CN117808902B

CN117808902B - Three-dimensional lookup table construction method, image processing method, device and storage medium

Info

Publication number: CN117808902B
Application number: CN202410234580.4A
Authority: CN
Inventors: 刘德志; 张艳红
Original assignee: Wuhan Haoyiyuan Technology Co ltd
Current assignee: Wuhan Haoyiyuan Technology Co ltd
Priority date: 2024-03-01
Filing date: 2024-03-01
Publication date: 2024-06-04
Anticipated expiration: 2044-03-01
Also published as: CN117808902A

Abstract

The embodiment of the application provides a three-dimensional lookup table construction method, an image processing method, a computer program product, equipment and a storage medium. When a three-dimensional lookup table for correcting an initial color in an image to a target color is constructed, the adjustment value of the target color in a certain channel can be obtained by adjusting the difference value of the channel values of the target color and the initial color in the channel by adopting different adjustment amplitudes for different target sampling points which need to be subjected to color correction in a plurality of sampling points. The adjustment amplitude of different target sampling points in a certain channel can be determined based on the proximity degree of the target sampling points and the channel values of the target colors in the channel, and/or based on the channel values of the target sampling points in the channel. In this way, a finer and more accurate three-dimensional lookup table can be constructed, so that finer color correction can be performed on the target image, and color faults in the corrected image are reduced.

Description

Three-dimensional lookup table construction method, image processing method, device and storage medium

Technical Field

The present application relates to the field of image processing technology, and in particular, to a method for constructing a three-dimensional lookup table, an image processing method, a computer program product, a device, and a storage medium.

Background

In the process of shooting an image, the shot image may have chromatic aberration due to the influence of various factors such as illumination conditions, external environment and the like, so that the image needs to be subjected to color correction processing to meet the requirement of a user on the color of the image. Currently, when performing color correction on an image, a three-dimensional lookup table (i.e., 3D-Lut) for performing color correction on an image is generally constructed, and based on the three-dimensional lookup table, one or more frames of images can be subjected to color correction.

At present, when a three-dimensional lookup table is constructed, sampling is usually performed at intervals under a certain color space to obtain a plurality of sampling points, and then the sampling points required to be subjected to color correction are determined from the plurality of sampling points based on an initial color to be corrected and a target color expected by a user. For all sampling points needing to be color corrected, the channel values of the sampling points in all channels are adjusted by adopting uniform adjustment amplitude at present, so that the adjusted channel values of the sampling points in all channels are obtained. The three-dimensional lookup table constructed by the method is used for carrying out color correction on the image, the color correction is not fine enough and is rough, and the corrected image is easy to have the problem of color fault. Therefore, it is necessary to provide a more refined color correction scheme to improve the display effect of the color corrected image.

Disclosure of Invention

In view of this, the present application provides a three-dimensional lookup table constructing method, an image processing method, a computer program product, an apparatus, and a storage medium.

According to a first aspect of the present application, there is provided a method of constructing a three-dimensional look-up table, the method comprising:

acquiring an initial color to be corrected and a corrected target color expected by a user;

Sampling at intervals in the channel value range of each channel of the target color space to obtain a plurality of sampling points, and determining a target sampling point to be subjected to color correction from the plurality of sampling points;

For each channel of the target color space of the target sampling point, determining an adjustment value of the channel, wherein the adjustment value is obtained by adjusting a difference value of the channel values of the target color and the initial color in the channel by using an adjustment amplitude of the channel, and the adjustment amplitude is determined based on a difference between the channel value of the target sampling point in the channel and the channel value of the target color in the channel and/or the channel value of the target sampling point in the channel;

And constructing a three-dimensional lookup table based on the original channel values of the target sampling points in each channel of the target color space and the adjustment values, wherein the three-dimensional lookup table is used for carrying out color correction on the image.

According to a second aspect of the present application, there is provided an image processing method, the method comprising:

acquiring a target image to be subjected to color correction;

The color correction processing is performed on the target image based on a pre-built three-dimensional lookup table, which is built based on the method mentioned in the first aspect.

According to a third aspect of the present application there is provided a computer program product comprising a computer program which, when executed by a processor, implements the method of the first and/or second aspects mentioned above.

According to a fourth aspect of the present application there is provided an electronic device comprising a processor, a memory, and a computer program stored in the memory for execution by the processor, the processor implementing the method of the first and/or second aspects as described above when the computer program is executed.

According to a fifth aspect of the present application there is provided a computer readable storage medium having stored thereon a computer program which when executed by a processor performs the method of the first and/or second aspects described above.

By applying the scheme provided by the application, when a three-dimensional lookup table for correcting the initial color in the image into the target color expected by the user is constructed, a plurality of sampling points can be obtained by sampling at intervals under the target color space, then the three-dimensional lookup table for correcting the color of the image is constructed based on the original channel value of each sampling point in each channel and the adjustment value of each sampling point in each channel, wherein in order to realize fine color correction, the target sampling points which need to be subjected to color correction in the plurality of sampling points can be subjected to differentiation processing when the adjustment values of the target sampling points in each channel are determined, and the adjustment values of different target sampling points in a certain channel can be obtained by adopting different adjustment amplitudes to adjust the difference values of the target color and the initial color in the channel. The adjustment amplitude of different target sampling points in a certain channel can be determined based on the proximity degree of the target sampling points and the channel values of the target colors in the channel, and/or based on the channel values of the target sampling points in the channel. In this way, a finer and more accurate three-dimensional lookup table can be constructed, so that finer color correction can be performed on the target image, and color faults in the corrected image are reduced.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application as claimed.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort to a person skilled in the art.

