Method, device, computer device and medium for generating a print preview image

Abstract

This application relates to the field of printed image color management technology, and in particular to a method, apparatus, computer device, and medium for generating a print preview image. The method includes: obtaining a gamut factor, a white balance factor, a hue response function, and a saturation function based on the printing scheme of the image to be printed and the default printing scheme corresponding to a mapping table; obtaining a first color value for each node based on the PreviewRGB value corresponding to each node in the mapping table; determining a second color value for the node based on the product of the gamut factor and the first color value of the node; obtaining a temporary RGB value for the node based on the product of the white balance factor, the hue response function, and the PreviewRGB value; obtaining a third color value for the node based on the temporary RGB value; obtaining a fourth color value based on the saturation function and the third color value of the node; converting the fourth color value into a target PreviewRGB value to obtain an updated mapping table; and generating a print preview image based on the updated mapping table. This method can save memory.

Description

Technical Field

[0001] This application relates to the field of color management technology for printed images, and in particular to a method, apparatus, computer device, and medium for generating print preview images. Background Technology

[0002] With the rapid development of digital imaging and printing technologies, people have placed higher demands on the accuracy and consistency of color output in printed images. Traditional print preview functions can usually only roughly reflect the content of the printed image, but they are difficult to accurately reproduce the color performance of the printing device on the printing medium, resulting in a large difference between the actual printed effect and the print preview effect, and also greatly wasting the utilization rate of consumables.

[0003] To address the issue of poor print quality, patent application CN113727017A uses a pre-stored mapping table of various printing schemes to convert the color space of the image to be printed. However, this requires a significant amount of memory to store the mapping table. Summary of the Invention

[0004] Therefore, it is necessary to provide a method, apparatus, computer device, and medium for generating print preview images that can save memory, in order to address the aforementioned technical problems.

[0005] A method for generating a print preview image, the method comprising:

[0006] S1. Based on the printing scheme of the image to be printed and the default printing scheme corresponding to the mapping table, obtain the gamut factor, white balance factor, hue response function and saturation function; the mapping table is a mapping table for converting the color space of the image to be printed;

[0007] S2. Based on the PreviewRGB values ​​corresponding to each node in the mapping table, obtain the first color value of each node;

[0008] S3. Determine the second color value of the node based on the product of the gamut factor and the first color value of the node, and obtain the temporary RGB value of the node based on the product of the white balance factor, the hue response function and the PreviewRGB value.

[0009] S4. Based on the temporary RGB value of the node, obtain the third color value of the node; based on the saturation function and the third color value of the node, obtain the fourth color value; convert the fourth color value into the target PreviewRGB value to obtain the updated mapping table.

[0010] S5. Based on the updated mapping table, generate a print preview image of the image to be printed.

[0011] In this application, the color gamut factor, white balance factor, hue response function, and saturation function are obtained based on the printing scheme of the image to be printed and the default printing scheme corresponding to the mapping table. Based on the PreviewRGB value corresponding to each node in the mapping table, the first color value of each node is obtained. Based on the product of the color gamut factor and the first color value of the node, the second color value of the node is determined. Based on the product of the white balance factor, hue response function, and PreviewRGB value, the temporary RGB value of the node is obtained. Based on the temporary RGB value of the node, the third color value of the node is obtained. Based on the saturation function and the third color value of the node, the fourth color value is obtained. The fourth color value is converted into the target PreviewRGB value to obtain the updated mapping table. Based on the updated mapping table, a print preview image of the image to be printed is generated. In this way, while ensuring the printing effect, a mapping table adapted to the printing scheme of the image to be printed can be dynamically generated by only multiple calculations, without storing mapping tables of multiple printing schemes at the same time, which greatly saves storage resources.

[0012] In one embodiment, the process of determining the second color value in step S3 includes:

[0013] The initial color value is determined based on the product of the gamut factor and the first color value of the node;

[0014] When the initial color value is greater than a first preset value, the first preset value is used as the second color value;

[0015] When the initial color value is less than the second preset value, the second preset value is used as the second color value, and the first preset value is greater than the second preset value.

[0016] In this application, an initial color value is determined by multiplying the gamut factor by the first color value of the node. When the initial color value is greater than a first preset value, the first preset value is used as the second color value. When the initial color value is less than a second preset value, the second preset value is used as the second color value. The first preset value is greater than the second preset value, which ensures that the second color value is always between the first preset value and the second preset value, preventing color overflow and ensuring color fidelity.

[0017] In one embodiment, the process of obtaining the mapping table in step S1 includes:

[0018] Obtain a first mapping relationship between the color space of the image to be printed and the color space of the printing device, and a second mapping relationship between the color space of the printing device and the color space of the display device; the color space of the printing device is determined based on the model of the printing device and the default printing scheme;

[0019] Based on the first mapping relationship and the second mapping relationship, a third mapping relationship is established between the color space in the image to be printed and the color space of the display device;

[0020] Based on the third mapping relationship, the mapping table is obtained.

[0021] In this application, a mapping table is obtained based on a third mapping relationship. This allows for the production preview image to be obtained with only one color space conversion when using the updated mapping table for conversion, thus improving the conversion processing speed.

[0022] In one embodiment, the formula for calculating the gamut factor F_gamut in step S1 is: ;

[0023] The white balance factor includes a green channel factor, a red channel factor, and a blue channel factor. The calculation formula for the green channel factor F_wb_g is as follows: ;

[0024] The formula for calculating the red channel factor F_wb_r is as follows: ;

[0025] The formula for calculating the blue channel factor F_wb_b is as follows: ;

[0026] Where Y1 is the theoretical color gamut coverage of the ink, Y2 is the ink absorption coefficient of the printing medium, Y is the reference color gamut coverage corresponding to the default printing scheme; kk2 and k3 are both fitting coefficients, and ΔCCT is the color temperature difference between the color temperature of the printing medium in the printing scheme and the color temperature of the printing medium in the default printing scheme.

