Colorful image six-color color separation printing method, system, equipment and medium

Abstract

The invention relates to a colorful image six-color color separation printing method, system and device and a medium, and relates to the technical field of color printing, and the method comprises the steps that a six-color mixing model based on a Neugebauer equation is expanded according to the roughness, ink absorbency and whiteness parameters of printing paper; dynamically distributing the proportion of the spot color to the CMYK in the design draft through the six-color mixed model, and generating printing dot data; analyzing the printing dot data, and extracting a color distribution area and an edge transition zone of the design draft; an ink compensation channel is established for the edge transition zone. The color difference of edge transition colors can be reduced for the color gamut fault phenomenon at the edges of different colors, and then the visual effect of a final printed matter is improved.

Description

Technical Field

[0001] The present application relates to the field of color printing technology, and in particular, to a six-color separation printing method, system, device and medium for a multi-color image. Background Art

[0002] Traditional CMYK color separation printing technology achieves color reproduction through the superposition of cyan, magenta, yellow, and black inks. However, its color gamut range is limited by the spectral characteristics of the base inks, making it difficult to accurately present high-saturation colors or special spot colors. In actual printing, there are still problems such as insufficient color reproduction accuracy and unnatural transition regions, especially in complex design drafts, where color gamut breaks or detail loss are likely to occur.

[0003] Currently, color separation methods based on spectral prediction optimize color matching by analyzing the spectral absorption and reflection characteristics of inks, but their computational complexity is high, making it difficult to meet the real-time color separation requirements. In addition, multi-channel color separation technologies (such as seven-color and eight-color systems) further expand the color gamut by increasing the number of spot colors, but significantly increase the printing cost and equipment complexity, and still generally rely on the standardized Neugebauer equation model.

[0004] In the actual application of the above methods, the mixing ratio distribution of spot colors and CMYK inks depends on fixed rules, making it difficult to dynamically adapt to the fine requirements of the color transition zone in complex design drafts, and it is easy to have hue mutations or edge blurring at the color gamut junction. Therefore, a printing method is needed to solve the problem of darkening at the edges of different colors, reduce the color difference of the edge transition colors, and thus improve the visual effect of the final printed product. Summary of the Invention

[0005] A first object of the present application is to provide a six-color separation printing method for a multi-color image, which can address the color gamut break phenomenon at the edges of different colors, reduce the color difference of the edge transition colors, and thus improve the visual effect of the final printed product.

[0006] In a first aspect, a six-color separation printing method for a multi-color image provided by the present application adopts the following technical solution: A six-color separation printing method for a multi-color image includes: Expanding a six-color mixing model based on the Neugebauer equation according to the roughness, ink absorbency, and whiteness parameters of the printing paper; Dynamically allocating the ratio of spot colors to CMYK in the design draft through the six-color mixing model to generate printing dot data; Analyzing the printing dot data to extract the color distribution area and edge transition zone of the design draft; Establishing an ink compensation channel for the edge transition zone.

[0007] By adopting the above technical solution, the six-color mixing model can be expanded according to the characteristics of the printing paper to generate more adaptable printing dot data, and the ratio of spot colors to CMYK can be more accurately and dynamically allocated. Then, the color distribution area of the printing dot data and the edge transition zone located in the color distribution area are analyzed, and an ink compensation channel is established to change the printing color in the edge transition zone, alleviate the color difference problem of the edge transition color, and effectively reduce the color gamut fault phenomenon caused by color superposition during printing, thereby improving the overall quality of the printed image; and,

[0008] In a preferred example, the present application may be further configured as follows: the step of extending the six-color mixing model based on the Neugeborg equation according to the roughness, ink absorbency, and whiteness parameters of the printing paper includes: Assign weight coefficients to the roughness, ink absorption, and whiteness of printing paper, and obtain the printing paper factor α through linear combination weight calculation paper ; The six-color mixing model based on the Neuberger model is extended as follows: Where R is the total reflectivity of the mixed area, R i is the reflectance of the ith primary color, f i is the area coverage of the ith primary color, and n is the Yule-Nielsen correction coefficient.

[0009] By adopting the above technical solution, a six-color mixing model is generated based on the Neuberger model that combines the roughness, ink absorbency and whiteness of the printing paper. This improves the adaptability to different paper characteristics during the printing process, thereby optimizing the printed color performance. The Yule-Nielsen coefficient n is used to correct the multiple scattering effect of light between the paper and the ink layer, so that the theoretical reflectivity prediction of the six-color mixing model is more in line with the actual printing effect.

