Interpolation method for obtaining actual color gamut distribution in thermal printing

Abstract

The present invention provides an interpolation method for obtaining the actual distribution of color gamut in thermal printing, comprising the following steps: receiving a color target output by a printing device; scanning the color target, recording the CMY data of each color block in the color target and any color space data other than the CMY data; classifying the color blocks of the color target based on the CMY data according to preset conditions; sorting the color blocks of each category according to the C value, M value or Y value to obtain multiple sequences; and linearly interpolating the CMY data and any color space data other than the CMY data between the adjacent colors of each group of color targets. The present invention proposes the concept of adjacent colors of color targets. According to the linear interpolation of adjacent colors of color targets, a one-to-one correspondence between CMY color space data and other color space data can be obtained, and a picture composed of any color space data can be corresponded to the CMY color space of the self-developed device, which is equivalent to obtaining the actual distribution of the color gamut of the thermal printer.

Description

Technical Field

[0001] The invention relates to the technical field of thermal printing color management modules, and in particular to an interpolation method for obtaining actual color gamut distribution in thermal printing. Background Art

[0002] The color management module (CMM) provides a method for the color management system (CMS) to convert colors from the source device color space to PCS, and from PCS to any target device space. In order to ensure the consistency of color processing of self-developed printing equipment and give full play to the advantages of equipment and consumables, it is necessary to research and develop a color management module. This application does not involve the entire process of color management development, but obtaining the actual distribution of the color gamut of thermal printing equipment is the basis for the next step of developing a color management module. At present, research data on color management modules mainly comes from foreign companies or teams. Domestic companies / universities are basically limited to the application layer development of color management modules, but there is very little research on how color management modules are established.

[0003] The ink used in thermal printing equipment is very different from the ink used in traditional printing. The ink consumables used in thermal printing equipment are called thermal transfer ribbons, and the thermal sublimation ribbons can theoretically output any shade of color, because the temperature output of the print head is theoretically continuous, so the ink transfer amount of the thermal sublimation ribbon can also be a continuous value in theory. The color gamut of the printing device is affected by the parameters of the printing device and the color gamut of the ribbon itself. Although the color gamut range of the ribbon is fixed, how the colors within the color gamut are expressed through device parameters is controlled by the device, that is, the CMY printing color space is device-related. Digital printing input is RGB images, and the colors of the images belong to the sRGB space. The colors of these color spaces cannot be used directly for printing. The corresponding relationship between these color spaces and the device color gamut must be established to know the specific ratio of the color to be printed for a certain color to be printed, otherwise the color reproduction cannot be consistent. This is the basis for the establishment of the color management module.

[0004] The simplest and crudest way to obtain the color gamut of a printing device is to output all the colors that the printing device can display, then measure the Lab values ​​of all colors and directly establish the relationship between CMY and Lab. Obviously, there are at least 100 combinations of each CMY color, and it is an impossible task to proof all colors. At this time, the only way is to use the existing CMM module to establish a relationship table between CMY and Lab. The CMM modules currently available on the market are all established by some foreign companies and teams, and domestic attempts have not made effective progress. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for obtaining the actual distribution of the color gamut of a thermal printing device, fill the technical gap of the domestic color management module, and serve as the basis for establishing the color management module.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] The present invention provides an interpolation method for obtaining the actual distribution of a color gamut by thermal printing, comprising the following steps:

[0008] Receiving a color target output by a printing device, wherein the color target includes a plurality of color blocks;

[0009] Scanning the color target, recording CMY data of each color block in the color target and any color space data other than CMY data;

[0010] According to a preset condition, the color blocks of the color target are classified based on the CMY data, and the preset condition is: in the same type of color blocks, any two values ​​of the C value, M value, and Y value of the CMY data are the same, and the other value is different;

[0011] Sort the color blocks of each category by C value, M value or Y value to obtain multiple sequences;

[0012] Between each group of color target adjacent colors, linear interpolation is performed on the CMY data and any color space data other than the CMY data, wherein any two adjacent color blocks in each sequence form a group of color target adjacent colors.

[0013] The beneficial effects of the present invention are:

[0014] The present invention proposes the concept of adjacent colors of color targets. According to the linear interpolation of adjacent colors of color targets, a one-to-one correspondence between CMY color space data and other color space data can be obtained. For example, CMY color space and Lab space can be converted to each other. A picture composed of any color space data can be corresponded to the CMY color space of the self-developed equipment, which is equivalent to obtaining the actual distribution of the color gamut of the thermal printer. Therefore, it can be used as the basis for establishing a color management module, filling the technical gap of domestic color management modules.

