Low Illumination Image Enhancement Algorithm Based on DT-CWT and Tone Mapping

To improve the quality of low illumination image, based on DT-CWT and tone mapping, an image enhancement algorithm is proposed. First, the RGB image is converted into the HSV color space whose luminance component V will be divided into high and low frequency sub-bands by DT-CWT. The high-frequency sub-band is processed by Butterworth filter to enhance the image details and suppress the noise while the low-frequency sub-band is managed by the improved tone mapping to adjust the image illumination. Finally, DT-CWT inverse transformation is applied to obtain the reconstructed V component which is synthesized with the H and S components to obtain a clear RGB image. In this paper, we make full use of excellent characteristics of accurate image-detail expression of DT-CWT which is combined with the improved tone mapping algorithm based on Retinex theory to achieve the enhancement of low illumination image. The experiment results show that the proposed algorithm can obviously improve the visual effect of the low illumination color image.