Local Color Correction Using Non-Linear Masking

Tone reproduction is a key component in image quality and historically tone correction has been performed on a global basis for a given device or image. Several recent investigations have used a variety of algorithms to demonstrate that local color correction provides a significant improvement in image quality relative to a global correction. This paper presents a local color correction operation that is based on non-linear masking. The operation is very fast and does not require any manual adjustments, such as those involved in dodging and burning. The algorithm is roughly equivalent to deriving a specific tone reproduction curve for each pixel in the image. An example image is processed using the proposed masking scheme and the resulting effect is discussed. Finally, the relationship to CIECAM97s is explored and it is proposed that dynamically setting the background parameter results in similar local color corrections.