CN110099193B - Spot color correction method and device - Google Patents
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- H04N1/46—Colour picture communication systems
- H04N1/56—Processing of colour picture signals
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- H04N1/6075—Corrections to the hue
Abstract
The invention provides a spot color correction method and a spot color correction device, wherein the tone parameters of the tone of a spot color to be corrected are obtained; then, according to the tone parameters and a pre-obtained spot color one-dimensional lookup table, obtaining color parameters of the spot color tone to be corrected in a color space of the printing equipment; and correcting the special tone to be corrected according to the color parameters on the color space of the printing equipment. According to the method, the correction of the special tone to be corrected can be quickly realized through the pre-obtained special color one-dimensional lookup table, so that the corrected special color is more matched with the target color, and the reproduction capability of the printing equipment on the special tone is improved.
Description
Technical Field
The invention relates to the technical field of printing, in particular to a spot color correction method and device.
Background
With the improvement of the requirements of people on the quality of printed products, the application of spot colors is more and more extensive particularly in the field of packaging. When digital printing and digital proofing equipment are used for outputting, the implementation mechanism of the spot color is substantially different from that of four colors. First, their color matching processes are different, with the four-color output focusing on the overall output effect, and the spot color output targeting accurate simulation and reproduction of individual specific colors. Because the number and the variety of the spot colors are various, the accurate simulation and the output of the spot colors are one of the key problems to be solved urgently by the current digital printing and digital proofing systems; in addition, many spot colors exceed the color range which can be realized by a digital printer and a digital printer, which brings great difficulty to digital printing and proofing, so that the conventional proofing mode is mostly adopted for spot color simulation at present, and the problems of time and labor waste, low efficiency, inaccurate simulation and the like exist in the mode, so that the accurate reproduction of the spot colors is always a technical difficulty.
A spot color calibration method based on digital printing and digital printing modes is to use several ink colors carried by equipment to simulate spot colors instead of using spot color ink, since the simulation has the problem of accuracy or not. The color difference Δ E in the color space of CIE1976L a b was used in the simulation to measure the accuracy of the simulation, wherein a larger color difference value indicates that the spot color simulation is less similar. There are various methods to solve the problem of large color difference, such as increasing the color gamut of the device, replacing paper, increasing the number of colors of ink, etc., but these improvements require high cost, have large application limitations, and it is difficult to effectively exert these properties without a good spot color calibration mechanism.
Disclosure of Invention
The invention provides a spot color correction method and a spot color correction device, which are used for effectively improving the reproduction capability of printing equipment on spot color gradations, ensuring that the corrected spot color gradations are more matched with target colors and ensuring the reproduction accuracy of the whole gradations of the spot colors.
One aspect of the present invention provides a spot color correction method, including:
obtaining the tone parameters of the special tone to be corrected;
acquiring color parameters of the to-be-corrected spot color tone on a printing equipment color space according to the tone parameters and a pre-acquired spot color one-dimensional lookup table, wherein the spot color one-dimensional lookup table is a comparison table of the tone parameters of each tone of the spot color to which the to-be-corrected spot color tone belongs and the color parameters on the printing equipment color space;
and correcting the special tone to be corrected according to the color parameters on the color space of the printing equipment.
Another aspect of the present invention provides a spot color correction apparatus, including:
the acquisition module is used for acquiring the tone parameters of the special tone to be corrected;
the processing module is used for acquiring color parameters of the to-be-corrected spot color tone in the color space of the printing equipment according to the tone parameters and a pre-acquired spot color one-dimensional lookup table, wherein the spot color one-dimensional lookup table is a comparison table of the tone parameters of each tone of the spot color to which the to-be-corrected spot color tone belongs and the color parameters in the color space of the printing equipment;
and the correction module is used for correcting the special tone to be corrected according to the color parameters on the color space of the printing equipment.
