CN117074247A - Method, apparatus and medium for determining ink density of ink to be measured - Google Patents
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
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Abstract
Embodiments of the present invention relate to a method, apparatus and medium for determining an ink density of an ink to be measured, the method comprising: constructing a digital filter template, so that the maximum peak wavelength of the digital filter template can be adjusted; determining wavelength characteristic data of complementary colors of the ink to be detected based on the color of the ink to be detected; adjusting a digital filter template based on the determined wavelength characteristic data of the complementary color of the ink to be measured to obtain a target digital filter, wherein the target digital filter is matched with the determined complementary color of the ink to be measured; and determining the ink density of the ink to be measured based on the obtained target digital filter. Thus, the present invention can accurately determine the ink density of the ink even for cyan (C), magenta (M), yellow (Y) inks, which are not in the CMY color system, and spot color inks, which are not in the CMY color system.
Description
Technical Field
Embodiments of the present invention relate generally to the field of dyeing and finishing and printing industry, and more particularly, to a method, computing device, and computer storage medium for determining ink density of an ink under test.
Background
Ink density is a common physical quantity used in the printing industry to measure the transmittance of photographic films and to estimate the thickness of the ink film. Because the ink density is in direct proportion to the ink layer thickness in a certain range, the absorption degree of printing ink for different color lights can be reflected by measuring the ink density under different color filters, and the thickness of the ink film layer is calculated, so that the color of a printed matter and the printing condition are known. The Ink used in the present disclosure includes organic solvent Ink (Ink) and dyes, pigment Ink and the like commonly used in the art, and it is understood by those skilled in the art that the Ink encompasses various dyes corresponding to english Ink.
The density of the ink has a large application range in printing color reproduction, the brightness is converted into an equidifferent change which is similar to human vision by logarithm, and the density change ranges of the inks with different colors are basically in the same dimension level, so that the ink is easy to compare and describe uniformly. Therefore, practical applications rely heavily on density values, because the linearization curves (representing the output characteristics of the machine) are based on density, and it is often necessary to control the linearization curves to achieve different color rendering effects during production. Different dot expansion ratios TVI are selected according to different ink and paper, and are also determined according to the density of the ink. It follows that the accuracy of density is critical.
In the traditional printing industry, the ink and paper are standard, and the complementary color density value can accurately reflect the printing ink quantity and can be controlled, so that the established printing effect is achieved. For the emerging digital printing industry, spot colors are often used in large quantities in order to present high-precision and high-saturation colors. The color light of the ink produced by different manufacturers is different, and the problem of ink density calculation can be generated by adopting the traditional red, green and blue complementary color filters. This is mainly because: fixing as red, green, blue filters means that the color light of the absorbed light is fixed, for example, if the complementary color of orange is not red, green or blue for the density of the spot color ink of orange, but also the calculation can be measured only by the fixed red, green, blue complementary color filters according to the existing conditions. In practical application, it is found that: when the color light of the ink to be measured is not matched with the color light of the standard color filter, the calculated density of the ink is greatly different. For example, the ink density calculated according to the conventional method is very small, which is clearly not in line with the subjective perception of the human eye, with a visually darker color.
In summary, the conventional method for determining the ink density of the ink to be measured has the following disadvantages: it is difficult to accurately determine the ink density of cyan (C), magenta (M), yellow (Y) inks, and spot color inks of non-CMY color systems, which are not accurate in color.
Disclosure of Invention
In view of the above, the present invention provides a method, a computing device, and a computer storage medium for determining an ink density of an ink to be measured, which can accurately determine the ink density of the ink even for an ink with inaccurate color light and a spot color ink of a non-CMY color system.
According to a first aspect of the present invention there is provided a method for determining ink density, the method comprising: the template enables the maximum peak wavelength of the digital filter template to be adjustable; determining wavelength characteristic data of complementary colors of the ink to be detected based on the color of the ink to be detected; adjusting a digital filter template based on the determined wavelength characteristic data of the complementary color of the ink to be measured to obtain a target digital filter, wherein the target digital filter is matched with the determined complementary color of the ink to be measured; and determining the ink density of the ink to be measured based on the obtained target digital filter.
According to a second aspect of the present invention there is provided a computing device comprising: at least one processor; and a memory communicatively coupled to the at least one processor; the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method of the first aspect of the invention.
In a third aspect of the invention, there is provided a non-transitory computer readable storage medium storing computer instructions for causing a computer to perform the method of the first aspect of the invention.
In some embodiments, the wavelength characteristic data of the complementary color is a center wavelength corresponding to the complementary color.
In some embodiments, constructing the digital filter template includes: a band-pass filter of a predetermined state, whose maximum peak wavelength is adjustable, is selected as a digital filter template from among a plurality of candidate band-pass filters corresponding to the ISO standard.