[0015] Further, the color target output by the printing device specifically includes: the printing device uses the ECI2002 color manager to select n values ​​for the C value, M value, and Y value of the CMY data for proofing, and obtains a color target containing n×n×n color blocks. The output process specifically includes: the printing device uses the ECI2002 color manager to select at least 15 values ​​for the C value, M value, and Y value of the CMY data for proofing, and obtains a color target containing 15×15×15 color blocks.

[0016] ECI2002 Color Manager is currently the most widely used tool for easy sampling. It reduces the amount of system calculations and ensures that the color error after interpolation is small and the saturation is sufficient, exceeding the ability of the naked eye to identify.

[0017] Furthermore, any color space data other than the CMY data is Lab data.

[0018] A relationship table between CMY and Lab is established, and other color spaces can be converted to and from the Lab color space, thereby improving the processing speed for colors in any format.

[0019] Further, the CMY data includes C value, M value, and Y value; the Lab data includes L value, a value, and b value;

[0020] The process of scanning the color target includes: recording the C value, M value and Y value of each color block of the color target belonging to the CMY color space, and obtaining and recording the L value, a value and b value of each color block of the color target belonging to the Lab color space.

[0021] It is convenient for subsequent classification, sorting and interpolation operations.

[0022] The sorting process includes: for a class of color blocks with the same M value and Y value but different C values, sorting them according to the C value; for a class of color blocks with the same C value and Y value but different M values, sorting them according to the M value; for a class of color blocks with the same C value and M value but different Y values, sorting them according to the Y value.

[0023] The beneficial effect of the above further solution is that the adjacent colors of the color target are prominently displayed, the program is easy to obtain and error-prone.

[0024] The linear interpolation of CMY data and any color space data other than CMY data between adjacent colors of each group of color targets specifically includes:

[0025] Between adjacent colors of each group of color targets, several intermediate value points of CMY data are selected at intervals, and according to a linear rule, any color space data other than the CMY data is set for each intermediate value point.

[0026] The interval selects several intermediate value points of the CMY data, and sets any color space data other than the CMY data for each intermediate value point according to a linear rule, specifically including:

[0027] ① For the color blocks sorted by C value, a number of intermediate value points of C value are selected between the two end points of the adjacent colors of the color target in the group, and any color space data other than the CMY data is set for each intermediate value point according to a linear rule;

[0028] ② For the color blocks sorted by M value, a number of intermediate value points of M value are selected between the two end points of the adjacent colors of the color target in the group, and any color space data other than the CMY data is set for each intermediate value point according to a linear rule;

[0029] ③ For the color blocks sorted by Y value, several intermediate value points of Y value are selected at intervals between the Y values ​​of the two end points of adjacent colors of the color target group, and any color space data other than the CMY data is set for each intermediate value point according to a linear rule.

[0030] The interpolation rule is cyclic, that is, the color blocks sorted by C value are interpolated first, then L value, a value and b value are inserted in sequence, and then the color blocks sorted by M value and Y value are interpolated cyclically. The program structure is simple and error-prone; and the correspondence between all continuous CMY data and Lab data can be obtained, and the interpolation error is small.

[0031] Further, any color space data other than the CMY data is Lab data; and setting any color space data other than the CMY data for each intermediate value point specifically includes: setting the L value, a value and b value of each intermediate value point respectively.

[0032] Between the two end point C values ​​of the adjacent colors of the color target group, a plurality of intermediate value points of C value are selected at intervals, wherein the C values ​​of the two end points and the C values ​​of the plurality of intermediate value points are continuous natural numbers;

[0033] A plurality of intermediate value points of M value are selected at intervals between the two end point M values ​​of the adjacent colors of the color target group, wherein the M values ​​of the two end points and the M values ​​of the plurality of intermediate value points are continuous natural numbers;

[0034] A plurality of intermediate value points of Y value are selected at intervals between the two end point Y values ​​of the adjacent colors of the color target group, wherein the Y values ​​of the two end points and the Y values ​​of the plurality of intermediate value points are continuous natural numbers.

[0035] By using natural numbers as values ​​and taking values ​​continuously, the corresponding relationship between all continuous CMY data and Lab data can be obtained, and the interpolation error is small. DETAILED DESCRIPTION

[0036] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0037] The present invention provides an interpolation method for obtaining the actual distribution of a color gamut by thermal printing, comprising the following steps:

[0038] Receiving a color target output by a printing device, wherein the color target includes a plurality of color blocks;

[0039] Scanning the color target, recording CMY data of each color block in the color target and any color space data other than CMY data;

[0040] According to a preset condition, the color blocks of the color target are classified based on the CMY data, and the preset condition is: in the same type of color blocks, any two values ​​of the C value, M value, and Y value of the CMY data are the same, and the other value is different;

[0041] Sort the color blocks of each category by C value, M value or Y value to obtain multiple sequences;

[0042] Between each group of color target adjacent colors, linear interpolation is performed on the CMY data and any color space data other than the CMY data, wherein any two adjacent color blocks in each sequence form a group of color target adjacent colors.