According to the spot color correction method and device, the tone parameters of the tone of the spot color to be corrected are obtained; then, according to the tone parameters and a pre-obtained spot color one-dimensional lookup table, obtaining color parameters of the spot color tone to be corrected in a color space of the printing equipment; and correcting the special tone to be corrected according to the color parameters on the color space of the printing equipment. According to the method, the correction of the special tone to be corrected can be quickly realized through the pre-obtained special color one-dimensional lookup table, so that the corrected special color is more matched with the target color, and the reproduction capability of the printing equipment on the special tone is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a flow chart of a spot color correction method according to an embodiment of the present invention;
FIG. 2 is a flow chart of a spot color correction method according to another embodiment of the present invention;
FIG. 3 is a flow chart of a spot color correction method according to another embodiment of the present invention;
fig. 4 is a structural diagram of a spot color correction apparatus according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Fig. 1 is a flowchart of a spot color correction method according to an embodiment of the present invention. As shown in fig. 1, the embodiment provides a spot color correction method, which includes the following specific steps:
and S101, obtaining the tone parameters of the special tone to be corrected.
In this embodiment, the tone parameters of the spot tone to be corrected are used to distinguish different tones, and may be any value within the range of 0 to 255, and the dot percentage of each tone is normalized from 0 to 100% and then mapped into the range of 0 to 255. In this embodiment, the tone parameter of the special tone to be corrected may be directly obtained, or the dot percentage of the special tone to be corrected may be obtained first, and then the dot percentage is mapped to the range of 0 to 255 to obtain the tone parameter of the special tone to be corrected, and specifically, the later-described tone parameter X for obtaining any special tone may be applied reverselytCorresponding dot percentage parameter STtThe formula (2).
And S102, acquiring color parameters of the to-be-corrected spot color tone in a printing equipment color space according to the tone parameters and a pre-acquired spot color one-dimensional lookup table, wherein the spot color one-dimensional lookup table is a comparison table of the tone parameters of each tone of the spot color to which the to-be-corrected spot color tone belongs and the color parameters in the printing equipment color space.
In this embodiment, the color parameters on the color space of the printing device corresponding to the tone parameters are obtained by searching the spot color one-dimensional lookup table obtained in advance according to the tone parameters. The spot color one-dimensional lookup table is a comparison table of the tone parameters of each tone of the spot color to which the tone of the spot color to be corrected belongs and the color parameters on the color space of the printing equipment, and the comparison table is obtained through correction. More specifically, the spot color space generally employs L a b color space, while the printing device color space is typically a CMYK color space. That is, in this embodiment, the special color one-dimensional lookup table is a comparison table of the special tone parameters 0 to 255 and the CMYK color parameters, and the CMYK color parameters of the special tone to be corrected are obtained by inputting the special tone parameters.
S103, correcting the special tone to be corrected according to the color parameters on the color space of the printing equipment.
In this embodiment, the printing is performed according to the color parameters in the color space of the printing device corresponding to the to-be-corrected special tone, so that the printed special tone is more matched with the target color, and is closer to the real color of the to-be-corrected special tone, thereby improving the reproducibility of the printing device to the special tone.
In the spot color correction method provided by this embodiment, the tone parameters of the tone of the spot color to be corrected are obtained; then, according to the tone parameters and a pre-obtained spot color one-dimensional lookup table, obtaining color parameters of the spot color tone to be corrected in a color space of the printing equipment; and correcting the special tone to be corrected according to the color parameters on the color space of the printing equipment. The correction of the special tone to be corrected can be quickly realized through the pre-acquired special color one-dimensional lookup table, so that the corrected special color is more matched with the target color, and the reproduction capability of the printing equipment on the special tone is improved.
On the basis of the above embodiment, before obtaining the tone parameters of the special tone to be corrected in S101, the method further includes a step of obtaining a one-dimensional look-up table of the special tone, as shown in fig. 2, and the specific steps are as follows:
s201, correcting the color parameters of the spot color output by the printing equipment.
In this embodiment, the color parameters of the spot color output by the printing device are corrected to make the color output by the printing device approach the target color of the spot color, and only when the color parameters of the spot color output by the printing device are more accurate, the subsequently obtained spot color one-dimensional lookup table can be more accurate, and further, the tone of the spot color to be corrected can be accurately corrected. Specifically, in this embodiment, a spot color calibration method as in patent CN201110390678.1 can be adopted: 1) setting a spot color target value as a spot color standard value; 2) setting a plurality of spot color values by taking a spot color standard value as a center, wherein the spot color standard value and the spot color values form a group of spot color enumerated values; 3) printing by the printing equipment according to the spot color enumeration value, and outputting to obtain a color target graph; 4) Measuring each color block on the color target graph to obtain a spot color measured value of each color block; 5) determining the color difference between each spot color measured value and a spot color target value; 6) determining a spot color enumeration value of a color block corresponding to a spot color measured value with the minimum color difference; 7) correcting the determined spot color enumerated value by a set amplitude to be used as a new spot color standard value; 8) And (5) circularly executing the steps 2-7 until the minimum color difference rebounds, ending the circulation, and determining the spot color enumeration value of the spot color measured value with the minimum color difference corresponding to the color block as a final printing value. Of course, other methods may be adopted in this embodiment to correct the color parameters of the spot color output by the printing device, and details are not described here.
