Noise-induced contrast enhancement of dark images using non-dynamic stochastic resonance

In this paper, a nonlinear non-dynamic stochastic resonance-based technique has been proposed for enhancement of dark and low contrast images. A low contrast image is treated as a subthreshold signal and noise-enhanced signal processing is applied to improve its contrast. The proposed technique uniquely utilizes addition of external noise to neutralize the effect of internal noise (due to insufficient illumination) of a low contrast image. Random noise is added repeatedly to an image and is successively hard-thresholded followed by overall averaging. By varying the noise intensities, noise induced resonance is obtained at a particular optimum noise intensity. Performance of the proposed technique has been investigated for four types of noise distributions - gaussian, uniform, poisson and gamma. Quantitative evaluation of their performances have been done in terms of contrast enhancement factor, color enhancement and perceptual quality measure. Comparison with other existing spatial domain techniques shows that the proposed technique gives remarkable enhancement while ascertaining good perceptual quality.