[0043] Principle explanation: First, any other color space mentioned above, currently common color spaces include sRGB, XYZ, Lch and Lab color spaces, etc. The color management module (CMM) of traditional digital printing, the computer program ECI2002 color manager, etc., all have universal formulas to convert these color spaces to each other, such as matching the color value of the sRGB space with the color value of the Lab space (RGB→XYZ→Lab). All the color spaces involved here are device-independent, that is, the color values ​​of all these spaces can be converted to each other through a series of formulas. However, as explained in the background technology, the colors of these color spaces cannot be used directly for printing, and the corresponding relationship between these color spaces and the device color space (CMY) must be established.

[0044] It is emphasized here that the CMY printing color space is device-dependent, that is, the target device of the traditional color management module (CMM) color conversion method is only the device provided by the provider, and does not include other developers' self-developed devices. Traditional digital printing uses CMYK values. Since thermal printing uses only C, M, and Y as the three primary colors, K in the color target can be directly removed.

[0045] The present application proposes the concept of adjacent colors of color targets. According to the three-dimensional arrangement characteristics of the ECI2002 color target according to the printed color value, it is found that: for example, the color target has 15 samples, and each sample has 15×15 colors in the horizontal and vertical directions. (1) In a single sample, there are two identical printed color values ​​and a different printed color value in the horizontal and vertical directions of the 15 colors (for example, the horizontal M value and Y value are the same, but the C value is different; the vertical Y value and C value are the same, but the M value is different); (2) In different samples, there are two identical printed color values ​​and a different printed color value in the same position of the 15 colors (for example, the C value and M value are the same, but the Y value is different). Then, two color blocks adjacent to each other with the same horizontal C value are color target adjacent colors (because they are samples, the C values ​​are only adjacent in order, not continuous). The same is true for color target adjacent colors in the same vertical direction and in different samples at the same position, which will not be elaborated.

[0046] In summary, in each group of adjacent colors of the color target above, the CMY data of the two color blocks can be directly recorded according to the printing parameters, and any color space data other than the CMY data is obtained by scanning. By linearly interpolating the CMY data and other color space data between a group of adjacent colors of the color target, a one-to-one correspondence between the CMY data and the other color space data can be obtained, and each color value according to the aforementioned other color spaces can be converted to each other. Therefore, it is equivalent to obtaining the actual distribution of the color gamut of the thermal printer. When the digital printing input is a picture composed of any color space data, it can be corresponded to the CMY color space of the self-developed equipment. Therefore, the present invention can be used as the basis for establishing a color management module.

[0047] The present invention proposes the concept of adjacent colors of color targets. According to the linear interpolation of adjacent colors of color targets, a one-to-one correspondence between CMY color space data and other color space data can be obtained. For example, CMY color space and Lab space can be converted to each other. A picture composed of any color space data can be corresponded to the CMY color space of the self-developed equipment, which is equivalent to obtaining the actual distribution of the color gamut of the thermal printer. Therefore, it can be used as the basis for establishing a color management module, filling the technical gap of domestic color management modules.

[0048] Embodiment 2:

[0049] In the above embodiment, the following improvements can be made:

[0050] Further, the color target output by the printing device specifically includes: the printing device uses the ECI2002 color manager to select n values ​​for the C value, M value, and Y value of the CMY data for proofing, and obtains a color target containing n×n×n color blocks. The output process specifically includes: the printing device uses the ECI2002 color manager to select at least 15 values ​​for the C value, M value, and Y value of the CMY data for proofing, and obtains a color target containing 15×15×15 color blocks.

[0051] The beneficial effects of the above further scheme are: ECI2002 color manager is currently a widely used tool and is convenient for sampling; the color target cannot include all CMY value combinations. There are at least 100 combinations of each CMY color value for printing, and only some of the values ​​can be selected for sampling and combination. For example, 15 values ​​of each CMY ink are selected for proofing here, then the total number of CMY color block combinations of this color target is 15×15×15=3375, and these 3375 color blocks can be scanned and sampled later; using 15 value combinations, while reducing the amount of system calculations, it is ensured that the color error after interpolation is small and the saturation is sufficient, which exceeds the recognition ability of the naked eye.

