A method, system, device and readable storage medium for converting LAB to CMYK values
By using a reverse lookup table and K-value layered color gamut matching method, the complexity and multiple solutions in LAB to CMYK value conversion are solved, achieving high-precision color replication and improving conversion accuracy and stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XIAN UNIV OF TECH
- Filing Date
- 2026-05-22
- Publication Date
- 2026-07-31
AI Technical Summary
In existing technologies, the conversion from LAB to CMYK values is complex, has multiple solutions leading to low accuracy, and suffers from inflexible black plate adjustment during four-color separation, making it difficult to meet the needs of high-precision color reproduction.
By employing a reverse lookup table combined with K-value hierarchical color gamut matching, and by acquiring the characteristic data of the target output device, a weight matrix and lookup table are constructed to achieve high-precision conversion of CMYK values and flexibly adjust the amount of black plate.
It achieves high-precision LAB to CMYK value conversion, improves conversion accuracy and stability, meets the needs of high-precision color reproduction, and reduces production costs caused by color distortion.
Smart Images
Figure CN122496594A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of image processing technology, and more specifically to a method, system, device, and readable storage medium for converting LAB to CMYK values. Background Technology
[0002] In modern high-precision color reproduction workflows, the conversion from device-independent color spaces to device-dependent color spaces is a core step connecting digital image editing and physical output. In the ICC color management workflow, the device-independent color space is called the PCS (Profile Connection Space), typically represented by CIELab and CIEXYZ values. Converting PCS color values to the corresponding CMYK values for the output device is a crucial step in determining the final color reproduction quality. The complexity of this conversion process stems primarily from two core issues: first, the black (K) channel and the cyan (C), magenta (M), and yellow (Y) channels exhibit a non-linear relationship in their visual characteristics, meaning their color contributions cannot be described by a simple linear relationship; second, when gray balance is constructed by mixing the C, M, and Y channels, the mixing ratio dynamically adjusts with changes in grayscale levels, resulting in significant differences in gray balance ratios at different brightness levels. This makes the four-color separation process more complex than the three-color CMY separation process.
[0003] In existing technologies, three-color separation, with both input and output having three variables, allows many classic conversion models (such as multinomial regression models and linear conversion models) to be directly used to solve its conversion relationship, resulting in relatively controllable conversion accuracy and stability. However, these methods face numerous insurmountable difficulties when directly applied to four-color separation: First, because the color gamut distribution of different output devices often exhibits highly irregular shapes, traditional methods struggle to construct lookup tables with regular structures, leading to the easy loss or distortion of colors outside the gamut during the conversion process; second, regression methods are typically applicable to three-variable models, and introducing a fourth variable (K channel) will drastically increase the number of terms in the conversion expression, significantly increasing the computational complexity of model solving and reducing color separation accuracy due to the strong correlation between K and CMY; furthermore, although neural network technology can handle the mapping problem from three inputs to four outputs to some extent, its conversion relationship is determined through a single training calculation. Once the model training is complete, the amount of black plate cannot be flexibly adjusted according to actual output requirements, limiting its applicability in different printing scenarios. Meanwhile, the multiple solutions that the same set of LAB values may correspond to multiple sets of CMYK combinations also limit the application effect of neural networks in four-color separation to a certain extent, making it difficult to meet the requirements of high-precision color reproduction in terms of conversion accuracy.
[0004] GCR (Gray Component Replacement) technology, a mature black plate generation technique, works by replacing perceptible achromatic CMY components with an appropriate amount of K-channel color. This technique decomposes all colors into achromatic (gray) and chromatic components. The achromatic components can be formed by mixing the CMY three channels during printing, or by replacing some or all of them with the K channel. However, there is currently no simple and flexible method for converting LAB to CMYK values.
[0005] Therefore, how to provide a new technical path for the conversion of LAB to CMYK values, and how to provide a method, system, device and readable storage medium for the conversion of LAB to CMYK values that is adjustable and fast are problems that urgently need to be solved by those skilled in the art. Summary of the Invention
[0006] In view of this, the present invention provides a method, system, device, and readable storage medium for converting LAB to CMYK values. It aims to provide a new method for achieving efficient, accurate, and flexible conversion from LAB to CMYK color space. By employing a reverse lookup table combined with K-value layered color gamut matching, the range of candidate CMYK values is accurately identified. Then, combined with a flexible black plate generation method, the final black plate quantity is determined, ultimately achieving high-precision conversion from LAB to CMYK, meeting the application needs of high-precision color reproduction.
