TWI702587B - Image adjustment method and associated image adjustment circuit applicable to display - Google Patents

Abstract

The present invention provides an image adjustment circuit applicable to a display. The image adjustment circuit includes a storage unit and a processor. The processor is configured to perform following steps: defining multiple areas on a display region of the display; obtaining statistics of grayscale of a preliminary image; determining an image type of the preliminary image according to the statistics of grayscale of the preliminary image; generating a Cumulative Distribution Function of luminance according to the statistics of grayscale of the preliminary image; individually adjusting a backlight level for each of the areas according to the Cumulative Distribution Function of luminance and the image type of the preliminary image; and generating an output image with each of the areas being individually adjusted.

Description

Image adjustment method applied to display and related image adjustment circuit

The present invention relates to a picture compensation technology, and more particularly to a technology for dynamically adjusting the backlight level of each area of a light emitting diode (LED) display.

LED-backlit (LED-backlit) is a flat display technology that uses LEDs as a backlight source to replace cold cathode fluorescent (CCFL). LED-backlit displays can provide lower power consumption, higher contrast, and brightness.

Since the LED backlight technology can control the backlight level of each LED, local dimming technology can be further used to make the dark parts of the picture appear pure black.

The traditional local dimming method has some disadvantages, such as high power consumption and lower luminance. In addition, the traditional local dimming method may bring some non-ideal side effects and deteriorate the picture quality. For example, the traditional local dimming method may cause halo effect or mosaic effect, making the picture appear blocky or pixelated.

In summary, there is a need for a novel method to solve the above problems.

One of the objectives of the present invention is to provide a scene-based adaptive backlight adjustment method and related circuits for local dimming. In detail, the present invention provides a method and related device for dynamically adjusting the backlight level of each area of the LED display to solve the above-mentioned problems.

An embodiment of the present invention provides an image adjustment method applicable to a display. The image adjustment method includes: defining a plurality of areas in a display area of the display; obtaining grayscale data of a preliminary image; The grayscale data of the preliminary image is used to determine the image type of the preliminary image; the Cumulative Distribution Function (CDF) is generated according to the grayscale data of the preliminary image; and the Cumulative Distribution Function (CDF) is generated according to the brightness cumulative distribution function and the preliminary image The image type is used to adjust the backlight level of each of the regions individually; and to generate an output image with each of the regions individually adjusted.

An embodiment of the present invention provides an image adjustment circuit applicable to a display. The image adjustment circuit includes a storage unit and a processor for performing the following steps: defining a plurality of areas in the display area of the display; Obtain the grayscale data of a preliminary image; determine the image type of the preliminary image according to the grayscale data of the preliminary image; generate a Cumulative Distribution Function (CDF) according to the grayscale data of the preliminary image ; According to the brightness cumulative distribution function and the image type of the preliminary image to individually adjust the backlight level of each of the regions (backlight level); and generate an individually adjusted backlight level of each of the regions Output image.

100: Image generating circuit

110: processor

120: storage unit

125, 630: lookup table

1000: display

1050: display area

202~216: steps

600: hardware architecture

610, 620, 630, 640, 650, 660, 670: block

631, 632, 633: sub-block

FIG. 1A is a schematic diagram of an image adjustment circuit according to an embodiment of the invention.

FIG. 1B is a schematic diagram of an example of a display including the image adjustment circuit shown in FIG. 1A.

FIG. 2 is a flowchart of an image adjustment method corresponding to the image adjustment circuit shown in FIG. 1A.

Figure 3A is a histogram of gray levels.

Figure 3B is a schematic diagram of the cumulative distribution function converted from the histogram shown in Figure 3A.

Figures 4A-4D describe various examples of luminance cumulative distribution functions, each of which exhibits a different distribution.

Figures 5A-5D are respectively the inverse CDF of brightness converted from the cumulative distribution function of brightness in Figures 4A-4D.

Figure 6 is a schematic diagram of a hardware architecture according to an embodiment of the invention.

In the specification and subsequent patent applications, certain words are used to refer to specific elements. Those with general knowledge in the field should understand that hardware manufacturers may use different terms to refer to the same components. The scope of this specification and subsequent patent applications does not use differences in names as a way to distinguish elements, but uses differences in functions of elements as a criterion for distinguishing. The "include" mentioned in the entire manual and subsequent requests is an open term, so it should be interpreted as "include but not limited to". In addition, the term "coupling" here includes any direct and indirect electrical connection means. Therefore, if it is described that a first device is coupled to a second device, it means that the first device can be directly electrically connected to the second device, or indirectly electrically connected to the second device through other devices or connection means.