[0010] In a preferred example, the present application may be further configured as follows: the step of dynamically allocating the ratio of spot colors to CMYK in the design draft by using the six-color mixing model to generate printing dot data includes: Convert the design to the CIELAB color gamut and mark the spot color area; Mark the spot color areas that need to be retained and distinguish the mixed areas that need to be simulated by mixing CMYK and spot colors; Dynamically allocate the ratio of spot colors to CMYK based on printing requirements, including spot color priority or CMYK and spot color mixed simulation; Constructing an objective function to minimize the color difference between the target color and the predicted color, with constraints including the base color area coverage range and the six-color mixing model; Calculate the six-color coverage rate in the color area of the design draft, adjust the color difference of the predicted color according to the six-color coverage rate of the target color, and generate printing dot data based on the six-color coverage rate of the optimized predicted color.

[0011] By adopting the above technical solution, differentiating the spot color areas and the mixed areas to be retained enables the spot colors to be preferentially used or reasonably mixed and simulated for color adjustment, reducing the levels of overprinting and meeting different printing requirements; constructing an objective function to minimize the color difference between the target color and the predicted color to improve the accuracy and visual effect of color reproduction.

[0012] In a preferred example of the present application, it can be further configured that: the step of analyzing the printing dot data and extracting the color distribution area and the edge transition band of the design draft includes: Convert the printing dot data into a coverage matrix with a preset resolution, where each element in the matrix represents the base color dot coverage rate at the corresponding position, and the preset resolution is greater than the resolution of the printing dot data; Preprocess the coverage matrix, and based on the similarity of the base color combinations in the coverage matrix, use a clustering algorithm to divide the color gamut of the design draft to obtain a candidate transition zone, where the candidate transition zone is a strip area where the hue mutation between adjacent color gamuts is greater than or equal to a preset value; Obtain the color gradient vector fields of several candidate transition zones, and extract the pixels with a gradient amplitude higher than a preset threshold to form several edge transition bands.

[0013] By adopting the above technical solution, converting the printing dot data into a higher-resolution coverage matrix to accurately represent the base color dot coverage rate at each position in the design draft; preprocessing the coverage matrix and using a clustering algorithm to divide the color gamut of the design draft to identify the candidate transition zones with a large hue mutation between adjacent color gamuts; further extracting the pixels with a higher gradient amplitude in the color gradient vector field to form accurate edge transition bands, providing a reliable basis for subsequent ink compensation, thereby effectively alleviating the color difference problem of edge transition colors and improving the visual effect of printed products.

[0014] In a preferred example of the present application, it can be further configured that: the step of establishing an ink compensation channel for the edge transition band includes: Calculate and obtain the actual reflectance of the mixed color in the edge transition band through a six-color mixing model; Through the initial Neugebauer equation without adding the printing paper factor α paper Calculate and obtain the preset reflectance of the mixed color in the edge transition band; Calculate and obtain the reflectance deviation of the mixed color, where the reflectance deviation is the difference between the actual reflectance and the preset reflectance; determine whether the reflectance deviation is within the error range; If the reflectance deviation is within the error range, use the mixed color for printing; If the reflectance deviation is not within the error range, establish an ink compensation channel for dynamically adjusting the base color ratio of the edge transition zone.

[0015] By adopting the above technical solution, calculate the actual reflectance of the mixed color in the edge transition zone to ensure that the true printing effect is reflected; calculate the preset reflectance through the initial Neugebauer equation to provide a theoretical reference value for accurately positioning the part that needs to be adjusted and specifically solving the color difference problem.

[0016] In a preferred example of the present application, it can be further configured as: the step of establishing an ink compensation channel for dynamically adjusting the base color ratio of the edge transition zone if the reflectance deviation is within the error range includes: Based on the base color coverage rate, calculate the weighted hue angle of the mixed color in the six-color mixing area; Construct an objective function for minimizing the hue angle deviation, and adjust the base color ratio according to the objective function so that the reflectance of the adjusted base color ratio meets the preset reflectance.

[0017] By adopting the above technical solution, calculating the weighted hue angle of the mixed color in the six-color mixing area can accurately reflect the color characteristics of the mixed color, thereby providing a quantitative basis for subsequent adjustments; constructing an objective function for minimizing the hue angle deviation and adjusting the base color ratio accordingly can effectively reduce the color difference problem in the edge transition zone and improve the smoothness of color transition; ensuring that the reflectance of the adjusted base color ratio meets the preset reflectance, thereby ensuring the stability and consistency of the printing effect, reducing the gamut break phenomenon, and improving the visual experience of the printed image.

[0018] In a preferred example of the present application, it can be further configured as: before the steps of defining the dynamic allocation ratio of spot color and CMYK according to the printing requirements, including giving priority to the use of spot color or simulating the mixture of CMYK and spot color, further includes: Establish a six-color separation parameter database to record the characteristics of different printing papers and the base color ratios required for each CMYK and spot color in the CIELAB color gamut in the mixing area.