[0027] In this application, by using the formula , , Calculate the white balance factor to account for the influence of the printing medium on color in the printing scheme, and ensure that the final print preview image of the image to be printed is consistent with the actual printed result.

[0028] In one embodiment, the temporary RGB value in step S3 includes a temporary adjustment value PR_temp for the red channel, a temporary adjustment value PG_temp for the green channel, and a temporary adjustment value PB_temp for the blue channel. The formula for calculating the temporary RGB value is as follows:

[0029] PR_temp=PR×F_wb_r×F_tone(PR / 255.0);

[0030] PG_temp=PG×F_wb_g×F_tone(PG / 255.0);

[0031] PB_temp=PB×F_wb_b×F_tone(PB / 255.0);

[0032] Where PR is the red channel value in the PreviewRGB value, PG is the green channel value in the PreviewRGB value, PB is the blue channel value in the PreviewRGB value, F_wb_r is the red channel factor in the white balance factor, F_wb_g is the green channel factor in the white balance factor, F_wb_b is the blue channel factor in the white balance factor, and F_tone is the tone response function.

[0033] In this application, the formulas PR_temp=PR×F_wb_r×F_tone(PR / 255.0), PG_temp=PG×F_wb_g×F_tone(PG / 255.0), and PB_temp=PB×F_wb_b×F_tone(PB / 255.0) are used to generate intermediate temporary RGB values ​​with accurate color and optimized visual appearance, laying the foundation for high-quality image output. Furthermore, this method combines white balance correction and tone curve adjustment into a single multiplication operation, improving computational efficiency.

[0034] In one embodiment, the formula for calculating the fourth color value S_final in step S4 is:

[0035] S_final=S_temp×F_sat(ρ,S_temp);

[0036] Where F_sat(ρ,S_temp) is the saturation function, S_temp is the third color value of the node, and ρ is the brightness of the node.

[0037] In this application, the fourth color value is calculated by using S_final=S_temp×F_sat(ρ,S_temp), where F_sat(ρ,S_temp) is a function, not a fixed value. This allows different color value adjustment strategies to be used in different brightness areas, avoiding the problems of noise in dark areas and oversaturation in bright areas.

[0038] In one embodiment, the method further includes:

[0039] Determine the desired print image;

[0040] When the desired print image does not match the print preview image, in response to the adjustment operation of the print scheme and / or the image parameters of the image to be printed, the print scheme and / or the image parameters of the image to be printed are adjusted until the print preview image matches the desired print image.

[0041] In this application, by determining the desired print image, when the desired print image does not match the print preview image, in response to the adjustment operation of the print scheme and / or the image parameters of the image to be printed, the print scheme and / or the image parameters of the image to be printed are adjusted until the print preview image matches the desired print image. This makes the generated print preview image meet the user's expectations, thereby making the final printed effect meet the user's expectations.

[0042] An apparatus for generating a print preview image, the apparatus comprising:

[0043] The factor calculation module is used to obtain the color gamut factor, white balance factor, hue response function, and saturation function based on the printing scheme of the image to be printed and the default printing scheme corresponding to the mapping table; the mapping table is a mapping table for converting the color space of the image to be printed.

[0044] The color value calculation module is used to obtain the first color value of each node based on the PreviewRGB value corresponding to each node in the mapping table;

[0045] The temporary RGB value calculation module is used to determine the second color value of the node based on the product of the color gamut factor and the first color value of the node, and to obtain the temporary RGB value of the node based on the product of the white balance factor, the hue response function and the PreviewRGB value.

[0046] The update module is used to obtain a third color value of the node based on the temporary RGB value of the node, obtain a fourth color value based on the saturation function and the third color value of the node, convert the fourth color value into a target PreviewRGB value, and obtain an updated mapping table;

[0047] An image generation module is used to generate a print preview image of the image to be printed based on the updated mapping table.

[0048] A computer device includes a memory and a processor, the memory storing a computer program, the processor executing the computer program to implement the steps of the method described above.

[0049] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the above-described method.

[0050] The aforementioned print preview image generation device, computer equipment, and medium obtain the color gamut factor, white balance factor, hue response function, and saturation function based on the printing scheme of the image to be printed and the default printing scheme corresponding to the mapping table. Based on the PreviewRGB values ​​corresponding to each node in the mapping table, the first color value of each node is obtained. Based on the product of the color gamut factor and the first color value of the node, the second color value of the node is determined. Based on the product of the white balance factor, hue response function, and PreviewRGB value, the temporary RGB value of the node is obtained. Based on the temporary RGB value of the node, the third color value of the node is obtained. Based on the saturation function and the third color value of the node, the fourth color value is obtained. The fourth color value is converted into the target PreviewRGB value to obtain an updated mapping table. Based on the updated mapping table, a print preview image of the image to be printed is generated. In this way, while ensuring the printing effect, a mapping table adapted to the printing scheme of the image to be printed can be dynamically generated through multiple calculations, without having to store mapping tables of multiple printing schemes at the same time, which greatly saves storage resources. Attached Figure Description

[0051] Figure 1 This is an application environment diagram of a method for generating print preview images in one embodiment;

[0052] Figure 2 This is a flowchart illustrating a method for generating a print preview image in one embodiment;

[0053] Figure 3 This is a flowchart of color space conversion for an image to be printed in one embodiment;

[0054] Figure 4 This is an overall flowchart of a method for generating a print preview image in one embodiment;

[0055] Figure 5 This is a schematic diagram of an image to be printed in one embodiment;

[0056] Figure 6 This is a print preview image corresponding to printing scheme 1 in one embodiment;

[0057] Figure 7 This is a print preview image corresponding to printing scheme 2 in one embodiment;

[0058] Figure 8 This is a print preview image corresponding to printing scheme 3 in one embodiment;

[0059] Figure 9 This is a schematic diagram illustrating the automatic matching of the target PreviewRGB in the updated mapping table for the printing scheme in one embodiment.

