Color differences based fuzzy filter for extremely corrupted color images

• Adaptive fuzzy membership functions have been constructed in the proposed technique for both bell-shaped and triangle-shaped fuzzy sets.
• Idea of multiple fuzzy membership functions has been incorporated in an effective manner for the removal of impulse noise from degraded images.
• Detailed sensitivity analysis is presented, showing that different fuzzy membership functions perform better for different types of images at different noise ratio.
• Automatic selection of best suitable fuzzy membership function will definitely give the better filtering results.

In this paper, a color difference based fuzzy filter is presented for fix and random-valued impulse noise. Noise detection scheme of two stages was applied to detect noise efficiently whereas for noise removal an improved Histogram based Fuzzy Color Filter (HFC) is presented. Pixels detected as noisy by the noise detection scheme are deliberated as candidate for the removal of noise. Candidate noisy pixels are then processed using a modified Histogram based Fuzzy Color Filter to estimate their non-noisy values. The idea of using multiple fuzzy membership functions is presented, so that best suitable membership function for local image statistics can be used automatically. In the proposed technique we have used three different types of fuzzy membership functions (bell-shaped, trapezoidal-shaped, and triangular-shaped) and their fuzzy number construction algorithms are proposed. Experimentation is also performed with three, five, and seven membership functions. Type and number of suitable fuzzy membership functions are then identified to remove noise. Comparison with the existing filtering techniques is established on the basis of objective quantitative measures including structural similarity index measure (SSIM) and peak-signal-to-noise-ratio (PSNR). Simulations show that this filter is superior to that of the existing state-of-the-art filtering techniques in removing fix and random-valued impulse noise whereas retaining the details of the image contents.