[0019] By adopting the above technical solution, when the printing requirements are obtained, quickly call the ratio parameters of the base colors required for each color according to the printing paper characteristics, improve the efficiency of selecting printing colors, and further improve the overall printing efficiency.

[0020] In a second aspect, the present application provides a six-color separation printing system for a colorful image, adopting the following technical solution: A six-color separation printing system for a colorful image, comprising: Six-color expansion module: used to expand the six-color mixing model based on the Neugebauer equation according to the roughness, ink absorption, and whiteness parameters of the printing paper; Dot generation module: used to dynamically allocate the ratio of spot colors to CMYK in the design draft through the six-color mixing model to generate printing dot data; Edge extraction module: used to analyze the printing dot data and extract the color distribution area and edge transition zone of the design draft; Ink compensation module: used to establish an ink compensation channel for the edge transition zone.

[0021] Thirdly, the present application provides an electronic device, adopting the following technical solution: An electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the above-mentioned six-color separation printing method for colorful images.

[0022] Fourthly, the present application provides a computer storage medium, adopting the following technical solution: A computer-readable storage medium stores a computer program. When the computer program is executed by a processor, it implements the steps of the above-mentioned six-color separation printing method for colorful images.

[0023] In summary, the present application has the following beneficial technical effects: The present application expands the six-color mixing model based on the Neugebauer equation and combines the characteristics of the printing paper to dynamically allocate the ratio of spot colors to CMYK, generating printing dot data, effectively improving the color reproduction accuracy and transition effect; establishing an ink compensation channel for the edge transition zone can accurately adjust the ratio of basic colors, reduce the gamut break phenomenon caused by paper characteristics, and improve the color difference problem of edge transition colors; by analyzing the printing dot data, extracting the color distribution area and edge transition zone, and combining the optimized six-color mixing model, more delicate color transitions and higher visual consistency are achieved. Description of the Drawings

[0024] Figure 1 is a flowchart of a six-color separation printing method for colorful images in one embodiment of the present application.

[0025] Figure 2 is a sub-step flowchart of step S1 in one embodiment of the present application.

[0026] Figure 3 is a sub-step flowchart of step S2 in one embodiment of the present application.

[0027] Figure 4 is a sub-step flowchart of step S3 in one embodiment of the present application.

[0028] Figure 5 It is a flowchart of sub-steps of step S4 in one embodiment of the present application.

[0029] Figure 6 It is a flowchart of sub-steps of step S45 in one embodiment of the present application.

[0030] Figure 7 It is a flowchart of the steps added after step S22 in one embodiment of the present application.

[0031] Figure 8 It is a schematic structural diagram of a six-color separation printing system for multi-color images in one embodiment of the present application.

[0032] Figure 9 It is a principle block diagram of an electronic device in one embodiment of the present application.

[0033] Reference numerals: 1, six-color expansion module; 2, dot generation module; 3, edge extraction module; 4, ink compensation module; Detailed implementation manners

[0034] The following further elaborates on the present application in conjunction with the attached Figures 1-9 drawings.

[0035] It should be noted that all actions of obtaining data or all actions of obtaining information or data in the present application are carried out in accordance with the corresponding data protection regulations and policies of the country where the location is located and with the authorization of the corresponding users.

[0036] Referring to Figure 1 , a six-color separation printing method for multi-color images specifically includes: S1. Expand the six-color mixing model based on the Neugebauer equation according to the roughness, ink absorbency, and whiteness parameters of the printing paper.

[0037] Specifically, the roughness, ink absorbency, and whiteness parameters of the printing paper will affect the final quality of printing. Papers with high roughness will result in uneven ink transfer, poor dot reproduction, increased printing pressure, thinner ink layers, reduced gloss, and affect the color vividness and detail performance of printed matter. Papers with strong ink absorbency will cause the ink to penetrate quickly, resulting in dot gain, fast ink fixation but decreased saturation and gloss, and at the same time affect printing contrast and ink consumption. Papers with high whiteness can better set off the ink color, making the printed matter colorful and with high contrast, while papers with low whiteness will make the colors appear dull and affect the overall quality of printed matter.

[0038] Moreover, using the six-color separation method can not only increase the color gamut of two spot colors for extended printing, but also reduce the usage amount of spot color inks compared with seven-color and eight-color systems, so as to reduce the printing cost.

[0039] S2. Dynamically allocate the ratio of spot colors and CMYK in the design draft through the six-color mixing model to generate printing dot data.

[0040] Specifically, by incorporating the physical properties of printing paper into the Neugeborg equation, additional consideration is given to the printing paper. During pre-print color selection, the final output color can be visually determined based on the paper's physical properties, ensuring the desired color for the design. Therefore, the six-color mixing model is expanded based on the paper's characteristics to generate more adaptable printing dot data, enabling more precise and dynamic allocation of spot color to CMYK ratios.