FIG. 1 is a schematic diagram of a method of constructing a three-dimensional look-up table according to one embodiment of the present application.

FIG. 2 is a schematic diagram of an interactive interface for inputting an initial color and a target color according to one embodiment of the application.

FIG. 3 is a schematic diagram of sampling at intervals to obtain a plurality of sampling points according to one embodiment of the present application.

FIG. 4 is a schematic diagram of a three-dimensional look-up table according to one embodiment of the application.

Fig. 5 is a schematic diagram of the logic structure of an electronic device according to an embodiment of the application.

Detailed Description

The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

At present, when a three-dimensional lookup table is constructed, sampling is usually performed at intervals under a certain color space to obtain a plurality of sampling points, and then the sampling points required to be subjected to color correction are determined from the plurality of sampling points based on an initial color to be corrected and a target color expected by a user. For all sampling points needing to be color corrected, the channel values of the sampling points in all channels are adjusted by adopting uniform adjustment amplitude at present, so that the adjusted channel values of the sampling points in all channels are obtained. The three-dimensional lookup table constructed by the method is used for carrying out color correction on the image, the color correction is not fine enough and is rough, and the corrected image is easy to have the problem of color fault.

For example, taking the example of representing an image color in the HSL color space, assume that the user wishes to correct an initial color (h=20°, l=0.1, s=0.1) in the image to a target color (h=30°, l=0.2, s=0.2). One processing manner that is easy to think is that sampling is performed at intervals in the HSL space to obtain a plurality of sampling points, and then a sampling point that needs to be color-corrected and a sampling point that does not need to be color-corrected can be determined from the plurality of sampling points, where the sampling point that needs to be color-corrected can be selected based on actual requirements, for example, for each color channel, the sampling points that need to be color-corrected can be consistent, for example, channel values of H, L, S channels meet the following conditions: the sampling points of H epsilon (20-30 degrees), L epsilon (0.1-0.2) and S epsilon (0.1-0.2) are sampling points needing to be subjected to color correction, and the rest sampling points are sampling points needing not to be subjected to color correction. Wherein, for the sampling points which do not need to be color corrected, the adjustment value of the sampling points in H, L, S channels is 0, for the sampling points which need to be color corrected, the adjustment values of the sampling points in H channels are the same, namely, the adjustment values of the sampling points in L channels are the same, namely, the adjustment values of the sampling points in S channels are the same, namely, the adjustment values of the sampling points in L channels are the adjustment values of the sampling points in the L channels are the adjustment values of the sampling points in 30 ° -20 ° =10°.1. A three-dimensional look-up table may then be constructed based on the original channel values for each sample point at H, L, S channels and the adjusted channel values for each sample point at H, L, S channels. For each pixel point in the image to be subjected to color correction, the channel value of each channel of the pixel point after the color correction can be determined by searching the three-dimensional lookup table, so that the color correction of the image is completed.

It is obvious that when the three-dimensional lookup table is constructed, the color adjustment amplitude is consistent for all sampling points needing to be subjected to color correction, namely, the sampling points are adjusted by adopting a uniform adjustment value. Therefore, when the three-dimensional lookup table is used for correcting the color of the image, the color of all the pixels needing to be corrected in the image is correspondingly adjusted by adopting the same adjustment range, the color of different pixels is different from the color of the target color, the color of the pixels is adjusted by adopting the uniform adjustment range, the color of the pixels is rough, and if the color of the pixels which are close to the target color is also adjusted by adopting the larger adjustment range, the color of the pixels with the color adjusted and the color of the pixels with the adjacent peripheral colors are in fault. In addition, if the sampling points with different saturation and brightness are all adjusted by adopting uniform adjustment amplitude, the problems of overexposure and supersaturation of the image are easy to occur, so that the color of the image after color correction is unnatural, and the effect of the image after color correction is poor.

Based on this, first, the embodiment of the application provides a method for constructing a three-dimensional lookup table, so as to construct a more accurate and refined three-dimensional lookup table for performing more refined color correction on an image. For example, if the three-dimensional lookup table to be constructed is used for correcting an initial color in an image to a target color desired by a user, a plurality of sampling points can be obtained by sampling at intervals in a target color space, then the three-dimensional lookup table for correcting the color of the image is constructed based on original channel values of the sampling points in each channel and adjustment values of the sampling points in each channel, wherein in order to achieve fine color correction, for target sampling points which need to be subjected to color correction in a plurality of sampling points, when the adjustment values of the target sampling points in each channel are determined, differentiation processing can be performed on the target sampling points, and the adjustment values of different target sampling points in a certain channel can be obtained by adjusting differences of the channel values of the target color and the initial color in each channel by adopting different adjustment amplitudes. The adjustment amplitude of different target sampling points in a certain channel can be determined based on the proximity degree of the target sampling points and the channel values of the target colors in the channel, and/or based on the channel values of the target sampling points in the channel. For example, if the proximity is large, the adjustment amplitude may be appropriately reduced, or if the channel value itself of the channel is large, the adjustment amplitude may be appropriately reduced, or the like. Wherein, for different channels, the adjustment amplitude can be flexibly set based on the characteristics of the channel.

The adjustment amplitude can be set differently for different target sampling points to construct a three-dimensional lookup table, so that more refined color correction can be performed on the target image, and color fault phenomenon in the corrected image is reduced.

