Dynamic range compression and contrast enhancement for digital images in the compressed domain

Abstract

We develop a simple and efficient algorithm for dynamic range compression and contrast enhancement of digital images in the compressed domain. The basic idea of our approach is to separate illumination and reflectance components of an image in the compressed domain. We adjust the amount of contribution of the illumination component to effectively compress the dynamic range of the image. For contrast enhancement, we modify the reflectance component based on a new measure of the spectral contents of the image. The spectral content measure is computed from the energy distribution across different spectral bands in a discrete cosine transform (DCT) block. The advantages of the proposed algorithm are (1) high dynamic range scenes are effectively mapped to the smaller dynamic range of the image, (2) the details in very dark or bright areas become clearly visible, (3) the computational cost is low, and (4) the compressibility of the original image is not affected by the algorithm. We evaluate the performance of the proposed algorithm with well-known existing methods, such as histogram equalization and alpha-rooting algorithm, using a few different enhancement quality metrics. (c) 2006 Society of Photo-Optical Instrumentation Engineers.