In some embodiments, the bandpass filter corresponding to the ISO standard includes the following: an a-state bandpass filter, an M-state bandpass filter, a T-state bandpass filter, an E-state bandpass filter, an I-state bandpass filter, and a standard narrow band bandpass filter.
In some embodiments, determining wavelength characteristic data for a complementary color of the ink under test includes: acquiring the reflectivity, absorption coefficient and scattering coefficient of the ink to be tested; and calculating the center wavelength corresponding to the complementary color of the ink to be measured by using the obtained reflectivity, absorption coefficient and scattering coefficient.
In some embodiments, calculating the center wavelength corresponding to the complementary color of the ink to be measured further includes: calculating a pseudo tristimulus value corresponding to the ink to be measured based on the determined ratio of the absorption coefficient to the scattering coefficient; summing the calculated pseudo tri-stimulus values, thereby determining the color depth of the ink to be measured; and determining a center wavelength corresponding to the complementary color of the ink to be measured based on the determined color depth.
In some embodiments, adjusting the digital filter template includes: acquiring the center wavelength corresponding to the determined complementary color of the ink to be measured; the maximum peak wavelength of the digital filter template is adjusted to be matched with the center wavelength corresponding to the complementary color; and taking the adjusted digital filter template as a target digital filter corresponding to the ink to be tested.
In some embodiments, determining the ink density of the ink to be measured based on the obtained target digital filter comprises: determining the maximum peak position of the target digital filter; and determining the ink density of the ink to be measured based on the product of the incident spectrum of the measuring light source and the spectral distribution of the target digital filter and the spectral reflectance of the ink to be measured.
It should be understood that the description in this section is not intended to identify key or critical features of the embodiments of the invention or to delineate the scope of the invention. Other features of the present invention will become apparent from the description that follows.
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The above and other features, advantages and aspects of embodiments of the present invention will become more apparent by reference to the following detailed description when taken in conjunction with the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements.
Fig. 1 shows a schematic diagram of a system 100 for implementing a method for determining an ink density of an ink to be measured according to an embodiment of the invention.
Fig. 2 shows a flow chart of a method for determining the ink density of an ink to be measured according to an embodiment of the invention.
Fig. 3 shows the spectral reflectance curve of an orange ink according to an embodiment of the present invention.
FIG. 4 is a schematic diagram showing the determination of the position of the complementary color center wavelength of the spectral reflectance curve of orange ink according to an embodiment of the present invention.
Fig. 5 is a schematic diagram showing that the peak wavelength of the digital filter corresponding to the orange ink is dynamically adjusted to the position of the complementary color center wavelength of the orange ink according to the embodiment of the invention.
Fig. 6 shows a flow chart of a method for adjusting digital filter template inclusion according to an embodiment of the invention.
Fig. 7 shows a block diagram of an electronic device according to an embodiment of the invention.
Detailed Description
Preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present invention are illustrated in the drawings, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
The term "comprising" and variations thereof as used herein means open ended, i.e., "including but not limited to. The term "or" means "and/or" unless specifically stated otherwise. The term "based on" means "based at least in part on". The terms "one example embodiment" and "one embodiment" mean "at least one example embodiment. The term "another embodiment" means "at least one additional embodiment". The terms "first," "second," and the like, may refer to different or the same object.
As described above, the conventional method for determining the ink density of the ink to be measured is disadvantageous in that: it is difficult to accurately determine the ink density of cyan (C), magenta (M), yellow (Y) inks, and spot color inks of non-CMY color systems, which are not accurate in color.
To at least partially address one or more of the above problems, as well as other potential problems, example embodiments of the present invention provide a solution for determining an ink density of an ink to be tested. In the scheme, a digital filter template with adjustable maximum peak wavelength is constructed; determining the complementary color of the ink to be measured based on the color of the ink to be measured; and adjusting the digital filter template based on the determined complementary color of the ink to be measured to obtain a target digital filter, wherein the target digital filter is matched with the determined complementary color of the ink to be measured; and determining the ink density of the ink to be measured based on the obtained target digital filter. The invention can accurately determine the ink density of the ink even for cyan (C), magenta (M), yellow (Y) ink with inaccurate chromatic light and spot color ink of non-CMY color system. .
Fig. 1 shows a schematic diagram of a system 100 for implementing a method for determining an ink density of an ink to be measured according to an embodiment of the invention. As shown in fig. 1, system 100 includes a computing device 110 and an ink density data management device 130 and a network 140. The computing device 110, the ink density data management device 130 may interact with data via a network 140 (e.g., the internet).
