateral triangle to complete the threshold setting.

Further, the minimum threshold matrix [M _min , N _min ] is obtained, and at this time, M _min =34, N _min =20.

Another object of the present invention is to provide an AM screening device with parallel dots, including: a matrix module, used for a threshold value matrix for parallel AM screening with dots in regular triangle.

Further, the matrix module includes:

The tiling module is used for tiling the regular triangle network points in the threshold matrix. The tiling module includes:

A division module, configured to divide the threshold matrix into a plurality of tiled feature rectangles;

The building block is used to set each characteristic rectangle to include: two regular triangle dots D01 and D02 in the middle, and four 1/2 regular triangle dots D1, D2, D3, D4, respectively located at the four corners of the characteristic rectangle, and Adjacent to D01 and D02. Wherein, take the horizontal line of the tiling direction as the cutting line, pass through the midline of the regular triangle, and divide the regular triangle dots into two parts.

Compared with the prior art, the beneficial effects of the present invention are:

The side-by-side screening method proposed by the present invention makes the gradation effect of the colorless fluorescent halftone color image better, can well show the gradation level of the image, and has better reproducibility.

Description of drawings

The accompanying drawings used here are used to provide a further understanding of the present invention and constitute a part of the application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations to the present invention. In the attached picture:

FIG. 1 is a schematic diagram of the regular triangle dot shape change rule according to an embodiment of the present invention.

FIG. 2 is a flow chart of constructing a threshold value matrix with equilateral triangle network points according to an embodiment of the present invention.

Fig. 3 is a schematic diagram of a feature rectangle created according to an embodiment of the present invention.

Fig. 4 is a schematic diagram of dividing a threshold matrix into a plurality of tiled feature rectangles according to an embodiment of the present invention.

Fig. 5 is a schematic diagram of regular triangle division in each characteristic rectangle according to an embodiment of the present invention.

Fig. 6 is a schematic diagram of the threshold setting trend in the equilateral triangle when the three-color thresholds of R, G, and B are set according to an embodiment of the present invention.

FIG. 7 is a schematic diagram of simulated printing of R, G, and B three-color halftone images according to an embodiment of the present invention.

FIG. 8 is a schematic diagram of a minimum threshold matrix of an R color separation chip obtained by the threshold matrix processing method according to an embodiment of the present invention.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Example 1

This embodiment provides a method for screening a colorless fluorescent halftone image with parallel dots, including: forming a threshold value matrix for AM screening with regular triangle dots.

Specifically include the following steps:

S1. Constitute the threshold value matrix used for the parallel AM screening of network points with equilateral triangle network points;

S2. Set different threshold matrixes for the three color separations of R, G, and B. When performing threshold processing on the image, it is satisfied that the dot coverage area of the bright tone part of the image increases with the increase of the bright tone, so as to meet the requirements of the three color separations of R, G, and B. The color screen dots form the effect of dot overlap in the bright tone part, so that the restored bright tone part is consistent with the original image; the dot coverage area of the dark tone part of the image decreases with the increase of the dark tone, so as to meet the three-color dots of R, G, and B. The juxtaposition of dots is formed in the dark part, so that the restored dark part is consistent with the original image;

S3. Using the threshold matrix corresponding to the three color separations R, G, and B to perform amplitude modulation screening on the R, G, and B color separation chips of the color image, so that the color separation chips form a halftone image.

FIG. 1 is a schematic diagram of the dot change rule of the regular triangular dot shape according to the change process of the gradation of 0-100 in this embodiment. According to the difference between the principle of color addition and color subtraction, the left side with the darkest color after halftone screening in Figure 1 is actually the lightest white area (highlight area) in the original image; after halftone screening The lightest right side is actually the darkest black area (shadow area) in the original image.

Fig. 2 has shown the flow chart that constitutes threshold value matrix with equilateral triangle network point according to a preferred embodiment of the present invention, comprises:

Step S11, tiling regular triangular network points in the threshold matrix;

Step S12, setting different threshold matrixes for the three color separations of R, G, and B;

Step S13, mapping each pixel of the corresponding threshold value matrix to each regular triangular mesh point of the corresponding R, G, and B trichromatic colors;

Step S14 , for each regular triangle dot on the three color separations of R, G, and B, a threshold is set for each pixel therein.

