Contrast enhancement of dark images using stochastic resonance

Two stochastic resonance (SR)-based techniques are introduced for enhancement of very low-contrast images. In the proposed SR-based image enhancement technique-1, an expression for optimum threshold has been derived. Gaussian noise of increasing standard deviation has been added iteratively to the low-contrast image until the quality of enhanced image reaches maximum. A quantitative parameter `distribution separation measure (DSM)` is used to measure the enhancement quality. In order to reduce the required number of iterations in the second enhancement technique the author`s have derived an expression for optimum noise standard deviation `_optimum that maximises signal-to-noise ratio (SNR). Image enhancement is obtained by iterating only with few noise standard deviations around σ_optimum. This reduces number of iterations drastically. Comparison with the existing methods shows the superiority of the proposed method.