With respect to the ink density data management apparatus 130, it is used, for example, to provide data required to determine the ink density, and to construct a plurality of bandpass filters for the digital filter template. The ink density management device 130 may send the relevant data for determining the ink density, the band pass filter, to the computing device 110. In some embodiments, the ink density data management device 130 may provide digital filter templates to the computing device 110, and the ink density data management device 130 may have one or more processing units, including special purpose processing units such as GPUs, FPGAs, and ASICs, and general purpose processing units such as CPUs, for example, without limitation: desktop computers, laptop computers, netbook computers, tablet computers, web browsers, e-book readers, personal Digital Assistants (PDAs), wearable computers (such as smartwatches and activity tracker devices), and the like, which may perform chinese data reading and modification.
With respect to computing device 110, it is for example for providing the data needed to determine ink density based on data from ink density data management device 130 via network 140; the ink density of the ink to be measured is determined. Computing device 110 may have one or more processing units, including special purpose processing units such as GPUs, FPGAs, ASICs, and the like, as well as general purpose processing units such as CPUs. In addition, one or more virtual machines may also be running on each computing device 110. In some embodiments, computing device 110 and ink density data management device 130 may be integrated or may be separate from each other. In some embodiments, computing device 110 includes, for example: a digital filter template construction unit 112, a complementary color wavelength feature data determination unit 114, a target digital filter obtaining unit 116, and an ink density determination unit 118.
And a digital filter template construction unit 112 for constructing the digital filter template such that the maximum peak wavelength of the digital filter template is adjustable.
And a complementary-color wavelength characteristic data determination unit 114 for determining wavelength characteristic data of complementary colors of the ink to be measured based on the color of the ink to be measured.
And a target digital filter obtaining unit 116 for adjusting the digital filter template based on the determined wavelength characteristic data of the complementary color of the ink to be measured to obtain a target digital filter, the target digital filter being matched with the determined complementary color of the ink to be measured.
An ink density determining unit 118 for determining the ink density of the ink to be measured based on the obtained target digital filter.
The data relating to the printing color in the field of inkjet printing generally includes the ink densities of the four color channels, i.e., CMYK density values, of the cyan channel C, the magenta channel M, the yellow channel Y, and the black channel K. Ink density may in turn refer to the thickness, concentration, of the ink in the art. The ink thickness value typically ranges from 0 to 100%. In the original image to be printed, some areas often belong to pure color areas, and the thickness values of the rest color channels except the pure color are all 0 corresponding to the pure color areas. It will be appreciated by those skilled in the art that the ink density processing method of the present invention is equally applicable to determining ink thickness and ink concentration.
As described above, the ink thickness, ink concentration, or ink density measuring apparatus measures the absorption amounts of red, green, and blue light by cyan (C), magenta (M), and yellow (Y) inks. Therefore, red, green and blue color filters are placed in front of the photodetectors of the ink thickness, ink concentration or ink density measuring device, respectively, for transmitting red, green and blue light, respectively.
Since the human eyes perceive R, G and B three-color light, different color sensations can be formed by mixing RGB three primary colors, so long as the stimulation amount of the RGB color light entering the human eyes can be effectively controlled (increased or decreased), the surface color of an object is relatively controlled. Therefore, for color printing, the complementary colors (cyan (C), magenta (M) and yellow (Y)) of red, green and blue are selected to control the quantity of red, green and blue light entering eyes, so that the aim of controlling color development is achieved.
Therefore, when the ink density of the C, M, Y, K ink is measured in color printing, the color of the color filter depends on the complementary color of the corresponding color of the ink to be measured. For example: the density of the cyan ink (C) was measured, the color filter was red (R), and the amount of absorption of red light by the cyan ink was measured. It should be appreciated that the more the cyan ink absorbs red, the higher the ink density. Since cyan, magenta, and Huang Fenbie are complementary colors to red, green, and blue, the density obtained by measuring the amount of absorption of the complementary color by the ink to be measured is referred to as the complementary color density. As described above, if the color light of the CMY ink to be measured is inaccurate, or the ink to be measured is other ink than CMY color, in the conventional method for measuring the ink density, there is an error in the ink density determined based on the absorption amount of the ink to the corresponding complementary color of the standard red, green or blue complementary color filter, thereby affecting the color control effect of the color control based on the ink density.
The invention provides a method for determining ink density or ink concentration of ink to be measured. And dynamically matching corresponding complementary color filters according to the color spectrum reflectivity curve of the ink to be measured through the constructed digital filter template, so as to calculate the ink density or concentration of the more accurate ink to be measured. Because the maximum peak wavelength of the digital filter template constructed by the invention can be adjusted, the method can be suitable for calculating the ink density and concentration of any macroscopic ink color, thereby solving the technical problem that the ink density of some colors (such as CMY ink with inaccurate chromatic light or spot color ink of non-CMY color system) can not be accurately measured by adopting a fixed color filter in the traditional method.
