CN115410524A - Image processing method and image display device - Google Patents

Abstract

An image processing method includes calculating brightness information of multiple brightness gray-scale values of multiple pixels of image data, combining a first sub-gamma correction curve and a second sub-gamma correction curve at a turning point to generate a target gamma correction curve, and setting the turning point according to the brightness information. The first gamma value of the first sub-gamma correction curve is different from the second gamma value of the second sub-gamma correction curve, and the brightness gray-scale value range corresponding to the first sub-gamma correction curve is not overlapped with the brightness gray-scale value range corresponding to the second sub-gamma correction curve.

Description

Image processing method and image display device

technical field

The present invention relates to an image processing method and an image display device, and in particular to an image processing method and an image display device capable of dynamically adjusting a gamma correction curve.

Background technique

Today's light-emitting diode (LED) video wall is mostly composed of multiple light boxes for high-resolution applications, such as 4K resolution or even 8K resolution applications. However, the power consumption of the LED video wall will grow exponentially with the number of spliced light boxes. Take the 480×270 resolution LED light boxes spliced together to form an 8K resolution LED video wall as an example. Assuming that a single LED light box consumes 80 watts of power in a bright scene, then splicing it into an 8K resolution (7680×4320 resolution) LED video wall The TV wall requires 256 LED light boxes, and the power consumption is 20480 watts, which is 256 times the power consumption of a single LED light box. Therefore, the application of the existing high-resolution LED video wall consumes a lot of power.

In order to improve the power consumption problem of the high-resolution LED video wall application, the existing common practice is to linearly reduce the brightness grayscale value of each pixel of the LED video wall to achieve the purpose of power saving. However, since the pixel-to-pixel contrast of an image is highly correlated with the brightness gray-scale value difference between image pixels, if only the brightness gray-scale value of each pixel of the LED video wall is linearly lowered, the brightness gray-scale value difference between pixels will also As a result, the contrast of the image screen is reduced. How to balance the power consumption and picture contrast of LED video wall is an important issue in the application of high-resolution LED video wall.

Contents of the invention

The invention provides an image processing method and an image display device, which can dynamically adjust the gamma correction curve (Gamma Correction Curve) according to the brightness information of the input image data, so as to take into account the power consumption of the display screen and the contrast of the display screen.

The image processing method of the present invention includes calculating the luminance information of multiple luminance grayscale values of multiple pixels of the image data, combining the first sub-gamma correction curve and the second sub-gamma correction curve at turning points, and according to the brightness information to set the location of the turning point. Wherein the first sub-gamma correction curve has a first gamma value, the second sub-gamma correction curve has a second gamma value, and the first gamma value is different from the second gamma value. Wherein the first sub-gamma correction curve corresponds to the first brightness grayscale value range, and the second sub-gamma correction curve corresponds to the second brightness grayscale value range. The first brightness grayscale value range does not overlap with the second brightness grayscale value range, and any brightness grayscale value in the first brightness grayscale value range is smaller than any brightness grayscale value in the second brightness grayscale value range.

The image display device of the present invention includes a display screen and a controller. The display screen is used for displaying output images, and the controller is coupled to the display screen. The controller is configured to receive image data, calculate brightness information of multiple brightness gray scale values of multiple pixels of the image data, make the first sub-gamma correction curve and the second sub-gamma correction curve combine with each other at the turning point, according to the brightness Information to set the position of the turning point, convert multiple brightness grayscale values of the image data into multiple output brightness grayscale values according to the target gamma correction curve, and convert the image data according to the image data and the multiple output brightness grayscale values Convert to an output image, and output the output image to the display screen. Wherein the first sub-gamma correction curve has a first gamma value, the second sub-gamma correction curve has a second gamma value, and the first gamma value is different from the second gamma value. Wherein the first sub-gamma correction curve corresponds to the first brightness grayscale value range, and the second sub-gamma correction curve corresponds to the second brightness grayscale value range. The first brightness grayscale value range does not overlap with the second brightness grayscale value range, and any brightness grayscale value in the first brightness grayscale value range is smaller than any brightness grayscale value in the second brightness grayscale value range.

Based on the above, the image processing method and image display device of the present invention can dynamically adjust the Gamma Correction Curve (Gamma Correction Curve) according to the brightness information of the input image data, so that different brightness The information dynamically adjusts the corresponding gamma correction curve to save power consumption and improve contrast when displaying output images.

Description of drawings

FIG. 1 is a flowchart of an embodiment of the image processing method of the present invention.

FIG. 2 is a combined schematic diagram of a target gamma correction curve of an embodiment of the image processing method of the present invention.

FIG. 3A and FIG. 3B are schematic diagrams of setting turning point positions for different brightness information in an embodiment of the image processing method of the present invention.

FIG. 4 is a block diagram of an embodiment of the image display device of the present invention.

5A and 5B are schematic diagrams of calculating brightness information for different image data in an embodiment of the image processing method of the present invention.

6A and 6B are schematic diagrams of setting turning points for different brightness information in an embodiment of the image processing method of the present invention.

7A and 7B are schematic diagrams of setting gamma values for different brightness information in an embodiment of the image processing method of the present invention.