[0060] Figure 10This is a structural block diagram of a device for generating a print preview image in one embodiment;

[0061] Figure 11 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0062] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0063] The method for generating print preview images provided in this application embodiment can be applied to, for example, Figure 1 The application environment shown is as follows. The terminal interacts with the server via a wired / wireless channel. The printing device receives the input image to be printed. The server, based on the printing scheme of the image to be printed and the default printing scheme corresponding to the mapping table, obtains the gamut factor, white balance factor, hue response function, and saturation function. The mapping table is a mapping table that converts the color space of the image to be printed. The server obtains the first color value of each node based on the PreviewRGB values ​​(Preview-Red-Green-Blue) corresponding to each node in the mapping table. The server determines the second color value of the node based on the product of the gamut factor and the first color value of the node, and obtains the temporary RGB value of the node based on the white balance factor, hue response function, and PreviewRGB value. The server obtains the second color value of the node based on the temporary RGB value of the node, and obtains the third color value based on the saturation function and the second color value of the node. It then converts the third color value to the target PreviewRGB value to obtain the updated mapping table. The server generates a print preview image of the image to be printed based on the updated mapping table. The terminal can be, but is not limited to, various personal computers, laptops, smartphones, tablets, IoT devices, etc. A server can be a single server, a server cluster consisting of multiple servers, or a cloud computing center consisting of multiple servers.

[0064] In some embodiments, the terminal's display screen is used to display the generated print preview image.

[0065] In one embodiment, such as Figure 2 As shown, a method for generating a print preview image is provided, which can be applied to... Figure 1 Taking the server in the example, the following steps are included:

[0066] S1. Based on the printing scheme of the image to be printed and the default printing scheme corresponding to the mapping table, obtain the gamut factor, white balance factor, hue response function and saturation function; the mapping table is a mapping table for converting the color space of the image to be printed.

[0067] The image to be printed is the image that the user needs to print. The image to be printed can be in various formats, such as JPEG (Joint Photographic Experts Group), PNG (Portable Network Graphics), TIFF (Tagged Image File Format), and GIF (Graphics Interchange Format). The image to be printed can be a raw, unprocessed photograph or image captured by a camera, or an image generated by a scanner. The image to be printed can be a multi-layered composite image, or an image composed of both images and graphics.

[0068] A printing plan is the printing scheme selected by the user. Printing plans include, but are not limited to, printing ink, printing media, color values, and printer model. Available printing inks include, but are not limited to, water-based inks, oil-based inks, and water-based inks. Available printing media include, but are not limited to, plastic printing media and paper printing media. A color value is a numerical combination used to uniquely describe a color in a color space that explicitly uses saturation as a component of color representation. Color values ​​are typically composed of hue, saturation, and brightness. The default printing plan is a set of preset, fixed printing schemes. For example, the default printing plan is water-based ink + PP film (polypropylene film). Other possible printing plans include water-based ink + PP film + color value adjustment, or water-based ink + paper + color value adjustment, or oil-based ink + PP film + no color value adjustment, or oil-based ink + PP film + no color value adjustment + modification of the printer's profile. Different printing plans will produce images with inconsistent color effects.

[0069] A color space mapping table is used to convert the color space of an image to be printed to the color space corresponding to the default printing scheme. In other words, the color space mapping table is used to obtain the printed image of the image under the default printing scheme. Color space conversion includes converting pixel values.

[0070] The gamut factor F_gamut is a parameter used to scale the color gamut range of the default printing scheme. Specifically, F_gamut = 1.0 means that the color gamut range of the default printing scheme is maintained, without expansion or clipping; F_gamut > 1 means that the color gamut of the default printing scheme needs to be expanded, such as 1.25, which means expanding the color gamut by 25% compared to the default printing scheme; F_gamut < 1 means that the color gamut of the default printing scheme needs to be clipped, such as 0.78, which means shrinking the color gamut by 22% compared to the default printing scheme.

[0071] The white balance factor is a parameter characterizing the white balance offset. The tone response function is a non-linear curve primarily used to adjust brightness, ensuring the adjusted brightness adapts to the non-linear perception of the human eye while preserving more visual detail within a limited dynamic range. When using the tone response function for brightness adjustment, the brightness to be adjusted is a normalized value. The tone response function can be a piecewise linear function, an S-curve, or an exponential function. One form of the tone response function F_tone(ρ) is... ρ is the normalized brightness, Media_Type is the printing media in the printing scheme, and Device_Profile_Modification is the modified device characteristic.

[0072] In some embodiments, if the profile requires "improved shadow detail," then when the input brightness value is less than a third preset value, the output brightness value is a first preset brightness value. This allows the output brightness value to adapt to the human eye's sensitivity to subtle changes in shadows, conforming to human perception. When the input brightness value is greater than a fourth preset value, the output brightness value is a second preset brightness value. This prevents overexposure and loss of detail. The third preset value is less than the fourth preset value, and the first preset brightness value is greater than the second preset brightness value. For example, if the profile requires "20% improvement in shadow detail," then when ρ < 0.3, F_tone(ρ) = 1.2, which is sensitive to subtle changes in shadows and conforms to human perception. When ρ > 0.7, F_tone(ρ) = 1.0, preventing overexposure and loss of detail. ρ is the input brightness value, and F_tone(ρ) is the adjusted output brightness value.

