Screen soft proofing color correction method and chromatic value measurement device

Abstract

The invention discloses a screen soft proofing color correction method and a chromatic value measurement device, and relates to the technical field of printing, and the method comprises the steps: collecting a first display chromatic value of an original image on a screen soft proofing display; the original image is printed on selected art paper to form a first sample, and a first printing chromatic value on the first sample is collected; and the first display chromatic value and the first printing chromatic value are substituted into a chromatic aberration formula to calculate a first chromatic aberration, then multiple times of adjustment are performed through the obtained first chromatic aberration, objective evaluation and subjective evaluation are performed on the multiple times of adjustment, and an adjustment scheme in which the display effect of the display and the printing effect of the correspondingly printed sample sheet are closest is selected. The color effect of printing content on a printing carrier can be accurately restored on a screen, and time and cost are saved.

Description

Technical Field

[0001] The invention relates to the technical field of printing, and in particular to a screen soft proofing color correction method and a chromaticity value measuring device. Background Art

[0002] Proofing is a key link in the printing production process. Traditional proofing often requires the printing house to communicate with the customer many times and repeatedly debug the effect of the printed product, wasting time and money. With the continuous advancement of digital technology, screen soft proofing technology has gradually matured. This technology aims to preview the effect of the final printed product on the screen in advance. The color seen on the screen is the color of the printed product, and the purpose is to ensure that the color displayed on the screen is consistent with the color of the printed product to the greatest extent. As an efficient and flexible proofing technology, screen soft proofing technology can greatly save the time of proofreading samples, so that users can get satisfactory, high-quality, and device-independent color reproduction effects, truly realizing "what you see is what you get".

[0003] Art paper is also called specialty paper. Different from ordinary printing paper, art paper requires special processing equipment and technology, and has rich colors and unique textures. Rice paper, cardboard, and Japanese paper that are familiar in life all belong to the category of art paper. The existing pre-press screen soft proofing system can only simulate the effect on ordinary printing paper, and cannot show the proofing effect of the printed content on art paper. In addition, the color effect presented by the existing screen soft proofing system often has a large deviation from the actual color effect presented on art paper.

[0004] Usually, the combination of printing carriers such as art paper and printing inks causes serious color distortion of the printed product. In the production of environmentally friendly art paper prints, since the color of environmentally friendly art paper is not actually white, the color of the printed product will be distorted due to the color of the environmentally friendly art paper itself. The general practice is to use manual color adjustment to set the ink for a specific printing carrier in a targeted manner. However, due to the variety of printing carriers, the debugging results of each printing carrier are different. If you rely entirely on manual debugging, it will be time-consuming and labor-intensive, and sometimes it is even impossible to effectively and accurately debug. Summary of the invention

[0005] The purpose of the present invention is to provide a screen soft proofing color correction method and a chromaticity value measuring device to solve the problems existing in the above-mentioned prior art, and to achieve accurate restoration of the color effect of the printed content on the printing carrier on the screen, saving time and cost.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a screen soft proofing color correction method, comprising the following steps:

[0008] S1, collecting a first display chromaticity value of an original image on a display of a screen soft proofing; printing a first sample of the original image on a selected art paper, and collecting a first printing chromaticity value on the first sample; substituting the first display chromaticity value and the first printing chromaticity value into a color difference formula to calculate a first color difference;

[0009] S2, performing a first adjustment on the original image displayed on the screen soft proofing display by using image color correction software according to the obtained first color difference; collecting a second display chromaticity value of the image after the first adjustment on the screen soft proofing display and a second printing chromaticity value of the image after the first adjustment on a second sample printed on the same art paper; substituting the second display chromaticity value and the second printing chromaticity value into a color difference formula to calculate a second color difference;

[0010] S3, similarly, according to the adjustment method in S2, the third adjustment...the nth adjustment is obtained in sequence;

[0011] S4, objectively and subjectively evaluate the samples corresponding to the second adjustment, the third adjustment, ... the nth adjustment, and select the xth adjustment that is closest to the display of the screen soft proofing and the corresponding printed sample.