[0041] S3. Analyze the printing dot data and extract the color distribution area and edge transition zone of the design draft.

[0042] Specifically, the FM-AM method is used to analyze the mixed dots in the edge transition zone and select the appropriate ones. In this embodiment, 20μm random FM dots are used in the center of the transition zone to eliminate moiré patterns, and 40μm chain AM dots are used in the edge extension area to maintain sharpness.

[0043] S4. Establish an ink compensation channel for the edge transition zone.

[0044] Specifically, by establishing an ink compensation channel to change the printing color in the edge transition zone, the color gamut fault phenomenon caused by the color superposition at the joining edges between different colors of the image displayed after printing is alleviated, thereby alleviating the color difference problem of the edge transition color and improving the overall quality of the printed image.

[0045] refer to Figure 2 Furthermore, in one embodiment, step S1 is further divided into the following sub-steps: S10. Assign weight coefficients to the roughness, ink absorption, and whiteness of the printing paper, and obtain the printing paper factor α by linear combination weight calculation. paper .

[0046] Specifically, several typical paper types were selected, such as coated paper, offset paper, matte paper, and newsprint, covering different ranges of roughness, ink absorbency, and whiteness. Then, using a measurement tool to measure roughness S, ink absorbency C, and whiteness W, the corresponding values were obtained. At the same time, a standard color target was printed on each sheet of paper, and the color difference ΔE of key color blocks was measured.

[0047] Furthermore, the data of roughness, ink absorbency, and whiteness of each printing paper were normalized to eliminate dimensional differences.

[0048] Furthermore, the color difference ΔE is selected as the dependent variable and the multivariate linear regression equation is established: ΔE=k1·S norm+ k2·C norm + k3·W norm + ∈, where k1, k2, and k3 are weight coefficients to be determined, and ∈ is the error term.

[0049] Furthermore, the least squares method is used to fit the data, and the regression coefficients are normalized to the weight ratio of α paper using the formula: Then, the data set is divided into a training set and a test set to verify the model prediction error. Finally, several new papers are selected, the predicted ΔE is calculated and compared with the measured value, and the weight coefficients are dynamically adjusted.

[0050] α paper = k ′ 1·S norm + k ′ 2·C norm + k ′ 3·W norm , where S norm is the surface roughness of the printing paper, C norm is the ink absorbency, and W norm is the whiteness. k ′ 1, k ′ 2, k ′ 3 are the weight coefficients of roughness, ink absorbency, and whiteness, respectively. In this embodiment, the weight coefficient range of roughness k ′ 1 is 0.4 - 0.5, the weight coefficient range of ink absorbency k ′ 2 is 0.2 - 0.4, and the weight coefficient range of whiteness k ′ 3 is 0.1 - 0.2, and the user further confirms the weight values according to the actual situation. The output range of α paper is α paper ∈ [0, 1], and the larger the value, the stronger the negative impact of the paper on the printing effect.

[0051] S11. The extended six-color mixing model based on the Neugebauer model is: where R is the total reflectance of the mixing area, R i is the reflectance of the i-th primary color, f i is the area coverage of the i-th primary color, and n is the Yule - Nielsen correction coefficient.

[0052] Specifically, the Yule-Nielsen coefficient n is used to correct the multiple scattering effect of light between the paper and the ink layer, making the theoretical reflectance prediction of the six-color mixing model more consistent with the actual printing effect. By considering roughness, ink absorbency, and whiteness, the adaptability to different paper characteristics during printing is improved for the effects presented by inks of different colors on the printing paper, thereby optimizing the printing color performance.

[0053] In addition, referring to Figure 3 , further, in one embodiment, step S2 is refined into the following sub-steps: S20: Convert the design draft into the CIELAB color gamut and mark the spot color areas.

[0054] Specifically, convert the design draft from RGB / CMYK to the CIELAB space, accurately locate the spot color areas through the a*b* coordinates, and be able to obtain the hue angle of each spot color area.

[0055] S21: Mark the spot color areas to be retained and distinguish the mixed areas that need to be simulated by the mixture of CMYK and spot colors.

[0056] Specifically, use an image segmentation algorithm to distinguish the spot color retention areas and the mixed areas. Among them, the spot color retention areas must be printed with the added spot color inks to reduce the situation of multiple colors overprinting and darkening. The mixed areas can be areas simulated by the overprint of CMYK and spot colors, such as the gradient edges, to reduce the usage of spot color inks. And the overprint effect of the mixed areas can be predicted through the Neugebauer equation, and the color difference is controlled within the threshold range.