[0073] The saturation function is used to non-linearly adjust color values. The saturation function can be expressed as: Here, `Base_Factor` is the global color value adjustment base in the printing scheme. `Gain_High` is the additional gain coefficient for high-saturation regions, and `Gain_Low` is the additional gain coefficient for low-saturation regions. Low-saturation regions refer to image regions where the proportion of red, green, and blue colors is less than a first proportion value, and low-saturation regions refer to image regions where the proportion of red, green, and blue colors is greater than a second proportion value, where the first proportion value is less than the second proportion value. `w_high(ρ)` is the weight function for high-saturation regions, and `w_low(ρ)` is the weight function for low-saturation regions, with the weight of the high and low saturation regions determined by the input brightness `ρ`. For example, `w_high(ρ)` approaches 1 when `ρ>0.8`, smoothly decays to 0 in other regions, and when `ρ` is in the range of 0.7~0.9, `w_high(ρ)=max(0.0,min(1.0,(ρ-0.7) / (0.9-0.7))`, thus achieving differentiated adjustment for different regions.

[0074] By inputting the printing scheme into the color influence factor calculation model, you can obtain the standardized, dimensionless gamut factor, white balance factor, hue response function, and saturation function. Standardization means that regardless of whether the printing ink is water-based or oil-based, or the printing medium is paper or PP film, the overall impact on the color gamut is ultimately "standardized" into an easily understandable and intuitive scaling ratio. Dimensionless is a scaling factor, not a specific quantity with units, such as "increase the color temperature by 200K" or "increase the color value by 15%".

[0075] S2. Based on the PreviewRGB values ​​corresponding to each node in the mapping table, obtain the first color value of each node;

[0076] In this mapping table, each node is a discrete sampling point, and each node corresponds to a PreviewRGB value. The pixel value of each color channel is represented by a level from 0 to 255. Each color channel is divided into N equal parts. For example, if N=16, there are N+1=17 nodes. With 3 color channels, there are 3 dimensions and 17*17*17 nodes. Therefore, (Ri,Gj,Bk) is one of these 17*17*17 nodes.

[0077] Furthermore, based on the PreviewRGB values ​​corresponding to each node in the mapping table, the brightness of each node can also be obtained. The process of converting the PreviewRGB values ​​to the HSL (Hue-Saturation-Lightness) color space to obtain the first color value and brightness is as follows: obtain the maximum component value max and the minimum component value min in the PreviewRGB values, and calculate the brightness using the formula (max+min) / 2; if the difference Δ between the maximum component value and the minimum component value is 0, then the first color value S is 0; if the brightness is less than 0.5, then S=Δ / (max+min), and if the brightness is greater than 0.5, then S=Δ / (2-max-min).

[0078] When converting PreviewRGB values ​​to the HSV (Hue-Saturation-Value) color space, the brightness is the maximum component value (max) in the PreviewRGB values, and the first color value is the quotient of the difference divided by the maximum component value.

[0079] S3. Determine the second color value of the node based on the product of the gamut factor and the first color value of the node. Obtain the temporary RGB value of the node based on the product of the white balance factor, the hue response function, and the PreviewRGB value.

[0080] The formula for calculating the second color value S' is S'=S×F_gamut, where S is the first color value and F_gamut is the gamut factor.

[0081] Since the PreviewRGB value has three channel components, the temporary RGB value for each channel is calculated separately. The formula for calculating the temporary RGB value of a node can be PR_temp = PR × F_wb_r × F_tone (PR), PG_temp = PG × F_wb_g × F_tone (PG), PB_temp = PB × F_wb_b × F_tone (PB), where PR is the red channel value in the PreviewRGB value, PG is the green channel value in the PreviewRGB value, PB is the blue channel value in the PreviewRGB value, F_wb_r is the red channel factor in the white balance factor, F_wb_g is the green channel factor in the white balance factor, F_wb_b is the blue channel factor in the white balance factor, and F_tone is the hue response function.

[0082] S4. Based on the temporary RGB value of the node, obtain the third color value of the node. Based on the saturation function and the third color value of the node, obtain the fourth color value. Convert the fourth color value into the target PreviewRGB value to obtain the updated mapping table.

[0083] The fourth color value is the fourth color value corresponding to the node. The process of converting temporary RGB values ​​to the HSL color space to obtain the third color value is as follows: Obtain the maximum and minimum component values ​​(max and min) from the temporary RGB values. Calculate the brightness using (max + min) / 2. If the difference Δ between the maximum and minimum values ​​is 0, the third color value S_temp is 0. If the brightness is less than 0.5, the third color value S_temp = Δ / (max + min). If the brightness is greater than 0.5, the third color value S_temp = Δ / (2 - max - min). When converting temporary RGB values ​​to the HSV color space, the third color value is the quotient of the difference divided by the maximum component value; the difference is the difference between the maximum component value (max) and the minimum component value (min).

[0084] Substituting the third color value and brightness into the saturation function, the saturation factor can be obtained. Based on the product between the saturation factor and the third color value, the fourth color value can be obtained.

[0085] The process of converting the fourth color value to the target PreviewRGB value is as follows: If the fourth color value S_final is zero, then each component value in the target PreviewRGB value is a specific value of brightness; if the brightness of the fourth color value is less than 0.5, then q = brightness × (1 + S_final), p = 2 × brightness - q .... Spend If the value is greater than 0.5, then q = luminance + S_final - luminance × S_final, p = 2 × luminance - q, H norm =H / 360, R=hue2rgb(p,q,H) norm +1 / 3), G=hue2rgb(p,q,H) norm B = hue2rgb(p, q, H) norm -1 / 3), H is the hue obtained when the PreviewRGB value is converted to the HSL color space, H norm For the normalized hue, R is the red channel component value in the target PreviewRGB value, G is the green channel component value in the target PreviewRGB value, B is the blue channel component value in the target PreviewRGB value, p and q are intermediate parameters, and hue2rgb is an auxiliary function for calculating the target PreviewRGB value.

[0086] After obtaining the target PreviewRGB value of each node, the obtained target PreviewRGB value is written to the corresponding node of the mapping table, thereby obtaining the updated mapping table.

[0087] The calculation processes of steps S2, S3, S4, and S5 can be integrated into the same parameterized dynamic mapping model.

[0088] S5. Based on the updated mapping table, generate a print preview image of the image to be printed.