[0012] Preferably, the method further comprises S5, inputting a print sample of the original image on the selected art paper according to the display color calibration file corresponding to the x-th adjustment determined in S4.

[0013] Preferably, according to the print sample obtained in S5 and its corresponding display effect on the display of the screen soft proofing, steps S2, S3 and S4 can be repeated in sequence to obtain the yth adjustment with better effect.

[0014] Preferably, before S1, color calibration is performed on the display and printer for screen soft proofing.

[0015] Preferably, after color correction is performed on the display and printer of the screen soft proofing, the background color of the art paper on the display of the screen soft proofing is corrected.

[0016] The present invention also provides a chromaticity value measuring device based on any of the above screen soft proofing color correction methods, comprising an image acquisition system, an illumination system, a color measuring device and a closed chamber; the closed chamber has a closed cavity, and the closed cavity has a first side and a second side opposite to each other; the illumination system is arranged at the top of the closed cavity, and the illumination system is used to provide a standard light source; the image acquisition system and the color measuring device are arranged on the first side, and the second side is used to fix the object to be measured; the image acquisition system is used to acquire images; and the color measuring device is used to acquire specific values ​​of colors.

[0017] Preferably, the image acquisition system is a camera, the lighting system provides a D65 standard light source, and the color measurement device is a spectrophotometer.

[0018] Compared with the prior art, the present invention has achieved the following technical effects:

[0019] The screen soft proofing color correction method provided by the present invention calculates color difference information according to the display effect of the original image on the display and the printing effect on the art paper with special surface texture, and uses the color difference information to perform color adjustment on the display image on the display, forming multiple adjustments, and conducting color difference objective evaluation experiments and subjective evaluation experiments, so as to select the adjustment scheme that is closest to the display effect on the display and the printing effect on the art paper from the multiple adjustments. When printing is performed again subsequently, the original image only needs to be automatically adjusted through the corresponding file of the obtained adjustment scheme, so as to realize accurate restoration of the color effect of the printed content on the special printing carrier on the screen, without using the traditional manual color adjustment method, saving time and cost, and ensuring the stability of the printing effect.

[0020] Furthermore, by using the display color calibration file corresponding to the selected adjustment scheme to adjust the effect displayed on the display, the printed sample on the selected art paper can be automatically completed, and the operation is simple and convenient.

[0021] Furthermore, the selected adjustment scheme can be further adjusted to achieve better results, that is, the adjustment can be further refined to obtain a better adjustment scheme, so as to obtain a scheme with better consistency between the display effect of the display and the printing effect on the selected art paper.

[0022] Furthermore, the display and printer are color-calibrated before adjustment, so that their color references are calibrated to reduce subsequent color difference interference.

[0023] Furthermore, after color correction is performed on the display and printer, the background color of the art paper on the display is corrected, thereby ensuring that the display can more accurately display the background color of the art paper and ensuring the accuracy of subsequent adjustments.

[0024] The present invention also provides a chromaticity value measuring device, which acts as a bridge to obtain corresponding color information from art paper and transmit it to a display and a printer so as to reproduce the original texture and color on these two devices, providing a standard measurement to ensure consistency and comparability.

[0025] Furthermore, the image acquisition system uses a camera, the lighting system uses a fixed standard D65 standard light source, and the color measurement device is used to stably collect color data, and its components are common and easy to obtain. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 This is a schematic diagram of the overall structure of the chromaticity value measuring device provided by the present invention.

[0028] In the figure: 100 - chromaticity value measuring device; 1 - closed chamber; 2 - image acquisition system; 3 - lighting system; 4 - color measuring device; 5 - schematic diagram of paper placement. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The purpose of the present invention is to provide a screen soft proofing color correction method and a chromaticity value measurement device 100 to solve the problems existing in the prior art, and to achieve accurate restoration of the color effect of the printed content on the printing carrier on the screen, saving time and cost.