The method for constructing the three-dimensional lookup table in the embodiment of the application can be executed by various electronic devices such as a mobile phone, a camera, a computer, a cloud server and the like. For example, in some scenarios, the method may be used in a device (such as a camera) with an image acquisition function, where after acquiring a target image, a user may input an initial color to be corrected and a target color desired by the user through an interactive interface of the device, so that the device may automatically construct a three-dimensional lookup table based on information set by the user, and then perform color correction on one or more acquired images using the constructed three-dimensional lookup table. Of course, in some scenes, the three-dimensional lookup table may be also be built by a computer, a cloud server, and other devices, and after the device (for example, a camera) with an image acquisition function acquires the image, the device sends the image to the device, and the device performs color correction processing on the image based on the pre-built three-dimensional lookup table.

As shown in fig. 1, the method for constructing the three-dimensional lookup table may include the following steps:

s102, acquiring an initial color to be corrected and a corrected target color expected by a user;

In step S102, an initial color to be corrected and a target color after color correction of the initial color desired by the user may be acquired. The initial color may be a color corresponding to a single pixel, i.e., a specific color represented by a certain color coordinate, for example, the initial color is (h=20°, l=0.1, s=0.1), or the initial color may be a designated color range, for example, the initial color is a whole color range of red, green, etc., or the initial color is a color between two color coordinates, for example, (h=20 °, l=0.1, s=0.1) — (h=60 °, l=0.1, s=0.1), and the target color may be a specific color represented by a certain color coordinate, for example, the target color is (h=60 °, l=0.5, s=0.5).

There are various ways to obtain the initial color and the target color, for example, an interactive interface may be provided, through which a user may directly input the color coordinates or the color coordinate ranges corresponding to the initial color and the target color. Or the image to be subjected to color correction can be displayed in the interactive interface, a user can select a certain image area or a certain pixel point from the image, and the initial color or the target color can be determined based on the color of the image area or the pixel point selected by the user. Or the color setting control can be displayed in the interactive interface, the user can set the channel value of the initial color or the target color in each channel through the color setting control, and meanwhile, when the user sets the channel value of each channel by utilizing the color setting control, the color currently set by the user can be displayed through the preview window. As shown in fig. 2, for example, a color setting control may be displayed on the interactive interface, for H, L, S channels, the user may adjust the channel values of H, L, S channels by adjusting the adjustment slider in the color setting control, and at the same time, the color currently set by the user may be displayed in the preview window, so that the user determines whether the color is the color desired by the user.

S104, sampling at intervals in the range of channel values of all channels of a target color space to obtain a plurality of sampling points, and determining a target sampling point to be subjected to color correction from the plurality of sampling points;

in step S104, since the finally constructed three-dimensional lookup table needs to cover the pixel points of the entire color space, sampling can be performed at intervals within the channel value ranges of the respective channels of the target color space, so as to obtain a plurality of sampling points. The target color space may be an RGB color space, an HSL color space, an HSV color space, or the like. For example, taking the target color space as the HSL color space as an example, for H, S, L channels, sampling can be performed at intervals in the channel value ranges of the three channels, so as to obtain a plurality of sampling points. For example, as shown in fig. 3, for the H channel, the value of the H channel is 0 to 360 °, one sampling value may be collected at intervals of 10 ° or 5 °, for the S and L channels, the value of the H channel is 0 to 1, one sampling value may be collected at intervals of 0.1 or 0.2, and then the sampling values obtained by collecting the three channels may be combined to obtain a plurality of sampling points. For example, (h=0°, l= 0,S =0) (h=5°, l= 0,S =0), (h=10°, l= 0,S =0), (h=5°, l=0.1, s=0), (h=5°, l= 0,S =0.1), and the like. Wherein the sampling interval may be flexibly set based on the size of the three-dimensional look-up table that is desired to be built, e.g. if a finer three-dimensional look-up table is desired to be built, the sampling interval may be set smaller, otherwise the sampling interval may be set larger.

Since not all sampling points need to be color-corrected, after obtaining a plurality of sampling points, a target sampling point that needs to be color-corrected may be determined from the plurality of sampling points, where the target sampling point may be determined based on an initial color set by a user and a target color. For example, the target sampling point may be a sampling point with the same color as the initial color, or a sampling point with a color located in a color range where the initial color is located, or a sampling point with a proximity degree between the color and the initial color being greater than a preset proximity degree threshold value, which may be set based on actual requirements.

S106, determining an adjustment value of each channel of the target color space for the target sampling point, wherein the adjustment value is obtained by adjusting the difference value of the channel value of each channel of the target color and the initial color by using the adjustment amplitude of the channel, and the adjustment amplitude is determined based on the difference of the channel values of each channel of the target sampling point and the target color and/or the channel value of each channel of the target sampling point;

In step S106, after the target sampling points are obtained, for each channel of the target color space for each target sampling point, an adjustment value of the channel may be determined. For example, if the target color space is the HSL space, the adjustment values of the target sampling point in the three channels H, S, L may be determined, and the adjusted channel values of the target sampling point after color correction in the three channels may be obtained by adding or subtracting the adjustment values to or from the original values of the three channels by using the target sampling point.

In the related art, for any channel, the adjustment values of different sampling points are the same, namely the difference value between the target color and the initial color in the channel, so that accurate regulation and control cannot be realized in the mode, and the color fault problem is easy to occur. In the embodiment of the application, different adjustment amplitudes can be set for different target sampling points of any channel, and the difference value between the target color and the initial color in the channel value of the channel is adjusted by using the adjustment amplitudes to obtain a final adjustment value. For some channels (for example, hue channels in HSL color space), considering that the approach degree of different target sampling points and target colors in the channel values of the channels is different, if the approach degree of the two is higher, the adjustment amplitude can be reduced by a little, otherwise, the adjustment amplitude can be increased by a little. Thus, when determining the adjustment amplitude of the different target sampling points in the channel, the difference determination of the target sampling points and the channel value of the target color in the channel can be combined. Whereas for some channels (e.g., the luminance channel of the HSL space), it is considered that if the luminance of the target sampling point itself is large, if a large adjustment amplitude is also adopted, the problem of overexposure easily occurs. Thus, the adjustment amplitude may also be set in connection with the channel value of the channel at the point of use, e.g. the channel value is larger and the adjustment amplitude may be set smaller. Of course, for other types of color spaces, such as HSV color space, YUV color space, or RGB color space, the adjustment amplitude of each channel may be flexibly set based on the characteristics of the channel, for example, may be set based on the difference between the channel value of the channel and the target color, may be set based on the channel value of the channel and the target sampling point, or may be set simultaneously.