Fig. 3-Fig. 5 shows the schematic diagram of tiling equilateral triangle (step S11) in the threshold value matrix according to the preferred embodiment of the present invention, and Fig. 3 shows the characteristic rectangle of creation; Fig. 4 shows that the threshold value matrix is divided into A plurality of characteristic rectangles tiled; Figure 5 shows that each characteristic rectangle includes: two regular triangle dots D01 and D02, in the middle position, and four 1/2 regular triangle dots D1, D2, D3, D4, They are respectively located at the four corners of the characteristic rectangle and adjacent to D01 and D02. Wherein, take the horizontal line of the tiling direction as the cutting line, pass through the midline of the regular triangle, and divide the regular triangle dots into two parts.

FIG. 6 is a schematic diagram showing the direction of threshold setting within an equilateral triangle when different threshold matrices are set for the three color separations of R, G, and B described in step S12. Among them, the threshold value setting of the R color separation chip starts from the left vertex of the regular triangle, and follows the direction indicated by the arrow in the figure, and ends at the upper vertex of the regular triangle, and the threshold value setting is completed; the threshold value setting of the G color separation chip starts from the right vertex of the regular triangle. as the starting point, follow the direction indicated by the arrow in the figure, and end at the left apex of the equilateral triangle, and complete the threshold setting; the threshold setting of B color separation film starts from the upper apex of the equilateral triangle, and follows the direction indicated by the arrow in the figure, to the right of the equilateral triangle. The vertex ends and the threshold setting is completed;

Since regular triangles cannot be tiled in the threshold matrix compared to square or rectangular dots, the characteristic rectangle A (as shown in Figure 3) is defined, and the threshold matrix tiling operation is performed using the characteristic rectangle A (as shown in Figure 4) Finally, divide regular triangles (as shown in FIG. 5 ) in each characteristic rectangle A, so as to realize the effect of tiling regular triangle mesh points in the threshold value matrix.

Fig. 7 is a schematic diagram showing simulated printing of R, G, and B three-color halftone images according to a preferred embodiment of the present invention, wherein the black color is the simulated color rendering effect of natural-color paper under a purple light. The enlarged image on the left side of Figure 7 shows the side-by-side arrangement effect of R and B two-color dots in the dark part of the original image; the middle enlarged image shows the side-by-side arrangement effect of R, G and B three-color dots in the mid-tone part of the original image. Among them, R and B two-color dot overlap effect has appeared; the enlarged image on the right shows the overlapping arrangement effect of R, G, B three-color dots in the bright tone part of the original image. The addition of color and light to present white, and the three-color overprinting method avoids the darkening of the bright tone part of the image due to the juxtaposition of dots.

Preferably, the method for dividing the threshold matrix into a plurality of tiled feature rectangles includes:

Set the length s and width t of the feature rectangle to be relatively prime, and satisfy

Set the tiling direction θ, where tgθ=a/b, and a and b are also relatively prime;

Set the length M and width N of the threshold matrix, where:

Among them, Min{,} means the operation of taking the minimum value, <,> means the operation of taking the greatest common divisor, the symbol int() means the operation of taking a positive number, res is the printing output resolution, and freq is the number of printing screen lines;

Preferably, when θ=0, set s=17, t=10, at this time obtain the minimum threshold matrix [M _min , N _min ], at this time M _min =34, N _min =20, so that the amount of calculation can be reduced, Accelerate the screen processing speed, it is easy to realize with the computer.

Fig. 8 shows the minimum threshold value matrix of the R color separation chip obtained according to the threshold value matrix processing method described in the preferred embodiment of the present invention. Similarly, the minimum threshold value matrix of the G and B color separation chips can be obtained, and satisfy R, G, The threshold matrix for the B trichroic patch is completely different.

Example 2

This embodiment provides a colorless fluorescent halftone color image screening device based on dot juxtaposition, which includes: a matrix module for forming a threshold matrix for amplitude modulation screening with equilateral triangle dots. The matrix module also includes a tiling module, which is used to tile regular triangle meshes in the threshold matrix.

Preferably, the tiling module includes:

A division module, configured to divide the threshold matrix into a plurality of tiled feature rectangles;

The building block is used to set each characteristic rectangle to include: two regular triangle dots D01 and D02 in the middle, and four 1/2 regular triangle dots D1, D2, D3, D4, respectively located at the four corners of the characteristic rectangle, and Adjacent to D01 and D02. Wherein, take the horizontal line of the tiling direction as the cutting line, pass through the midline of the regular triangle, and divide the regular triangle dots into two parts.