FIG. 2 illustrates a flow chart of a method 200 for determining an ink density of an ink under test, according to an embodiment of the invention. The method 200 may be performed by the computing device 110 shown in fig. 1, or at the electronic device 700 shown in fig. 7. It should be understood that method 200 may also include additional blocks not shown and/or that the blocks shown may be omitted, as the scope of the invention is not limited in this respect.
At step 202, the computing device 110 builds a digital filter template such that the maximum peak wavelength of the digital filter template is adjustable.
Regarding the method of constructing the digital filter template, in some embodiments, the computing device 110 may select, as the digital filter template, a band-pass filter of a predetermined state whose maximum peak wavelength is adjustable from among a plurality of candidate band-pass filters corresponding to the ISO standard based on the property of ink to be measured for digital printing. For example, in some embodiments, the computing device 110 may be configured to digitally print the ink properties to be measured, using a standard A-state density medium blue passband filter as a digital filter template. Compared with a T-state passband filter which is more commonly used in the industry, the passband filter in the A state is narrower than the passband filter in the T state, has strong adaptability to the chromatic light of the ink to be detected, and is beneficial to accurate calculation of the density of the ink.
With respect to band pass filters, it is meant digital filters that allow waveforms of a particular frequency band to pass while masking other frequency bands. The plurality of band pass filters of the ISO standard may include: an a-state bandpass filter, an M-state bandpass filter, a T-state bandpass filter, an E-state bandpass filter, an I-state bandpass filter, and a standard narrow band bandpass filter. The band-pass filters allow waveforms of specific frequency bands to pass through and shield signals of other frequency bands. In addition, the computing device 110 may also customize a standard state bandpass filter according to the ISO standard to meet the practical application requirements of the subsequent measurement of the ink concentration.
The computing device 110 may dynamically adjust the maximum peak wavelength of the digital filter template to match the calculated complementary center wavelength of the ink to be measured. The dynamic adjustment of the maximum peak wavelength of the digital filter template ensures that the digital filter template can accurately filter and measure the ink to be measured.
In some embodiments, computing device 110 may construct a dedicated digital filter template, or referred to as a standard state bandpass filter. It should be appreciated that a digital filter template or standard state bandpass filter is a digital filter whose peaks are movable within the measured spectral range. The digital filter template can select passband filters of various state densities (e.g., standard a-state density, standard M-state density, standard T-state density, standard E-state density, standard I-state density, standard narrow band density) in the ISO 5 standard according to practical application requirements. Passband filters having different state densities all have a particular maximum peak location for representing the frequency response characteristics of the filter. Based on these passband filters of different state densities, the computing device 110 may construct an adaptive, dynamically tunable digital filter template of maximum peak wavelength (or position). Specifically, the computing device 110 dynamically adjusts the maximum peak position of the digital filter template until the maximum peak wavelength of the digital filter template matches the complementary center wavelength of the color light (or the sample color) of the ink to be measured, for example, the target digital filter.
It should be appreciated that computing device 110 may determine a digital filter template appropriate for the color of ink to be measured; and dynamically adjusting the maximum peak wavelength of the determined digital filter template, thereby obtaining the target digital filter. In some embodiments, the computing device 110 may also obtain a digital filter template, i.e., a standard state bandpass filter, from the ink density data management device 130, the digital filter template being selected from, for example, the following bandpass filters: an a-state bandpass filter, an M-state bandpass filter, a T-state bandpass filter, an E-state bandpass filter, an I-state bandpass filter, and a standard narrow band bandpass filter, each bandpass filter having a specific maximum peak position. The computing device 110 may obtain a target digital filter whose maximum peak wavelength matches the complementary center wavelength of the ink color to be measured based on the digital filter template obtained from the ink density data management device 130. Through the above steps, the computing device 110 can construct a digital filter template suitable for the ink to be tested. This template will play a key role in subsequent spectroscopic analysis to accurately calculate the ink density or concentration of the ink to be measured. Note that in practical applications, further adjustments and optimization of the filter parameters may be required to further improve accuracy and reliability, depending on the specific requirements.
In step 204, computing device 110 determines wavelength characteristic data for the complementary color of the ink under test based on the color of the ink under test. Generally, two colorants are black when mixed, and are complementary colors, for example, if white is formed when the two colors are mixed. The application scene of the invention is mainly pigment.
The relationship between the ink color and the complementary color will be specifically described below. The ratio of the luminous flux reflected by the object to the luminous flux incident on the object, i.e. the light reflectance versus wavelength. The spectral reflectance curve of an object reflects the combined properties of spectrally selective absorption of incident light, light scattering, and specular reflection from the object surface. Since the property of an object with respect to color is selective absorption of electromagnetic waves of different wavelengths, this property of an object can be expressed with a spectral reflectance curve.