In the present embodiment, the spot color reproducibility, i.e., the degree of difference between the actually output spot color and the target data, is evaluated, and the international commission on illumination specifies the color difference (denoted by Δ E), and the present embodiment adopts the color difference formula published by the international commission on illumination in 1976, and the color difference formula is as follows:
wherein:
color parameters that may represent a target color of a spot color,
color parameters that represent the spot color output by the printing device, i.e., color parameters that are measured after output on the device. By correcting the color parameters of the spot color output by the printing apparatus so that Δ E between it and the color parameters of the target color is as small as possible, accurate reproduction of the color parameters of the spot color is ensured.
S202, acquiring color parameters of paper white.
In this embodiment, since the color of the white (paper white) affects the print proofing effect of the medium gradation of the spot color, the color parameters of the white are obtained in this embodiment, and the respective gradations of the spot color are corrected by combining the color parameters of the solid spot color after correction. Of course, the paper white color parameter in this embodiment may also be an ideal value, namely SCw＝{100,0,0}。
S203, obtaining the spot color one-dimensional lookup table according to the corrected spot color parameters, the paper white color parameters and the equipment characteristic lookup table of the printing equipment, wherein the equipment characteristic lookup table is a comparison table of a spot color space and a color space of the printing equipment.
In this embodiment, the mapping relationship between each spot color tone parameter and the corresponding color parameter in the color space of the printing device is obtained through the corrected spot color parameter, the paper white color parameter, and the device characteristic lookup table of the printing device, so as to obtain the spot color one-dimensional lookup table.
Specifically, as shown in fig. 3, the obtaining the spot color one-dimensional lookup table according to the corrected color parameter of the spot color area, the color parameter of the paper white, and the device characteristic lookup table of the printing device in S203 specifically includes:
s2031, acquiring color parameters of any spot color gradation on the spot color space according to the corrected color parameters of the spot color and the color parameters of the paper white.
S2032, searching the device characteristic lookup table according to the color parameters of any special tone in the special color space, and obtaining the mapping relation between the tone parameters of each special tone and the corresponding color parameters in the printing device color space, thereby obtaining the special color one-dimensional lookup table.
More specifically, the obtaining, by the color parameter of the spot solid after the correction and the color parameter of the paper white in S2031, the color parameter of any spot tone in the spot color space may specifically include:
s301, acquiring color parameters of the spot tone of any dot percentage parameter on the spot color space according to the following formula, and establishing a color parameter lookup table on the spot color space:
wherein, STiPercentage parameter of dots for ith tone of spot color, i ∈ [1, p]P is n × m, m is the number of the tone parameters of the special tone, and n is a positive integer;
brightness component values, a component values and b component values of the ith level of the spot color respectively; ST (ST)pThe corrected dot percentage parameter of the spot color is the corrected dot percentage parameter of the spot color;
the corrected brightness component values, a component values and b component values of the spot solid are respectively; ST (ST)1The dot percentage parameter of the paper white;
the lightness component value, a component value and b component value of the paper white are respectively.
In this embodiment, first, color parameters of the gradations of p different halftone dot percentage parameters on the spot color space are obtained, a color parameter lookup table on the spot color space is established, then, the gradation parameters of the spot gradations of the required gradation parameters are converted into dot percentage parameters, and the color parameters on the spot color space corresponding to the gradation parameters are obtained by looking up the color parameter lookup table on the spot color space. In this embodiment, m is the number of tone parameters of the spot tone, and for the tone parameters of 0 to 255, m is 256, n is a positive integer, for example, n is 256, that is, p is 65536, and by thinning the halftone dot percentage parameter, that is, by making the color parameter lookup table on the spot color space more detailed, it is convenient to find the corresponding color parameter on the spot color space after the tone parameter is converted into the halftone dot percentage parameter.