The above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. All modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (10)

1. A colorless fluorescent halftone color image screening method based on dots juxtaposed, is characterized in that, adopts equilateral triangle dots to constitute the threshold value matrix for the amplitude modulation screening that dots are juxtaposed. 2. the colorless fluorescent halftone color image screening method based on dot juxtaposition according to claim 1, is characterized in that, comprises the following steps: S1. Constitute the threshold value matrix used for the parallel AM screening of network points with equilateral triangle network points; S2. Set different threshold matrixes for the three color separations of R, G, and B. When performing threshold processing on the image, it is satisfied that the dot coverage area of the bright tone part of the image increases with the increase of the bright tone, so as to meet the requirements of the three color separations of R, G, and B. The color screen dots form the effect of dot overlap in the bright tone part, so that the restored bright tone part is consistent with the original image; the dot coverage area of the dark tone part of the image decreases with the increase of the dark tone, so as to meet the three-color dots of R, G, and B. The juxtaposition of dots is formed in the dark part, so that the restored dark part is consistent with the original image; S3. Using the threshold matrix corresponding to the three color separations R, G, and B to perform amplitude modulation screening on the R, G, and B color separation chips of the color image, so that the color separation chips form a halftone image. 3. the colorless fluorescent halftone color image screening method based on dot juxtaposition according to claim 2, step S1 specifically comprises: Step S11, tiling regular triangular network points in the threshold matrix; Step S12, setting different threshold matrixes for the three color separations of R, G, and B; Step S13, mapping each pixel of the corresponding threshold value matrix to each regular triangular mesh point of the corresponding R, G, and B trichromatic colors; Step S14 , for each regular triangle dot on the three color separations of R, G, and B, a threshold is set for each pixel therein. 4. the colorless fluorescent halftone color image screening method based on dot juxtaposition according to claim 3, step S11 specifically comprises: dividing the threshold matrix into a plurality of tiled feature rectangles; Set each feature rectangle to include: two regular triangle dots D01 and D02, in the middle, and four 1/2 regular triangle dots D1, D2, D3, D4, respectively located at the four corners of the feature rectangle, and similar to D01 and D02 adjacent. Wherein, take the horizontal line of the tiling direction as the cutting line, pass through the midline of the regular triangle, and divide the regular triangle dots into two parts. 5. the colorless fluorescent halftone color image screening method based on dot juxtaposition according to claim 4, in the step S11, the method for dividing the threshold value matrix into a plurality of tiled characteristic rectangles comprises: setting the characteristic rectangle The length s and width t are mutually prime, and satisfy Set the tiling direction θ, where tgθ=a/b, and a and b are also relatively prime; Set the length M and width N of the threshold matrix, where: Among them, Min{,} means the operation of taking the minimum value, <,> means the operation of taking the greatest common divisor, the symbol int() means the operation of taking positive numbers, res is the printing output resolution, and freq is the number of printing screen lines. 6. according to claim 3 or 4 or 5 described based on dot juxtaposition colorless fluorescent halftone color image screening method, step S12 specifically comprises: The threshold setting of the R color separation chip starts from the left vertex of the regular triangle, follows the direction indicated by the arrow in the figure, and ends at the upper vertex of the regular triangle to complete the threshold setting; The threshold setting of the G color separation chip starts from the right vertex of the equilateral triangle, follows the direction indicated by the arrow in the figure, and ends at the left vertex of the equilateral triangle to complete the threshold setting; The threshold setting of the color separation chip of B starts from the upper vertex of the equilateral triangle, follows the direction indicated by the arrow in the figure, and ends at the right vertex of the equilateral triangle to complete the threshold setting. 7. according to claim 3 or 4 or 5 described based on dot juxtaposition achromatic fluorescent halftone color image screening method, it is characterized in that, obtain minimum threshold value matrix [M _min , N _min ], now M _min =34 , N _min =20. 8. A colorless fluorescent halftone color image screening device based on dot juxtaposition, characterized in that it comprises: The matrix module is used to form a threshold matrix for parallel AM screening with regular triangular dots. 9. The colorless fluorescent halftone color image screening device based on dot juxtaposition according to claim 8, wherein the matrix module comprises: The tiling module is used for tiling the regular triangle network points in the threshold matrix. 10. The colorless fluorescent halftone color image screening device based on dot juxtaposition according to claim 9, wherein the tiling module comprises: A division module, configured to divide the threshold matrix into a plurality of tiled feature rectangles; The building block is used to set each characteristic rectangle to include: two regular triangle dots D01 and D02 in the middle, and four 1/2 regular triangle dots D1, D2, D3, D4, respectively located at the four corners of the characteristic rectangle, and Adjacent to D01 and D02. Wherein, take the horizontal line of the tiling direction as the cutting line, pass through the midline of the regular triangle, and divide the regular triangle dots into two parts.