The red object, which we can see is red because the light from the light source reaches the object surface, the object itself absorbs the blue, green and yellow light of the light, and only the red light is not absorbed, but the red light that is not absorbed is reflected out to reach the observer. Since the observer can only see the reflected red light, we see that the object is red. In theory, each color of ink has its corresponding complementary color, the more light is absorbed by the complementary color, the purer the light reflected from the ink, based on which the density of the ink can be calculated using the complementary color as a color filter.
The wavelength characteristic data about the complementary color of the ink to be measured is, for example and without limitation, the complementary color center wavelength of the ink to be measured. It should be appreciated that based on the test and data, the spectral reflectance profile of the ink may be determined. Specifically, the maximum position of the absorption peak of the spectral reflectance curve of the ink is the position of the complementary color center wavelength. The maximum position of the absorption peak (or the position of the complementary color center wavelength) can be determined by the following methods: K/S value method and Integ value method.
In some embodiments, the computing device 110 may use the K/S values (reflectivity, absorption coefficient, and scattering coefficient) to determine the maximum position of the absorption peak of the ink under test and the center wavelength corresponding to its complementary color. The K/S value is an index for measuring the color characteristics of ink and represents the reflection, absorption and scattering of light rays with different wavelengths by the ink. Wherein the K value represents the absorption coefficient of the ink and the S value represents the scattering coefficient of the ink. The absorption peak position and the corresponding intensity of the ink to be measured in the spectral range can be obtained by measuring the reflectivity and the absorption coefficient of the ink sample to be measured under different wavelengths. In general, the maximum position of the absorption peak corresponds to the complementary color wavelength of the ink, and may be used to calculate wavelength characteristic data of the complementary color of the ink, for example, calculate a center wavelength corresponding to the complementary color of the ink to be measured.
Specifically, the computing device 110 may analyze and calculate light at different wavelengths according to the reflectivity, absorption coefficient, and scattering coefficient of the ink sample to be measured. By finding the wavelength with the maximum absorption peak, the computing device 110 may determine the complementary wavelength of the ink, i.e., the center wavelength to which the complementary color corresponds.
It should be noted that the specific calculation method and algorithm may vary depending on the application scenario and the color model used. Based on the above characteristics, computing device 110 may determine the reflectivity, absorption coefficient, scattering coefficient of the ink under test. And calculating the center wavelength corresponding to the complementary color of the ink to be measured by using the determined reflectivity, absorption coefficient and scattering coefficient.
Specifically, the K/S value of the maximum absorption peak is used to represent the color depth. The advantage of using the K/S value to indicate the color depth is that it is linear with the color concentration over a range. The larger the K/S value, the darker the color. It should be appreciated that the K/S value is an important parameter in the color formulation, color mixing, and the library Bei Ka Mang (Kubelka-Munk) law. The manner of calculating the K/S value is described below in conjunction with equation (1).
（1）
In the above formula (1), R represents the reflectivity of the object. S represents the scattering coefficient of the object, and the larger the value thereof, the stronger the scattering of light. K represents the absorption coefficient of the object, and the larger the value thereof, the more light is absorbed. The larger the K/S value, the darker the color is indicated.
Regarding the method of determining the center wavelength corresponding to the complementary color of the ink to be measured, in some embodiments, the computing device 110 may further calculate a pseudo tristimulus value corresponding to the ink to be measured based on the determined ratio of the absorption coefficient and the scattering coefficient; summing the calculated pseudo tri-stimulus values so as to determine the color depth of the ink to be measured; and determining a center wavelength corresponding to the complementary color of the ink to be measured based on the determined color depth.
As mentioned above, the computing device 110 may also determine the maximum position of the absorption peak of the ink to be measured and the center wavelength corresponding to its complementary color by using the intelg value. With respect to the Integ value, it is the sum of pseudo tristimulus values. Specifically, the intelg value is a color depth parameter added to the light source factor, which calculates a tristimulus value by replacing the reflectance with a K/S value at each wavelength, and sums it (Gardland formula below). Based on experiments, it was found that it is more suitable to express the color depth in terms of the Integ value for dyes, blended dyes, and partially non-blended monochromatic dyes where the maximum absorption peak is not apparent, such as black. In some color lifting tests, the intelg value is also more suitable for indicating color depth, since shifts in the maximum absorption wavelength occur.
Therefore, the maximum position of the absorption peak can be expressed using the intelg value. The color depth of the color sample is evaluated by comprehensively considering the light source, the color sample and the observer, and the color depth is characterized by calculating the sum of pseudo tristimulus values of the colored object in the visible light range. The larger the Integ value, the darker the color it characterizes. The following describes the calculation method of the intelg value in conjunction with the formula (2).