S302, obtaining the tone parameter X of any special tone according to the following formulatCorresponding dot percentage parameter STt：
Wherein, Xm、X1The corrected special solid color and the paper white gradation parameters are respectively.
S303, according to the tone parameter X of any special tonetCorresponding dot percentage parameter STtAnd acquiring corresponding color parameters from the color parameter lookup table on the spot color space.
In this embodiment, each tone parameter X is obtainedtCorresponding dot percentage parameter STtAnd then, acquiring corresponding color parameters from a color parameter lookup table on a spot color space, and then searching an equipment characteristic lookup table to acquire color space parameters of the color space of the printing equipment corresponding to the color parameters of each tone, thereby acquiring the spot color one-dimensional lookup table.
Further, between S302 and S303, there may be further included:
s304, tone parameter X of each spot tone according to the following formulatCorresponding dot percentage parameter STtPerforming jitter calculation to obtain corrected STt', and with said corrected STt' as a novelt：
Wherein, STrmIs a random number, q is the number of layers of jitter and is an odd number, STrm% represents STrmAnd (5) taking the remainder of q.
In this embodiment, to avoid the transition of the spot color intermediate tone, a random number ST is introducedrmFor STtPerforming jitter calculation by setting the layer number of jitter in the formula and using the random number STrmBy taking the remainder of q, so that different ST's are used depending on the remaindertThe' value can effectively solve the quality problems of color cast, jump and the like of the middle tone.
The spot color correction method of the above embodiment is described in detail below with reference to a specific example.
In this example, the output device used was an Epson7910 printer, the ink was Epson original 10 color ink, the Paper was a Fantac Inkjet Proofing Paper (190g), and the measuring device was EyeOne-iSis of Achrome. The printing device color space CMYK color space. The spot color space is a device independent L*a*b*In the color space, this embodiment takes the example of correcting the pantong color library PANTONE solid coated spot color PANTONE 330C.
1) First, the color parameters of the spot color output by the printing apparatus are corrected.
The spot color PANTONE 330C has a color parameter value before correction, i.e. the target color parameter value is SCstAfter output on the device, the color difference Δ E between the output color (measured value) and the target color is calculated to be 1.75 by using a color difference formula. The spot color is corrected based on closed-loop correction by adopting a spot color calibration method as in patent CN201110390678.1, and the corrected spot color parameter value SC is the spot color parameter values31.82, -25.87, -5.85, and the color difference Δ E between the output color (measured value) and the target color is 0.59. The spot color after correction is closer to the target color, and accurate correction is realized. It should be noted that the term "equal sign" means "expressed as" and all the values and data of the color parameters referred to later are expressed in this way.
2) The color parameters of the paper white are obtained.
In this embodiment, the paper white color parameter value is taken as ideal data, namely SCw＝{100,0,0}。
3) And establishing a color parameter lookup table on a spot color space.
In order to improve the accuracy of the subsequent table lookup, the percentage of mesh points parameter in the embodiment takes 65536 levels, that is, p is 65536, and for the convenience of calculation and storage, the percentage of mesh points parameter is normalized and then mapped into the range of 0 to 65535, and the percentage of mesh points parameter is also mapped into the range of 0 to 65535Namely ST1＝0，STp＝65535，i∈ [0,65535 ] SCstAnd SCsThe numerical values of (a) are respectively substituted into the formula:
according to the formula, the color parameters of the spot tone of any dot percentage parameter on the spot color space are obtained, and a color parameter lookup table on the spot color space is established, as shown in table 1.
TABLE 1
4) Obtaining the tone parameter X of any special tonetCorresponding dot percentage parameter STt。
In this embodiment, the tone parameter of the spot tone is 0 to 255, that is, m is 256, and the paper white tone parameter is X10, the contrast parameter of spot color is XmWhen the value is 255, the formula is substituted into each of the following formulas:
the tone parameter X of any special tone can be obtained by the formulatCorresponding dot percentage parameter STt。
5) For each spot tone parameter XtCorresponding dot percentage parameter STtAnd carrying out jitter calculation.
Tone parameter X for each spot tone according to the following formulatCorresponding dot percentage parameter STtPerforming jitter calculation to obtain corrected STt', and with said corrected STt' as a novelt：
Wherein, the layer number of the dithering is q equal to 3, and the random number
(wherein ST)r＇m∈ [0,255]Random number of). Namely:
by using random numbers STrmBy taking a remainder of 3, so that different ST's are used depending on the remaindertThe' value can effectively solve the quality problems of color cast, jump and the like of the middle tone.