8A and 8B are schematic diagrams of setting turning points and gamma values for different brightness information in an embodiment of the image processing method of the present invention.

9A to 9C are histogram comparisons of brightness gray scale values of input image data and output images in an embodiment of the image display device of the present invention.

Wherein, the reference signs are explained as follows:

400: Image display device

401: display screen

402: Controller

C1: the first sub-gamma correction curve

C1_1～C1_4: Candidate first sub-gamma correction curve

C2: Second sub-gamma correction curve

C2_1～C2_4: candidate second sub-gamma correction curve

IIM: image data

L1, L1': the first average brightness grayscale value

L2, L2': the second average brightness grayscale value

Lall, Lall’: the global average brightness grayscale value

LD, LD': brightness level

S101～S103: steps

TC, TC’, TC_sel, TC_sel’, TC_fix, TC_fix’: target gamma correction curve

TP, TP’: turning points

TP_I, TP_I': input brightness gray scale value

VIM: output image

Detailed ways

Please refer to FIG. 1 . FIG. 1 is a flowchart of an image processing method according to an embodiment of the present invention. The image processing method of the present invention can be used in a display device or a controller for controlling the display device to display images. In step S101 , the display device calculates luminance information of a plurality of luminance grayscale values of a plurality of pixels of the image data. The image data is the input image data of the image to be displayed, and the image data has a plurality of pixel data. The image processing method of the present invention can calculate multiple brightness grayscale values of multiple pixels to obtain brightness information. The luminance information may be information related to the luminance grayscale values of multiple pixels in the image data, such as the size of the luminance grayscale values, the distribution histogram of the luminance grayscale values, or the information of multiple luminance grayscale values of multiple pixels Various statistical values can also be the overall brightness state of the image to be displayed in the input image data, such as information about whether the image to be displayed is a bright scene or a dark scene.

In step S102 , the display device combines the first gamma sub-correction curve and the second sub-gamma sub-correction curve at turning points to generate a target gamma correction curve. Wherein the first sub-gamma correction curve and the second sub-gamma correction curve have different gamma values. In other words, the gamma correction curve (target gamma correction curve) generated by the image processing method of the present invention is formed by combining two curves with different gamma values. Reference can also be made to the illustration of FIG. 2 , which is a combined schematic diagram of the target gamma correction curve according to an embodiment of the present invention. It is worth noting that the first sub-gamma correction curve C1 and the second sub-gamma correction curve C2 can correspond to different gamma values, so as shown in Figure 2, the first sub-gamma correction curve C1 and the second sub-gamma correction curve The curvature performance of the two calibration curves C2 is not the same. The first sub-gamma correction curve C1 is combined with the second sub-gamma correction curve C2 at the turning point TP to generate the target gamma correction curve TC. In this embodiment, the first sub-gamma correction curve C1 constitutes the range of brightness grayscale values of the target gamma correction curve TC and the second sub-gamma correction curve C2 constitutes the range of brightness grayscale values of the target gamma correction curve TC. overlap, and in this embodiment, any brightness gray-scale value in the brightness gray-scale value range of the first sub-gamma correction curve C1 is smaller than any brightness gray-scale value range of the second sub-gamma correction curve C2 Brightness grayscale value.

In step S103, the display device sets the position of the turning point TP according to the brightness information of the image data calculated in step S101. 3A and FIG. 3B can be referred to simultaneously. FIG. 3A and FIG. 3B are schematic diagrams of generating target gamma correction curves for different brightness information in an image processing method according to an embodiment of the present invention. Take FIG. 3A and FIG. 3B as an example. In the embodiment of FIG. 3A, the display device sets the position of the turning point TP according to a brightness information of an image data. As shown in FIG. 3A, the position of the turning point TP corresponds to the input brightness grayscale value TP_I; relatively, in the embodiment of FIG. 3B, the display device sets the position of the turning point TP' according to another brightness information of another image data. As shown in FIG. 3B, the position of the turning point TP' corresponds to To the input brightness grayscale value TP_I'.

It can be seen from step S103 in FIG. 1 and FIG. 3A and FIG. 3B that the positions of turning points TP and TP' are determined according to different brightness information in FIG. 3A and FIG. Are not the same. Since the turning points TP and TP' are where the first sub-gamma correction curve and the second sub-gamma correction curve with different gamma values are combined, the target gamma correction curves TC and TC' have different turning performances. For example, the input brightness grayscale value TP_I corresponding to the position of the turning point TP in FIG. The second luminance grayscale value range corresponding to the second sub-gamma correction curve is large, because the luminance grayscale value of the larger range part corresponding to the first sub-gamma correction curve on the left side of the turning point TP, as shown in FIG. 3A, is at In the target gamma correction curve, the grayscale value of the output brightness is suppressed, so the target gamma correction curve TC has a better power saving effect. In the embodiment of FIG. 3A , near the turning point TP, since the output brightness grayscale value of the target gamma correction curve TC rises steeply with the input brightness grayscale value, there is good contrast. For another example, in the embodiment of FIG. 3B , the input brightness gray scale value TP_I' corresponding to the position of the turning point TP' is a relatively low second value. Since the output luminance gray-scale value near the turning point TP' increases sharply with the increase of the input luminance gray-scale value as shown in Figure 3B, the target gamma correction curve TC' is in the darker luminance gray-scale value area (near the turning point TP' ) has better contrast.