（2）
In the above formula (2), F (X), F (Y), F (Z) represent functions for characterizing color depths, respectively, or are referred to as pseudo tristimulus values. X, Y, Z is the tristimulus value of a color sample (e.g., of the ink to be measured). S (λ) represents the spectral energy distribution. (K/S) (λ), x (λ), y (λ), z (λ) represent the K/S value, x value, y value, z value, respectively, at wavelength λ. In the above manner, the center wavelength corresponding to the complementary color of the ink to be measured can be obtained by the maximum position of the absorption peak in the ink reflection spectrum.
In step 206, the computing device 110 adjusts the digital filter template based on the determined wavelength characteristic data of the complementary color of the ink under test to obtain a target digital filter that matches the determined complementary color of the ink under test.
In some embodiments, the computing device 110 may adjust the digital filter template based on a center wavelength corresponding to a complementary color of the ink to be measured to obtain the target digital filter.
For example, the computing device 110 may determine, based on the K/S peak, a center wavelength corresponding to the complementary color of the ink to be determined at 490nm, where 490nm is the center wavelength corresponding to the complementary color of the ink to be determined. The computing device 110 may then dynamically adjust the maximum peak position of the digital filter template constructed in step 202 to match the center wavelength corresponding to the complementary color of the ink to be measured (e.g., adjust the maximum peak wavelength of the digital filter template to the center wavelength corresponding to the complementary color). For example, the maximum peak position of the digital filter template constructed in step 202 is 400nm, and in step 206, the computing device 110 performs a parallel shift on the digital filter template (e.g., by shifting the digital filter template to the right, i.e., increasing the wavelength of the digital filter template), such that the maximum peak position of the digital filter template is shifted from 400nm to 490nm, thereby matching to the complementary color.
Fig. 3 shows the spectral reflectance curve of an orange ink according to an embodiment of the present invention. Fig. 3 includes standard a-state density red (R filter), green (G filter), blue (B filter) passband filter spectral distributions and a digital filter template constructed. As shown in fig. 3, the digital filter template, i.e., the digital filter template formed by the curves with the "" -marks, can be moved left and right within the spectral range of the orange ink. The double-headed arrow indicates that the peak wavelength of the digital filter template used in the present invention can be adjusted from side to side as desired in the spectral range. As previously described, the computing device 110 may locate the spectral reflectance absorption peak maximum position (i.e., the complementary color center wavelength position) of the orange ink by calculating the K/S value.
FIG. 4 is a schematic diagram showing the determination of the position of the complementary color center wavelength of the spectral reflectance curve of orange ink according to an embodiment of the present invention. The calculated K/S value distribution is shown in FIG. 4, and the K/S peak value is at the wavelength of 490nm, namely the complementary color center wavelength of the orange ink to be detected is located to be 490nm.
At step 208, computing device 110 determines an ink density of the ink under test based on the obtained target digital filter.
Fig. 5 is a schematic diagram showing that the peak wavelength of the digital filter corresponding to the orange ink is dynamically adjusted to the position of the complementary color center wavelength of the orange ink according to the embodiment of the invention. The computing device 110 uses the digital filter whose adjusted maximum peak position matches the calculated center wavelength corresponding to the complementary color as the target digital filter corresponding to the ink to be measured.
Regarding the method of determining the ink density of the ink to be measured, in some embodiments it includes, for example: computing device 110 determines a maximum peak position for the target digital filter; and determining the ink density of the ink to be measured based on the product of the incident spectrum of the measuring light source and the spectral distribution of the target digital filter and the spectral reflectance of the ink to be measured. An algorithm for calculating and determining the ink density of the ink to be measured is described below in conjunction with the formula (3).
（3）
In the above-mentioned formula (3),representing the spectral reflectance of the ink to be measured (or a sample thereof,)>To measure the product of the incident spectrum of the light source and the spectral distribution of the target digital filter. It should be understood that the spectral reflectance of the ink (or a sample thereof) to be measured indicates the reflectivity of the ink at a particular wavelength, while the measured light source's incident spectrum is the spectral characteristics of the light source used by the measuring deviceSex. And calculating the product of the two factors and the spectral distribution of the target digital filter, so as to obtain the ink density of the ink to be measured.
For example, the target digital filter determined for orange ink acquired according to method 200 is positioned between conventional density passband filter B, G, which is clearly more desirable because the complement of orange is neither blue nor green. The calculated determined density of ink to be measured was 1.682 using the obtained target digital filter of method 200.
The ink density calculated by method 200 maintains a relatively uniform trend with respect to the ink density calculated by conventional methods for the same ink, as shown in fig. 5; for some spot color inks, such as O, YF, the novel method of the present invention can effectively avoid some ink density calculation errors. Meanwhile, the method 200 has better consistency of the maximum density values of different color light inks, and is beneficial to improving the color control of the color light deviation ink and the spot color ink. The method 200 of the present invention is applicable to ink density calculations for almost all color inks.
