Single image dehazing via reliability guided fusion

• Dark Channel Prior (DCP) accuracy is improved by block- and pixel-level processing.
• Reliability guided fusion of block and pixel dark channels produce fine transmission.
• DCP failure probability is reduced by an edge-preserving increase of the patch-size.
• DCP failure in sky is handled by limiting contrast boost of the sky-like regions.
• A downscaling method for fast transmission computation has also been proposed.

This work addresses the shortcomings of the dark channel prior (DCP) and proposes a new and efficient method for transmission estimation. First, the accuracy of block-level and pixel-level dark channels is improved and a reliability map is generated. Then, through reliability guided fusion of block-level and pixel-level dark channels, a high-quality refined transmission map is obtained. The proposed method reduces the DCP failure probability and haloes by increasing the patch-size in an edge-preserving manner. DCP failure in the sky (bright) regions is handled by limiting the contrast boost of sky-like surfaces. This produces a more natural recovery of the sky regions. A downscaling method for fast transmission computation has also been proposed. Quantitative and qualitative comparisons show that the proposed method outperforms existing methods in terms of quality and speed. The proposed reliability guided fusion scheme is about 60 times faster than other well-known DCP based approaches.