CN114565529A - Optical environment self-adaptive high dynamic range image modulation method - Google Patents
Optical environment self-adaptive high dynamic range image modulation method Download PDFInfo
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Abstract
The invention discloses an optical environment self-adaptive high dynamic range image modulation method. First, the Sensitivity of the human eye to different luminances when the human eye is adapted to a certain lighting environment is calculated using a Contrast Sensitivity Function (Contrast Sensitivity Function). On the basis, the perception sensitivity is characterized as the contrast between adjacent digital driving values of the display device, so that the perception brightness of human eyes under the current illumination environment adaptation state is quantized. A one-dimensional lookup table is established by utilizing the perceived brightness quantization curve and an Electro-Optical Transfer Function (Electro-Optical Transfer Function) of the display device and is loaded in a brightness channel of an image, and the converted image can enable an observer to obtain visual perception similar to that of an original image under dim illumination conditions in the current illumination environment. The invention utilizes the contrast sensitivity function to adjust the display effect of the high dynamic range image under different illumination environments, and can compensate the influence of the illumination of the luminous environment on the display effect of the high dynamic range image.
Description
Technical Field
The invention belongs to the field of high dynamic range image modulation methods, and particularly relates to a light environment self-adaptive high dynamic range image modulation method.
Background
As one of the key technologies in the ultra-high definition video industry, a High Dynamic Range (HDR) image can bring users with more exquisite and real visual experience and more appeal. In order to obtain the best viewing experience, the reference viewing environment of the high dynamic range image is a darkroom, which is contradictory to the complicated and changeable use environment of the mobile terminal, and is not beneficial to the mobile terminal user to obtain high-quality high dynamic range image perception. The optical environment adaptive image modulation method can compensate for the visual perception difference caused by the change of the illumination condition.
Currently, the compensation measures of the display device for the light environment can be mainly divided into physical brightness adjustment and pixel adjustment, and when the display device displays high dynamic range content, the brightness adjustment function is usually disabled, that is, peak brightness is utilized to obtain the optimal highlight rendering effect. On the other hand, the conventional pixel adjustment method only aims at the Standard Dynamic Range (SDR) image, and the effect of applying the conventional pixel adjustment method to the high dynamic range image is liable to be degraded.
Disclosure of Invention
In order to enable the display equipment to have similar visual perception when displaying high dynamic range contents in different light environments, the invention provides a light environment self-adaptive high dynamic range image modulation method to compensate image visual perception difference caused by illumination condition change.
The invention adopts the following specific technical scheme:
the invention provides an optical environment self-adaptive high dynamic range image modulation method, which comprises the following steps:
s1: calculating the maximum perception sensitivity and the minimum perception contrast of different brightness when human eyes are adaptive to a target illumination environment by using a contrast sensitivity function;
s2: representing the minimum perception contrast as the contrast between adjacent digital driving values of the display equipment to obtain a perception brightness quantization curve of human eyes in a target illumination environment;
s3: establishing a one-dimensional lookup table by using the perceived brightness quantization curve and an electro-optic conversion function of the display equipment;
s4: converting the original image to Y' CB’CRAnd in the color space, the Y' channel is loaded with the one-dimensional lookup table and then recalculated to obtain a modulation image of the color space related to the display equipment.
