Method for tone mapping based on histogram equalization

A histogram equalization and tone mapping technology, which is applied in image enhancement, image data processing, instrumentation, etc., can solve the problems of loss of image details, inability to adapt to different areas of the image, etc., and achieve suppression of oversaturation and good color performance Effect

Inactive Publication Date: 2013-10-16
SUN YAT SEN UNIV
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Problems solved by technology

But its disadvantage is that the fixed transformation curve cannot adapt to different areas of the image, resulting in the loss of details in the dark and bright parts of the image.

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  • Method for tone mapping based on histogram equalization
  • Method for tone mapping based on histogram equalization
  • Method for tone mapping based on histogram equalization

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Embodiment Construction

[0051] The present invention will be described in further detail below in conjunction with the accompanying drawings. In the embodiment, the method of the present invention is used to process a picture such as figure 1 The high dynamic range image shown is processed as follows:

[0052] Step 1: Input a high dynamic range image.

[0053] Step 2: Obtain the brightness value of the image according to the RGB color channel value of the input image and convert it to the logarithmic domain LI .

[0054] Step 3: Histogram statistics. Specifically: Find the logarithmic domain formula obtained in the second step LI the minimum value in L min and the maximum L max ,will be[ L min , L max ]’s dynamic range is evenly divided into N parts, so that the continuous logarithmic brightness value falling within a certain interval is discrete into the corresponding brightness level in [0, N-1], namely:

[0055] (1)

[0056] in, Indicates a round down operation. ...

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Abstract

The invention discloses a method for tone mapping based on histogram equalization. The method comprises the steps of: 1) inputting a high-dynamic range image; 2) acquiring the image brightness and converting the image brightness into a log domain; 3) carrying out histogram statistics; 4) calculating the average brightness of the image, and carrying out segmentation on the histogram by taking the average brightness as a segmentation point; 5) carrying out differentiation setting on mapping parameters of two segments of the histogram; 6) carrying out a histogram equalization algorithm in a segmentation mode; 7) restoring a brightness channel after the tone mapping to an RGB color space; and 8) outputting a displayable low-dynamic range image. According to the invention, the differentiation setting is carried out on the mapping parameters of the two segments after the histogram is segmented, and a bright background is enabled to map linearly as far as possible so as to reduce missing of a highlight part, and a foreground part is still subjected to histogram equalization processing so as to expand the contrast ratio of the image. The method disclosed by the invention can effectively maintain the original brightness of the image while increasing the contrast ration of the image, and effectively improves a phenomenon of brightness saturation in a classical histogram equalization algorithm.

Description

technical field [0001] The present invention relates to a method for displaying a high dynamic range image on a low dynamic range display device, and more specifically, to a mapping method for segmenting the histogram according to the average brightness of the input image and setting two segments differentially parameters, so that the tone mapping method based on histogram equalization is better than the classic histogram equalization algorithm. Background technique [0002] A high dynamic range image is an image that can represent high dynamic range luminance information in a real scene. In recent years, it has been widely used in digital photography, film special effects, image-based virtual reality, satellite remote sensing technology and other fields. However, most display devices today only support low dynamic range displays. High dynamic range images cannot be reproduced well on traditional display devices, and it is also difficult to store, transmit, and process the...

Claims

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Application Information

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IPC IPC(8): G06T5/00
Inventor 谭洪舟朱雄泳徐燕丽陈荣军
Owner SUN YAT SEN UNIV
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