[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for converting LAB to CMYK values includes: Step 1: Obtain characteristic data containing the color response patterns of the target output device, and calculate the weight matrix reflecting the relationship between CMYK and the corresponding LAB values; Step 2: Within the preset channel value range of CMYK, evenly divide each channel into a preset number of sampling points, and calculate the LAB value corresponding to the sampled CMYK value according to the weight matrix, and construct a lookup table from CMYK to LAB value; Step 3: Extract the CMY 3D color range under different K values in the lookup table to construct the corresponding layered color gamut, and traverse the layered color gamut through the color gamut matching algorithm to obtain the target color gamut containing the target LAB value to be converted. Further, through reverse deduction based on the lookup table, obtain the CMYK value output corresponding to the target LAB value to be converted.
[0008] Optionally, in step 1, the characteristic data is obtained by extracting from an ICC characteristic file that conforms to industry standards or by accurately measuring each color patch on the color card using a professional colorimeter.
[0009] Optionally, in step 1, based on the characteristic data, a weight matrix reflecting the relationship between CMYK and the corresponding LAB values is calculated, specifically as follows: Based on the spatial correlation strength between CMYK color sample points in the characteristic data, a multi-quadratic kernel spatial relationship matrix is constructed among CMYK color sample points, as follows:
[0010] in, This is the quadratic kernel spatial relationship matrix between CMYK color sample points; For the first The CMYK color sample point and the first Spatial correlation strength between CMYK color sample points; This represents the number of sample points. Based on the multi-quadratic kernel spatial relationship matrix, and according to the LAB value matrix corresponding to each sample point, the weight matrix reflecting the relationship between CMYK and the corresponding LAB value is calculated as follows:
[0011] in, This is the LAB value matrix corresponding to each sample point; , , The first The L, A, and B values corresponding to each CMYK color sample point; This is the weight matrix; , , The first The contribution weights of each CMYK color sample point to the L, A, and B components.
[0012] Optionally, in step 2, within the preset channel value range of CMYK, a preset number of sampling points are evenly divided into each channel. The values of the four CMYK channels after sampling are as follows:
[0013] in, This is the maximum value of the channel, which is the upper limit of the preset range of channel values; The preset number of sampling points; , which are the sampling indices for channels C, M, Y, and K, respectively; the values for channels C, M, Y, and K are rounded down.
[0014] Optionally, in step 2, the LAB values corresponding to the sampled CMYK values are calculated based on the weight matrix, and a lookup table from CMYK to LAB values is constructed, specifically as follows: Calculate the spatial correlation strength between the sampled CMYK values and CMYK color sample points, and construct the quadratic kernel spatial relationship matrix between the sampled CMYK values and CMYK color sample points, as follows:
[0015] in, This is the quadratic kernel spatial relationship matrix between the sampled CMYK values and the CMYK color sample points; For the sampled first The CMYK value and the first Spatial correlation strength between CMYK color sample points , ; The preset number of sampling points; This represents the number of sample points. For the first time after sampling One CMYK value; No. One CMYK color sample point; Based on the multi-quadratic kernel spatial relation matrix, the LAB value corresponding to the sampled CMYK value is calculated according to the weight matrix, and a lookup table from CMYK to LAB value is constructed as follows:
[0016] in, , , They are the sampling numbers after the first sampling. The LAB value corresponding to each CMYK value; This is the weight matrix; , , The first The contribution weights of each CMYK color sample point to the L, A, and B components.
[0017] Optionally, in step 3, the CMY three-dimensional color ranges under different K values in the lookup table are extracted to construct the corresponding layered color gamuts, specifically as follows: Different K-value levels are extracted from the lookup table and rounded down. Through clustering and boundary extraction of the lookup table data, the CMY three-dimensional color range under different K values is constructed into corresponding independent layered color gamuts. The number of K values in the lookup table is the same as the preset number of channel sampling points.
[0018] Optionally, in step 3, after obtaining the CMYK value output corresponding to the target LAB value to be converted, the following steps are also included: When there is only one target color gamut containing the target LAB value to be converted, the lookup table of the current target color gamut is directly used to reverse the derivation result as the CMYK value output; where, within each layered color gamut, there is a unique correspondence between the LAB value and the CMYK value; When there are only multiple target color gamuts containing the target LAB values to be converted, the CMYK values are output as follows:
[0019] in, The number of target color gamuts containing the target LAB values to be converted; This is the index parameter, used to locate the median of the target color gamut; , , , To sort the K values corresponding to the target color gamut containing the target LAB values to be converted by size, the first... Output the CMYK values corresponding to each K value.