[0057] S22: Define the dynamic allocation ratio of spot colors and CMYK according to the printing requirements, including giving priority to the use of spot colors or simulating with the mixture of CMYK and spot colors.

[0058] Specifically, if the colors appearing in the color areas of the design draft and the printing paper factor of the printing paper cannot be matched in the six-color separation parameter database, then this color is considered a new color, and it is necessary to reconfirm the ratio of spot colors and CMYK in the mixed areas.

[0059] S23: Construct an objective function to minimize the color difference between the target color and the predicted color, and the constraint conditions include the range of the base color area coverage rate and the six-color mixing model.

[0060] Specifically, construct an objective function to minimize the color difference between the target color and the predicted color to improve the accuracy and visual effect of color reproduction, solve it using the CIELAB color difference formula, and the constraint conditions are 0 ≤ f i ≤ 1 (i = 1, 2,..., 6) and the six-color mixing model.

[0061] S24. Calculate and obtain the six-color coverage rate in the color area of the design draft, adjust the color difference of the predicted color according to the six-color coverage rate of the target color, and generate printing dot data based on the optimized six-color coverage rate of the predicted color.

[0062] Specifically, according to the optimized six-color coverage rate, amplitude modulation, frequency modulation or hybrid dots are generated. Among them, amplitude modulation dots can avoid moiré patterns as much as possible, and frequency modulation dots are smooth transitions of 20-μm random dot matrices.

[0063] In addition, referring to Figure 4 , further, in one embodiment, step S3 is refined into the following sub-steps: S30. Convert the printing dot data into a coverage matrix with a preset resolution. Each element in the matrix represents the base color dot coverage rate at the corresponding position, and the preset resolution is greater than the resolution of the printing dot data.

[0064] Specifically, a high-resolution grid can accurately describe the distribution of printing dots, reduce printing sawteeth and edge burrs, provide sub-pixel-level information for subsequent transition zone analysis, and identify tiny color level breaks.

[0065] S31. Preprocess the coverage matrix. Based on the similarity of the base color combinations in the coverage matrix, use a clustering algorithm to divide the color gamut of the design draft and obtain candidate transition zones. The candidate transition zones are strip-shaped areas where the hue mutation between adjacent color gamuts is greater than or equal to a preset value.

[0066] Specifically, perform Gaussian filtering and noise reduction on the coverage matrix, normalize the coverage rate to the same dimension, and then use the K-means or DBSCAN algorithm to classify similar base color combinations, such as mixed colors of C+M and O+Y, into the same color gamut, and calculate the color difference ΔH° between adjacent color gamuts. Mark the areas where ΔH° is greater than the threshold as candidate transition zones to identify color areas with large hue mutations between adjacent color gamuts.

[0067] S32. Obtain the color gradient vector fields of several candidate transition zones, and extract the pixels with gradient amplitudes higher than the preset threshold to form several edge transition zones.

[0068] Specifically, extract the pixels with higher gradient amplitudes in the color gradient vector field to form accurate edge transition zones, which provides a reliable basis for subsequent ink compensation, effectively alleviates the color difference problem of edge transition colors, and improves the visual effect of printed products.

[0069] In addition, referring to Figure 5 , further, in one embodiment, step S4 is refined into the following sub-steps: S40. Calculate and obtain the actual reflectance of the mixed colors in the edge transition zone through a six-color mixing model.

[0070] Specifically, using the improved six-color mixing model, calculate and obtain the actual reflectance of the mixed color in the edge transition zone with the addition of the printing paper factor α paper so that the actual reflectance can reflect the true printing effect on the current printing paper.

[0071] S41. Through the initial Neugebauer equation without the printing paper factor α paper calculate and obtain the preset reflectance of the mixed color in the edge transition zone.

[0072] Specifically, the preset reflectance calculated through the initial Neugebauer equation can reflect the default printing effect without the influence of the printing paper factor α paper to provide a theoretical reference value for accurately locating the parts that need to be adjusted and specifically solving the color difference problem.

[0073] S42. Calculate and obtain the reflectance deviation of the mixed color, where the reflectance deviation is the difference between the actual reflectance and the preset reflectance.

[0074] S43. Determine whether the reflectance deviation is within the error range.

[0075] S44. If the reflectance deviation is within the error range, use the mixed color for printing.

[0076] Specifically, at this time, the unadjusted mixed color composed of spot colors and CMYK can meet the printing requirements of the current printing paper under the default printing effect, and the color difference of the printed color of the transition edge zone has little impact on the printing effect, so no ink compensation is required.

[0077] S45. If the reflectance deviation is not within the error range, establish an ink compensation channel for dynamically adjusting the base color ratio of the edge transition zone.