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Embodiment 1

[0033] This embodiment provides a screen soft proofing color correction method, including the following steps:

[0034] S1, collecting a first display chromaticity value of an original image on a display of a screen soft proofing; printing a first sample of the original image on a selected art paper, and collecting a first printing chromaticity value on the first sample; substituting the first display chromaticity value and the first printing chromaticity value into a color difference formula to calculate a first color difference;

[0035] S2, performing a first adjustment on the original image displayed on the screen soft proofing display by using image color correction software according to the obtained first color difference; collecting a second display chromaticity value of the image after the first adjustment on the screen soft proofing display and a second printing chromaticity value of the image after the first adjustment on a second sample printed on the same art paper; substituting the second display chromaticity value and the second printing chromaticity value into a color difference formula to calculate a second color difference;

[0036] S3, similarly, according to the adjustment method in S2, the third adjustment...the nth adjustment is obtained in sequence;

[0037] S4, objectively and subjectively evaluate the samples corresponding to the second adjustment, the third adjustment, ... the nth adjustment, and select the xth adjustment that is closest to the display of the screen soft proofing and the corresponding printed sample.

[0038] According to the display effect of the original image on the monitor and the printing effect on the art paper with special surface texture, the color difference information is calculated, and the color of the displayed image on the monitor is adjusted using the color difference information, forming multiple adjustments, and conducting objective and subjective evaluation experiments on color difference, so as to select the adjustment scheme that is closest to the display effect on the monitor and the printing effect on the art paper from the multiple adjustments. When printing again subsequently, it is only necessary to automatically adjust the original image through the corresponding file of the obtained adjustment scheme, so as to achieve accurate restoration of the color effect of the printed content on the special printing carrier on the screen, without the traditional manual color adjustment method, saving time and cost, and ensuring the stability of the printing effect.

[0039] In the optional scheme of this embodiment, it is more preferred to further include S5, inputting a print sample of the original image on the selected art paper according to the display color calibration file corresponding to the x-th adjustment determined in S4. By using the display color calibration file corresponding to the selected adjustment scheme, the effect displayed on the display is adjusted, and the print sample on the selected art paper can be automatically completed, which is simple and convenient to operate.

[0040] In the optional scheme of this embodiment, it is more preferred that according to the print sample obtained in S5 and its corresponding display effect on the display of the screen soft proofing, steps S2, S3 and S4 can be repeated in sequence to obtain a yth adjustment with better effect. It is also possible to make another adjustment with better effect according to the selected adjustment scheme, that is, further refine the adjustment to obtain a better adjustment scheme, and obtain a scheme with better consistency between the display effect of the display and the printing effect on the selected art paper.

[0041] In the optional scheme of this embodiment, it is more preferred that before S1, the display and printer of the screen soft proofing are color-calibrated. Before adjustment, the display and printer are color-calibrated so that their color reference is calibrated to reduce subsequent color difference interference.

[0042] In the optional scheme of this embodiment, it is more preferred that after the display and printer of the screen soft proofing are color-calibrated, the background color of the art paper on the display of the screen soft proofing is calibrated. After the display and printer are color-calibrated, the background color of the art paper on the display is calibrated, thereby ensuring that the display can more accurately display the background color of the art paper and ensuring the accuracy of subsequent adjustments.

[0043] Specifically, in order to ensure consistency, the two output devices, monitor and printer, need to be color-calibrated later. Monitor color calibration allows the colors on the art paper to be accurately displayed on the monitor; printer color calibration is then performed to ensure that the printed image is consistent with the expected color. In the color calibration process (i.e., color correction), color matching between the monitor and printer can be achieved by generating and applying appropriate ICC files.