It is worth mentioning that since the position of the turning point of the target gamma correction curve is determined by the brightness information in the present invention, the image processing method of the present invention can determine a suitable turning point position according to the brightness information. For example, if the luminance information indicates that the input image data is a bright scene image, then the image processing method of the present invention can set the turning point TP at a high value corresponding to the input luminance grayscale value TP_I as shown in FIG. 3A , In this way, the target gamma correction curve TC will make the overall display screen have a better power-saving effect and maintain good contrast in the high-brightness area of the screen. If the luminance information shows that the input image data is a dark scene image, then the image processing method of the present invention can set the turning point TP' at a place where the corresponding input luminance gray scale value TP_I' is a low value, as shown in FIG. 3B , so that The target gamma correction curve TC' will enhance the contrast of the low-brightness area of the image.

Please refer to FIG. 4 , which is a block diagram of an embodiment of the image display device of the present invention. The image display device 400 in FIG. 4 includes a display screen 401 and a controller 402 coupled to the display screen 401 . The display screen 401 is used to display the output image VIM. The controller 402 can receive the input image data IIM in a wired or wireless manner, and can execute the image processing methods of various embodiments of the present invention, such as steps S101-S103 in FIG. 1 , which will not be repeated here. After the controller 402 executes the image processing method of the present invention to generate the target gamma correction curve, the controller 402 can convert multiple luminance grayscales of multiple pixels in the input image data IIM according to the generated target gamma correction curve Values are converted into corresponding multiple output brightness grayscale values. The controller 402 can convert the input image data into an output image VIM according to the color information of a plurality of pixels in the image data IIM and the output brightness gray scale value. The controller 401 also outputs the output image VIM to the display screen 401 in a wired or wireless manner.

According to the above-mentioned image processing method in FIG. 1 and the image display device in FIG. 4 , the image processing method and the image display device of the present invention can generate a corresponding target gamma correction curve according to brightness information, so that when displaying an output image, based on the input The brightness information of the video data can save power consumption and improve the contrast.

In the embodiment of the present invention, the controller 402 can calculate multiple brightness grayscale values of multiple pixels of the image data IIM according to various color space models. For example, in one embodiment of the present invention, when the controller 402 calculates the brightness gray scale value according to the Hue, Saturation, Value, HSV color space model, the brightness (Value, V) value can be calculated as the brightness gray value order value. In another embodiment of the present invention, when the controller 402 calculates the brightness grayscale value according to the hue, saturation, lightness (Hue, Saturation, Lightness, HSL) color space model, the brightness (Lightness, L) value can be calculated as the brightness gray value order value. In another embodiment of the present invention, when the controller 402 calculates the brightness gray scale value according to the Hue, Saturation, Intensity, HSI color space model, the intensity (Intensity, I) value can be calculated as the brightness gray value order value. In another embodiment of the present invention, when the controller 402 calculates the brightness grayscale value according to the YCbCr color space model, it may calculate the Y value representing the Luminance value as the brightness grayscale value. In another embodiment of the present invention, when the controller 402 calculates the brightness grayscale value according to the CIELAB color space model, the L* value representing black and white brightness values can be calculated as the brightness grayscale value. In the present invention, the calculation of the brightness grayscale value is not limited to the above-mentioned embodiments, and the chromaticity intensity values of pixels in the image data can be calculated according to any color space model to obtain the brightness grayscale value.

In an embodiment of the present invention, as shown in FIG. 2 , the first sub-gamma correction curve C1 corresponding to the low input brightness grayscale value has a notch upward curvature performance, and the second sub-gamma correction curve C1 corresponding to the high input brightness grayscale value The sub-gamma correction curve C2 has a notched downward curvature performance. In this way, near the turning point TP, the target gamma correction curve TC has the characteristic that the output grayscale value of brightness rises sharply as the grayscale value of the input brightness increases. That is to say, near the turning point TP, the target gamma correction curve TC will strengthen the contrast of the output brightness gray scale value. In an embodiment of the present invention, the gamma value of the first sub-gamma correction curve is greater than 1, and the gamma value of the second sub-gamma correction curve is less than 1.

In an embodiment of the present invention, as shown in FIG. 3A and FIG. 3B , the input brightness grayscale value TP_I corresponding to the turning point TP will be equal to the output brightness grayscale value corresponding to the turning point TP, and the input brightness value corresponding to the turning point TP' The grayscale value TP_I' will be equal to the output brightness grayscale value corresponding to the turning point TP'. That is to say, the turning points TP and TP' are respectively located at the intersection points of the target gamma correction curves TC and TC' and the straight line where the input equals the output (the oblique dotted line shown in FIG. 3A and FIG. 3B ). That is to say, near the turning point TP, the target gamma correction curve TC will make the output gray scale value of brightness close to the value of the input gray scale value of brightness.