[0078] Specifically, at this time, the unadjusted mixed color composed of spot colors and CMYK cannot meet the printing requirements of the current printing paper under the default printing effect, and there is an obvious gap in the color difference of the printed color of the transition edge zone, so further ink compensation is required.

[0079] In addition, referring to Figure 6 , further, in one embodiment, step S45 is refined into the following sub-steps: S450. Based on the base color coverage rate, calculate and obtain the weighted hue angle of the mixed color in the six-color mixing area.

[0080] Specifically, in the CIELAB color gamut, calculate the weighted hue angle of the mixed color in the six-color mixing area, so as to further reflect the color characteristics of the mixed color and provide a quantitative basis for subsequent ink compensation.

[0081] S451. Construct an objective function to minimize the hue angle deviation, and adjust the base color ratio according to the objective function so that the reflectance of the adjusted base color ratio meets the preset reflectance.

[0082] Specifically, construct an objective function to minimize the hue angle deviation and adjust the base color ratio accordingly, and the reflectance of the mixed color must meet the preset reflectance, thereby effectively reducing the color difference problem in the edge transition zone, improving the smoothness of color transition, reducing the gamut break phenomenon, and improving the visual experience of the printed image.

[0083] In addition, refer to Figure 7 , further, in one embodiment, before step S22, there is an additional step S220: S220. Establish a six-color separation parameter database to record the base color ratios required for mixing each CMYK and spot color in the mixing area in the CIELAB color gamut for different printing paper characteristics.

[0084] Specifically, if the colors and the printing paper factor in the color area of the design draft match in the six-color separation parameter database, then the color is considered an old color, and directly obtain the ratio of the spot color to CMYK in the mixing area from the base color ratios required for mixing each CMYK and spot color in the CIELAB color gamut for different printing paper characteristics, so as to improve the efficiency of selecting printing colors and ultimately improve the overall printing efficiency.

[0085] It should be understood that the magnitudes of the sequence numbers of the steps in the above embodiments do not mean the order of execution. The order of execution of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0086] The embodiments of the present application also provide a six-color separation printing system for a multi-color image, and the six-color separation printing system for a multi-color image corresponds one-to-one with the six-color separation printing method in the embodiments.

[0087] Refer to Figure 8 , a six-color separation printing system for a multi-color image includes: a six-color expansion module 1, a dot generation module 2, an edge extraction module 3, and an ink compensation module 4. The detailed descriptions of each functional module are as follows: Six-color expansion module 1: used to expand the six-color mixing model based on the Neugebauer equation according to the roughness, ink absorption, and whiteness parameters of the printing paper; Dot generation module 2: used to dynamically allocate the ratio of spot color to CMYK in the design draft through the six-color mixing model to generate printing dot data; Edge extraction module 3: used to analyze the printing dot data and extract the color distribution area and edge transition zone of the design draft; Ink compensation module 4: used to establish an ink compensation channel for the edge transition zone.

[0088] Among them, the six-color expansion module 1 expands the six-color mixing model based on the Neugebauer equation according to the roughness, ink absorption, and whiteness parameters of the printing paper. The improved model can more accurately reflect the influence of different paper characteristics on the printing effect; the dot generation module 2 dynamically allocates the proportion of spot colors and CMYK in the design draft by using the expanded six-color mixing model and generates printing dot data, so as to achieve accurate color restoration; the edge extraction module 3 analyzes the printing dot data, extracts the color distribution area and the edge transition zone of the design draft, and effectively identifies the complex situation at the color junction; the ink compensation module 4 establishes an ink compensation channel for the edge transition zone, optimizes the edge transition effect by adjusting the ink proportion, reduces the gamut break phenomenon and alleviates the color difference problem. Through the collaborative work of each module, the full-process control from model expansion to final printing effect optimization is realized, the color difference problem of the edge transition color is improved, and the quality and accuracy of the six-color separation printing of the colorful image are enhanced.

[0089] For the specific limitations of the six-color separation printing system for colorful images, reference can be made to the limitations of the six-color separation printing method for colorful images in the context, which will not be elaborated here. Each module in the above six-color separation printing system for colorful images can be implemented in whole or in part by software, hardware, and their combinations. The above modules can be embedded in the processor of the electronic device in the form of hardware or be independent of it, or can be stored in the memory of the electronic device in the form of software, so that the processor can call and execute the corresponding operations of the above modules. In one embodiment, an electronic device is provided, and this electronic device is a client. Refer to Figure 9 , this electronic device includes a processor, a memory, a network interface, and a database connected through a system bus. Among them, the processor of this electronic device is used to provide computing and control capabilities. The memory of this electronic device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of this electronic device is used to store the detection data table. The network interface of this electronic device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, it realizes a six-color separation printing method for colorful images.

