Multi-region Nonuniform Brightness Correction Algorithm Based on L-Channel Gamma Transform

Nonuniform brightness distribution of collimator reticle images leads to the recognition difficulty of reticle grids and coordinate scales on images and affects the digitalization of reticle coordinate system. The article proposes an image quality improvement algorithm that operates on L channel of LAB color space to perform brightness correction. It designs four typical image modules depending on representative brightness features. Corresponding brightness correction models for all typical image modules are constructed by designing the new correction functions based on nonlinear gamma transform. A concept of brightness similarity is defined for automatic matching between typical image modules and the image region to be processed. On this basis, the algorithm can automatically adjust brightness correction mode to ensure the brightness of each pixel tends to be uniform, which is reflected in a visible improvement in the color distortion of the image. The algorithm can effectively reduce the complexity of model processing and adaptively adjust brightness correction intensity according to the pixel brightness value. It enables more accurate corrections with good results.