Brightness Preserving Image Contrast Enhancement Using Weighted Mixture of Global and Local Transformation Functions

Transformation functions utilizing the global information content of an input image have been long serving contrastenhancement by stretching the dynamic range of intensity levels. Other transformation functions focus on local informationcontent to correct image details, such as edges and texture. In this paper, an effective method for image contrast enhancementis presented with a mapping function, which is a mixture of global and local transformation functions that improve both thebrightness and fine details of the input image. The final mapping function incorporates a local intensity-pair distributiongenerated expansion function from each image block to control the enhancement of image details that the globaltransformation function alone may fail to improve. Contribution from the global transformation function preserves the overallimage brightness and contrast stretching. Experiments show that the proposed method competes well with the existingenhancement methods, both subjectively and quantitatively