[0044] Specifically, color calibration ensures that the output of the monitor and printer is consistent with the color and texture of the original art paper, which is achieved by adjusting the parameters of the equipment and generating the corresponding ICC files. The whole process relies on international standards and color space models to ensure consistency and comparability.

[0045] Embodiment 2

[0046] This embodiment provides a chromaticity value measuring device 100 based on the screen soft proofing color correction method of embodiment 1. Figure 1 As shown, it includes an image acquisition system 2, an illumination system 3, a color measurement device 4 and a closed chamber 1; the closed chamber 1 has a closed cavity, and the closed cavity has a first side and a second side opposite to each other; the illumination system 3 is arranged at the top of the closed cavity, and the illumination system 3 is used to provide a standard light source; the image acquisition system 2 and the color measurement device 4 are arranged on the first side, and the second side is used to fix the object to be measured; the image acquisition system 2 is used to acquire images; and the color measurement device 4 is used to acquire specific values ​​of colors. As a bridge, it can obtain corresponding color information from art paper and transmit it to the display and the printing indicator, so as to reproduce the original texture and color on these two devices, provide a standard measurement, and ensure consistency and comparability; at the same time, it can also acquire color information on the screen, obtain specific display chromaticity values ​​and printing chromaticity values, substitute them into the color difference formula, and obtain color difference values, so as to continuously adjust and reduce the color difference.

[0047] Specifically, Figure 1As shown, there is paper placed in the second side (Fig. 5).

[0048] Specifically, there is a close relationship between the colorimetric value measuring device 100 and the display and printer. The colorimetric value measuring device 100 can convert the texture and color characteristics on the art paper into data for further analysis, processing and reproduction. After the colorimetric value measuring device 100 captures the color and texture on the art paper, these characteristics are reproduced through the display and printer.

[0049] Specifically, the entire closed cavity provides a light-tight environment, and only the lighting system 3 provides a simulated light source.

[0050] Specifically, the image acquisition system 2 is composed of a color image acquisition sensor, which can be a camera, to acquire the texture and color of the art paper to obtain a high-quality digital image of the art paper.

[0051] Specifically, the lighting system 3 may be installed with a CIE standard light source, and a D65 standard light source may be selected.

[0052] Specifically, the color measuring device 4 uses a spectrophotometer to collect the specific value of the color of the art paper and the color value displayed on the screen. For the color collection of the art paper, it determines the color parameters by detecting the spectral components of the sample, and can provide the absolute values ​​of X, Y, Z, △E color difference value and the spectral reflectance value of the object, and can draw the spectral reflectance curve of the object color. Therefore, it is widely used in color matching and color analysis.

[0053] In the optional scheme of this embodiment, it is more preferred that the image acquisition system 2 is a camera, the lighting system 3 provides a D65 standard light source, and the color measurement device 4 is a spectrophotometer. The image acquisition system 2 uses a camera, the lighting system 3 uses a fixed standard D65 standard light source, and the color measurement device 4 is used to stably collect color data, and its components are common and easy to obtain.

[0054] Specifically, there are two types of spectrophotometers, one for measuring spectrum and the other for measuring color chromaticity; this embodiment uses an X-Rite spectrophotometer for measuring color.

[0055] Specifically, after collecting the texture and color characteristics of art paper, color correction will be performed on the selected devices - display and printer. After color correction, the background color of specialty paper needs to be corrected first. Because different papers have different gradation curve values, and the target value loaded in the software is based on standard paper, it does not conform to the color cast paper with background color in specialty paper, so the background color of the paper needs to be corrected. The Lab value measurement and recording is performed on different positions of the paper with background color to obtain the degree of color cast. The method of measuring color blocks with a spectrophotometer is used to compare the color gamut of the experimental paper and the standard paper. At the same time, the device correction based on the background color paper is combined with the physical properties of the paper's inkjet ink to complete the linear basic correction of the printer, creating a good characteristic file for the paper with background color.

