Image contrast enhancement based on noise aware shadow-up function

摘要

This paper proposes a novel image contrast enhancement method based on a noise aware shadow-up function. Images taken by digital cameras have low contrast in dark or bright regions. This is due to a limited dynamic range which imaging sensors have. For this reason, various contrast enhancement methods have so far been proposed. However, conventional enhancement methods cause the loss of details in bright regions due to over-enhancement of contrast. In addition, most of conventional methods amplify noise in dark regions because they do not consider noise included images. The proposed method can enhance the image contrast without over-enhancement and noise amplification. In the proposed method, a shadow-up function is used for preventing over-enhancement and the loss of details in bright regions. In addition, a mapping function designed by using a noise aware histogram allows not only to enhance contrast of dark region, but also to avoid amplifying noise. Experimental results show the effectiveness of the proposed method by comparing the proposed ones with conventional ones.