[0090] In one embodiment, an electronic device is provided, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the following steps are implemented: S1. Expand the six-color mixing model based on the Neugebauer equation according to the roughness, ink absorption, and whiteness parameters of the printing paper.

[0091] S2. Dynamically allocate the proportion of spot colors and CMYK in the design draft through the six-color mixing model and generate printing dot data.

[0092] S3. Analyze the printed dot data, and extract the color distribution area and the edge transition zone of the design draft.

[0093] S4. Establish an ink compensation channel for the edge transition zone.

[0094] In one embodiment, the refined sub-steps of step S1 include: S10. Assign the weight coefficients of the roughness, ink absorbency, and whiteness of the printing paper, and obtain the printing paper factor α through linear combination weighting calculation paper .

[0095] S11. Expand the six-color mixing model based on the Neugebauer model to: where R is the total reflectance of the mixing area, R i is the reflectance of the i-th primary color, f i is the area coverage rate of the i-th primary color, and n is the Yule-Nielsen correction coefficient.

[0096] In one embodiment, the refined sub-steps of step S2 include: S20. Convert the design draft to the CIELAB color gamut and mark the spot color areas.

[0097] S21. Mark the spot color areas to be retained, and distinguish the mixing areas that need to be simulated by mixing CMYK and spot colors.

[0098] S22. Define the dynamic allocation ratio of spot colors and CMYK according to the printing requirements, including giving priority to using spot colors or simulating by mixing CMYK and spot colors.

[0099] S23. Construct an objective function to minimize the color difference between the target color and the predicted color, and the constraint conditions include the range of the area coverage rate of the primary colors and the six-color mixing model.

[0100] S24. Calculate and obtain the six-color coverage rate in the color area of the design draft, adjust the color difference of the predicted color according to the six-color coverage rate of the target color, and generate the printed dot data based on the optimized six-color coverage rate of the predicted color.

[0101] In one embodiment, the refined sub-steps of step S3 include: S30. Convert the printed dot data into a coverage matrix with a preset resolution, and each element in the matrix represents the primary color dot coverage rate at the corresponding position. The preset resolution is greater than the resolution of the printed dot data.

[0102] S31. Preprocess the coverage matrix. Based on the similarity of the base color combinations in the coverage matrix, use a clustering algorithm to divide the color gamut of the design draft and obtain candidate transition zones. The candidate transition zones are strip-shaped regions where the hue mutation between adjacent color gamuts is greater than or equal to a preset value.

[0103] S32. Obtain the color gradient vector fields of several candidate transition zones, and extract the pixels with gradient amplitudes higher than a preset threshold to form several edge transition zones.

[0104] In one embodiment, the refined sub-steps of step S4 include: S40. Calculate and obtain the actual reflectance of the mixed color in the edge transition zone through a six-color mixing model.

[0105] S41. Calculate and obtain the preset reflectance of the mixed color in the edge transition zone through the initial Neugebauer equation without adding the printing paper factor α paper of the initial Neugebauer equation.

[0106] S42. Calculate and obtain the reflectance deviation of the mixed color. The reflectance deviation is the difference between the actual reflectance and the preset reflectance.

[0107] S43. Determine whether the reflectance deviation is within the error range.

[0108] S44. If the reflectance deviation is within the error range, use the mixed color for printing.

[0109] S45. If the reflectance deviation is not within the error range, establish an ink compensation channel for dynamically adjusting the base color ratio of the edge transition zone.

[0110] In one embodiment, the refined sub-steps of step S45 include: S450. Calculate and obtain the weighted hue angle of the mixed color in the six-color mixing region based on the base color coverage rate.

[0111] S451. Construct an objective function for minimizing the hue angle deviation, and adjust the base color ratio according to the objective function so that the reflectance of the adjusted base color ratio meets the preset reflectance.

[0112] In one embodiment, the steps added after step S22 include: S220. Establish a six-color separation parameter database, and record the base color ratios required for mixing each CMYK and spot color in the mixing region in the CIELAB color gamut for different printing paper characteristics.

[0113] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, storage, database, or other medium used in the embodiments provided in the present application can include non-volatile and / or volatile memories. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and Rambus dynamic RAM (RDRAM), etc.

[0114] Those skilled in the art can clearly understand that, for the convenience and simplicity of description, only the above division of each functional unit and module is used as an example. In actual applications, the above functions can be allocated to different functional units and modules according to needs, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above.

Claims

1. A six-color separation printing method for a multi-color image, characterized in that: include: According to the roughness, ink absorption and whiteness parameters of the printing paper, the six-color mixing model based on the Neugeborg equation is expanded; Dynamically allocating the ratio of spot colors to CMYK in the design draft through the six-color mixing model to generate printing dot data; Analyze the printing dot data to extract the color distribution area and edge transition zone of the design draft; An ink compensation channel is established for the edge transition zone.