[0020] The present invention also provides a LAB to CMYK value conversion system utilizing a LAB to CMYK value conversion method, comprising: Weight matrix calculation module: used to acquire characteristic data containing the color response rules of the target output device, and calculate the weight matrix reflecting the relationship between CMYK and the corresponding LAB values; Lookup table construction module: It is used to evenly divide each channel into a preset number of sampling points within the preset channel value range of CMYK, and calculate the LAB value corresponding to the sampled CMYK value according to the weight matrix, and construct a lookup table from CMYK to LAB value. The CMYK value output module is used to extract the CMY three-dimensional color range under different K values in the lookup table to construct the corresponding layered color gamut. It then traverses the layered color gamut through a color gamut matching algorithm to obtain the target color gamut containing the target LAB value to be converted. Finally, through reverse deduction based on the lookup table, it outputs the CMYK value corresponding to the target LAB value to be converted.
[0021] The present invention also provides an electronic device, comprising: Memory, used to store computer programs; A processor is used to implement a method for converting LAB to CMYK values when executing a computer program.
[0022] The present invention also provides a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, it implements the steps of a method for converting LAB to CMYK values.
[0023] As can be seen from the above technical solution, compared with the prior art, this invention discloses a method, system, device, and readable storage medium for converting LAB to CMYK values. Addressing the core problems of existing LAB-to-CMYK technologies, such as low accuracy due to complexity and multiple solutions, and inflexible black plate adjustment during four-color separation, this invention forms a complete high-precision conversion scheme through an innovative K-value layered color gamut construction and reverse lookup mechanism, combined with a K-value determination mechanism. This scheme not only effectively solves the problem of multiple solutions for the same LAB value corresponding to multiple sets of CMYK values, but also achieves flexible and precise adjustment of the black plate quantity, significantly improving conversion accuracy and stability. Applying the conversion method of this invention allows the color difference in LAB-to-CMYK conversion to be controlled within an industry-recognized high-precision range, effectively improving the color reproduction quality of printing and dyeing products, reducing increased production costs due to color distortion, and providing an efficient and reliable technical solution for the field of high-precision color reproduction. Attached Figure Description
[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0025] Figure 1 This is a schematic diagram of the method flow provided by the present invention.
[0026] Figure 2 This is a schematic diagram of color difference statistics provided by the present invention. Detailed Implementation
[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0028] Example 1: Embodiment 1 of this invention discloses a method for converting LAB to CMYK values, such as... Figure 1 As shown, it includes: Step 1: Obtain characteristic data containing the color response patterns of the target output device, and calculate the weight matrix reflecting the relationship between CMYK and the corresponding LAB values.
[0029] The characteristic data is obtained by extracting from ICC characteristic files that conform to industry standards or by accurately measuring each color patch on the color chart using professional colorimetric instruments.
[0030] Specifically, if there is no readily available ICC profile, the IT8.7 / 4 or ISO standard color chart can be printed out, and each color patch on the color chart can be accurately measured using a professional colorimeter to obtain its LAB value or XYZ value (where the XYZ value can be further converted into a LAB value using the internationally recognized CIE conversion formula) to obtain the profiled data.
[0031] Based on the characteristic data, a weight matrix reflecting the relationship between CMYK and the corresponding LAB values is calculated, specifically as follows: Based on the spatial correlation strength between CMYK color sample points in the characteristic data, a multi-quadratic kernel spatial relationship matrix is constructed among CMYK color sample points, as follows:
[0032] in, This is the quadratic kernel spatial relationship matrix between CMYK color sample points; For the first The CMYK color sample point and the first Spatial correlation strength between CMYK color sample points; This represents the number of sample points. Based on the multi-quadratic kernel spatial relationship matrix, and according to the LAB value matrix corresponding to each sample point, the weight matrix reflecting the relationship between CMYK and the corresponding LAB value is calculated as follows:
[0033] in, This is the LAB value matrix corresponding to each sample point; , , The first The L, A, and B values corresponding to each CMYK color sample point; This is the weight matrix; , , The first The contribution weights of each CMYK color sample point to the L, A, and B components.
[0034] Step 2: Within the preset channel value range of CMYK, evenly divide each channel into a preset number of sampling points, and calculate the LAB value corresponding to the sampled CMYK value according to the weight matrix, and construct a CMYK to LAB value lookup table (A2B) that conforms to the ICC standard.