6) By STt' tone parameter X as spot tonetAnd acquiring corresponding color parameters from a color parameter lookup table on a spot color space according to the corresponding dot percentage parameters.
In this embodiment, each ST is looked up through a color parameter lookup table in the spot color spacet' corresponding color parameters, thereby obtaining a tone parameter X for each spot tonetThe corresponding color parameters are shown in table 2.
TABLE 2
7) And establishing a spot color one-dimensional lookup table.
In this embodiment, the device characteristic lookup table is searched according to the color parameters of any special tone in the special color space, the special color space is mapped to the CMYK color space, and the mapping relationship between the tone parameters of each special tone and the corresponding color parameters in the printing device color space is obtained, so as to obtain the special color one-dimensional lookup table, as shown in table 3.
TABLE 3
In this embodiment, the establishment of the spot color one-dimensional lookup table is completed through steps 1 to 7.
And for the application of the spot color one-dimensional lookup table, the step 8-10 is adopted.
8) And obtaining the tone parameters of the special tone to be corrected.
In this embodiment, for example, if the spot tone with the tone parameter 251 is corrected, the tone parameter is known as 251.
9) And acquiring the color parameters of the special tone to be corrected in the color space of the printing equipment according to the tone parameters and a pre-acquired special color one-dimensional lookup table.
In this embodiment, by looking up the spot color one-dimensional lookup table shown in table 3, the CMYK color parameters of the spot tone can be obtained as {91,55,67,34 }.
10) And correcting the special tone to be corrected according to the color parameters on the color space of the printing equipment.
In this embodiment, if the spot tone with the tone parameter of 251 needs to be proofing, the printing device outputs the CMYK color parameters as {91,55,67,34}, so that the spot tone has pure color and a good reproduction effect of the spot tone.
In addition, the spot color one-dimensional lookup table provided in this embodiment may also be used for reverse lookup, that is, the CMYK color parameters are first obtained, and then the corresponding tone parameters are determined through the spot color one-dimensional lookup table, so as to know which spot color tone is.
Fig. 4 is a structural diagram of a spot color correction apparatus according to an embodiment of the present invention. As shown in fig. 4, the spot color correction apparatus of this embodiment includes an obtaining module 401, a processing module 402, and a correcting module 403.
The obtaining module 401 is configured to obtain a tone parameter of a special tone to be corrected;
a processing module 402, configured to obtain color parameters of the to-be-corrected spot color tone in a color space of the printing device according to the tone parameters and a pre-obtained spot color one-dimensional lookup table, where the spot color one-dimensional lookup table is a comparison table between the tone parameters of each tone of the spot color to which the to-be-corrected spot color tone belongs and the color parameters in the color space of the printing device;
a correcting module 403, configured to correct the to-be-corrected spot tone according to the color parameter in the color space of the printing apparatus.
Further, the spot color correction apparatus of the present embodiment further includes:
a solid correction module 404 for correcting color parameters of the spot solid output by the printing apparatus;
a paper white obtaining module 405, configured to obtain a color parameter of paper white;
the processing module 402 is further configured to obtain the spot color one-dimensional lookup table according to the corrected spot color parameter, the white paper color parameter, and the device characteristic lookup table of the printing device, where the device characteristic lookup table is a comparison table of a spot color space and a color space of the printing device.
Further, the processing module 402 is specifically configured to:
acquiring color parameters of any special tone on the special color space according to the corrected color parameters of the spot special color and the color parameters of the paper white;
and searching the equipment characteristic lookup table according to the color parameters of any special tone in the special color space, and acquiring the mapping relation between the tone parameters of each special tone and the corresponding color parameters in the printing equipment color space, thereby acquiring the special color one-dimensional lookup table.