Preferably, the step S1 is as follows:
s101: for peak brightness of LWDark field brightness of LBK surface reflectance, calculating the reflected luminance L of the target illumination environment over its surfacerefl：
In the formula, EambIndicating an illumination level reached by the target lighting environment at the display surface;
s102: calculating the maximum perception sensitivity of the human eye to the brightness L when the human eye is adapted to the target illumination environment by using a Barten contrast sensitivity model:
where u denotes the spatial frequency, CSF (-) denotes the Barten contrast sensitivity function, LSRepresents the adapted brightness of the human eye to the target lighting environment, and LS＝Eamb/π；
S103: calculating the minimum perception contrast of human eyes under the target lighting environment:
preferably, the step S2 is as follows:
s201: given an initial luminance, the luminance distribution that satisfies the minimum perceived contrast of the human eye is recursively calculated:
in the formula, LiAnd Li+1Representing the digital drive values of the display device in proximity, and Li+1>Li(ii) a Initial luminance L0＝LB+LreflWhen L is presenti+1≥LW+LreflWhen so, the recursion ends;
s202: the luminance distribution obtained in step S201 is normalized and fitted with the mathematical form of the perceptually quantized PQ curve:
wherein L' represents normalized luminance, E represents normalized digital drive value, m1、m2、c1、c2、c3Representing the coefficient to be fitted, and marking the fitted quantized curve of the perceived brightness as EOTFA(·)。
Preferably, the step S3 is as follows:
using fitted perceptual luma quantization curve EOTFAThe inverse function of (·) and PQ curve builds a one-dimensional lookup table:
where d represents the input digital drive value, d' represents the output digital drive value, n represents the bit depth of the display, PQ-1(. cndot.) represents the inverse function of the PQ curve.
Preferably, the step S4 is as follows:
s401: converting an input high dynamic range image to Y' CB’CR' color space:
where RGB represents the pixel value of the device-dependent color space, Y' represents the luminance component, CB' and CR' each represents a chrominance component;
s402: loading a one-dimensional lookup table on the brightness component of the image:
Y1'＝LUT(Y'),
in the formula, Y' and Y1' respectively represent luminance components before and after image mapping;
s403: the chrominance components of the image are adjusted to compensate for the saturation change caused by the luminance adjustment:
in the formula, CB' and CR' denotes a chrominance component before adjustment, CB1' and CR1' denotes an adjusted chrominance component;
s404: mixing the modulated Y' CB’CR' component conversion back to RGB color space, obtaining modulated image pixel values R1G1B1：
S405: normalizing the modulated image to a PQ code value corresponding to the peak brightness of the display to prevent the truncation phenomenon during final display:
[Rout,Gout,Bout]T＝[R1,G1,B1]T/max(R1,G1,B1)·PQ-1(LW-LB),
in the formula, RGBoutNamely, the image pixel value is output to the display after the influence of the compensation light environment on the visual perception of human eyes.
Compared with the prior art, the invention has the following beneficial effects:
the invention uses a Contrast Sensitivity Function (Contrast Sensitivity Function) to quantify the perceived brightness of human eyes under a certain illumination environment adaptation state, and establishes a one-dimensional lookup table with an Electro-Optical Transfer Function (Electro-Optical Transfer Function) of a display device. The method is loaded in a brightness channel of an image to obtain a modulation image, and the modulation image can enable an observer to obtain visual perception similar to that of an original image under dim illumination conditions in the current illumination environment.
Drawings
Fig. 1 is a comparison of a PQ curve and a quantized perceptual brightness curve calculated by a display device used in an embodiment of the present invention in different indoor office environments, where the illumination levels are the illumination levels of the display surface of the illumination environment.
Fig. 2 shows the effect of modulating the test image to a level of 200lx (when the illumination of the desktop is about 300lx) according to the embodiment of the present invention.
Fig. 3 shows the effect of modulating the test image to a 500lx level (when the desktop illuminance is about 800lx) according to the embodiment of the present invention.
FIG. 4 shows the effect of modulating the test image to a level of 1000lx (when the desktop illuminance is about 1400lx) according to the embodiment of the present invention.
Detailed Description
The invention will be further elucidated and described with reference to the drawings and the detailed description. The technical characteristics of the embodiments of the invention can be correspondingly combined without mutual conflict.
Example 1
In this embodiment, a high dynamic range display is taken as an example to describe a light environment adaptive high dynamic range image modulation method. Dark field luminance L of the high dynamic range displayB＝0.05cd/m2Peak luminance LW＝1000cd/m2The surface reflectance k is 6.5%, and the electro-optic conversion curve meets the PQ standard and is placed in an indoor office environment.