[0089] The updated mapping table corresponds to the printing scheme of the image to be printed. Using the updated mapping table, the pixel values ​​of each point in the image to be printed can be converted to pixel values ​​suitable for the printing scheme, thus obtaining a print preview image of the image under the printing scheme. Specifically, using interpolation methods, the color space of the image to be printed is converted based on the updated mapping table to convert the pixel values ​​of the image to be printed to the pixel values ​​corresponding to the printing scheme, thus obtaining a print preview image of the image under the printing scheme. Interpolation methods include, but are not limited to, tetrahedral interpolation or solid interpolation. A flowchart illustrating the color space conversion of the image to be printed using tetrahedral interpolation or solid interpolation is shown below. Figure 3 As shown.

[0090] Furthermore, in response to a print operation on the print preview image, the generated print preview image is printed.

[0091] In the above method for generating print preview images, the color gamut factor, white balance factor, hue response function, and saturation function are obtained based on the printing scheme of the image to be printed and the default printing scheme corresponding to the mapping table. Based on the PreviewRGB values ​​corresponding to each node in the mapping table, the first color value of each node is obtained. Based on the product of the color gamut factor and the first color value of the node, the second color value of the node is determined. Based on the product of the white balance factor, hue response function, and PreviewRGB value, the temporary RGB value of the node is obtained. Based on the temporary RGB value of the node, the third color value of the node is obtained. Based on the saturation function and the third color value of the node, the fourth color value is obtained. The fourth color value is converted into the target PreviewRGB value to obtain the updated mapping table. Based on the updated mapping table, the print preview image of the image to be printed is generated. In this way, while ensuring the printing effect, a mapping table that matches the printing scheme of the image to be printed can be dynamically generated through multiple calculations, without having to store mapping tables of multiple printing schemes at the same time, which greatly saves storage resources. Furthermore, the hue response function and saturation function are both brightness-related functions, rather than fixed values. This means that the adjustment is dynamically adjusted based on the input brightness and color values. This solves the technical problem of distortion in dark and bright areas caused by traditional global adjustment, and achieves uniform adjustment in human eye perception. It can accurately simulate the color output effect of printing equipment and printing media before printing, so that the print preview image is highly consistent with the final printed image. This can also reduce the cost of consumables and improve the utilization rate of consumables.

[0092] In one embodiment, the process of determining the second color value in step S3 includes:

[0093] The initial color value is determined based on the product of the gamut factor and the first color value of the node;

[0094] When the initial color value is greater than the first preset value, the first preset value is used as the second color value;

[0095] When the initial color value is less than the second preset value, the second preset value is used as the second color value, and the first preset value is greater than the second preset value.

[0096] The initial color value is the product of the gamut factor and the first color value of the node.

[0097] The first and second preset values ​​are values ​​preset based on the physical display range of color. The physical display range of color is [0,1]. Therefore, the first preset value is less than 1, and the second preset value is greater than 0. In typical scenarios, the first preset value is 1, and the second preset value is 0.

[0098] In some embodiments, if the initial color value is between a first preset value and a second preset value, then the initial color value is the second color value.

[0099] In this embodiment, an initial color value is determined by multiplying the color gamut factor by the first color value of the node. When the initial color value is greater than a first preset value, the first preset value is used as the second color value. When the initial color value is less than a second preset value, the second preset value is used as the second color value. Since the first preset value is greater than the second preset value, the second color value can always be between the first preset value and the second preset value, preventing color overflow and ensuring color fidelity.

[0100] In one embodiment, the process of obtaining the mapping table in step S1 includes:

[0101] Obtain the first mapping relationship between the color space of the image to be printed and the color space of the printing device, and the second mapping relationship between the color space of the printing device and the color space of the display device; the color space of the printing device is determined based on the model of the printing device and the default printing scheme;

[0102] Based on the mapping relationship and the second mapping relationship, a third mapping relationship is established between the color space in the image to be printed and the color space of the display device;

[0103] Based on the third mapping relationship, a mapping table is obtained.

[0104] A color space is a model or system used to mathematically describe and quantify color. A color space defines how to represent the various colors visible to the human eye using a set of numerical values ​​(usually multiple channels). Different color spaces are suitable for different applications, such as display, printing, image processing, and color science. Color spaces include, but are not limited to, RGB, sRGB (standard Red Green Blue), and CMYK (Cyan-Magenta-Yellow-Key).

[0105] Obtaining the first mapping relationship between the color space of the image to be printed and the color space of the printing device includes: parsing the color information of the image to be printed to obtain the color space of the image to be printed; determining the color space corresponding to the printing device; and using the ICC (International Color Consortium) configuration file to obtain the first mapping relationship from the color space of the image to the color space corresponding to the printing device.

[0106] Obtaining the second mapping relationship between the color space of the printing device and the color space of the display device includes: establishing the second mapping relationship based on the respective ICC profiles of the printing device and the display device;

[0107] By combining the first mapping relationship with the second mapping relationship, a third mapping relationship can be obtained, which can then form a mapping table.

[0108] In this embodiment, a mapping table is obtained based on a third mapping relationship. This allows for the production preview image to be obtained with only one color space conversion when using the updated mapping table for conversion, thus improving the conversion processing speed.

[0109] In one embodiment, the formula for calculating the gamut factor F_gamut in step S1 is: ;

[0110] The white balance factor includes the green channel factor, red channel factor, and blue channel factor. The formula for calculating the green channel factor F_wb_g is: ;

[0111] The formula for calculating the red channel factor F_wb_r is: ;

[0112] The formula for calculating the blue channel factor F_wb_b is: ;

[0113] Where Y1 is the theoretical color gamut coverage of the ink, Y2 is the ink absorption coefficient of the printing medium, Y is the reference color gamut coverage corresponding to the default printing scheme; k1, k2, and k3 are all fitting coefficients, and ΔCCT is the color temperature difference between the color temperature of the printing medium in the printing scheme and the color temperature of the printing medium in the default printing scheme.