[0056] The image is displayed on the display of the selected device, and the first display chromaticity value of the original image displayed on the screen is measured by the spectrophotometer of the color measuring device 4 under the standard illuminant D65. Then, a print sample is printed on the selected art paper with special paper surface texture according to the original image, and the first printing chromaticity value of the art paper sample under the standard lighting body D65 is measured by using the color measuring device 4 spectrophotometer and (X,Y,Z).

[0057] Substitute the first display chromaticity value and the first printing chromaticity value into the color difference formula CIE1976L*a*b* to calculate the color difference. The specific calculation method of the CIE1976L*a*b* color difference formula is:

[0058] Color difference formula:

[0059] Brightness difference: ΔL = L 1 * -L 2 *

[0060] Chromatic difference:

[0061]

[0062] In the above formula They represent the coordinate parameters of any two points in the coordinate system, and their calculation can be completed according to the following formula.

[0063]

[0064] in,

[0065]

[0066] (X, Y, Z) are the three stimulus values ​​of color; (X n ,Yn ,Z n ) is the tristimulus value of the light source used for color measurement. The first display chromaticity value of the original image on the screen measured under the standard illuminant D65 is The first printing chromaticity value of the selected art paper sample under the standard illuminant D65 The two values ​​are calculated using the color difference formula to obtain the color difference Chromatic aberration is an important method to measure the color reproduction quality of color-biased paper. It refers to the difference between two colors. The smaller the color difference, the smaller the color difference and the better the color block restoration. The maximum ink volume and single-channel ink volume of the printer are adjusted to reduce the color difference. During each calibration process, the color difference value will decrease. The color difference is significantly reduced in the first few times, but it will stabilize in the next few color difference calibrations, and the color difference changes are very small.

[0067] The printed samples were objectively evaluated, i.e., standard paper and art paper were used for proofing, and the color difference and solid density of the standard samples and art paper samples were analyzed. The objective evaluation process and results were expressed in digital form. At the same time, observers with normal color vision were organized to conduct subjective evaluation experiments, and the display of the monitor after the previous calibration was evaluated in six levels (several adjustments means several levels) with reference to the printed samples. The ICC color management file of the monitor was further adjusted according to the results of the subjective evaluation experiment, so that the monitor can better restore the actual printing effect of the art paper.

[0068] Specific program operation:

[0069] (1) Monitor and printer color calibration

[0070] Monitor color calibration: adjust the monitor's brightness, color temperature, and gamma value. Use ColorNavigator and Eye-One pro to calibrate the monitor, and after each calibration, test the display effect of 134 color blocks in ISO 12646 Profile Quality, evaluate the calibrated monitor, and determine the best display effect.

[0071] Printer color calibration: Profilemaker color management CMYK printer. The color card ECI2002CMYKiSis (A4) is selected with a size of A4. No color management file is selected when printing. The measurement starts about 30 minutes after the color card is printed. For color card data collection, open ProfileMaker 5.0, select the Printer tab, select the name of the printed color card ECI2002CMYK iSis (A4) in "Reference Data", select the EyeOne_iSis used in "Measurement Data", and start the Measurement interface to measure the printed color card. Insert the previously printed non-color management sample along the left end of the instrument according to the prompts on the measurement interface, and the instrument starts to detect the sample for automatic positioning. After the sample is positioned, Eye-One Isis starts to scan the color card line by line for automatic measurement. After a few minutes of automatic color block measurement, when all the color blocks on the color card are measured, click the "Close" button according to the prompts on the measurement interface to confirm that the measurement is completed. After the color block measurement is completed, it will automatically return to the ProfileMaker5.0 interface to save the measurement data. At this time, the "Save measurement data" option will pop up. Click the "Yes" button, and then the "Save as" dialog box will pop up. Determine the appropriate location and name, and click the "Save" button to successfully complete the collection of a large amount of color block data. Before generating the printer profile file, you need to set the parameters of the options in ProfileMaker. Select "Default" for "Profile Size", "Neutral Gray" for "PerceptualRendering Intent", "Log Colorful" for "Gamut Mapping", and D50 for "Viewing Light Source". When all options are set, you can click "Start", the "Save ICC" dialog box will pop up, select the appropriate ICC file name and click the "Save" soft button, and the software will automatically start generating the color profile file.

