Variational Retinex Algorithm with its Application to a High - Quality Chroma Key

The Retinex theory deals with separation of irradiance and reflectance from an image. Recently, Kimmel and others proposed a variational framework that unifies the previous Poisson-equation-type Retinex algorithms developed by Horn and others, and presented a separation algorithm with the time-evolution of a linear diffusion process. However, this separation algorithm cannot achieve physically rational separation, if true irradiance varies among color channels. To cope with this problem, we introduce a nonlinear diffusion process into the time-evolution. Moreover, we introduce an approach to treat all color channels collectively. Furthermore, we apply our separation algorithm to a high quality chroma key where a color of each pixel in the foreground frame are adaptively corrected through transformation of the separated irradiance.