[0114] The theoretical color gamut coverage of the ink is determined based on the printing inks used in the printing scheme. Each printing ink corresponds to a specific theoretical color gamut coverage. The ink absorption coefficient of the printing media refers to the ink absorption coefficient corresponding to the printing media in the printing scheme. Each printing media corresponds to a specific ink absorption coefficient. For example, the ink absorption coefficient of PP film is 0.3, and that of paper is 0.7. Printing media with lower ink absorption coefficients exhibit better color gamut performance. The reference color gamut coverage corresponding to the default printing scheme refers to the theoretical color gamut coverage of the printing inks used in the default printing scheme.

[0115] The gamut factor can unify the physical properties of printing inks and printing media in different printing schemes into a calculable scalar, thus eliminating the need to build a complete physical rendering model for each printing scheme and significantly reducing algorithm and storage overhead.

[0116] In some embodiments, the color temperature of the printing media can be obtained based on the difference between the white point coordinates of the printing media and the standard white point coordinates. Specifically, the intermediate value n is calculated using the formula n=(x-0.3320) / (0.1858-y). The calculated value of n is then substituted into the cubic polynomial T=449×n³+3525×n²+6823.3×n+5520.33, where T is the color temperature of the printing media in the printing scheme, (x,y) are the white point coordinates of the printing media, and (0.3320, 0.1858) are the standard white point coordinates. The printing media includes the printing media in the printing scheme and the printing media in the default printing scheme. The fitting coefficient can be preset.

[0117] In a specific application, k1=-0.1, k2=0.1, k3=-0.1, ΔCCT is 200K, then F_wb_r = 1.02, F_wb_g = 1.00, F_wb_b = 0.98.

[0118] In this embodiment, the formula is used. , , Calculate the white balance factor to account for the influence of the printing medium on color in the printing scheme, and ensure that the final print preview image of the image to be printed is consistent with the actual printed result.

[0119] In one embodiment, the white balance factor can also be obtained through a preset conversion lookup table, which includes green channel factors, red channel factors, and blue channel factors corresponding to various printing media. For example, if the printing media in the printing scheme is media A, then the green channel factor, red channel factor, and blue channel factor corresponding to media A can be obtained from the conversion lookup table.

[0120] In one embodiment, the temporary RGB values ​​in step S3 include the temporary adjustment value PR_temp for the red channel, the temporary adjustment value PG_temp for the green channel, and the temporary adjustment value PB_temp for the blue channel. The formula for calculating the temporary RGB values ​​is as follows:

[0121] PR_temp= PR × F_wb_r × F_tone(PR / 255.0);

[0122] PG_temp = PG × F_wb_g × F_tone(PG / 255.0);

[0123] PB_temp = PB × F_wb_b × F_tone(PB / 255.0);

[0124] Where PR is the red channel value in the PreviewRGB value, PG is the green channel value in the PreviewRGB value, PB is the blue channel value in the PreviewRGB value, F_wb_r is the red channel factor in the white balance factor, F_wb_g is the green channel factor in the white balance factor, F_wb_b is the blue channel factor in the white balance factor, and F_tone is the tone response function.

[0125] PR / 255.0, PG / 255.0, and PB / 255.0 indicate that PR, PG, and PG are normalized to ensure the continuity of the adjustment. Substituting the PreviewRGB values ​​into the hue response function yields the corresponding hue response factor.

[0126] In this embodiment, the formulas PR_temp=PR×F_wb_r×F_tone(PR / 255.0), PG_temp=PG×F_wb_g×F_tone(PG / 255.0), and PB_temp=PB×F_wb_b×F_tone(PB / 255.0) generate intermediate temporary RGB values ​​with accurate color and optimized visual appearance, laying the foundation for high-quality image output. Furthermore, this method combines white balance correction and tone curve adjustment into a single multiplication operation, improving computational efficiency.

[0127] In one embodiment, the formula for calculating the fourth color value S_final in step S4 is:

[0128] S_final = S_temp× F_sat(ρ,S_temp)

[0129] Here, F_sat(ρ, S_temp) is the saturation function, S_temp is the third color value of the node, and ρ is the brightness of the node. Substituting the specific ρ and S_temp into the saturation function yields the saturation factor. The fourth color value S_final is essentially the product of the third color value and the saturation factor.

[0130] In this embodiment, the fourth color value is calculated by using S_final=S_temp×F_sat(ρ,S_temp), where F_sat(ρ,S_temp) is a function, not a fixed value. This allows for different color value adjustment strategies to be used in different brightness areas, avoiding the problems of noise in dark areas and oversaturation in bright areas.

[0131] In one embodiment, the method further includes:

[0132] Obtain the image to be printed;

[0133] If the desired print image does not match the print preview image, adjust the print scheme and / or the image parameters of the image to be printed until the print preview image matches the desired print image.

[0134] The desired print image is the image the user expects to print. This desired print image can be input into the server. The server determines whether the desired print image and the print preview image match based on their pixel values. Further, it checks whether the difference between the pixel values ​​of corresponding points in the desired print image and the print preview image is less than a preset difference. Points with a difference less than the preset difference are identified as qualified points. If the number of qualified points is greater than a preset number, the desired print image and the print preview image are considered to match; if the number of qualified points is less than the preset number, the desired print image and the print preview image are considered to not match.

[0135] Adjusting the printing scheme refers to adjusting the printing media, ink, and color values ​​within the printing scheme.

[0136] Adjusting the image parameters of the image to be printed includes, but is not limited to, adjusting the brightness, contrast, and saturation of the image to be printed.

[0137] In this embodiment, by determining the desired print image, when the desired print image does not match the print preview image, in response to the adjustment operation of the print scheme and / or the image parameters of the image to be printed, the print scheme and / or the image parameters of the image to be printed are adjusted until the print preview image matches the desired print image. This ensures that the generated print preview image meets the user's expectations, thereby ensuring that the final printed effect meets the user's expectations.

