Luma-Dependend Nonlinear Image Enhancement (LDNE)
Direct observation from human eyes and recorded color images from digital camera or camcorder of a scene are often significantly different, because human visual perception computes the conscious representation with vivid color and details in shadows under unexposed light condition, and with resistance to spectral shifts in the scene luminance. Image enhancement for color images which approaches fidelity to scene observation must combine dynamic range compression, color consistency and lightness tonal rendition. Luma-dependent nonlinear enhancement (LDNE) is a luminance based multi-scale center/surround retinex algorithm, which achieves simultaneous dynamic range compression, color consistency and lightness rendition. LDNE processes images captured under extremely dark environmental conditions. LDNE rectifies the drawbacks of other conventional algorithms by maintaining the dynamic range compression and automatically adjusting the color.LDNE algorithm can be implemented in a real time environment for nonlinear enhancement of images captured by a video camera.
Integrated Neighborhood Dependent Approach for Image Enhancement (INDANE)
INDANE (Integrated Neighborhood Dependent Approach for Nonlinear Enhancement of Color Images) is a new image enhancement algorithm, which combines two independent processes: luminance enhancement and contrast enhancement. The luminance enhancement is regarded as a process of dynamic range compression. It is based on a specifically designed nonlinear transfer function which can largely increase the luminance for dark regions but just slightly change the luminance for the bright regions. The contrast enhancement transforms the pixel’s intensity based on the relationship between the center pixel and its surrounding pixels. INDANE processes images with deep shadow and light contrast. After contrast enhancement, the intensity image is converted back to color image through a linear color restoration process with color saturation and hue (white balance) adjustment.