[0035] Within the preset channel value range of CMYK (as defined in this embodiment of the invention) Within the range of the halftone dot area ratio percentage commonly used in the printing industry, each channel is evenly divided into a preset number of sampling points (17 in this embodiment, conforming to the lookup table specification in the ICC file). The values of the four CMYK channels after sampling are as follows:
[0036] in, This is the maximum value of the channel, i.e., the upper limit of the preset range of channel values (in this embodiment of the invention, it is taken as...). ); The preset number of sampling points (in this embodiment of the invention) ); , which are the sampling indices for channels C, M, Y, and K, respectively; the values for channels C, M, Y, and K are rounded down.
[0037] The LAB value corresponding to the sampled CMYK value is calculated based on the weight matrix (in this embodiment of the invention). (This yields 83,521 corresponding relationships), and a lookup table is constructed to map CMYK values to LAB values, specifically as follows: Calculate the spatial correlation strength between the sampled CMYK values and CMYK color sample points, and construct the quadratic kernel spatial relationship matrix between the sampled CMYK values and CMYK color sample points, as follows:
[0038] in, This is the quadratic kernel spatial relationship matrix between the sampled CMYK values and the CMYK color sample points; For the sampled first The CMYK value and the first Spatial correlation strength between CMYK color sample points , ; The preset number of sampling points; This represents the number of sample points. For the first time after sampling One CMYK value; No. One CMYK color sample point; Based on the multi-quadratic kernel spatial relation matrix, the LAB value corresponding to the sampled CMYK value is calculated according to the weight matrix, and a lookup table from CMYK to LAB value is constructed as follows:
[0039] in, , , They are the sampling numbers after the first sampling. The LAB value corresponding to each CMYK value; This is the weight matrix; , , The first The contribution weights of each CMYK color sample point to the L, A, and B components.
[0040] The above calculation has good nonlinear fitting ability and local approximation characteristics, and can accurately fit the color response curve of the output device. After the calculation, an A2B lookup table with one-to-one correspondence between CMYK values and LAB values can be obtained.
[0041] Step 3: Extract the CMY 3D color range under different K values in the lookup table to construct the corresponding layered color gamut, and traverse the layered color gamut through the color gamut matching algorithm to obtain the target color gamut containing the target LAB value to be converted. Further, through reverse deduction based on the lookup table, obtain the CMYK value output corresponding to the target LAB value to be converted.
[0042] The CMY 3D color ranges under different K values in the lookup table are extracted to construct the corresponding layered color gamuts, specifically as follows: Extract different K-value levels from the lookup table and round down. Since different C, M, and Y combinations under the same K-value correspond to LAB values that form a continuous color range, i.e., constitute an independent color gamut, clustering and boundary extraction of the lookup table data are used to construct the CMY three-dimensional color ranges under different K-values into corresponding independent layered color gamuts. These color gamuts completely cover the reproducible color space of the target output device, providing a clear basis for subsequent LAB value color gamut matching. The number of K-values in the lookup table is the same as the preset number of channel sampling points (in this embodiment, the preset number of channel sampling points...). Then, the CMY three-dimensional color ranges under 17 different K values are extracted. The 17 K values are rounded down to [0,6,12,18,25,31,37,43,50,56,62,68,75,81,87,93,100]. Finally, the color ranges corresponding to the 17 K values are constructed into 17 independent layered color gamuts.
[0043] After obtaining the CMYK value output corresponding to the target LAB value to be converted, the following is also included: When there is only one target color gamut containing the target LAB value to be converted, the lookup table of the current target color gamut is directly used to reverse the derivation result as the CMYK value output; where, within each layered color gamut, there is a unique correspondence between the LAB value and the CMYK value; When there are only multiple target color gamuts containing the target LAB values to be converted, the CMYK values are output as follows:
[0044] in, The number of target color gamuts containing the target LAB values to be converted; This is the index parameter, used to locate the median of the target color gamut; , , , To sort the K values corresponding to the target color gamut containing the target LAB values to be converted by size, the first... The CMYK values corresponding to each K value are output, that is, when When the K value is odd, the CMYK value corresponding to the median of the sorted K values is taken as the output; when... When the value is even, the average of the two middle CMYK values after arranging the K values in ascending and descending order is taken as the output.