In summary, according to the method for determining ink density based on the adaptive filter provided by the invention, even for CMY ink with inaccurate chromatic light and spot color ink of non-CMY color system, the ink density of the ink can be accurately determined.
Fig. 6 shows a flowchart of a method 600 for adjusting digital filter template inclusion according to an embodiment of the invention. Method 600 may be performed by computing device 110 as shown in fig. 1, or at electronic device 700 as shown in fig. 7. It should be understood that method 600 may also include additional blocks not shown and/or that the blocks shown may be omitted, as the scope of the invention is not limited in this respect.
At step 602, the computing device 110 obtains a center wavelength corresponding to the determined complementary color of the ink under test.
At step 604, the computing device 110 adjusts the maximum peak wavelength of the digital filter template to match the center wavelength corresponding to the complementary color.
For example, the computing device 110 obtains a constructed digital filter template from image or color data of the ink to be measured. The digital filter template describes the response characteristics of the bandpass filter at different wavelengths. Computing device 110 determines a maximum peak position of the digital filter template. For example, in the constructed digital filter template, the peak position with the largest response is found. For example, the maximum peak position of the digital filter template is 400nm. The computing device 110 calculates a distance for translating the maximum peak position of the digital filter template based on the center wavelength corresponding to the complementary color of the ink to be measured. For example, the center wavelength corresponding to the complementary color of the ink to be measured is 490nm, and the distance that the digital filter template needs to be shifted rightward is calculated based on the difference (for example, the difference is 490nm-400 nm=90 nm) between the maximum peak position of the digital filter template and the center wavelength corresponding to the complementary color. The computing device 110 translates the digital filter template based on the calculated difference. For example, the computing device 110 translates the digital filter template 90nm to the right, i.e., increases the wavelength of the digital filter template. Regarding the manner of translation, it is possible to realize the translation operation by, for example, performing phase adjustment for each frequency component in the digital filter template. It should be appreciated that the particular implementation of the method of adjusting the digital filter may vary depending on the application scenario and algorithm selection.
At step 606, the computing device 110 takes the adjusted digital filter template as a target digital filter corresponding to the ink to be measured.
The computing device 110 determines the adjusted digital filter template as the target digital filter. For example, a digital filter template having the adjusted maximum peak position at 490nm is determined as the target digital filter. The determined target digital filter may be used as a digital filter corresponding to the ink under test, may be used to process the ink under test image or color data to achieve a desired color effect or complementary color effect, and may better match the center wavelength of the complementary color of the ink under test.
Fig. 7 shows a schematic block diagram of an example electronic device 700 that may be used to implement embodiments of the present inventive content. For example, computing device 110 as shown in fig. 1 may be implemented by electronic device 700. As shown, the electronic device 700 includes a Central Processing Unit (CPU) 701 that can perform various suitable actions and processes in accordance with computer program instructions stored in a Read Only Memory (ROM) 702 or loaded from a storage unit 708 into a Random Access Memory (RAM) 703. In the random access memory 703, various programs and data required for the operation of the electronic device 700 may also be stored. The central processing unit 701, the read only memory 702, and the random access memory 703 are connected to each other through a bus 704. An input/output (I/O) interface 705 is also connected to bus 704.
Various components in the electronic device 700 are connected to the input/output interface 705, including: an input unit 706 such as a keyboard, mouse, microphone, etc.; an output unit 707 such as various types of displays, speakers, and the like; a storage unit 708 such as a magnetic disk, an optical disk, or the like; and a communication unit 709 such as a network card, modem, wireless communication transceiver, etc. The communication unit 709 allows the device 700 to exchange information/data with other devices via a computer network, such as the internet, and/or various telecommunication networks.
The various processes and treatments described above, such as the methods 200, 600, may be performed by the central processing unit 701. For example, in some embodiments, the methods 200, 600 may be implemented as a computer software program tangibly embodied on a machine-readable medium, such as the storage unit 708. In some embodiments, part or all of the computer program may be loaded and/or installed onto device 700 via read only memory 702 and/or communication unit 709. One or more of the acts of the methods 200, 600 described above may be performed when a computer program is loaded into the random access memory 703 and executed by the central processing unit 701.
The present invention relates to methods, apparatus, systems, electronic devices, computer readable storage media and/or computer program products. The computer program product may include computer readable program instructions for carrying out aspects of the present invention.
