Visibility improvement in color video stream

Abstract

A new image enhancement process based on an integrated neighborhood dependent nonlinear approach for color images captured in various environments such extremely low lighting, fog or underwater. The new process is a combination of two independent processes: luminance enhancement and contrast enhancement. The luminance enhancement, also regarded as a process of dynamic range compression, is essentially an intensity transformation based on a specifically designed nonlinear transfer function, which can largely increase the luminance for dark regions of the image but only slightly change the luminance for the bright regions of the image. The contrast enhancement transforms each pixel's intensity based on the relationship between the pixel and its surrounding pixels. The output of the contrast enhancement is a power function of the luminance of the input image. The exponent of the power function is determined by the information obtained in the original luminance image, which is the ratio between the result of neighborhood averaging and the luminance of the center pixel. After contrast enhancement, the luminance image is converted back to a color image through a linear color restoration process with color saturation and hue adjustment.