[0052] Furthermore, any color space data other than the CMY data is Lab data.

[0053] The beneficial effect of the above further solution is that a relationship table between CMY and Lab is established, and other color spaces can be converted to and from the Lab color space, thereby improving the processing speed for colors in any format.

[0054] Further, the CMY data includes C value, M value, and Y value; the Lab data includes L value, a value, and b value;

[0055] The process of scanning the color target includes: recording the C value, M value and Y value of each color block of the color target belonging to the CMY color space, and obtaining and recording the L value, a value and b value of each color block of the color target belonging to the Lab color space.

[0056] The beneficial effect of the above further solution is that it facilitates subsequent classification, sorting and interpolation operations.

[0057] Furthermore, the sorting process includes: for a class of color blocks with the same M value and Y value but different C values, sorting by C value; for a class of color blocks with the same C value and Y value but different M values, sorting by M value; for a class of color blocks with the same C value and M value but different Y values, sorting by Y value.

[0058] The beneficial effect of the above further solution is that the adjacent colors of the color target are prominently displayed, the program is easy to obtain and error-prone.

[0059] The linear interpolation of CMY data and any color space data other than CMY data between adjacent colors of each group of color targets specifically includes:

[0060] Between adjacent colors of each group of color targets, several intermediate value points of CMY data are selected at intervals, and according to a linear rule, any color space data other than the CMY data is set for each intermediate value point.

[0061] The interval selects several intermediate value points of the CMY data, and sets any color space data other than the CMY data for each intermediate value point according to a linear rule, specifically including:

[0062] ① For the color blocks sorted by C value, a number of intermediate value points of C value are selected between the two end points of the adjacent colors of the color target in the group, and any color space data other than the CMY data is set for each intermediate value point according to a linear rule;

[0063] ② For the color blocks sorted by M value, a number of intermediate value points of M value are selected between the two end points of the adjacent colors of the color target in the group, and any color space data other than the CMY data is set for each intermediate value point according to a linear rule;

[0064] ③ For the color blocks sorted by Y value, several intermediate value points of Y value are selected at intervals between the Y values ​​of the two end points of adjacent colors of the color target group, and any color space data other than the CMY data is set for each intermediate value point according to a linear rule.

[0065] The beneficial effect of the above further scheme is that the interpolation rule is cyclic, that is, the color blocks sorted by C value are interpolated first, and then L value, a value and b value are inserted in sequence, and then the color blocks sorted by M value and Y value are interpolated cyclically. The program structure is simple and not prone to errors; and the correspondence between all continuous CMY data and Lab data can be obtained, and the interpolation error is small.

[0066] Further, any color space data other than the CMY data is Lab data; and setting any color space data other than the CMY data for each intermediate value point specifically includes: setting the L value, a value and b value of each intermediate value point respectively.

[0067] Between the two end point C values ​​of the adjacent colors of the color target group, a plurality of intermediate value points of C value are selected at intervals, wherein the C values ​​of the two end points and the C values ​​of the plurality of intermediate value points are continuous natural numbers;

[0068] A plurality of intermediate value points of M value are selected at intervals between the two end point M values ​​of the adjacent colors of the color target group, wherein the M values ​​of the two end points and the M values ​​of the plurality of intermediate value points are continuous natural numbers;

[0069] A plurality of intermediate value points of Y value are selected at intervals between the two end point Y values ​​of the adjacent colors of the color target group, wherein the Y values ​​of the two end points and the Y values ​​of the plurality of intermediate value points are continuous natural numbers.

[0070] The beneficial effect of the above further solution is that natural numbers are used for value taking, and the values ​​are taken continuously, so that the correspondence between all continuous CMY data and Lab data can be obtained, and the interpolation error is small. For example, the CMY value of a color block is (8,13,18), and its Lab value obtained by scanning with a colorimeter is (94.6,-0.19,3.55); its adjacent color target is (8,18,18), and its Lab value obtained by scanning with a colorimeter is (93.53,2.09,2.49). At this time, the C value and Y value of the two color blocks are the same, and they are sorted in ascending order of M value as (8,13,18) and (8,18,18). The Lab values ​​are correspondingly arranged as (94.6,-0.19,3.55) and (93.53,2.09,2.49). It is easy to find that there are 4 consecutive M value points according to natural numbers, "14, 15, 16, 17". At this time, the L value should be interpolated in descending order as M ascends, the a value should be interpolated in ascending order as M ascends, and the b value should be interpolated in descending order as M ascends. Therefore, as long as the method stipulates linear interpolation between adjacent colors of two color targets, the changing directions of L value, a value and b value can be naturally found, and the interpolation interval can be calculated according to the linear law.