In addition, considering that the different channels may also affect each other, for example, when the brightness of the target sampling point is adjusted, if the saturation of the target sampling point is low, the adjusting amplitude is greatly prone to the problem of overexposure, for example, the saturation and the hue may also affect each other, so when the adjusting amplitude of the hue (H channel) of the target sampling point is determined, the saturation determination of the target sampling point may also be combined at the same time. Or the saturation also affects the brightness to some extent, so that when determining the adjustment amplitude of the brightness (L channel) of the target sampling point, the saturation determination of the target sampling point may be combined at the same time.

In summary, for any channel, when determining the adjustment amplitude of different target sampling points in the channel, the adjustment amplitude may be determined by combining the difference between the channel values of the target sampling points and the channel values of the target colors in the channel, or of course, the adjustment amplitude may be determined by combining the channel values of the target sampling points in other channels, or by combining the difference between the channel values of the target sampling points and the channel values of the target colors in other channels.

S108, constructing a three-dimensional lookup table based on the channel values of the target sampling points in each channel of the target color space and the adjustment values, wherein the three-dimensional lookup table is used for carrying out color correction on the image.

In step S108, after determining the adjustment values of the channels of the target sampling points in the target color space, the adjusted channel values of the target sampling points in the channels may be determined based on the original channel values of the target sampling points in the channels and the adjustment values, so that a mapping relationship between the original channel values of the target sampling points and the adjusted channel values may be established, and a three-dimensional lookup table may be further constructed.

Wherein, after the three-dimensional lookup table is obtained, the three-dimensional lookup table can be utilized to perform color correction on the image. For example, for any image, if the initial color in the image is to be corrected to the target color, the image may be color corrected by means of the three-dimensional lookup table. For example, for any pixel point in the image, a sampling point whose original channel value is the same as the channel value of each channel of the pixel point can be found from the three-dimensional lookup table, and then the adjusted channel value of the sampling point in each channel is used as the channel value after color correction of the pixel point. Of course, if no sampling point is found from the three-dimensional lookup table, where the original channel value of each channel is the same as the channel value of each channel of the pixel, the channel value after color correction of the pixel may be determined by interpolation.

When the user sets the initial color to be adjusted, the initial color may be a color of a single pixel (i.e., a color expressed by a single color coordinate), for example, the initial color is (h=20°, l=0.1, s=0.1). For this case, if color correction is performed only on the pixel point with the color of the initial color, some more abrupt pixel areas may appear in the corrected image, which may affect the display effect of the image. Thus, in some embodiments, if the initial color is a single pixel color, then at the time of color correction, color correction may be performed on all pixel points whose colors lie in the interval between the initial color and the target color, i.e., the target sampling point is all sampling points whose colors lie in the interval between the initial color and the target color.

In some scenarios, the sampling points that need to be color corrected may be consistent for each color channel. For example, if the initial color is (h=20°, l=0.1, s=0.1), the target color is (h=30°, l=0.2, s=0.2), and for H, L, S channels, sampling points of H e (20 ° -30 °), S e (0.1-0.2), and L e (0.1-0.2) can be used as sampling points of the three channels that need to be color corrected.

In some scenarios, in order to achieve fine tuning, for each channel, the target sampling points that need to be corrected for the channel value of that channel may be set differently based on the characteristics of that channel, i.e. the target sampling points of different channels may not be identical. For example, taking HLS color space as an example, since the H-channel, S-channel, and color representation are related, the target sampling point for which color correction is required (i.e., channel value correction is required for the channel value of the channel) for these two channels may be a sampling point where the channel values of the above two channels are located within a range interval formed by the channel values of the corresponding channels, respectively. For the L channel, the target sampling point to be color corrected may be a sampling point where the channel value of the H channel is located in a range interval formed by the channel values of the H channel and the target color, and the channel value of the S channel is greater than the first preset threshold and the channel value of the L channel is greater than the second preset threshold. The first preset threshold value and the second preset threshold value may be the same or different, and the purpose of the first preset threshold value and the second preset threshold value is to ensure that the saturation and the brightness of the adopted point needing to perform brightness correction are not too low.

For example, the initial color is (h=20°, l=0.1, s=0.1), the target color is (h=30°, l=0.2, s=0.2), and for H, S channels, the sampling points of H e (20 ° -30 °) and S e (0.1-0.2) are sampling points to be corrected, and the remaining sampling points are sampling points to be corrected without color correction. For the L channel, sampling points of H epsilon (20-30 degrees), S epsilon (0.065-1) and L epsilon (0.065-1) are sampling points which need to be subjected to color correction, and the rest sampling points are sampling points which do not need to be subjected to color correction.

In some embodiments, to make color transition of the color corrected image area and the surrounding area more natural, the target sampling points for both the H-channel and the S-channel that require color correction (i.e., that require channel value correction for the channel values of the channel) may be sampling points where the channel values of the H-channel are in the first range interval and the channel values of the S-channel are in the second range interval. For the L channel, the target sampling point to be color corrected may be a sampling point where the channel value of the H channel is located in the first range section, the channel value of the S channel is greater than the first preset threshold, and the channel value of the L channel is greater than the second preset threshold. The first range section includes a range section formed by channel values of the H channel for each of the initial color and the target color. The second range section is a range section formed by channel values of the S channel for each of the initial color and the target color.