In an embodiment of the present invention, the target gamma correction curves TC and TC' as shown in FIG. 3A and FIG. 3B are at the maximum value of the input brightness grayscale value (as shown in the figure at the end of TC and TC') , the output brightness gray scale value corresponding to the target gamma correction curve TC, TC' is equal to the input brightness gray scale value. That is to say, the ends of the target gamma correction curves TC, TC' will intersect with the straight line where the input is equal to the output (the oblique dotted line shown in FIG. 3A and FIG. 3B ). In this way, even after the conversion of the target gamma correction curve of the image processing method of the present invention, the maximum brightness grayscale value of the output image will be equal to the maximum brightness grayscale value of the input image data. The image processing method of the present invention The maximum brightness of the image data may not be changed.

Please refer to step S101 of FIG. 1. In one embodiment of the present invention, the step S101 of calculating the brightness information of the gray scale value of the pixel of the image data may include calculating the global average brightness gray scale value Lall of the brightness gray scale value, Calculate the first average brightness gray-scale value L1 of the brightness gray-scale values that are smaller than the global average brightness gray-scale value Lall, and calculate the first average brightness gray-scale value L1 of the brightness gray-scale values that are not less than the global average brightness gray-scale value Lall A second average brightness gray-scale value L2 of the brightness gray-scale value, and calculate the first average brightness gray-scale value L1 and the second average brightness gray-scale value L2 to obtain the brightness state and brightness degree, the brightness state includes the first brightness state and Second brightness state.

In an embodiment of the present invention, the first brightness state may be the dark scene state of the image frame of the input image data, the second brightness state may be the bright scene state of the image frame of the image data; the brightness degree may be the image data The brightness or darkness of the image screen. The microcontroller or the image display device can calculate the first average brightness grayscale value L1 and the second average brightness grayscale value L2 to obtain the brightness state as the first brightness state or the second brightness state and the brightness level.

Please refer to FIG. 5A and FIG. 5B . FIG. 5A and FIG. 5B are schematic diagrams of calculating brightness information for different image data according to an embodiment of the present invention. FIG. 5A is a brightness gray scale histogram of image data of a bright scene, and FIG. 5B is a brightness gray scale histogram of image data of a dark scene. In the embodiment of the bright scene in FIG. 5A , the controller or the image display device can calculate the global average brightness grayscale value Lall, which is 216, for example. The controller or the image display device also calculates the average of the brightness gray-scale values on the left side of the global average brightness gray-scale value Lall to obtain the first average brightness gray-scale value L1 of the low brightness gray-scale part, for example, 173, and calculates the global average brightness The average of the brightness gray-scale values on the right side of the gray-scale value Lall is used to obtain the second average brightness gray-scale value L2 of the high-brightness gray-scale part, for example, 237. Similarly, in the embodiment of the dark scene in FIG. 5B, the controller or the image display device can calculate the global average brightness grayscale value Lall', for example, 76, the first average brightness grayscale value L1', for example, 37, and the first average brightness grayscale value L1', for example, 37, and The second average brightness grayscale value L2' is, for example, 119. According to the above embodiments, it can be seen that the controller or the image display device can judge the scene state according to the calculated average brightness gray scale values L1, L1' and the second average brightness gray scale values L2, L2'.

In an embodiment of the present invention, the step of calculating the first average brightness gray scale value and the second average brightness gray scale value to obtain the brightness state by the controller or the image display device includes: comparing the first average brightness gray scale value with the second average brightness gray scale value a threshold value and comparing the second average brightness grayscale value with the second threshold value to obtain the brightness state. In an embodiment of the present invention, the first threshold may be the threshold of the average luminance grayscale value of the low luminance grayscale part, the first threshold may be, for example, 80, and the second threshold may be the average luminance grayscale value of the high luminance grayscale part. The second threshold may be 160, for example. In an embodiment of the present invention, if the first average brightness grayscale value is less than the first threshold and the second average brightness grayscale value is smaller than the second threshold, the brightness state can be obtained as the first brightness of a dark scene state State: if the first average brightness grayscale value is greater than the first threshold and the second average brightness grayscale value is greater than the second threshold, the brightness state can be obtained as a second brightness state of a bright scene state.

According to the above-mentioned embodiment with the scene of image data shown in FIG. 5A and FIG. 5B as an example, in the scene shown in FIG. The level value L2 is 237, which is also greater than the second threshold value of 160. Therefore, it can be judged that the scene of the image data in FIG. 5A is a bright scene. Therefore, the controller or the image display device can determine that the scene is a bright scene by calculating the first average brightness gray-scale value L1 and the second average brightness gray-scale value L2, thereby obtaining the brightness state of the image data in FIG. 5A as the first Two brightness states. Similarly, in the scene of 5B, the controller or the image display device can determine that the scene is a dark scene by calculating the first average brightness gray-scale value L1' and the second average brightness gray-scale value L2', thereby obtaining The brightness state of the image data in FIG. 5B is the first brightness state.

In an embodiment of the present invention, the brightness level LD can be obtained by calculating the first average brightness gray-scale value and the second average brightness gray-scale value. Wherein, the brightness level LD is information related to brighter or darker image data. In a specific embodiment of the present invention, brightness level LD=W1×L1+W2×L2, wherein L1 is the first average brightness gray scale value, L2 is the second average brightness gray scale value, W1, W2 are the first weight value and a second weight value. The system designer or developer can set the first weight value W1 and the second weight value W2 according to actual needs or experience, so as to effectively quantify the brightness level LD.