The method for modulating the image with the high dynamic range and the self-adaptive optical environment in the embodiment specifically comprises the following steps:
1) illumination level E on the display surface according to the current light environmentambCalculating the reflection brightness L of the illumination environment on the surface of the display according to the surface reflectivity k of the displayrefl：
2) The maximum perception sensitivity of the human eye to the brightness L when the human eye is adapted to the current lighting environment is calculated by using a Barten contrast sensitivity model:
where u denotes the spatial frequency, CSF (-) denotes the Barten contrast sensitivity function, LSRepresents the adapted brightness of the human eye to the current environment, and LS＝Eamb/π。
3) Calculating the minimum perceived contrast of the human eye in the current lighting environment:
4) given initial luminance L0＝LB+LreflRecursive computation of the luminance distribution that satisfies the minimum perceptual contrast of the human eye:
in the formula, LiAnd Li+1Representing the digital drive values of the display device in proximity, and Li+1>Li. When L isi+1≥LW+LreflWhen so, the recursion ends.
5) The luminance distribution is normalized and fitted with the mathematical form of a Perceptual Quantization (PQ) curve:
wherein L' represents normalized luminance, E represents normalized digital drive value, m1、m2、c1、c2、c3Representing the coefficient to be fitted, and marking the fitted perceived brightness quantitative curve as EOTFA(·)。
As shown in fig. 1, the comparison between the PQ curve and the quantized perceptual brightness curve obtained by fitting the indoor luminance under three indoor office environments is shown. It can be seen from the figure that the contrast of the dark part of the quantization curve of the perceived brightness calculated based on the method increases with the increase of the luminous ambient illumination, which is more suitable for the perception of human eyes to the details of the dark part in the bright environment, and can effectively compensate the perception differences of image details, contrast and the like caused by the luminous ambient illumination.
6) Using fitted perceptual luma quantization curve EOTFAThe inverse function of (·) and PQ curves builds a one-dimensional lookup table:
where d represents the input digital drive value, d' represents the output digital drive value, n represents the bit depth of the display, PQ-1(. cndot.) represents the inverse function of the PQ curve.
7) Converting an input original image to Y' CB’CR' color space:
where RGB represents the pixel value of the device-dependent color space, Y' represents the luminance component, CB' and CR' denotes a chrominance component.
8) Loading a one-dimensional lookup table for the luminance component of the image:
Y1'＝LUT(Y'),
in the formula, Y' and Y1' denotes luminance components before and after image mapping, respectively.
9) The chrominance components of the image are adjusted to compensate for the saturation change caused by the luminance adjustment:
in the formula, CB' and CR' denotes a chrominance component before adjustment, CB1' and CR1' denotes the adjusted chrominance component.
10) Mixing the modulated Y' CB’CR' component conversion back to RGB color space, obtaining modulated image pixel values R1G1B1：
11) Normalizing the modulated image to a PQ code value corresponding to the peak brightness of the display to prevent the truncation phenomenon during final display:
[Rout,Gout,Bout]T＝[R1,G1,B1]T/max(R1,G1,B1)·PQ-1(LW-LB),
in the formula, RGBoutNamely, the image pixel value is output to the display after the influence of the compensation light environment on the visual perception of human eyes.
As shown in fig. 2 to 4, the test images are modulated to 200lx, 500lx and 1000lx levels respectively, and the test images are displayed under corresponding lighting environments. It can be seen from the figure that 3 images have similar details of bright and dark portions and contrast perception, that is, the high dynamic range image modulation method provided by the invention can effectively compensate image perception differences caused by light environment illumination.
The above-described embodiments are merely preferred embodiments of the present invention, which should not be construed as limiting the invention. Various changes and modifications may be made by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present invention. Therefore, the technical scheme obtained by adopting the mode of equivalent replacement or equivalent transformation is within the protection scope of the invention.
