A Retinex-based Image Enhancement Scheme with Noise Aware Shadow-up Function
This is an incremental improvement for digital imaging applications, addressing noise issues in existing contrast enhancement methods.
The paper tackles low contrast in images under low light conditions by proposing a Retinex-based enhancement method with a noise-aware shadow-up function, achieving contrast improvement without over-enhancement or noise amplification.
This paper proposes a novel image contrast enhancement method based on both a noise aware shadow-up function and Retinex (retina and cortex) decomposition. Under low light conditions, images taken by digital cameras have low contrast in dark or bright regions. This is due to a limited dynamic range that imaging sensors have. For this reason, various contrast enhancement methods have been proposed. Our proposed method can enhance the contrast of images without not only over-enhancement but also noise amplification. In the proposed method, an image is decomposed into illumination layer and reflectance layer based on the retinex theory, and lightness information of the illumination layer is adjusted. A shadow-up function is used for preventing over-enhancement. The proposed mapping function, designed by using a noise aware histogram, allows not only to enhance contrast of dark region, but also to avoid amplifying noise, even under strong noise environments.