Logarithmic profile mapping and Retinex edge preserving for restoration of low illumination images

Contents carried in an image are valuable information sources for many scientific and engineering applications. However, if the image is captured under low illumination conditions a large portion of the image appears dark and this heavily degrades the image quality. In order to solve this problem, a restoration algorithm is developed here that transforms the low input brightness to a higher value using a logarithmic mapping function. The mapping is further refined by a linear weighting with the input to reduce the un-necessary amplification at regions with high brightness. Moreover, fine details in the image are preserved by applying the Retinex principle to extract and then re-insert object edges. Results from experiments using low and normal illumination images have shown satisfactory performances with regard to the improvement in information contents and the mitigation of viewing artifacts.