Fig. 1. Flow chart of the proposed algorithm

Fig. 2. Maping underwater color image to lαβ three channels. (a) Original image; (b) l channel; (c) α channel; (d) β channel

Fig. 3. Five basic tetrominoes

Fig. 4. Structure diagram of Tetrolet transformation

Fig. 5. Comparison of high-frequency details. (a) Tetrolet transform; (b) improved Tetrolet transform

Fig. 6. Effects on image edge of bilateral filtering. (a) Image region with noises; (b) value domain filtering; (c) bilateral filtering; (d) spatial domain filtering; e) filtering combination of spatial domain and value domain

Fig. 7. Images before and after Tetrolet processing. (a) Original images; (b) after Tetrolet processing

Fig. 8. Comparison of experiment results. (a) Original images; (b) Retinex method; (c) three-channel method; (d) proposed method