Unsymmetrical Trimmed Midpoint as Detector for Salt and Pepper Noise Removal

A fixed 3x3 window, Unsymmetrical trimmed midpoint is used as a detector for the detection of fixed valued impulse noise is proposed for the increasing noise densities. The processed pixel is termed as noisy, if the absolute difference between processed pixels and unsymmetrical trimmed midpoint is greater than fixed threshold. Under high noise densities the processed pixel is noisy, so the median of the ordered array is found. The median is checked using the above procedure. If found true then the computed median is considered as noisy hence the corrupted pixel is replaced by the Unsymmetrical Trimmed midpoint of the current processing window. If median is not noisy then replace the median of the current processing window else if the pixel is termed uncorrupted, it is left unaltered. The proposed algorithm (PA) is tested on different varying detail images. The proposed algorithm is compared with the standard algorithms and found to give good results both qualitative and quantitatively for increasing noise densities. The proposed algorithm eliminates salt and pepper noise up to 80% and preserves edges up to 70%.