Further, the processing module 402 is specifically configured to:
acquiring color parameters of spot tone of any dot percentage parameter on the spot color space according to the following formula, and establishing a color parameter lookup table on the spot color space:
wherein, STiDots of the ith tone of spot colorPercentage parameter, i ∈ [1, p]P is n × m, m is the number of the tone parameters of the special tone, and n is a positive integer;
brightness component values, a component values and b component values of the ith level of the spot color respectively; ST (ST)pThe corrected dot percentage parameter of the spot color is the corrected dot percentage parameter of the spot color;
the corrected brightness component values, a component values and b component values of the spot solid are respectively; ST (ST)1The dot percentage parameter of the paper white;
brightness component values, a component values and b component values of the paper white are respectively;
obtaining the tone parameter X of any special tone according to the following formulatCorresponding dot percentage parameter STt：
Wherein, Xm、X1Respectively obtaining the corrected special solid color and the tone parameters of the paper white;
tone parameter X according to any spot tonetCorresponding dot percentage parameter STtAnd acquiring corresponding color parameters from the color parameter lookup table on the spot color space.
Further, the processing module 402 is further configured to:
tone parameter X for each spot tone according to the following formulatCorresponding dot percentage parameter STtPerforming jitter calculation to obtain corrected STt', and with said corrected STt' as a novelt：
Wherein, STrmIs a random number, q is the number of layers of jitter and is an odd number, STrm% represents STrmAnd (5) taking the remainder of q.
The spot color correction device provided in the embodiment of the present invention may be specifically configured to perform the method embodiments provided in fig. 1 to 3, and specific functions are not described herein again.
The spot color correction device provided by the embodiment obtains the tone parameters of the tone of the spot color to be corrected; then, according to the tone parameters and a pre-obtained spot color one-dimensional lookup table, obtaining color parameters of the spot color tone to be corrected in a color space of the printing equipment; and correcting the special tone to be corrected according to the color parameters on the color space of the printing equipment. The correction of the special tone to be corrected can be quickly realized through the pre-acquired special color one-dimensional lookup table, so that the corrected special color is more matched with the target color, and the reproduction capability of the printing equipment on the special tone is improved.
In the embodiments provided in the present invention, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, or in a form of hardware plus a software functional unit.
The integrated unit implemented in the form of a software functional unit may be stored in a computer readable storage medium. The software functional unit is stored in a storage medium and includes several instructions to enable a computer device (which may be a personal computer, a server, or a network device) or a processor (processor) to execute some steps of the methods according to the embodiments of the present invention. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.
It is obvious to those skilled in the art that, for convenience and simplicity of description, the foregoing division of the functional modules is merely used as an example, and in practical applications, the above function distribution may be performed by different functional modules according to needs, that is, the internal structure of the device is divided into different functional modules to perform all or part of the above described functions. For the specific working process of the device described above, reference may be made to the corresponding process in the foregoing method embodiment, which is not described herein again.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (8)
1. A spot color correction method, comprising:
obtaining the tone parameters of the special tone to be corrected;
acquiring color parameters of the to-be-corrected spot color tone on a printing equipment color space according to the tone parameters and a pre-acquired spot color one-dimensional lookup table, wherein the spot color one-dimensional lookup table is a comparison table of the tone parameters of each tone of the spot color to which the to-be-corrected spot color tone belongs and the color parameters on the printing equipment color space;
correcting the special tone to be corrected according to the color parameters on the color space of the printing equipment;
before obtaining the tone parameters of the special tone to be corrected, the method further comprises:
correcting the color parameters of the spot solid output by the printing equipment;
acquiring a color parameter of paper white;
and acquiring the spot color one-dimensional lookup table according to the corrected spot color parameters, the corrected paper white color parameters and the equipment characteristic lookup table of the printing equipment, wherein the equipment characteristic lookup table is a comparison table of a spot color space and the color space of the printing equipment.
2. The method according to claim 1, wherein the obtaining the spot color one-dimensional lookup table according to the color parameter of the corrected spot color solid, the color parameter of the paper white, and the device characteristic lookup table of the printing device comprises:
acquiring color parameters of any special tone on the special color space according to the corrected color parameters of the spot special color and the color parameters of the paper white;
and searching the equipment characteristic lookup table according to the color parameters of any special tone in the special color space, and acquiring the mapping relation between the tone parameters of each special tone and the corresponding color parameters in the printing equipment color space, thereby acquiring the special color one-dimensional lookup table.