In an embodiment of the present invention, in step S103 of FIG. 1 , the step of setting the position of the turning point according to the brightness information may further include setting the position of the turning point according to the global average brightness gray scale value, brightness state and brightness level. That is to say, the controller or the image display device can select a suitable position of the turning point TP of the target gamma correction curve TC according to the brightness information of the scene. In an embodiment of the present invention, when the luminance state of the image data is the first luminance state, the input luminance grayscale value corresponding to the turning point TC is TP_I=Lall-LD, where Lall is the global average luminance grayscale value, LD is the brightness level. That is to say, when the scene of the image data is a dark scene, the position of the turning point TP will shift to a lower brightness gray-scale value relative to the global average brightness gray-scale value, and the position of the turning point TP will be determined according to the degree of darkness of the scene. amount of movement. In another embodiment of the present invention, when the brightness state of the image data is the second brightness state, the input brightness grayscale value corresponding to the turning point TC is TP_I=Lall+LD, where Lall is the global average brightness grayscale value, LD is the brightness level. That is to say, when the scene of the image data is a bright scene, the position of the turning point TP will be shifted to a higher brightness gray-scale value relative to the global average brightness gray-scale value, and the position of the turning point TP will be shifted to a higher brightness gray-scale value according to the brighter degree of the scene. amount of movement.

The above-mentioned embodiment can be embodied in the illustrations of FIG. 6A and FIG. 6B . FIG. 6A and FIG. 6B are schematic diagrams of setting turning points for different brightness information according to an embodiment of the present invention. In the embodiment of FIG. 6A , the brightness state is the second brightness state, that is to say, the image data is a bright scene. Under this condition, the input brightness gray scale value TP_I corresponding to the turning point TP of the target gamma correction curve TC is the global average brightness gray scale value Lall plus the value of the brightness level LD. Similarly, in the embodiment of FIG. 6B , the brightness state is the first brightness state, that is to say, the image data is a dark scene. Under this condition, the input brightness gray scale value TP_I' corresponding to the turning point TP' of the target gamma correction curve TC' is the global average brightness gray scale value Lall' minus the value of the brightness level LD.

In an embodiment of the present invention, the image processing method and the image display device can also set the first gamma value of the first sub-gamma correction curve and the second gamma value of the second sub-gamma correction curve according to the brightness information . In an embodiment of the present invention, the controller or the image display device can select an appropriate first sub-gamma correction curve from a plurality of candidate first sub-gamma correction curves according to the brightness information. Wherein the multiple candidate first sub-gamma correction curves all have a notch upward curvature performance and the multiple first gamma values corresponding to the multiple candidate first sub-gamma correction curves are greater than 1; the multiple Each of the candidate second sub-gamma correction curves has a downward notch curvature, and the plurality of second gamma values corresponding to the plurality of candidate second sub-gamma correction curves are less than 1. Please refer to the illustrations of FIG. 7A and FIG. 7B below. FIG. 7A and FIG. 7B are schematic diagrams of setting gamma values for different brightness information according to an embodiment of the present invention.

FIG. 7A depicts a plurality of candidate first sub-gamma correction curves C1_1~C1_4, wherein each of the plurality of candidate first sub-gamma correction curves C1_1~C1_4 has a corresponding first gamma value Gamma1_1~Gamma1_4, the first gamma value Gamma1_1～Gamma1_4 are all greater than 1 and Gamma1_4>Gamma1_3>Gamma1_2>Gamma1_1. In one embodiment of the present invention, for example, if there are four different first to fourth image data, the brightness of the scene of each image data is arranged from the darkest to the brightest as the first image data to the fourth video material. In this embodiment, the controller or the image display device can select corresponding candidate first sub-gamma correction curves C1_1 - C1_4 according to different brightness information. In this embodiment, the selected gamma value of the first gamma correction curve can be positively correlated with the brightness of the input image data, that is to say, when the scene is brighter, the controller or the image display device will select the gamma value The higher the candidate first sub-gamma correction curve. For example, when the input image data are the first, second, third, and fourth image data, the corresponding selected candidate first sub-gamma correction curves are candidate first sub-gamma correction curves C1_1, C1_2, C1_3, C1_4. The candidate first sub-gamma correction curves C1_1-C1_4 of the present invention are only examples, and the number is not limited to four. That is to say, in the embodiment of the present invention, there may be multiple candidate first sub-gamma correction curves. Set a target gamma correction curve with image data that is more conducive to different brightness information.