The computer readable storage medium may be a tangible device that can hold and store instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer-readable storage medium would include the following: portable computer disks, hard disks, random Access Memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static Random Access Memory (SRAM), portable compact disk read-only memory (CD-ROM), digital Versatile Disks (DVD), memory sticks, floppy disks, mechanical coding devices, punch cards or in-groove structures such as punch cards or grooves having instructions stored thereon, and any suitable combination of the foregoing. Computer-readable storage media, as used herein, are not to be construed as transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., optical pulses through fiber optic cables), or electrical signals transmitted through wires.
The computer readable program instructions described herein may be downloaded from a computer readable storage medium to a respective computing/processing device or to an external computer or external storage device over a network, such as the internet, a local area network, a wide area network, and/or a wireless network. The network may include copper transmission cables, fiber optic transmissions, wireless transmissions, routers, firewalls, switches, gateway computers and/or edge computing devices. The network interface card or network interface in each computing/processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium in the respective computing/processing device.
Computer program instructions for carrying out operations of the present invention may be assembly instructions, instruction Set Architecture (ISA) instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, c++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The computer readable program instructions may be executed entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any kind of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or may be connected to an external computer (for example, through the Internet using an Internet service provider). In some embodiments, aspects of the present invention are implemented by personalizing electronic circuitry, such as programmable logic circuitry, field Programmable Gate Arrays (FPGAs), or Programmable Logic Arrays (PLAs), with state information for computer readable program instructions, which can execute the computer readable program instructions.
Various aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer-readable program instructions.
These computer readable program instructions may be provided to a processing unit of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processing unit of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable medium having the instructions stored therein includes an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.
The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer, other programmable apparatus or other devices implement the functions/acts specified in the flowchart and/or block diagram block or blocks.
The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
It will be appreciated by persons skilled in the art that the present invention is not limited to the embodiments described above, but may be embodied in many other forms without departing from the spirit or scope thereof. Accordingly, the illustrated examples and embodiments are to be considered as illustrative and not restrictive, and the invention is intended to cover various modifications and substitutions without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A method for determining an ink density of an ink to be measured, the method comprising:
constructing a digital filter template, so that the maximum peak wavelength of the digital filter template can be adjusted;
determining wavelength characteristic data of complementary colors of the ink to be detected based on the color of the ink to be detected;
adjusting a digital filter template based on the determined wavelength characteristic data of the complementary color of the ink to be measured to obtain a target digital filter, wherein the target digital filter is matched with the determined complementary color of the ink to be measured; and
and determining the ink density of the ink to be measured based on the obtained target digital filter.
2. The method of claim 1, wherein the wavelength characteristic data of the complementary color is a center wavelength corresponding to the complementary color.
3. The method of claim 1, wherein constructing a digital filter template comprises:
a band-pass filter of a predetermined state, whose maximum peak wavelength is adjustable, is selected as a digital filter template from among a plurality of candidate band-pass filters corresponding to the ISO standard.
4. A method according to claim 3, characterized in that the band-pass filter corresponding to the ISO standard comprises the following multiple filters:
an a-state bandpass filter, an M-state bandpass filter, a T-state bandpass filter, an E-state bandpass filter, an I-state bandpass filter, and a standard narrow band bandpass filter.
5. The method of claim 1, wherein determining wavelength characteristic data for a complementary color of the ink under test comprises:
acquiring the reflectivity, absorption coefficient and scattering coefficient of the ink to be tested; and
and calculating the center wavelength corresponding to the complementary color of the ink to be measured by using the obtained reflectivity, absorption coefficient and scattering coefficient.
6. The method of claim 5, wherein calculating a center wavelength for a complementary color of the ink to be measured further comprises:
calculating a pseudo tristimulus value corresponding to the ink to be measured based on the determined ratio of the absorption coefficient to the scattering coefficient;
Summing the calculated pseudo tri-stimulus values, thereby determining the color depth of the ink to be measured; and
and determining the center wavelength corresponding to the complementary color of the ink to be measured based on the determined color depth.
7. The method of claim 1, wherein adjusting the digital filter template comprises:
acquiring the center wavelength corresponding to the determined complementary color of the ink to be measured;
the maximum peak wavelength of the digital filter template is adjusted to be matched with the center wavelength corresponding to the complementary color; and
and taking the adjusted digital filter template as a target digital filter corresponding to the ink to be tested.
8. The method of claim 1, wherein determining the ink density of the ink under test based on the obtained target digital filter comprises:
determining the maximum peak position of the target digital filter; and
and determining the ink density of the ink to be measured based on the product of the incident spectrum of the measuring light source and the spectral distribution of the target digital filter and the spectral reflectivity of the ink to be measured.
9. A computing device, comprising:
at least one processor; and
a memory communicatively coupled to the at least one processor;
the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method of any one of claims 1-8.
10. A non-transitory computer readable storage medium storing computer instructions for causing the computer to perform the method of any one of claims 1-8.
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