Claims (5)
1. An optical environment self-adaptive high dynamic range image modulation method is characterized by comprising the following steps:
s1: calculating the maximum perception sensitivity and the minimum perception contrast of different brightness when human eyes are adaptive to a target illumination environment by using a contrast sensitivity function;
s2: representing the minimum perception contrast as the contrast between adjacent digital driving values of the display equipment to obtain a perception brightness quantization curve of human eyes in a target illumination environment;
s3: establishing a one-dimensional lookup table by using the perceived brightness quantization curve and an electro-optic conversion function of the display equipment;
s4: converting the original image to Y' CB’CRAnd in the color space, the Y' channel is loaded with the one-dimensional lookup table and then recalculated to obtain a modulation image of the color space related to the display equipment.
2. The optical environment adaptive high dynamic range image modulation method according to claim 1, wherein said step S1 is specifically as follows:
s101: for peak brightness of LWDark field brightness of LBK surface reflectivity for calculating the reflection brightness L of the target illumination environment on its surfacerefl：
In the formula, EambIndicating an illumination level reached by the target lighting environment at the display surface;
s102: calculating the maximum perception sensitivity of the human eye to the brightness L when the human eye is adapted to the target illumination environment by using a Barten contrast sensitivity model:
where u denotes the spatial frequency, CSF (-) denotes the Barten contrast sensitivity function, LSRepresents the adapted brightness of the human eye to the target lighting environment, and LS＝Eamb/π；
S103: calculating the minimum perceived contrast of the human eye in the target lighting environment:
3. the optical environment adaptive high dynamic range image modulation method according to claim 1, wherein said step S2 is specifically as follows:
s201: given an initial luminance, the luminance distribution that satisfies the minimum perceived contrast of the human eye is recursively calculated:
in the formula, LiAnd Li+1Representing the digital drive values of the display device in proximity, and Li+1>Li(ii) a Initial luminance L0＝LB+LreflWhen L is presenti+1≥LW+LreflWhen so, the recursion ends;
s202: the luminance distribution obtained in step S201 is normalized and fitted with the mathematical form of the perceptually quantized PQ curve:
wherein L' represents normalized luminance, and E represents a normalized numberWord drive value, m1、m2、c1、c2、c3Representing the coefficient to be fitted, and marking the fitted quantized curve of the perceived brightness as EOTFA(·)。
4. The optical environment adaptive high dynamic range image modulation method according to claim 1, wherein said step S3 is specifically as follows:
using fitted perceptual luma quantization curve EOTFAThe inverse function of (·) and PQ curve builds a one-dimensional lookup table:
where d represents the input digital drive value, d' represents the output digital drive value, n represents the bit depth of the display, PQ-1(. cndot.) represents the inverse function of the PQ curve.
5. The optical environment adaptive high dynamic range image modulation method according to claim 1, wherein said step S4 is specifically as follows:
s401: converting an input high dynamic range image to Y' CB’CR' color space:
where RGB represents the pixel value of the device-dependent color space, Y' represents the luminance component, CB' and CR' each represents a chrominance component;
s402: loading a one-dimensional lookup table on the brightness component of the image:
Y1'＝LUT(Y'),
in the formula, Y' and Y1' respectively represent luminance components before and after image mapping;
s403: the chrominance components of the image are adjusted to compensate for the saturation change caused by the luminance adjustment:
in the formula, CB' and CR' denotes a chrominance component before adjustment, CB1' and CR1' denotes an adjusted chrominance component;
s404: mixing the modulated Y' CB’CR' component conversion back to RGB color space, obtaining modulated image pixel values R1G1B1：
S405: normalizing the modulated image to a PQ code value corresponding to the peak brightness of the display to prevent the truncation phenomenon during final display:
[Rout,Gout,Bout]T＝[R1,G1,B1]T/max(R1,G1,B1)·PQ-1(LW-LB),
in the formula, RGBoutNamely, the image pixel value is output to the display after the influence of the compensation light environment on the visual perception of human eyes.
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| CN116167950B (en) * | 2023-04-26 | 2023-08-04 | 镕铭微电子(上海)有限公司 | Image processing method, device, electronic equipment and storage medium |
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