For example, the initial color is (h=20°, l=0.1, s=0.1), the target color is (h=30°, l=0.2, s=0.2), and for the H channel, the range interval formed by the channel values of the H channel is H e (20 ° -30 °) for each of the initial color and the target color, so that the corrected region and the adjacent region of the corrected image transition more naturally, and thus the first target range interval may be slightly larger than the range interval, that is, the boundary of the interval expands outward, for example, may be H e (25 ° -35 °). For the S channel, the range interval formed by the channel values of the initial color and the target color in the S channel is S epsilon (0.1-0.2), and thus the second target range interval is S epsilon (0.1-0.2). Namely, for the H channel and the S channel, the target sampling points needing to be subjected to color correction are sampling points of H epsilon (25-35 degrees) and S epsilon (0.1-0.2), and for the L channel, the target sampling points needing to be subjected to color correction are sampling points of H epsilon (25-35 degrees), S epsilon (0.065-1) and L epsilon (0.065-1).

Of course, in some embodiments, the initial color may be a specific color range, for example, the initial color is a color of a color range of (h=20°, l=0.1, s=0.1) - (h=60°, l=0.2, s=0.2), and when performing color correction, color correction may be performed on sampling points whose color is located in the color range.

In some scenarios, the sampling points that need to be color corrected may be consistent for each color channel. For example, if the initial colors are (h=20°, l=0.1, s=0.1)/(h=60°, l=0.2, s=0.2), then for H, L, S channels, sampling points of H e (20 ° -60 °), S e (0.1-0.2), L e (0.1-0.2) can be used as sampling points of the three channels that need to be color corrected.

In some scenarios, in order to achieve fine tuning, for each channel, the target sampling points that need to be color-corrected (i.e., the channel values of that channel are corrected) may be set differently based on the characteristics of that channel, i.e., the target sampling points of different channels may not be identical. For example, taking HLS color space as an example, since the H-channel, S-channel, and color representation are related, the target sampling points for which color correction is required (i.e., channel value correction is required for the channel values of the channels) may be sampling points where the channel values of the two channels are located within the range interval formed by the channel values of the corresponding channels, respectively. For the L channel, the target sampling point to be color corrected may be a sampling point where the channel value of the H channel is located in a range interval formed by the channel values of the H channel and the channel value of the S channel is greater than the first preset threshold and the channel value of the L channel is greater than the second preset threshold, respectively, at the color boundary of the designated color range. The first preset threshold value and the second preset threshold value may be the same or different, and the purpose of the first preset threshold value and the second preset threshold value is to ensure that the saturation and the brightness of the sampling point needing brightness correction are not too low.

For example, the initial color is (h=20°, l=0.1, s=0.1)/(h=60°, l=0.2, s=0.2), and for H, S channels, the sampling points of H e (20 ° -60 °) and S e (0.1-0.2) are sampling points that need to be color-corrected, and the remaining sampling points are sampling points that do not need to be color-corrected. For the L channel, sampling points of H epsilon (20-60 degrees), S epsilon (0.065-1) and L epsilon (0.065-1) are sampling points which need to be subjected to color correction, and the rest sampling points are sampling points which do not need to be subjected to color correction.

In some embodiments, to make color transition of the color corrected image area and the surrounding area more natural, the target sampling points for both the H-channel and the S-channel that require color correction (i.e., that require channel value correction for the channel values of the channel) may be sampling points where the channel values of the H-channel are in the first range interval and the S-channel values are in the second range interval. For the L channel, the target sampling point to be color corrected may be a sampling point where the channel value of the H channel is located in the first range section, the channel value of the S channel is greater than the first preset threshold, and the channel value of the L channel is greater than the second preset threshold. The first range section includes range sections in which color boundaries of the specified color range are each composed of channel values of H channels. The second range section is a range section formed by the channel values of the S channel at each of the color boundaries of the specified color range.

For example, the initial color is (h=30°, l=0.1, s=0.1)/(h=60°, l=0.2, s=0.2) and the range interval of each specified color range formed by the channel values of the H channel is H e (30 ° -60 °) for the H channel, so that the corrected image correction area and the adjacent area transition more naturally, and therefore, the first range interval may be slightly larger than the range interval, i.e., the boundary of the interval is extended outward, for example, H e (30 ° -70 °). For the S channel, the range interval formed by the channel values of the S channel is S e (0.1-0.2), so that the second range interval is S e (0.1-0.2). The sampling points of H epsilon (30-70 degrees) and S epsilon (0.1-0.2) are sampling points which need to be subjected to color correction aiming at H, S channels, and the rest sampling points are sampling points which do not need to be subjected to color correction. The channel value for the L channel meets the following condition: the sampling points of H epsilon (30-70 degrees), S epsilon (0.065-1) and L epsilon (0.065-1) are sampling points needing to be subjected to color correction, and the rest sampling points are sampling points needing not to be subjected to color correction.

In some embodiments, if the initial color is a single pixel color, the difference between the channel values of the target color and the initial color in a certain channel is the difference between the channel values of the two color coordinates in the corresponding channel.