[0071] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art, within the scope of information available through public channels and in combination with the technical inspiration provided by the present application documents, may make changes, modifications, substitutions and variations to the above embodiments, which shall still be within the scope of protection of the present invention.

Claims

1. An interpolation method for obtaining the actual distribution of color gamut in thermal printing, characterized in that: The steps include: Receiving a color target output by a printing device, wherein the color target includes a plurality of color blocks; Scanning the color target, recording CMY data of each color block in the color target and any color space data other than CMY data; According to a preset condition, the color blocks of the color target are classified based on the CMY data, and the preset condition is: in the same type of color blocks, any two values ​​of the C value, M value, and Y value of the CMY data are the same, and the other value is different; Sort the color blocks of each category by C value, M value or Y value to obtain multiple sequences; Between each group of color target adjacent colors, linear interpolation is performed on the CMY data and any color space data other than the CMY data, wherein any two adjacent color blocks in each sequence are a group of color target adjacent colors; The linear interpolation of CMY data and any color space data other than CMY data between adjacent colors of each group of color targets specifically includes: Between adjacent colors of each group of color targets, several intermediate value points of CMY data are selected at intervals, and any color space data other than the CMY data is set for each intermediate value point according to a linear rule; The interval selects several intermediate value points of the CMY data, and sets any color space data other than the CMY data for each intermediate value point according to a linear rule, specifically including: ① For the color blocks sorted by C value, a number of intermediate value points of C value are selected between the two end points of the adjacent colors of the color target in the group, and any color space data other than the CMY data is set for each intermediate value point according to a linear rule; ② For the color blocks sorted by M value, a number of intermediate value points of M value are selected between the two end points of the adjacent colors of the color target in the group, and any color space data other than the CMY data is set for each intermediate value point according to a linear rule; ③ For the color blocks sorted by Y value, several intermediate value points of Y value are selected at intervals between the Y values ​​of the two end points of adjacent colors of the color target group, and any color space data other than the CMY data is set for each intermediate value point according to a linear rule.

2. The interpolation method for obtaining actual color gamut distribution by thermal printing according to claim 1, characterized in that: The color target output by the printing device specifically includes the following steps: the printing device uses the ECI2002 color manager to select n values ​​for the C value, M value, and Y value of the CMY data for proofing, and obtains a color target containing n×n×n color blocks.

3. The interpolation method for obtaining the actual distribution of color gamut by thermal printing according to claim 2, characterized in that: The output process specifically includes: the printing device uses the ECI2002 color manager to select at least 15 values ​​of the C value, M value, and Y value of the CMY data for proofing, and obtains a color target containing 15×15×15 color blocks.

4. The interpolation method for obtaining actual color gamut distribution by thermal printing according to claim 1, characterized in that: Any color space data other than the CMY data is Lab data.

5. The interpolation method for obtaining actual color gamut distribution by thermal printing according to claim 4, characterized in that: The CMY data includes C value, M value, and Y value; the Lab data includes L value, a value, and b value; The process of scanning the color target includes: recording the C value, M value and Y value of each color block of the color target belonging to the CMY color space, and obtaining and recording the L value, a value and b value of each color block of the color target belonging to the Lab color space.

6. The interpolation method for obtaining actual color gamut distribution by thermal printing according to claim 1, characterized in that: The sorting process includes: for a class of color blocks with the same M value and Y value but different C values, sorting them according to the C value; for a class of color blocks with the same C value and Y value but different M values, sorting them according to the M value; for a class of color blocks with the same C value and M value but different Y values, sorting them according to the Y value.

7. The interpolation method for obtaining actual color gamut distribution by thermal printing according to claim 1, characterized in that: Any color space data other than the CMY data is Lab data; and setting any color space data other than the CMY data for each intermediate value point specifically includes: setting the L value, a value and b value of each intermediate value point respectively.

8. The interpolation method for obtaining actual color gamut distribution by thermal printing according to claim 1, characterized in that: Between the two end point C values ​​of the adjacent colors of the color target group, a plurality of intermediate value points of C value are selected at intervals, wherein the C values ​​of the two end points and the C values ​​of the plurality of intermediate value points are continuous natural numbers; A plurality of intermediate value points of M values ​​are selected at intervals between the two end point M values ​​of the adjacent colors of the color target group, wherein the M values ​​of the two end points and the M values ​​of the plurality of intermediate value points are continuous natural numbers; A plurality of intermediate value points of Y value are selected at intervals between the two end point Y values ​​of the adjacent colors of the color target group, wherein the Y values ​​of the two end points and the Y values ​​of the plurality of intermediate value points are continuous natural numbers.