FIG. 7B depicts a plurality of candidate second sub-gamma correction curves C2_1~C2_4, wherein each of the plurality of candidate second sub-gamma correction curves C2_1~C2_4 has a corresponding second gamma value Gamma2_1~Gamma2_4, and the second gamma value Gamma2_1～Gamma2_4 are all less than 1 and Gamma2_4>Gamma1_3>Gamma1_2>Gamma2_1. In one embodiment of the present invention, for example, if there are four different first to fourth image data, the brightness of the scene of each image data is arranged from the darkest to the brightest as the first image data to the fourth video material. In this embodiment, the controller or the image display device may select corresponding candidate second sub-gamma correction curves C2_1 - C2_4 according to different brightness information. In this embodiment, the selected gamma value of the second gamma correction curve may be positively correlated with the brightness of the input image data, that is to say, when the scene is brighter, the controller or the image display device will select the gamma value The higher the candidate first sub-gamma correction curve. For example, when the input image data are the first, second, third, and fourth image data respectively, the correspondingly selected candidate second sub-gamma correction curves are candidate second sub-gamma correction curves C2_1, C2_2, C2_3, C2_4. The candidate second sub-gamma correction curves C2_1-C2_4 of the present invention are only examples, and the number is not limited to four. That is to say, in the embodiment of the present invention, there may be multiple candidate second sub-gamma correction curves. Set a target gamma correction curve with image data that is more conducive to different brightness information.

It is worth mentioning that, in the embodiment illustrated in FIG. 7A and FIG. 7B , the selection method of the first gamma correction curve and the second gamma correction curve in the target gamma correction curve will be based on the image data as a bright scene Under certain conditions, as the brightness increases, the first gamma correction curve expands outward and the second gamma correction curve shrinks inward, so as to achieve a better power saving effect. Under the condition that the image data is a dark scene, as the brightness decreases, the second gamma correction curve expands outward, so that the display screen has better contrast.

It should be noted that, in the embodiment of the present invention, the brightness of the display screen of the input image data can be obtained according to the brightness state and the brightness degree. When the display screen is the first brightness state of the dark scene, when the scene of the display screen is darker, the brightness level is higher; when the display screen is in the second brightness state of the bright scene, when the scene of the display screen is brighter, the brightness level is higher. high. Therefore, in the present invention, the controller and the image display device can determine the selected candidate first gamma correction curve and candidate second gamma correction curve according to the brightness state and brightness level. For example, when the brightness state is the first brightness state, both the first gamma value and the second gamma value are negatively correlated with the brightness level; when the brightness state is the second brightness state, the first gamma value and the second The gamma value is positively related to the brightness level.

In an embodiment of the present invention, the method of setting the turning point TP in FIG. 6A and FIG. 6B and the selection method of the first gamma correction curve and the second gamma correction curve in FIGS. 7A and 7B can be combined to set Target the gamma correction curve. Please refer to FIG. 8A and FIG. 8B . FIG. 8A and FIG. 8B are schematic diagrams of setting turning points, first gamma correction curves and second gamma correction curves for different brightness information according to this embodiment.

In the embodiment of FIG. 8A , the display screen of the input image data is a dark scene. In this embodiment, the position of the input brightness gray-scale value TP_I corresponding to the turning point TP can be determined according to the global average brightness gray-scale value Lall, the brightness state, and the brightness level LD. For example, in the input image data shown in FIG. 8A , the luminance state is the first luminance state, so the input luminance grayscale value TP_I corresponding to the turning point TP is located at the place where the global average luminance grayscale value Lall subtracts the luminance level LD. In an embodiment of the present invention, after the position of the turning point TP is determined, if the gamma values of the first gamma correction curve and the second gamma correction curve are a predetermined value, the target gamma correction curve can be For example, the target gamma correction curve TC_fix shown by the dotted curve in FIG. 8A . In another embodiment of the present invention, after the position of the turning point TP is determined, if the first gamma correction curve and the second gamma correction curve are selected according to the embodiment shown in FIG. 7A and FIG. 7B , the controller and the display device According to the first brightness state and the brightness level LD, the first gamma correction curve and the second gamma correction curve with smaller gamma values can be selected to obtain the target gamma correction curve TC_sel shown by the solid line curve in FIG. 8A . As shown in FIG. 8A , the target gamma correction curve TC_sel will be further expanded on the right side of the turning point TP than the target gamma correction curve TC_fix . Therefore, if the first gamma correction curve and the second gamma correction curve are selected according to the embodiments of FIG. 7A and FIG. 7B , the target gamma correction curve TC_sel will further improve the contrast of the output image.

In the embodiment of FIG. 8B , the display screen of the input image data is a bright scene. In this embodiment, the position of the input brightness gray-scale value TP_I' corresponding to the turning point TP' can be determined according to the global average brightness gray-scale value Lall', the brightness state, and the brightness level LD'. For example, in the image data input in FIG. 8B , the brightness state is the second brightness state, so the input brightness grayscale value TP_I' corresponding to the turning point TP' is located between the global average brightness grayscale value Lall' plus the brightness level LD'. place. In an embodiment of the present invention, after the position of the turning point TP is determined, if the gamma values of the first gamma correction curve and the second gamma correction curve are a predetermined value, the target gamma correction curve can be For example, the target gamma correction curve TC_fix' shown by the dotted curve in FIG. 8B . In another embodiment of the present invention, after the position of the turning point TP is determined, if the first gamma correction curve and the second gamma correction curve are selected according to the embodiment shown in FIG. 7A and FIG. 7B , the controller and the display device According to the second brightness state and the brightness level LD', the first gamma correction curve and the second gamma correction curve with a larger gamma value can be selected to obtain the target gamma correction curve TC_sel shown in the solid line curve in FIG. 8B '. As shown in FIG. 8B , the target gamma correction curve TC_sel' will be more outwardly expanded than the target gamma correction curve TC_fix' on the left side of the turning point TP', and the target gamma correction curve TC_sel' will be wider than the target gamma correction curve TC_fix' TC_fix' is more indented to the right of the turning point TP. Therefore, if the first gamma correction curve and the second gamma correction curve are selected according to the embodiment shown in FIG. 7A and FIG. 7B , the target gamma correction curve TC_sel' will further reduce the power consumption of the display screen.