In some embodiments, if the initial color is a specified color range, the difference between the channel values of the target color and the initial color at a channel is the greater of the difference between the channel values of the two boundary colors of the specified color range at the channel and the channel value of the target color at the channel. For example, the specified color range is (h=20°, l=0.1, s=0.1) to (h=40°, l=0.2, s=0.2), and the target color is (h=60°, l=0.2, s=0.2), and for the H channel, the channel values of the two boundary colors in the H channel are 20 ° and 40 °, respectively, and the difference between the two boundary colors and the channel value of the target color in the H channel are: 60 ° -20 ° =40°, 60 ° -40 ° =20°, so the larger one (i.e. 40 °) of the two can be selected as the difference between the target color and the initial color in the H channel, and the difference can be adjusted by using the adjustment amplitude to obtain the adjustment value of the target sampling point in the H channel. A similar approach is also used for other channels.

In some embodiments, for the case where the initial color is a single pixel color, if the target color space is the HSL/HSV color space, the relationship between hue and saturation is considered to be relatively close, i.e., the magnitude of saturation affects the final rendering of the color to some extent. Therefore, for the H-channel or the S-channel in the color space, when determining the adjustment amplitudes of the two channels at each target sampling point, the channel value of the H-channel at the target sampling point and the channel value of the H-channel at the target color and the channel value of the S-channel at the target sampling point can be simultaneously combined for determination.

In some embodiments, when the adjustment amplitude of the target sampling point H or S channel is determined based on the difference between the channel value of the target sampling point in the H channel and the channel value of the target color in the H channel and the channel value of the target sampling point in the S channel, in the case where the difference between the channel value of the target sampling point in the S channel and the channel value of the target color in the S channel is fixed, the adjustment amplitude increases as the difference between the channel value of the target sampling point in the H channel and the channel value of the target color in the H channel increases. That is, if the hue of the target sampling point and the hue of the target color are closer, the adjustment amplitude is smaller, whereas if the hue is closer, the adjustment amplitude is larger.

In some embodiments, when the adjustment amplitude of the target sampling point H or S channel is determined based on the difference between the channel value of the target sampling point H channel and the channel value of the target color H channel and the channel value of the target sampling point S channel, the adjustment amplitude is increased and then decreased as the channel value of the target sampling point S channel increases in the value range of the S channel under the condition that the difference between the channel value of the target sampling point H channel and the channel value of the target color H channel is fixed.

The perception of color by the human eye is considered non-linear, that is, the sensitivity of the human eye to color variations is different in different saturation ranges. In the lower saturation range the human eye is more sensitive to subtle color changes, so a smaller change in the adjustment amplitude is sufficient to produce a significant effect. However, as saturation increases, the sensitivity of the human eye to color changes gradually decreases. In this case, a larger adjustment range is required in order to generate a significant change. However, the adjustment amplitude cannot be increased all the time, and if the saturation is increased to a certain extent, the problem of supersaturation is likely to occur, and the display effect of the image is affected, so that the adjustment amplitude needs to be reduced at this time.

Therefore, the adjustment amplitude is increased and then reduced, so that the perception characteristic of human color on color change can be better adapted. In addition, the adjustment amplitude is increased and then reduced, so that the situation that the image is oversaturated due to the fact that the saturation is excessively increased can be avoided. Excessive saturation increases can lead to color distortion and unnatural effects, and therefore, moderate adjustment of amplitude can preserve the nature and balance of the image. For example, taking the value range of the saturation (S) as 0 to 1 as an example, in the range of 0 to 0.6, the adjustment amplitude gradually increases as the saturation (i.e., the value of the S channel) increases, and in the range of 0.6 to 1, the adjustment amplitude gradually decreases as the saturation increases.

In some embodiments, the adjustment amplitude of the target sampling point in the H-channel may be equal to the adjustment amplitude of the target sampling point in the S-channel.

In some embodiments, if the initial color is the designated color range and the target color space is the HSL/HSV color space, the adjustment value of the target sampling point in the H channel under the color space may directly take the difference between the channel value of the target color in the H channel and the channel value of the initial color in the H channel, that is, the adjustment value of each target sampling point in the H channel is consistent.

For the S channel in the color space, the adjustment value of the target sampling point in the channel may be set differently, that is, the difference between the channel value of the target color in the S channel and the channel value of the initial color in the S channel is adjusted by using the adjustment amplitude. The adjustment amplitude may be determined based on a channel value of the target sampling point in the S channel.

In some embodiments, as the difference between the channel value of the target sampling point in the S channel and the channel value of the target color in the S channel increases, the adjustment amplitude increases and decreases first, for the specific reasons explained above. For example, taking the value range of the saturation (S) as 0 to 1 as an example, in the range of 0 to 0.6, the adjustment amplitude gradually increases as the saturation (i.e., the value of the S channel) increases, and in the range of 0.6 to 1, the adjustment amplitude gradually decreases as the saturation increases.

In some embodiments, if the target color space is the HSL color space, for the L channel in the HSL color space, the adjustment amplitude of the target sampling point in the channel may be determined based on the channel value of the target sampling point in the L channel and the channel value of the target sampling point in the S channel.

In some embodiments, if the target color space is an HSV color space, for a V-channel in the HSV color space, the adjustment amplitude of the target sampling point at the channel may be determined based on the channel value of the target sampling point at the V-channel and the channel value of the target sampling point at the S-channel.

In order to better protect the detail and color information of the image and obtain a more natural and balanced visual effect, when adjusting the brightness, the adjustment amplitude can be determined based on the channel value of the target sampling point in the L or V channel and the saturation of the target sampling point at the same time. Considering that the perception of luminance by the human visual system is non-linear, the human eye is more sensitive to changes in luminance for low luminance areas, and therefore a smaller magnitude of luminance adjustment is sufficient to produce a perceptible change. For high brightness areas, the human eye has a lower sensitivity to brightness variations, and therefore a greater brightness adjustment range is required to produce a significant change. Whereas in areas where saturation is low, the color information is relatively small, mainly in gray scale, and if the brightness adjustment amplitude is too large, image distortion or overexposure may be caused, and therefore, in these areas, the brightness adjustment amplitude may be set smaller in order to protect the color information and details. In the areas with high saturation, the brightness adjustment range is larger than the saturation, so that the brightness and contrast of the color can be better highlighted, and therefore, the brightness adjustment range can be set larger in the areas.

