Rayleigh based bilateral filtering for flash and no-flash image pairs

Digital photography provides a quick and facile means to capture a pair of images i.e. flash and no-flash image. Digital images are often superimposed by noises at the acquisition stage depending upon the availability of lighting. Image denoising is a key technology to reduce the noise levels from the images while preserving the fine details and structures. Predominantly, conventional Bilateral filter is employed, providing better noise reduction capabilities with low noise density while preserving the edges. The spatial processing of pixels is reckoned by using a Gaussian function (symmetric and smoothly decaying function). This paper introduces a Bilateral filter which incorporates a Rayleigh distribution function in its domain filter to smoothen out the image pairs more effectively. This filter has been implemented on both the images (flash and no-flash) in the present work. Simulations are carried out on the images contaminated with different levels of Gaussian noise and are evaluated on the basis of Peak Signal-to-Noise Ratio (PSNR) and Structural Similarity (SSIM) as image quality parameters. Performance of the proposed filter has shown significant results when compared to the conventional Bilateral filter.