US 12,462,358 B2
Method and device for changing a dynamic range of luminance of an image
Chengqiang Liu, Sichuan (CN); Zhimin Qiu, Sichuan (CN); and Chia Chen Chang, Sichuan (CN)
Assigned to MONTAGE LZ TECHNOLOGIES (CHENGDU) CO., LTD., Chengdu (CN)
Filed by MONTAGE LZ TECHNOLOGIES (CHENGDU) CO., LTD., Sichuan (CN)
Filed on Mar. 7, 2023, as Appl. No. 18/180,088.
Claims priority of application No. 202210227302.7 (CN), filed on Mar. 8, 2022.
Prior Publication US 2023/0289931 A1, Sep. 14, 2023
Int. Cl. G06T 5/00 (2024.01); G06T 5/40 (2006.01); G06T 5/50 (2006.01); G06T 5/92 (2024.01)
CPC G06T 5/92 (2024.01) [G06T 5/40 (2013.01); G06T 5/50 (2013.01); G06T 2207/10016 (2013.01); G06T 2207/20208 (2013.01)] 10 Claims
OG exemplary drawing
 
1. A method for changing a dynamic range of luminance of an image, the method comprising:
extracting luminance histogram information of all pixels of a frame to be processed, wherein the frame to be processed has an original dynamic range of luminance;
clustering all the pixels of the frame to be processed into pixel groups divided by multiple points by counting based on a predetermined rule, wherein each of the pixel groups includes a predetermined number of pixels, and pixels of each two adjacent pixel groups are divided by one of the multiple points;
summing pixel numbers corresponding to luminance values in the luminance histogram information till each of the multiple points to determine each of multiple luminance flag values corresponding to each of the multiple points and
determining a Bessel curve control point for fitting a Bessel curve indicative of the Bessel curve control point based on the multiple luminance flag values such that the frame to be processed is converted into a target frame with a target dynamic range of luminance based on the Bessel curve, wherein the Bessel curve associates original luminance values in the original dynamic range of luminance with target luminance values in the target dynamic range of luminance;
wherein determining each of the multiple luminance flag values corresponding to each of the multiple points comprises:
determining a luminance flag value anchorvalue corresponding to a point anchorthr based on equations below, when a summed pixel number sumprev till a luminance value i−1 and another summed pixel number sumcurrent till a luminance value i satisfy sumprev<anchorthr≤sumcurrent:
anchorvalue=(i−1)+ra,  (4)
ra=((anchorthr−sumprev)/histtab[i])
where histtab[i] represents a pixel number corresponding to the luminance value i in the luminance histogram information.