Method and apparatus for adjusting image brightness

Patent metadata

Field	Value
Publication number	US-9824430-B2
Application number	US-201514806142-A
Country	US
Kind code	B2
Filing date	Jul 22, 2015
Priority date	Jan 23, 2013
Publication date	Nov 21, 2017
Grant date	Nov 21, 2017

Abstract

Provided are a method and an apparatus for adjusting image brightness. The method includes: acquiring an image to be processed, and acquiring a single-channel brightness image based on grayscales of each channel of the image to be processed; performing Gaussian filtering on the single-channel brightness image to acquire a Gaussian filtered image; adjusting grayscales of the Gaussian filtered image based on the grayscales of the Gaussian filtered image and a preset proportion; comparing the Gaussian filtered image after adjustment with the Gaussian filtered image before adjustment to acquire a grayscale change rate of each pixel through adjustment; processing the image to be processed based on the grayscale change rate of each pixel to acquire a processed image; and outputting the processed image.

First claim

What is claimed is:

1. A method for adjusting image brightness, comprising:
acquiring an image to be processed, and acquiring a single-channel brightness image based on grayscales of each channel of the image to be processed;
performing Gaussian filtering on the single-channel brightness image to acquire a Gaussian filtered image;
adjusting grayscales of the Gaussian filtered image based on the grayscales of the Gaussian filtered image and a preset proportion;
comparing the Gaussian filtered image after adjustment with the Gaussian filtered image before adjustment to acquire a grayscale change rate of each pixel through adjustment;
processing the image based on the grayscale change rate of each pixel to acquire a processed image; and
outputting the processed image.

2. The method according to claim 1 , wherein the acquiring of the image to be processed, and the acquiring of the single-channel brightness image based on grayscales of each channel of the image to be processed, comprises:
acquiring the image to be processed, and comparing grayscales of respective brightness channels of each pixel; and
acquiring a maximum value from the grayscales of each pixel and determining the maximum value as a grayscale of each pixel to obtain the single-channel brightness image.

3. The method according to claim 1 , wherein the adjusting of the grayscales of the Gaussian filtered image based on the grayscales of the Gaussian filtered image and the preset proportion, comprises:
acquiring based on the number of pixels of the Gaussian filtered image: a grayscale of each pixel and the preset proportion, a first grayscale used for distinguishing a shadowy area and a highlighted area of the image; and
adjusting the grayscales of the Gaussian filtered image based on the grayscale of each pixel of the Gaussian filtered image and the first grayscale.

4. The method according to claim 3 , wherein the acquiring, based on the number of pixels of the Gaussian filtered image: a grayscale of each pixel and the preset proportion, a first grayscale used for distinguishing a shadowy area and a highlighted area of the image, comprises:
determining the number of pixels corresponding to each grayscale in an ascending order of grayscale, based on the grayscale of each pixel of the Gaussian filtered image;
determining a first value based on the number of the pixels of the Gaussian filtered image and the preset proportion; and
acquiring the first grayscale based on the first value and the determined number of the pixels corresponding to each grayscale.

5. The method according to claim 4 , wherein the acquiring of the first grayscale based on the first value and the determined number of the pixels corresponding to each grayscale, comprises:
accumulating the determined number of the pixels corresponding to each grayscale one by one; and
determining one grayscale as the first grayscale, if an accumulation result obtained before adding the number of the pixels corresponding to the one grayscale is less than the first value, and an accumulation result obtained after adding the number of the pixels corresponding to the one grayscale is greater than or equal to the first value.

6. The method according to claim 3 , wherein the adjusting of the grayscales of the Gaussian filtered image based on the grayscale of each pixel of the Gaussian filtered image and the first grayscale, comprises:
determining that an area formed by a first pixel is a shadowy area if a grayscale of the first pixel of the Gaussian filtered image is less than the first grayscale, and adjusting the grayscale of the first pixel by applying

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performing no adjustment on a grayscale of a first pixel, if the grayscale of the first pixel of the Gaussian filtered image is equal to the first grayscale; or
determining that an area formed by a first pixel is a highlighted area if a grayscale of the first pixel of the Gaussian filtered image is greater than the first grayscale, and adjusting the grayscale of the first pixel by applying

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Assignees

• Tencent Tech Shenzhen Co Ltd
• Tencent Tech Shenzhen Co Ltd

Inventors

• Hu Shimin
• Wang Jianyu
• Li Baoli
• Deng Haifeng
• Li Xianying

Classifications

• G06T5/002

  Physics · mapped topic

• G06T5/20 Primary

  using local operators · CPC title

• G06T5/009

  Physics · mapped topic

• G06T5/40

  using histogram techniques · CPC title

• G06T5/50

  using two or more images, e.g. averaging or subtraction · CPC title