Abstract
With popularity of Digital Still Camera-DSC, higher image quality is required. One of the subjects is that invisibility of shadow area caused by the narrow dynamic range of the CCD elements is improved automatically. Conventionally, gamma transformation, histogram equalization, and etc. have been utilized for the improvement but they were not always good enough. Recently, examinations applying to Retinex theory taking into account of human eyes characteristics proposed by Land are paid attention. This algorithm renders image clearly in shadow area effectively using spatial information between surrounding pixels arranged in two dimensions. However, some subjects such as dependency by adjustment parameters for output images and decrease of the density have been pointed out. This paper describes about the improvement algorithm which solved these subjects for contrast based on the Retinex theory and the effectiveness is shown by experiments using actual DSC images. And also, we describe about processing method of this algorithm at a higher speed.
