Method and apparatus for lossless and minimal-loss color conversion

Abstract

A method and apparatus for perfectly lossless and minimal-loss interconversion of digital color data between spectral color spaces (RGB) and perceptually based luma-chroma color spaces (Y′C B C R ) is disclosed. In particular, the present invention provides a process for converting digital pixels from R′G′B′ space to Y′C B C R space and back, or from Y′C B C R space to R′G′B′ space and back, with zero error, or, in constant-precision implementations, with guaranteed minimal error. This invention permits digital video editing and image editing systems to repeatedly interconvert between color spaces without accumulating errors. In image codecs, this invention can improve the quality of lossy image compressors independently of their core algorithms, and enables lossless image compressors to operate in a different color space than the source data without thereby becoming lossy. The present invention uses fixed-point arithmetic with signed and unsigned rounding normalization at key points in the process to maintain reversibility.

1 . In an electronic device, a method of lossless interconversion from a spectral color space to a perceptual color space and back, or from a perceptual color space to a spectral color space and back, using fixed-point arithmetic and precision augmentation. 
     
     
         2 . The method of  claim 1 , wherein normalization is applied not only to the final results but also to intermediate results, thus reducing necessary arithmetic precision. 
     
     
         3 . The method of  claim 1 , wherein each of a plurality of chroma components is normalized more than once, in order to reduce a required arithmetic precision.