[0138] In one embodiment, the method further includes:

[0139] Determine the desired print image;

[0140] When the desired print image does not match the print preview image, in response to the adjustment operation of the print scheme and / or the image parameters of the image to be printed, the print scheme and / or the image parameters of the image to be printed are adjusted until the print preview image matches the desired print image.

[0141] The matching of the expected print image and the print preview image can be determined based on their pixel values. If the expected print image and the print preview image do not match, an adjustment operation for the image parameters of the print scheme and / or the image to be printed will be triggered. The server will respond to the adjustment operation for the image parameters of the print scheme and / or the image to be printed, and adjust the image parameters of the print scheme and / or the image to be printed according to the adjustment instructions carried in the adjustment operation until the print preview image matches the expected print image.

[0142] In this embodiment, by determining the desired print image, when the desired print image does not match the print preview image, in response to the adjustment operation of the print scheme and / or the image parameters of the image to be printed, the print scheme and / or the image parameters of the image to be printed are adjusted until the print preview image matches the desired print image. This can make the generated print preview image meet the user's expectations, thereby making the final printed effect meet the user's expectations.

[0143] This application also provides an application scenario in which the above-described method for generating print preview images is applied. Specifically, the method for generating print preview images is applied in this scenario as follows:

[0144] The default printing scheme corresponding to the mapping table is "water-based ink + paper". In the mapping table, the PreviewRGB value of node A corresponding to the input pixel value RGB_input=(250,0,0) is (230,10,10). The input pixel value RGB_input is the pixel value to be converted in the image to be printed.

[0145] Input the image to be printed into the printing device and determine the printing scheme for the image. The printing scheme for the image is "oil-based ink + PP film + saturation increased by 10%".

[0146] The printing scheme can be input into the color influence factor calculation model to obtain the gamut factor F_gamut=(1.10×1.05) / 0.85=1.36, red channel factor F_wb_r=1.02, green channel factor F_wb_g=1.0, blue channel factor F_wb_b=0.98, hue response function and saturation function.

[0147] If the first color value of node A is 0.95, then the initial color value of node A is 0.95 × 1.36 = 1.29, and the second color value after clipping is 1.0.

[0148] The temporary adjustment value for the red channel of node A is PR_temp = 230 × 1.02 × 1.0 = 235, the temporary adjustment value for the green channel is PG_temp = 10 × 1.0 × 1.0 = 10, and the temporary adjustment value for the blue channel is PB_temp = 10 × 0.98 × 1.0 = 10.

[0149] Color space conversion is performed based on the temporary adjustment values ​​of the red, green, and blue channels of node A, resulting in a third color value of 1.0 for node A. Based on the saturation function and the third color value of the node, a fourth color value S_final = 1.0 × 1.12 = 1.12 is obtained. This fourth color value of 1.12 is then cropped to 1.0. Finally, the target PreviewRGB value has R = 255. According to the formula luminance = 0.2126R + 0.7152G + 0.0722B, G = B = max([0.7874Y1 - 0.2126 × 255], MinInk), and the minimum MinInk value of the printing device is 5, we obtain G2 = B2 = 5. The final output target PreviewRGB = (255, 5, 5) for node A is redder and more saturated, matching the performance of oil-based ink on PP film. After obtaining the target PreviewRGB values ​​for each node, an updated mapping table can be obtained. Based on the updated mapping table, a print preview image of the image to be printed is generated. The desired print image is determined. If the desired print image does not match the print preview image, in response to adjustments to the image parameters of the printing scheme and / or the image to be printed, the image parameters of the printing scheme and / or the image to be printed are adjusted until the print preview image matches the desired print image. The overall flowchart of the print preview image generation method is as follows: Figure 4 As shown. Figure 5 The image to be printed. Figure 6 This is the print preview image corresponding to printing scheme 1. Figure 7This is the print preview image corresponding to printing scheme 2. Figure 8 This is the print preview image corresponding to printing scheme 3. Printing scheme 1 is water-based ink + PP film + color value adjustment, printing scheme 2 is water-based ink + paper + color value adjustment, and printing scheme 3 is oil-based ink + PP film + no color value adjustment. Figure 9 This is a schematic diagram of the target PreviewRGB in the automatically updated mapping table of the printing scheme.

[0150] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages in other steps.

[0151] Based on the same inventive concept, this application also provides a print preview image generation apparatus for implementing the print preview image generation method described above. The solution provided by this apparatus is similar to the implementation described in the above method; therefore, the specific limitations in one or more print preview image generation apparatus embodiments provided below can be found in the limitations of the print preview image generation method described above, and will not be repeated here.

[0152] In one embodiment, such as Figure 10 As shown, an apparatus for generating a print preview image is provided, comprising:

[0153] The factor calculation module is used to obtain the color gamut factor, white balance factor, hue response function, and saturation function based on the printing scheme of the image to be printed and the default printing scheme corresponding to the mapping table; the mapping table is a mapping table for converting the color space of the image to be printed.

[0154] The color value calculation module is used to obtain the first color value of each node based on the PreviewRGB value corresponding to each node in the mapping table;

[0155] The temporary RGB value calculation module is used to determine the second color value of a node based on the product of the gamut factor and the first color value of the node, and to obtain the temporary RGB value of the node based on the product of the white balance factor, the hue response function and the PreviewRGB value.

[0156] The update module is used to obtain the third color value of a node based on its temporary RGB value, obtain the fourth color value based on the saturation function and the third color value of the node, convert the fourth color value into the target PreviewRGB value, and obtain the updated mapping table.

[0157] The image generation module is used to generate print preview images of the images to be printed based on the updated mapping table.

[0158] Each module in the aforementioned device for generating print preview images can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the memory of a computer device as software, so that the processor can call and execute the operations corresponding to each module.