Please refer to FIG. 9A to FIG. 9C . FIG. 9A to FIG. 9C are comparisons of brightness grayscale histograms of the output image generated by the image display device according to the present invention and the input image data. In FIG. 9A and FIG. 9B , the display screen of the input image data is a bright scene, and in FIG. 9C , the display screen of the input image data is a dark scene. In FIG. 9A to FIG. 9C , the solid outline is a schematic diagram of the brightness grayscale histogram of the input image data, and the graph filled with oblique lines is a schematic diagram of the brightness grayscale histogram of the output image. As shown in Fig. 9A and Fig. 9B, the luminance grayscale histogram of the output image is shifted to the low luminance grayscale value compared with the luminance grayscale histogram of the input image data. Therefore, in the situation of Fig. 9A and Fig. 9B, the present The image processing method and image display device of the invention can reduce the power consumption of outputting images. As shown in FIG. 9C , the brightness grayscale histogram of the output image is more shifted to higher brightness grayscale values than the brightness grayscale histogram of the input image data, so the distribution of the brightness grayscale values of the output image is more uniform, so In the situation of FIG. 9C , the image processing method and image display device of the present invention can improve the contrast of the output image.

In summary, the image processing method and image display device of the present invention can generate a corresponding target gamma correction curve according to the brightness information, so as to save power consumption based on the brightness information of the input image data when displaying the output image. volume and increase the contrast. More specifically, the image processing method and image display device of the present invention can reduce the brightness of the overall output image without changing the maximum brightness when the input image data is a bright scene, thereby saving Electric effect, and can improve the contrast of the display screen of the output image when the input image data is a dark scene.

Claims (20)