2. The method according to claim 1, wherein The step of expanding the six-color mixing model based on the Neugeborg equation according to the roughness, ink absorbency and whiteness parameters of the printing paper includes: Assign weight coefficients to the roughness, ink absorption, and whiteness of the printing paper, and obtain the printing paper factor αpaper through linear combination weight calculation; The six-color mixing model based on the Neuberger model is extended as follows: Where R is the total reflectivity of the mixed area, R i is the reflectance of the ith primary color, f i is the area coverage of the ith primary color, and n is the Yule-Nielsen correction coefficient.

3. The method according to claim 2, characterized in that The step of dynamically allocating the ratio of spot colors to CMYK in the design draft by using the six-color mixing model to generate printing dot data includes: Convert the design to the CIELAB color gamut and mark the spot color area; Mark the spot color areas that need to be retained and distinguish the mixed areas that need to be simulated by mixing CMYK and spot colors; Dynamically allocate the ratio of spot colors to CMYK based on printing requirements, including spot color priority or CMYK and spot color mixed simulation; Constructing an objective function to minimize the color difference between the target color and the predicted color, with constraints including the base color area coverage range and the six-color mixing model; Calculate and obtain the six-color coverage in the color area of the design draft, adjust the color difference of the predicted color according to the six-color coverage of the target color, and generate printing dot data based on the optimized six-color coverage of the predicted color.

4. The method according to claim 3, characterized in that The step of analyzing the printing dot data and extracting the color distribution area and edge transition zone of the design draft includes: Converting the printing dot data into a coverage matrix of a preset resolution, wherein each element in the matrix represents the coverage of the primary color dot at the corresponding position, and the preset resolution is greater than the resolution of the printing dot data; Preprocess the coverage matrix and use a clustering algorithm to divide the color gamut of the design draft based on the similarity of the base color combinations in the coverage matrix to obtain transition zone candidate areas. The transition zone candidate areas are strip-shaped areas where the hue abrupt change between adjacent color gamuts is greater than or equal to a preset value. The color gradient vector fields of several transition zone candidate areas are obtained, and pixels with gradient amplitudes higher than a preset threshold are extracted to form several edge transition zones.

5. The method according to claim 4, wherein The step of establishing an ink compensation channel for the edge transition zone includes: The actual reflectivity of the mixed colors in the edge transition zone is calculated using a six-color mixing model; By not adding the printing paper factor α paper The initial Neugeborg equation is used to calculate the preset reflectivity of the mixed color of the edge transition zone; Calculating and obtaining a reflectivity deviation of the mixed color, where the reflectivity deviation is the difference between an actual reflectivity and a preset reflectivity; and determining whether the reflectivity deviation is within an error range; If the reflectivity deviation is within the error range, printing is performed using the mixed color; If the reflectivity deviation is not within the error range, an ink compensation channel is established to dynamically adjust the base color ratio of the edge transition zone.

6. The method according to claim 5, characterized in that, The step of establishing an ink compensation channel for dynamically adjusting the primary color ratio of the edge transition zone if the reflectivity deviation is within the error range includes: Based on the base color coverage, the weighted hue angle of the mixed color in the six-color mixing area is calculated; An objective function for minimizing the hue angle deviation is constructed, and the primary color ratio is adjusted according to the objective function so that the reflectivity of the adjusted primary color ratio meets the preset reflectivity.

7. The method according to claim 3, characterized in that Before the step of defining the ratio of spot colors to CMYK to be dynamically allocated according to printing requirements, including the step of prioritizing the use of spot colors or simulating the mixing of CMYK and spot colors, the method further includes: A six-color separation parameter database was established to record the characteristics of different printing papers and the ratio of base colors required for mixing each CMYK color and spot color in the mixing area in the CIELAB color gamut.

8. A six-color separation printing system for multicolored images, characterized in that, include: Six-color extension module (1): used to extend the six-color mixing model based on the Neugeborg equation according to the roughness, ink absorption and whiteness parameters of the printing paper; Dot generation module (2): used for dynamically allocating the ratio of spot colors to CMYK in the design draft through the six-color mixing model to generate printing dot data; The edge extraction module (3) is used to analyze the printing dot data and extract the color distribution area and edge transition zone of the design draft; the ink compensation module (4) is used to establish an ink compensation channel for the edge transition zone.

9. An electronic device, characterized in that, The method comprises a memory and a processor, wherein the memory stores a computer program that can be loaded by the processor and execute the six-color separation printing method for multi-color images according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer program is stored which can be loaded by a processor and executes the six-color separation printing method for a multi-color image according to any one of claims 1 to 7.

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