[0159] In one embodiment, a computer device is provided, which may be a server, and its internal structure diagram may be as follows: Figure 11 As shown. The computer device includes a processor, memory, and a network interface connected via a system bus. The processor provides computing and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system, computer programs, and a database. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The database stores the image to be printed, a default printing scheme, a printing scheme, a mapping table, PreviewRGB values, a first color value, a second color value, a third color value, a fourth color value, an updated mapping table, a target PreviewRGB value, and a print preview image. The network interface communicates with external terminals via a network connection. When executed by the processor, the computer program implements a method for generating a print preview image.

[0160] Those skilled in the art will understand that Figure 11 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0161] In one embodiment, a computer device is also provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps in the above method embodiments.

[0162] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon that, when executed by a processor, implements the steps in the above method embodiments.

[0163] In one embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps in the above method embodiments.

[0164] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments described above. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0165] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0166] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for generating a print preview image, characterized in that, The method includes: S1. Based on the printing scheme of the image to be printed and the default printing scheme corresponding to the mapping table, obtain the gamut factor, white balance factor, hue response function and saturation function; the mapping table is a mapping table for converting the color space of the image to be printed; S2. Based on the PreviewRGB values ​​corresponding to each node in the mapping table, obtain the first color value of each node; S3. Determine the second color value of the node based on the product of the gamut factor and the first color value of the node, and obtain the temporary RGB value of the node based on the product of the white balance factor, the hue response function and the PreviewRGB value. S4. Based on the temporary RGB value of the node, obtain the third color value of the node; based on the saturation function and the third color value of the node, obtain the fourth color value; convert the fourth color value into the target PreviewRGB value to obtain the updated mapping table. S5. Based on the updated mapping table, generate a print preview image of the image to be printed.

2. The method according to claim 1, characterized in that, The process of determining the second color value in step S3 includes: The initial color value is determined based on the product of the gamut factor and the first color value of the node; When the initial color value is greater than a first preset value, the first preset value is used as the second color value; When the initial color value is less than the second preset value, the second preset value is used as the second color value, and the first preset value is greater than the second preset value.

3. The method according to claim 1, characterized in that, The process of obtaining the mapping table in step S1 includes: Obtain a first mapping relationship between the color space of the image to be printed and the color space of the printing device, and a second mapping relationship between the color space of the printing device and the color space of the display device; the color space of the printing device is determined based on the model of the printing device and the default printing scheme; Based on the first mapping relationship and the second mapping relationship, a third mapping relationship is established between the color space in the image to be printed and the color space of the display device; Based on the third mapping relationship, the mapping table is obtained.

4. The method according to claim 1, characterized in that, The formula for calculating the gamut factor F_gamut in step S1 is as follows: ； The white balance factor includes a green channel factor, a red channel factor, and a blue channel factor. The calculation formula for the green channel factor F_wb_g is as follows: ； The formula for calculating the red channel factor F_wb_r is as follows: ； The formula for calculating the blue channel factor F_wb_b is as follows: ； Where Y1 is the theoretical color gamut coverage of the ink, Y2 is the ink absorption coefficient of the printing medium, Y is the reference color gamut coverage corresponding to the default printing scheme; k1, k2, and k3 are all fitting coefficients, and ΔCCT is the color temperature difference between the color temperature of the printing medium in the printing scheme and the color temperature of the printing medium in the default printing scheme.

5. The method according to claim 1, characterized in that, The temporary RGB values ​​in step S3 include the temporary adjustment value PR_temp for the red channel, the temporary adjustment value PG_temp for the green channel, and the temporary adjustment value PB_temp for the blue channel. The formula for calculating the temporary RGB values ​​is as follows: PR_temp= PR × F_wb_r × F_tone(PR / 255.0); PG_temp = PG × F_wb_g × F_tone(PG / 255.0); PB_temp = PB × F_wb_b × F_tone(PB / 255.0); Where PR is the red channel value in the PreviewRGB value, PG is the green channel value in the PreviewRGB value, PB is the blue channel value in the PreviewRGB value, F_wb_r is the red channel factor in the white balance factor, F_wb_g is the green channel factor in the white balance factor, F_wb_b is the blue channel factor in the white balance factor, and F_tone is the tone response function.

6. The method according to claim 1, characterized in that, The formula for calculating the fourth color value S_final in step S4 is as follows: S_final = S_temp × F_sat(ρ,S_temp); Where F_sat(ρ,S_temp) is the saturation function, S_temp is the third color value of the node, and ρ is the brightness of the node.

7. The method according to claim 1, characterized in that, The method further includes: Determine the desired print image; When the desired print image does not match the print preview image, in response to the adjustment operation of the print scheme and / or the image parameters of the image to be printed, the print scheme and / or the image parameters of the image to be printed are adjusted until the print preview image matches the desired print image.

8. An apparatus for generating a print preview image, characterized in that, The device includes: The factor calculation module is used to obtain the color gamut factor, white balance factor, hue response function, and saturation function based on the printing scheme of the image to be printed and the default printing scheme corresponding to the mapping table; the mapping table is a mapping table for converting the color space of the image to be printed. The color value calculation module is used to obtain the first color value of each node based on the PreviewRGB value corresponding to each node in the mapping table; The temporary RGB value calculation module is used to determine the second color value of the node based on the product of the color gamut factor and the first color value of the node, and to obtain the temporary RGB value of the node based on the product of the white balance factor, the hue response function and the PreviewRGB value. The update module is used to obtain a third color value of the node based on the temporary RGB value of the node, obtain a fourth color value based on the saturation function and the third color value of the node, convert the fourth color value into a target PreviewRGB value, and obtain an updated mapping table; An image generation module is used to generate a print preview image of the image to be printed based on the updated mapping table.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, It stores a computer program that, when executed by a processor, implements the steps of the method according to any one of claims 1 to 7.

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