[0072] (2) Paper background color correction

[0073] The paper background color correction of art paper mainly uses a spectrophotometer to measure the Lab value of experimental art paper to clarify the color cast of the paper. First, linearization. In the linearization correction stage, CGS has a custom window that can load the density values ​​of each color scale on the paper. Since the background color of the paper will affect the visual judgment of the human eye, the use of a visual-based gray balance guide table to derive the color scale curves is more in line with the visual perception of the human eye. After a series of numerical values ​​are obtained, they are manually input and loaded into the CGS software, and the linearization table is printed again until the measured value catches up with the target value. Then the maximum ink volume and each single-channel ink volume must be set. First, print out the ink volume table containing the maximum ink volume and the single-channel ink volume, and use a colorimeter to measure the L value by measuring the density value. When the L value reaches the peak, it corresponds to the maximum ink volume, completing the basic linearization of the printer. Second, device characterization. The device characterization is performed to establish the relationship between the device value and the chromaticity value, and the advantages and disadvantages of the four gamut mapping intentions, namely the gamut mapping of the perceptual intention, the gamut mapping of the saturation intention, the gamut mapping of the relative chromaticity intention, and the gamut mapping of the absolute chromaticity intention, are analyzed, and the relative colorimetric intention is finally selected. After determining the gamut mapping intention, print the Test Chart and use Eye-one iSis to scan and identify the test, repeat five times until the color difference reaches a reasonable value, and the characterization is completed. Finally, perform spot color correction for the art paper, and perform it five times until the color difference reaches a reasonable value, so that the paper background color correction for the specific art paper is achieved.

[0074] (3) Printer calibration

[0075] Use the printer in step 1 and select the color profile file generated in step 1 to print the IT8 color sample. Wait for 30 minutes after the printing is finished, and use the art paper digitization acquisition device to measure the printing chromaticity value of each color sample under the standard luminous body D65 standard chromaticity of the printed sample. and (X n ,Y n ,z n ). When using a color measuring device 4, such as a spectrophotometer, to measure the chromaticity value of a sample, it is necessary to randomly select at least 3 points on the sample for measurement, and take the average value as the chromaticity value of the sample. Using a color measuring device 4, such as a spectrophotometer, to measure the chromaticity value of the first display of the original image displayed on the screen

[0076] (4) Screen calibration

[0077] Substitute the first display chromaticity value and the first printed chromaticity value obtained in step (3) into the CIE1976 L*a*b* color difference formula to calculate the color difference. The first printing chromaticity value of the selected art paper sample under the standard illuminant D65 Substitute into the color difference formula to calculate and get the color difference The display chromaticity value of the screen is continuously corrected. During the correction process, the color difference value will decrease and stabilize until the color difference changes very little.

[0078] According to the correction formula obtained above, a set of corrected chromaticity values ​​(L * ,a * ,b * ), adjust the ICC file of the screen according to this chromaticity value in the color management software to obtain the ICC file after the first calibration of the screen. At this time, in the color gamut where the screen and the print overlap, the color performance effect is already very close.

[0079] (5) Objective and subjective evaluation

[0080] Objective evaluation mainly includes color difference analysis and solid density analysis. Among them, color difference is an important method for evaluating color reproduction quality. When the printer generates a characterization file for the original, it will automatically calculate the maximum color difference and the average color difference, print the characterization color standard at least 5 times, and make an objective evaluation based on the color difference data. Solid density analysis is to measure the solid density of the four-color blocks of C, M, Y, and K on the printed standard samples and art paper samples, and compare the four-color density values ​​of the art paper sample and the standard sample for objective evaluation.