Similarly, for a region with higher brightness, if the brightness adjustment range is too large, the problem of overexposure easily occurs, so that when the brightness is increased to a certain extent, the adjustment range can be reduced appropriately, while for a region with smaller brightness, the adjustment range can be set to be larger, so that the brightness of the image is improved.

Thus, in some embodiments, the higher the saturation of the target sample point, the greater the adjustment amplitude of the L or V channel, and the greater the brightness of the target sample point, the greater the adjustment amplitude of the L or V channel. In general, the human eye is more sensitive to subtle brightness variations in the lower brightness range. Thus, a smaller adjustment amplitude is sufficient to produce a significant brightness change. As brightness increases, we progressively decrease in sensitivity to brightness changes, requiring greater adjustment amplitude to produce significant changes. When the brightness is increased to a certain degree, if the adjustment amplitude is still relatively large, the overexposure problem is liable to occur, and therefore, the brightness can be reduced appropriately.

The adjusting amplitude of the L or V channel is increased and then reduced, so that the method can adapt to the characteristics of human eyes, and the situation that the image is overexposed or excessively dark due to excessive brightness adjustment can be avoided. An excessive increase in brightness may cause image distortion, while an excessive decrease in brightness may cause loss of detail. By increasing and then decreasing the adjustment amplitude, a moderate brightness adjustment can be performed while maintaining the image natural and balanced.

In some embodiments, for other sampling points of the plurality of sampling points than the target sampling point, since the sampling points do not need to be color corrected, the adjustment value of the sampling points in each channel of the target color space is 0. The three-dimensional lookup table may then be constructed based on the original channel values and adjustment values for the target sample points for each channel and the original channel values and adjustment values for the other sample points for each channel. As shown in fig. 4, a three-dimensional lookup table may be used to indicate the mapping of the original channel values of the sampling points at each channel to the adjusted channel values.

Furthermore, the embodiment of the application also provides an image processing method which can be executed by various electronic devices such as a mobile phone, a camera, a computer, a cloud server and the like. The image processing method may include the steps of:

acquiring a target image to be subjected to color correction;

The color correction processing is performed on the target image based on a pre-built three-dimensional lookup table, which is built based on the method mentioned in any of the above embodiments.

The specific details of constructing the three-dimensional lookup table may refer to the descriptions in the above embodiments, and are not repeated herein.

In some embodiments, considering that the HSL/HSV color space is more in line with the human eye vision requirement, the user typically sets both the initial color and the target color in the color space, and builds a three-dimensional lookup table in the color space when building the three-dimensional lookup table, i.e., the built three-dimensional lookup table is typically an HSL/HSV lookup table. When the three-dimensional lookup table is used for carrying out color correction on the image, if the image is an RGB format image, the RGB format image can be converted into an HSL/HSV format image, then the HSL/HSV lookup table is used for carrying out color correction on the image, and then the corrected image is converted into the RGB format image. Considering that the color correction is performed in a sampling manner, format conversion needs to be performed on all pixel points in an image twice, the data processing amount is large, and the processing efficiency is low. In consideration of scenes with high requirements on real-time performance of image color correction such as live broadcast and the like, the processing speed is high, in order to improve processing efficiency, after a three-dimensional lookup table is constructed, the HSL/HSV lookup table can be converted into an RGB lookup table, and then color correction is carried out on an RGB format image based on the RGB lookup table, so that processing efficiency is improved.

The solutions of the foregoing embodiments may be freely combined to obtain a new solution without any conflict, for reasons of space, which are not exemplified herein.

Furthermore, embodiments of the present application provide a computer program product comprising a computer program which, when executed by a processor, implements the method mentioned in any of the above embodiments.

The embodiment of the present application further provides an electronic device, as shown in fig. 5, where the electronic device includes a processor 51, a memory 52, and a computer program stored in the memory 52 and executable by the processor 51, where the processor 51 executes the computer program to implement the method mentioned in any one of the foregoing embodiments.

Accordingly, an embodiment of the present application further provides a computer storage medium having a computer program stored therein, which when executed by a processor, implements the method in any of the above embodiments.

Embodiments of the application may take the form of a computer program product embodied on one or more storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) having program code embodied therein. Computer-usable storage media include both permanent and non-permanent, removable and non-removable media, and information storage may be implemented by any method or technology. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of storage media for a computer include, but are not limited to: phase change memory (PRAM), static Random Access Memory (SRAM), dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), read Only Memory (ROM), electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), digital Versatile Disks (DVD) or other optical storage, magnetic cassettes, magnetic disks or other magnetic storage devices, or any other non-transmission medium, may be used to store information that may be accessed by a computing device.

For the device embodiments, reference is made to the description of the method embodiments for the relevant points, since they essentially correspond to the method embodiments. The apparatus embodiments described above are merely illustrative, wherein the elements illustrated as separate elements may or may not be physically separate, and the elements shown as elements may or may not be physical elements, may be located in one place, or may be distributed over a plurality of network elements. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art will understand and implement the present invention without undue burden.

The user information (including but not limited to user equipment information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, presented data, etc.) related to the present application are information and data authorized by the user or fully authorized by each party, and the collection, use and processing of related data is required to comply with the relevant laws and regulations and standards of the relevant country and region, and is provided with corresponding operation entries for the user to select authorization or rejection.