[0045] Experimental verification: The system uses Windows 11 and is compiled with PyCharm 3.6. The selected ICC profile data is FOGRA39, available at www.color.com. There are 1617 profile data points. First, uniform interpolation is performed to generate 83521 uniform data points to obtain an A2B lookup table. Then, a LAB value is input and recorded as the true value. Calculations are then performed to find all color gamuts containing that LAB value. Finally, the black plate determination method of this invention is used to obtain the final CMYK value. This CMYK value is then converted to a LAB value and recorded as the output value. The color difference ΔE76 between the true value and the output value is then calculated. The result is evaluated based on the color difference, and the color difference calculation formula is as follows:
[0046] in, , , The actual value; , , This is the output value.
[0047] The statistical test of 1000 color differences ΔE76 yielded the following results: Figure 2 As shown, the vast majority of color differences are controlled within 1. This demonstrates that the conversion accuracy of the method of this invention is very high.
[0048] This invention provides a method for LAB to CMYK color space conversion. The method involves acquiring characteristic data; interpolating the characteristic data to obtain 83,521 CMYK to LAB conversion records, forming an A2B lookup table; judging the 17 K color gamuts based on the LAB values within the color gamut that the ICC file can display, identifying all K value gamuts containing the LAB value, and then resolving all CMYK values; finally, based on the number of K values, combining this method with the K value (black plate) determination method specified in this invention, a high-precision conversion from LAB to CMYK color space is achieved. This provides a new method for LAB to CMYK color space conversion and allows for flexible adjustment of the black plate within a reasonable range according to actual needs, enabling more flexible conversion.
[0049] Example 2: Embodiment 2 of the present invention also discloses a LAB to CMYK value conversion system utilizing a LAB to CMYK value conversion method, comprising: Weight matrix calculation module: used to acquire characteristic data containing the color response rules of the target output device, and calculate the weight matrix reflecting the relationship between CMYK and the corresponding LAB values; Lookup table construction module: It is used to evenly divide each channel into a preset number of sampling points within the preset channel value range of CMYK, and calculate the LAB value corresponding to the sampled CMYK value according to the weight matrix, and construct a lookup table from CMYK to LAB value. The CMYK value output module is used to extract the CMY three-dimensional color range under different K values in the lookup table to construct the corresponding layered color gamut. It then traverses the layered color gamut through a color gamut matching algorithm to obtain the target color gamut containing the target LAB value to be converted. Finally, through reverse deduction based on the lookup table, it outputs the CMYK value corresponding to the target LAB value to be converted.
[0050] Example 3: Embodiment 3 of the present invention also discloses an electronic device, comprising: Memory, used to store computer programs; A processor is used to implement a method for converting LAB to CMYK values when executing a computer program.
[0051] Example 4: Embodiment 4 of the present invention also discloses a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, it implements the steps of a method for converting LAB to CMYK values.
[0052] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.
[0053] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A method for converting LAB to CMYK values, characterized in that, include: Step 1: Obtain characteristic data containing the color response patterns of the target output device, and calculate the weight matrix reflecting the relationship between CMYK and the corresponding LAB values; Step 2: Within the preset channel value range of CMYK, evenly divide each channel into a preset number of sampling points, and calculate the LAB value corresponding to the sampled CMYK value according to the weight matrix, and construct a lookup table from CMYK to LAB value; Step 3: Extract the CMY three-dimensional color ranges under different K values in the lookup table to construct the corresponding layered color gamuts, and traverse the layered color gamuts through the color gamut matching algorithm to obtain the target color gamut containing the target LAB value to be converted. Further, through reverse deduction based on the lookup table, obtain the CMYK value output corresponding to the target LAB value to be converted.
2. The method for converting LAB to CMYK values according to claim 1, characterized in that, In step 1, the characteristic data is obtained by extracting ICC characteristic files that conform to industry standards or by accurately measuring each color block on the color card using a professional colorimeter.
3. The method for converting LAB to CMYK values according to claim 1, characterized in that, In step 1, based on the characteristic data, a weight matrix reflecting the relationship between CMYK and the corresponding LAB values is calculated, specifically as follows: Based on the spatial correlation strength between CMYK color sample points in the aforementioned characteristic data, a multi-quadratic kernel spatial relationship matrix is constructed between CMYK color sample points, as follows: in, This is the quadratic kernel spatial relationship matrix between CMYK color sample points; For the first The CMYK color sample point and the first Spatial correlation strength between CMYK color sample points; This represents the number of sample points. Based on the aforementioned quadratic kernel spatial relationship matrix, and according to the LAB value matrix corresponding to each sample point, the weight matrix reflecting the relationship between CMYK and the corresponding LAB value is calculated as follows: in, This is the LAB value matrix corresponding to each sample point; , , The first The L, A, and B values corresponding to each CMYK color sample point; This is the weight matrix; , , The first The contribution weights of each CMYK color sample point to the L, A, and B components.