3. The method according to claim 2, wherein the obtaining, from the color parameters of the corrected spot solid color and the color parameters of the paper white, the color parameters of any spot tone on the spot color space specifically comprises:
acquiring color parameters of spot tone of any dot percentage parameter on the spot color space according to the following formula, and establishing a color parameter lookup table on the spot color space:
wherein, STiPercentage parameter of dots for ith tone of spot color, i ∈ [1, p]P is n × m, m is the number of the tone parameters of the special tone, and n is a positive integer;
brightness component values a of ith gradation of spot color*Component values and b*A component value; ST (ST)pThe corrected dot percentage parameter of the spot color is the corrected dot percentage parameter of the spot color;
the corrected brightness component values of the spot color, a*Component values and b*A component value; ST (ST)1The dot percentage parameter of the paper white;
brightness component values of the paper white, a*Component values and b*A component value;
obtaining the tone parameter X of any special tone according to the following formulatCorresponding dot percentage parameter STt：
Wherein, Xm、X1Respectively obtaining the corrected special solid color and the tone parameters of the paper white;
tone parameter X according to any spot tonetCorresponding dot percentage parameter STtAnd acquiring corresponding color parameters from the color parameter lookup table on the spot color space.
4. The method according to claim 3, wherein obtaining the tone parameter X of any spot tonetCorresponding dot percentage parameter STtAnd then, the method further comprises the following steps:
tone parameter X for each spot tone according to the following formulatCorresponding dot percentage parameter STtPerforming jitter calculation to obtain corrected ST'tAnd with the corrected ST'tAs a new STt：
Wherein, STrmIs a random number, q is the number of layers of dithering and q is an odd number, STrm% q denotes STrmAnd (5) taking the remainder of q.
5. A spot color correction apparatus, comprising:
the acquisition module is used for acquiring the tone parameters of the special tone to be corrected;
the processing module is used for acquiring color parameters of the to-be-corrected spot color tone in the color space of the printing equipment according to the tone parameters and a pre-acquired spot color one-dimensional lookup table, wherein the spot color one-dimensional lookup table is a comparison table of the tone parameters of each tone of the spot color to which the to-be-corrected spot color tone belongs and the color parameters in the color space of the printing equipment;
the correction module is used for correcting the special tone to be corrected according to the color parameters on the color space of the printing equipment;
wherein, the device still includes:
the solid correction module is used for correcting the color parameters of the spot solid output by the printing equipment;
the paper white obtaining module is used for obtaining the color parameters of the paper white;
the processing module is further configured to obtain the spot color one-dimensional lookup table according to the corrected spot color parameter, the white paper color parameter, and the device characteristic lookup table of the printing device, where the device characteristic lookup table is a comparison table of a spot color space and a color space of the printing device.
6. The apparatus of claim 5, wherein the processing module is specifically configured to:
acquiring color parameters of any special tone on the special color space according to the corrected color parameters of the spot special color and the color parameters of the paper white;
and searching the equipment characteristic lookup table according to the color parameters of any special tone in the special color space, and acquiring the mapping relation between the tone parameters of each special tone and the corresponding color parameters in the printing equipment color space, thereby acquiring the special color one-dimensional lookup table.
7. The apparatus of claim 6, wherein the processing module is specifically configured to:
acquiring color parameters of spot tone of any dot percentage parameter on the spot color space according to the following formula, and establishing a color parameter lookup table on the spot color space:
wherein, STiPercentage parameter of dots for ith tone of spot color, i ∈ [1, p]P is n × m, m is the number of the tone parameters of the special tone, and n is a positive integer;
brightness component values a of ith gradation of spot color*Component values and b*A component value; ST (ST)pThe corrected dot percentage parameter of the spot color is the corrected dot percentage parameter of the spot color;
the corrected brightness component values of the spot color, a*Component values and b*A component value; ST (ST)1The dot percentage parameter of the paper white;
brightness component values of the paper white, a*Component values and b*A component value;
obtaining the tone parameter X of any special tone according to the following formulatCorresponding dot percentage parameter STt：
Wherein, Xm、X1Respectively obtaining the corrected special solid color and the tone parameters of the paper white;
tone parameter X according to any spot tonetCorresponding dot percentage parameter STtAnd acquiring corresponding color parameters from the color parameter lookup table on the spot color space.
8. The apparatus of claim 7, wherein the processing module is further configured to:
tone parameter X for each spot tone according to the following formulatCorresponding dot percentage parameter STtPerforming jitter calculation to obtain corrected ST'tAnd with the corrected ST'tAs a new STt：
Wherein, STrmIs a random number, q is the number of layers of dithering and q is an odd number, STrm% q denotes STrmAnd (5) taking the remainder of q.
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