It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

The foregoing has outlined rather broadly the methods and apparatus provided in embodiments of the present application in order that the detailed description of the principles and embodiments of the present application may be implemented in any way that is used to facilitate the understanding of the method and core concepts of the present application; meanwhile, as those skilled in the art will appreciate, the present application is not limited to the above description, since modifications may be made in the specific embodiments and application ranges according to the idea of the present application.

Claims

1. A method of constructing a three-dimensional look-up table, the method comprising:

2. The method of claim 1, wherein if the initial color is a color of a single pixel, the color of the target sample point is located in an interval between the initial color and the target color; if the initial color is a specified color range, the color of the target sampling point is positioned in the specified color range;

and/or

If the initial color is the designated color range, the difference value between the channel values of the target color and the initial color in the channel is: the two boundary colors of the specified color range are each the greater of the differences in the channel value of the channel from the channel value of the target color in the channel.

3. The method of claim 1, wherein if the initial color is a single pixel color, the channel is an H-channel or an S-channel in the HSL/HSV color space, the adjusting the amplitude is determined based on a difference between a channel value of the target sampling point in the H-channel and a channel value of the target color in the H-channel, and a channel value of the target sampling point in the S-channel, comprising:

under the condition that the channel value of the target sampling point in the S channel is fixed, the adjustment amplitude is increased along with the increase of the difference between the channel value of the target sampling point in the H channel and the channel value of the target color in the H channel;

under the condition that the difference between the channel value of the target sampling point in the H channel and the channel value of the target color in the H channel is fixed, in the range of the channel value of the S channel, as the channel value of the target sampling point in the S channel increases, the adjustment amplitude increases first and then decreases.

4. A method according to claim 3, wherein the adjustment amplitude of the target sample point in the H-channel is equal to the adjustment amplitude of the target sample point in the S-channel.

5. The method of claim 1, wherein if the initial color is a designated color range and the channel is an H-channel in HSL/HSV color space, the adjustment value is a difference between a channel value of the target color in the H-channel and a channel value of the initial color in the H-channel;

And if the initial color is a designated color range and the channel is an S channel in the HSL/HSV color space, determining the adjustment amplitude based on the channel value of the target sampling point in the S channel.

6. The method of claim 5, wherein the adjustment amplitude increases and then decreases as the channel value of the target sample point increases in the S channel within the range of channel values of the S channel.

7. The method of claim 1, wherein if the channel is an L-channel in the HSL color space, the adjustment amplitude is determined based on a channel value of the target sampling point in the L-channel and a channel value of the target sampling point in the S-channel;

if the channel is a V channel in the HSV color space, the adjustment amplitude is determined based on the channel value of the target sampling point in the V channel and the channel value of the target sampling point in the S channel.

8. The method of claim 7, wherein the higher the channel value of the target sampling point in the S channel, the greater the adjustment amplitude; and/or

As the brightness of the target sampling point increases, the adjustment amplitude increases and then decreases.

9. The method of claim 1, wherein constructing a three-dimensional look-up table based on channel values of the target sampling points at respective channels of the target color space and the adjustment values comprises:

Constructing a three-dimensional lookup table based on the channel values of the target sampling points in the channels of the target color space and the adjustment values, and the channel values of the other sampling points except the target sampling points in the channels of the target color space and the adjustment values; wherein the adjustment value of the other sampling points is 0.

10. The method of claim 1, wherein if the initial color is a single pixel color, the channel is an H-channel or an S-channel in the HSL/HSV color space, the target sampling point is a sampling point where a channel value of the H-channel is located in a first range interval and a channel value of the S-channel is located in a second range interval; the channel is an L/V channel under an HSL/HSV color space, the target sampling point is a sampling point of which the channel value of the H channel is positioned in a first range interval, the channel value of the S channel is larger than a first preset threshold value, and the channel value of the L channel is larger than a second preset threshold value; the first range section comprises a range section formed by channel values of an H channel for each of the initial color and the target color, and the second range section is a range section formed by channel values of an S channel for each of the initial color and the target color; and/or

If the initial color is a designated color range, the channel is an H channel or an S channel in an HSL/HSV color space, the target sampling point is a sampling point with the channel value of the H channel being located in a first range interval and the channel value of the S channel being located in a second range interval; the channel is an L/V channel under an HSL/HSV color space, the target sampling point is a sampling point of which the channel value of the H channel is positioned in a first range interval, the channel value of the S channel is larger than a first preset threshold value, and the channel value of the L channel is larger than a second preset threshold value; the first range section includes a range section in which two color boundaries of the specified color range are each configured by a channel value of an H channel, and the second range section is a range section in which two color boundaries of the specified color range are each configured by a channel value of an S channel.

11. An image processing method, the method comprising:

acquiring a target image to be subjected to color correction;

color correction processing is performed on the target image based on a pre-built three-dimensional lookup table, wherein the pre-built three-dimensional lookup table is built based on the method of any one of claims 1-10.

12. The method of claim 11, wherein the target image is an RGB format image and the three-dimensional lookup table is an HSL/HSV lookup table, the method further comprising:

and converting the HSL/HSV lookup table into an RGB lookup table, and performing color correction on the target image based on the RGB lookup table.

13. A computer program product, characterized in that the computer program product comprises a computer program which, when executed by a processor, implements the method of any of the preceding claims 1-12.

14. An electronic device comprising a processor, a memory, and a computer program stored in the memory for execution by the processor, the processor executing the computer program to perform the method of any one of claims 1-12.

15. A computer readable storage medium, characterized in that the computer readable storage medium has stored thereon a computer program which, when executed by a processor, implements the method of any of the preceding claims 1-12.