Please refer to FIG. 1A. FIG. 1A is a schematic diagram of an image adjustment circuit 100 according to an embodiment of the present invention. The image adjustment circuit 100 can be applied to a display such as an LED display. As shown in FIG. 1A, the image adjustment circuit 100 includes a processor 110 and a storage unit 120. The processor 110 can be used to execute program codes and perform various operations, especially the operations in each step in FIG. 2. The storage unit 120 can store a look-up table (LUT) 125. Fig. 1B is a schematic diagram of an example of a display including the image adjustment circuit shown in Fig. 1A, wherein the display 1000 includes a display area 1050, and the display area 1050 can be divided into a plurality of grids as shown in Fig. 1B Area, and the light emitted by each area is generated by multiple LEDs within it.

Figure 2 is a flowchart of the image adjustment method 200 corresponding to the image adjustment circuit 100 shown in Figure 1A. If substantially the same result can be obtained, the steps do not have to be executed exactly in the order shown in Figure 2. The adjustment method can be summarized as follows.

Step 202: Start; Step 204: Define multiple areas in the display area of the display; Step 206: Obtain grayscale data of a preliminary image; Step 208: Determine the preliminary image based on the grayscale data of the preliminary image Step 210: Generate a Cumulative Distribution Function (CDF) based on the grayscale data of the preliminary image; Step 212: Generate an inverse CDF (inverse CDF) based on the Cumulative Distribution Function of brightness; Step 214 : Adjust the backlight level of each of the areas individually according to the brightness inverse cumulative distribution function and the image type of the preliminary image; Step 216: Generate an output screen including each of the adjusted areas.

In step 206, the grayscale data may be as shown in FIG. 3A, which is a histogram about grayscale, and the horizontal axis represents the grayscale. The histogram shown in FIG. 3A can be converted from the CDF shown in FIG. 3B via the processor 110, as described in step 210. The brightness cumulative distribution function is a kind of data used to provide information on how many pixels are distributed on each grayscale value, and the brightness cumulative distribution function can be used to determine the image type of the preliminary image, where the preliminary image can be understood as not yet Processed screen or data. Image types can be roughly divided into dark-dominant or light-dominant images.

Most of the pixels in the dark-color oriented picture have a lower gray level (for example, close to or equal to 0), and most of the pixels in the light-color oriented picture have a higher gray level (for example, close to or equal to 255). In other words, a dark-oriented picture represents a picture where low-gray-scale pixels occupies the majority, and a dark-oriented area represents an area where low-gray-scale pixels occupies most. Similarly, a light-color oriented picture represents a picture where high-gray-scale pixels occupy most of the picture, and a light-color oriented area represents an area where high-gray pixels occupies most of the picture.

Furthermore, image types can be classified into dark scene screens, text screens, and web page screens. Generally speaking, a dark scene picture can be, for example, a movie picture, and the dark pixels need to look darker so that some detailed lines and edges can be displayed more clearly. Therefore, reducing the backlight level of the dark-oriented area can improve the overall picture quality.

However, for light-color oriented pictures, such as text pictures or webpage pictures, dark pixels occupy only a small part of the entire display area 1050. In this case, lowering the backlight level of these dark-colored guiding areas will only make these dark-colored guiding areas more abrupt and will not bring any benefits. For example, the whole picture will look more blocky or pixelated, which will seriously affect the picture quality And greatly reduce the user experience.

In order to solve the aforementioned problems encountered by the prior art, the present invention considers the image type of the preliminary image (another image that has not yet been output), so that the light-colored oriented image looks smoother and more natural.

Fig. 3A is a gray-scale histogram of a dark-oriented picture according to an embodiment of the present invention, in which low-gray-scale pixels (for example, pixels with gray-scale between 0-50) The number is much higher than the number of high grayscale pixels. Therefore, in step 208, the image type of the preliminary image is determined according to the histogram shown in FIG. 3A. Then, in step 210, the luminance cumulative distribution function (for example, as shown in Figure 3B) can be generated according to the histogram in Figure 3A, and the luminance cumulative distribution function can be further used to generate the luminance inverse in step 212. Cumulative distribution function.

Figures 4A-4D describe various examples of luminance cumulative distribution functions, each of which exhibits a different distribution. Figures 5A-5D are the inverse CDFs (inverse CDF) converted from the brightness cumulative distribution functions in Figures 4A-4D. The "B/L" in Figures 5A-5D stands for "backlight" . The luminance inverse cumulative distribution function can be stored in the look-up table 125 in the storage unit 120 of the image adjustment circuit 100 for subsequent use. The multiple brightness inverse cumulative distribution functions shown in Figures 5A-5D can be used to perform local dimming. The so-called local dimming refers to adjusting the backlight of different areas individually.

In step 214, the backlight level of each of the regions is individually adjusted according to the brightness inverse cumulative distribution function and the image type of the preliminary image. As mentioned above, the step of referring to the image type of the preliminary image is very important to improve the blockiness or pixelation of the screen caused by the local dimming operation. The detailed operation of the image type of the preliminary image is described below.