[0081] 1. Color difference evaluation standards:

[0082] Excellent (ΔE*ab≤1.0): Almost indistinguishable color difference, the printing effect is very close to the original image.

[0083] Good (1.0 < ΔE*ab ≤ 2.0): Slight color difference, which is difficult for ordinary observers to detect.

[0084] Medium (2.0 < ΔE*ab ≤ 5.0): The color difference is noticeable, but still within the acceptable range and does not affect the overall effect.

[0085] Poor (ΔE*ab>5.0): Obvious color difference, poor color reproduction effect, and further adjustment is required.

[0086] 2. Evaluation criteria for field density:

[0087] Excellent: The solid density value is very close to the standard value (error ≤ 0.05), and the saturation and brightness of the color block are well restored.

[0088] Good: The solid density value is close to the standard value (the error is between 0.05-0.10), and the saturation and brightness of the color block are well restored.

[0089] Medium: There is a certain gap between the actual density value and the standard value (the error is between 0.10-0.20).

[0090] But the overall effect is still acceptable.

[0091] Poor: The solid density value is far from the standard value (error>0.20), and the saturation and brightness restoration of the color block are poor, which needs to be adjusted.

[0092] Generally, the smaller the color difference and the smaller the solid density error, the better the printing effect. After several calibrations, the color difference and solid density tend to be stable, which is a good evaluation result. If the color difference value and solid density error are large, the calibration process needs to be further optimized to improve the color reproduction quality.

[0093] Subjective evaluation mainly focuses on the restoration of gradation transfer and level restoration, the gradation level of the image and the clarity of the image edge. The sample is the S8.Tif file in ISO SCID, which contains 104 color blocks, and these colors are relatively evenly distributed in the color space. The image file is first converted to Lab mode, and its L*a*b* value is displayed on a color-managed monitor and printed by a printer, and the printed sample is used to approximate the printed sample. The printed sample is placed in a suitable position under the standard lighting body D65. In order to eliminate the observation error caused by visual fatigue, the observer should relax for 3 minutes every 10 minutes during observation. Through comparative observation, the subjective evaluation of the color restoration, gradation level restoration, gloss restoration, etc. of the printed sample is obtained.

[0094] Subjective evaluation details:

[0095] 1. Specific steps of evaluation:

[0096] 1. Observe the environment

[0097] Observation was conducted under standard lighting D65 to ensure consistent light sources and avoid the impact of light source changes on the evaluation results. At the same time, the observer was required to relax for 3 minutes every 10 minutes to avoid the impact of visual fatigue on the evaluation results.

[0098] 2. Evaluation Criteria

[0099] (1) Observe whether the color of the printed sample is consistent with the original image and whether the color difference is obvious. Focus on evaluating the consistency and accuracy of color.

[0100] (2) Observe whether the light and dark levels of the image are clear and whether the details can be well restored. Pay special attention to the level performance of the high brightness and shadow parts.

[0101] (3) Observe whether the glossiness of the printed sample surface is consistent with the original Figure 1 Is there any obvious difference in gloss?

[0102] 2. Specific evaluation criteria:

[0103] (1) Color restoration: evaluates the degree of color matching with the original image. The smaller the difference, the better.

[0104] (2) Tone restoration: evaluates the smoothness of light-dark transitions and the retention of details.

[0105] (3) Gloss restoration: evaluate the uniformity and consistency of gloss.

[0106] Excellent: Color, tone, and gloss are almost completely restored, and the observer can hardly detect any difference.

[0107] Good: Slight differences in color, tone, and gloss, but the overall effect is good and difficult for the average observer to detect.

[0108] Moderate: There are noticeable differences in color, tone, and gloss, but they are still within the acceptable range.

[0109] Poor: The color, tone and gloss are obviously different and need further adjustment and improvement.