1. An image processing method, comprising: calculating a luminance information of a plurality of luminance gray scale values of a plurality of pixels of an image data; Combining a first sub-gamma correction curve and a second sub-gamma correction curve at a turning point to generate a target gamma correction curve, wherein a first gamma value of the first sub-gamma correction curve and the A second gamma value of the second sub-gamma correction curve is different; and setting the position of the turning point according to the brightness information, Wherein the first sub-gamma correction curve corresponds to a first brightness grayscale value range, the second sub-gamma correction curve corresponds to a second brightness grayscale value range, the first brightness grayscale value range and the second brightness The ranges of gray scale values do not overlap, and any gray scale value of brightness in the first range of gray scale values of brightness is smaller than any gray scale value of gray scale of brightness in the second range of gray scale values of brightness. 2. The image processing method as claimed in claim 1, wherein the step of calculating the luminance information of the luminance gray scale value of the pixel of the image data comprises: calculating a global average brightness gray-scale value of the brightness gray-scale value; calculating a first average brightness gray-scale value of a plurality of brightness gray-scale values smaller than the global average brightness gray-scale value among the brightness gray-scale values; calculating a second average brightness gray-scale value of a plurality of brightness gray-scale values among the brightness gray-scale values not smaller than the global average brightness gray-scale value; and The first average brightness grayscale value and the second average brightness grayscale value are calculated to obtain a brightness state and a brightness level, wherein the brightness state includes a first brightness state and a second brightness state. 3. The image processing method according to claim 2, wherein the step of calculating the first average brightness gray scale value and the second average brightness gray scale value to obtain the brightness state and the brightness degree further comprises: Comparing the first average brightness grayscale value with a first threshold and comparing the second average brightness grayscale value with a second threshold to obtain the brightness state, wherein, When the first average brightness grayscale value is less than the first threshold and the second average brightness grayscale value is smaller than the second threshold, the brightness state is obtained as the first brightness state; When the first average brightness grayscale value is greater than the first threshold and the second average brightness grayscale value is greater than the second threshold, the brightness state is obtained as the second brightness state. 4. The image processing method as claimed in claim 2, wherein the brightness level LD=W1×L1+W2×L2, Wherein L1 is the first average brightness gray scale value, L2 is the second average brightness gray scale value, W1, W2 are a first weight value and a second weight value respectively. 5. The image processing method as claimed in claim 2, wherein the step of setting the position of the turning point according to the brightness information comprises: The position of the turning point is set according to the global average brightness gray scale value, the brightness state and the brightness degree, wherein, When the brightness state is the first brightness state, an input brightness grayscale value corresponding to the position of the turning point TP_I=Lall-LD; When the luminance state is the second luminance state, the input luminance grayscale value corresponding to the position of the turning point TP_I=Lall+LD, Among them, Lall is the average brightness gray scale value of the whole area, and LD is the brightness level. 6. The image processing method as claimed in claim 2, wherein the image processing method further comprises: The first gamma value and the second gamma value are set according to the brightness information, wherein the first gamma value is greater than 1 and the second gamma value is less than 1. 7. The image processing method according to claim 6, wherein the step of setting the first gamma value and the second gamma value according to the brightness information comprises: setting the first gamma value and the second gamma value according to the brightness state and the brightness level, wherein When the brightness state is the first brightness state, the first gamma value is negatively correlated with the brightness level and the second gamma value is negatively correlated with the brightness level, When the brightness state is the second brightness state, the first gamma value is positively correlated with the brightness level and the second gamma value is positively correlated with the brightness level. 8. The image processing method as claimed in claim 1, wherein the first gamma value is greater than 1 and the second gamma value is less than 1. 9. The image processing method according to claim 1, wherein an input brightness grayscale value corresponding to the turning point is equal to an output brightness grayscale corresponding to the turning point position. 10. The image processing method as claimed in claim 1, wherein based on the target gamma correction curve, a maximum input brightness grayscale value is equal to a maximum output brightness grayscale value. 11. An image display device, comprising: a display screen for displaying an output image; and a controller, coupled to the display screen, configured to: receiving an image data, and calculating a brightness information of a plurality of brightness gray scale values of a plurality of pixels of the image data; Combining a first sub-gamma correction curve and a second sub-gamma correction curve at a turning point to generate a target gamma correction curve, wherein a first gamma value of the first sub-gamma correction curve and the A second gamma value of the second sub-gamma correction curve is different; setting the position of the turning point according to the brightness information; converting the brightness grayscale value of the image data into a plurality of output brightness grayscale values according to the target gamma correction curve; and converting the image data into the output image according to the image data and the output brightness gray scale value, and outputting the output image to the display screen, Wherein the first sub-gamma correction curve corresponds to a first brightness grayscale value range, the second sub-gamma correction curve corresponds to a second brightness grayscale value range, the first brightness grayscale value range and the second brightness The ranges of gray scale values do not overlap, and any gray scale value of brightness in the first range of gray scale values of brightness is smaller than any gray scale value of gray scale of brightness in the second range of gray scale values of brightness. 12. The image display device as claimed in claim 11, wherein the controller is configured to: calculating a global average brightness gray-scale value of the brightness gray-scale value; calculating a first average brightness gray-scale value of a plurality of brightness gray-scale values smaller than the global average brightness gray-scale value among the brightness gray-scale values; calculating a second average brightness gray-scale value of a plurality of brightness gray-scale values among the brightness gray-scale values not smaller than the global average brightness gray-scale value; and The first average brightness gray scale value and the second average brightness gray scale value are calculated to obtain a brightness state and a brightness degree, wherein the brightness state includes a first brightness state and a second brightness state. 13. The image display device as claimed in claim 12, wherein the controller is configured to: Comparing the first average brightness grayscale value with a first threshold and comparing the second average brightness grayscale value with a second threshold to obtain the brightness state, wherein, When the first average brightness grayscale value is less than the first threshold and the second average brightness grayscale value is smaller than the second threshold, the brightness state is obtained as the first brightness state; When the first average brightness grayscale value is greater than the first threshold and the second average brightness grayscale value is greater than the second threshold, the brightness state is obtained as the second brightness state. 14. The image display device as claimed in claim 12, wherein the brightness level LD=W1×L1+W2×L2, Wherein L1 is the first average brightness gray scale value, L2 is the second average brightness gray scale value, W1, W2 are a first weight value and a second weight value respectively. 15. The image display device as claimed in claim 12, wherein the controller is configured to: The position of the turning point is set according to the global average brightness gray scale value, the brightness state and the brightness degree, wherein, When the brightness state is the first brightness state, an input brightness grayscale value corresponding to the position of the turning point TP_I=Lall-LD; When the luminance state is the second luminance state, the input luminance grayscale value corresponding to the position of the turning point TP_I=Lall+LD, Among them, Lall is the average brightness gray scale value of the whole area, and LD is the brightness level. 16. The image display device as claimed in claim 12, wherein the controller is configured to: The first gamma value and the second gamma value are set according to the brightness information, wherein the first gamma value is greater than 1 and the second gamma value is less than 1. 17. The image display device as claimed in claim 16, the controller is configured to: Setting the first gamma value and the second gamma value according to the brightness state and the brightness level, wherein, When the brightness state is the first brightness state, the first gamma value is negatively correlated with the brightness level and the second gamma value is negatively correlated with the brightness level, When the brightness state is the second brightness state, the first gamma value is positively correlated with the brightness level and the second gamma value is positively correlated with the brightness level. 18. The image display device as claimed in claim 11, wherein the first gamma value is greater than 1 and the second gamma value is less than 1. 19. The image display device as claimed in claim 11, wherein an input brightness grayscale value corresponding to the position of the turning point is equal to an output brightness gray scale value corresponding to the position of the turning point. 20. The image display device as claimed in claim 11, wherein based on the target gamma correction curve, a maximum input brightness gray scale value is equal to a maximum output brightness gray scale value.

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