Global DCT Domain Power Law Transformations in Image Enhancement Technique

Power Law Transformation (PLT) is a standard transformation function used in image enhancement techniques. PLT associates two constant parameters which can change an input value in different ways. The two PLT parameters can take different roles on different domains like spatial and transform domain. Discrete Cosine Transformation(DCT) is the popular transform domain used in image processing. Alpha Rooting (AR) and DCT block domain techniques are popular image contrast enhancement techniques which apply PLT on DCT domain. They are limited to edge contrast enhancement only. This paper describes an image enhancement technique which applies PLT on a global DCT domain like AR. PLT is applied only on AC coefficients while AR applies to all the DCT coefficients. This new technique can enhance global contrast, edge contrast and brightness of an image through a single function with three parameters. The results of this technique are compared with other techniques, applied on transformed domain for quality and quantity measure. This technique outperforms than the other techniques reported so far.