[0110] 3. Record subjective evaluation form

[0111] The observers filled in the subjective evaluation form according to the above standards, recorded the scores and evaluation opinions of each sample, and finally the subjective evaluation was conducted by multiple observers to ensure the comprehensiveness and fairness of the evaluation.

[0112] Therefore, we use a spectrophotometer to measure the Lab value of art paper, analyze the color cast, obtain the gradation curve through the gray balance table experiment, and complete the basic linearization and characterization. Print the Test Chart and use Eye-one iSis to scan and identify the test, repeat it many times until the color difference reaches a reasonable value, and complete the paper background correction. Select the standardized image file for printing, and compare the color, gradation and gloss of the display and the printed sample under the standard lighting body D65. According to our above subjective and objective evaluation results, repeatedly adjust the ICC file of the display to make the final display effect closer to the actual printing effect.

[0113] (6) Realize screen soft proofing

[0114] Screen soft proofing refers to a proofing method that simulates the printed output effect directly on the screen without material loss. It is intuitive, convenient and flexible to reproduce. The key technology of screen soft proofing is based on the precise calibration of the screen and the color management of the entire system. According to the results of objective and subjective evaluation tests, the ICC color management file of the screen is adjusted for the second time to make the color effect on the digital proofing display closer to the color effect of the actual proofing, thus realizing screen soft proofing.

[0115] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A screen soft proofing color correction method, characterized by: The following steps are involved: S1, collecting the first display chromaticity value of the original image on the display of screen soft proofing; Printing a first sample of the original image on the selected art paper, and collecting a first printing chromaticity value on the first sample; Substituting the first display chromaticity value and the first printing chromaticity value into a color difference formula to calculate a first color difference; S2, performing a first adjustment on the original image displayed on the screen soft proofing display by using image color correction software according to the obtained first color difference; collecting a second display chromaticity value of the image after the first adjustment on the screen soft proofing display and a second printing chromaticity value of the image after the first adjustment on a second sample printed on the same art paper; Substituting the second display chromaticity value and the second printing chromaticity value into the color difference formula to calculate the second color difference; S3, similarly, according to the adjustment method in S2, the third adjustment...the nth adjustment is obtained in sequence; S4, objectively and subjectively evaluate the samples corresponding to the second adjustment, the third adjustment, ... the nth adjustment, and select the xth adjustment that is closest to the display of the screen soft proofing and the corresponding printed sample.

2. The screen soft proofing color correction method according to claim 1, characterized in that: The method further includes S5, inputting a print sample of the original image on the selected art paper according to the display color calibration file corresponding to the x-th adjustment determined in S4.

3. The screen soft proofing color correction method according to claim 2, characterized in that: According to the print sample obtained in S5 and its corresponding display effect on the display of the screen soft proofing, steps S2, S3 and S4 can be repeated in sequence to obtain the yth adjustment with better effect.

4. The screen soft proofing color correction method according to claim 1, characterized in that: Prior to S1, color calibration was performed on monitors and printers for screen soft proofing.

5. The screen soft proofing color correction method according to claim 4, characterized in that: After color calibration of the monitor and printer for screen soft proofing, calibrate the background color of the art paper on the monitor for screen soft proofing.

6. A chromaticity value measuring device based on the screen soft proofing color correction method according to any one of claims 1 to 5, characterized in that: Includes image acquisition system, lighting system, color measurement device and closed chamber; The closed chamber has a closed cavity, and the closed cavity has a first side and a second side opposite to each other; The lighting system is arranged at the top of the closed cavity, and the lighting system is used to provide a standard light source; The image acquisition system and the color measurement device are arranged on the first side, and the second side is used for fixing the object to be measured; the image acquisition system is used for acquiring images; and the color measurement device is used for acquiring specific values ​​of colors.

7. The chromaticity value measuring device according to claim 6, characterized in that: The image acquisition system is a camera, the lighting system provides a D65 standard light source, and the color measurement device is a spectrophotometer.

Images