4. The method for converting LAB to CMYK values according to claim 1, characterized in that, In step 2, within the preset channel value range of CMYK, a preset number of sampling points are evenly divided into each channel. The values of the four channels of CMYK after sampling are as follows: in, This is the maximum value of the channel, which is the upper limit of the preset range of channel values; The number of sampling points is a preset number; , which are the sampling indices for channels C, M, Y, and K, respectively; the values for channels C, M, Y, and K are rounded down.
5. The method for converting LAB to CMYK values according to claim 1, characterized in that, In step 2, the LAB values corresponding to the sampled CMYK values are calculated based on the weight matrix, and a lookup table from CMYK to LAB values is constructed, specifically as follows: Calculate the spatial correlation strength between the sampled CMYK values and CMYK color sample points, and construct the quadratic kernel spatial relationship matrix between the sampled CMYK values and CMYK color sample points, as follows: in, This is the quadratic kernel spatial relationship matrix between the sampled CMYK values and the CMYK color sample points; For the sampled first The CMYK value and the first Spatial correlation strength between CMYK color sample points , ; The preset number of sampling points; This represents the number of sample points. For the first time after sampling One CMYK value; No. One CMYK color sample point; Based on the multi-quadratic kernel spatial relationship matrix, the LAB value corresponding to the sampled CMYK value is calculated according to the weight matrix, and a lookup table from CMYK to LAB value is constructed as follows: in, , , They are the sampling numbers after the first sampling. The LAB value corresponding to each CMYK value; This is the weight matrix; , , The first The contribution weights of each CMYK color sample point to the L, A, and B components.
6. The method for converting LAB to CMYK values according to claim 1, characterized in that, In step 3, the CMY three-dimensional color ranges under different K values in the lookup table are extracted to construct the corresponding layered color gamuts, specifically as follows: Different K-value levels are extracted from the lookup table and rounded down. Through clustering and boundary extraction of the lookup table data, the CMY three-dimensional color ranges under different K-values are constructed into corresponding independent layered color gamuts. The number of K-values in the lookup table is the same as the preset number of channel sampling points.
7. The method for converting LAB to CMYK values according to claim 1, characterized in that, Step 3, after obtaining the CMYK value output corresponding to the target LAB value to be converted, also includes: When there is only one target color gamut containing the target LAB value to be converted, the lookup table of the current target color gamut is directly used to reverse the derivation result as the CMYK value output; where, within each layered color gamut, there is a unique correspondence between the LAB value and the CMYK value; When there are only multiple target color gamuts containing the target LAB values to be converted, the CMYK values are output as follows: in, The number of target color gamuts containing the target LAB values to be converted; This is the index parameter, used to locate the median of the target color gamut; , , , To sort the K values corresponding to the target color gamut containing the target LAB values to be converted by size, the first... Output the CMYK values corresponding to each K value.
8. A LAB to CMYK value conversion system utilizing the LAB to CMYK value conversion method according to any one of claims 1-7, characterized in that, include: Weight matrix calculation module: used to acquire characteristic data containing the color response rules of the target output device, and calculate the weight matrix reflecting the relationship between CMYK and the corresponding LAB values; Lookup table construction module: used to evenly divide each channel into a preset number of sampling points within the preset channel value range of CMYK, and calculate the LAB value corresponding to the sampled CMYK value according to the weight matrix, and construct a lookup table from CMYK to LAB value; CMYK value output module: used to extract the CMY three-dimensional color range under different K values in the lookup table to construct the corresponding layered color gamut, and to traverse the layered color gamut through the color gamut matching algorithm to obtain the target color gamut containing the target LAB value to be converted. Furthermore, through the reverse deduction operation based on the lookup table, the CMYK value corresponding to the target LAB value to be converted is output.
9. An electronic device, characterized in that, include: Memory, used to store computer programs; A processor, configured to implement the steps of a method for converting LAB to CMYK values as described in any one of claims 1-7 when executing the computer program.
10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of a method for converting LAB to CMYK values as described in any one of claims 1-7.