When the image type is judged to be a dark-oriented picture rather than a light-oriented picture, the backlight level of all these areas will be reduced by a first extent, where the dark-oriented picture is low gray High-level pixels occupies most of the screen, and the dark guide area is the area where low-gray pixels occupies most.

On the other hand, when the image type is judged to be light-oriented rather than dark-oriented, the backlight level of any dark-oriented areas in these areas will be reduced by a second range (where the second range is less than The first amplitude, and the light-color oriented picture is a picture with high gray-scale pixels occupying most of it) to reduce the blockiness or pixelation effect. In another example, based on different user modes or settings, the backlight level of any dark-oriented areas in these areas can even be increased or maintained to further suppress the above-mentioned blocking or pixelation effect. After the compensation of the preliminary image is completed, step 216 will output the screen after the regions have been adjusted individually.

FIG. 6 is a schematic diagram of a hardware architecture 600 according to an embodiment of the present invention, where the hardware architecture 600 can be used by the above-mentioned image adjustment circuit 100, the display 1000, and the image adjustment method 200. The block 620 is labeled "HGL", which represents the preliminary image data from the block 610 (labeled as image input), such as the histogram shown in FIG. 3A. The block 630 represents a look-up table, which is further based on the data in the sub-block 631 to generate the luminance inverse cumulative distribution function in the sub-block 632 according to the luminance cumulative distribution function in the sub-block 632. The block 640 (labeled "spatial filter") is used to perform some image processing, such as Fourier Transformation and so on. The block 650 is used to receive the processing result from the block 640 and the brightness inverse cumulative distribution function from the block 630. Then, the block 660 uses the information from the block 650 (labeled "remap HGL") to compensate the preliminary image to generate the compensated output in the block 670 (labeled "image output").

In summary, the embodiments of the present invention can achieve the following effects: reducing the halo effect caused by the excessively pure blackening of the dark guide area in the dark scene of the display; and reducing the high-brightness image or Clipping effect caused by the large grayscale gap between adjacent areas in the web page screen.

The foregoing descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made in accordance with the scope of the patent application of the present invention shall fall within the scope of the present invention.

630: lookup table

600: hardware architecture

610, 620, 630, 640, 650, 660, 670: block

631, 632, 633: sub-block

Claims (10)

An image adjustment circuit applied to a display includes: a storage unit; and a processor for performing the following steps: defining a plurality of areas in the display area of the display; obtaining grayscale data of a preliminary image; Determine the image type of the preliminary image based on the grayscale data of the preliminary image; generate a Cumulative Distribution Function (CDF) based on the grayscale data of the preliminary image; and generate a Cumulative Distribution Function (CDF) based on the brightness cumulative distribution function and the preliminary image The image type adjusts the backlight level of each of the regions individually; and generates an output image with each region of the regions individually adjusted. The image adjustment circuit according to claim 1, wherein the step of individually adjusting the backlight level of each of the areas according to the luminance cumulative distribution function and the image type of the preliminary image further comprises: according to the luminance cumulative distribution The function generates a brightness inverse CDF; and according to the brightness inverse CDF, the backlight level of each of the regions is individually adjusted. The image adjustment circuit according to claim 2, wherein the brightness inverse cumulative distribution function is stored A look-up table in the storage unit for subsequent use. The image adjustment circuit according to claim 1, wherein the display is a light emitting diode (LED) display. The image adjustment circuit according to claim 1, wherein the step of determining the image type of the preliminary image according to the grayscale data of the preliminary image includes: if the image type is determined to be a dark-dominant ) Screen, the backlight level of all areas in these areas is reduced by a first extent (extent), where the dark-oriented screen is a screen in which low-gray pixels occupies the majority. The image adjustment circuit according to claim 5, wherein the image type is a dark scene frame. The image adjustment circuit according to claim 1, wherein determining the image type of the preliminary image according to the grayscale data of the preliminary image includes: if the image type is determined to be a light-dominant screen and If it is not judged as a dark-colored oriented image, the backlight level of any dark-colored oriented area in these areas is reduced by a second amplitude, the second amplitude is smaller than the first amplitude, and the light-colored oriented image is high gray The high-level pixels occupies most of the screen, the dark-color-oriented picture is a low-gray-level pixel occupies most of the picture, and the dark-color oriented area is an area where the low-gray pixel occupies the majority. The image adjustment circuit according to claim 7, wherein the image type is a webpage screen. The image adjustment circuit according to claim 7, wherein determining the image type of the preliminary image according to the grayscale data of the preliminary image includes: if the image type is determined to be the light-color guide screen, not changing the The backlight level of any dark-oriented areas in the area. The image adjustment circuit according to claim 1, wherein determining the image type of the preliminary image according to the grayscale data of the preliminary image includes: if the image type is determined to be a light-color oriented image, increasing all the In the backlight level of some areas, the light-color oriented picture is a picture with high gray-scale pixels occupying most of the picture.

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