A method and apparatus for efficiently encoding images using a set of
non-orthogonal basis functions, thereby allowing reduction of file size,
shorter transmission time, and improved accuracy. The non-orthogonal
basis functions include homogenous color basis functions,
luminance-encoding basis functions that have luminance edges and
chromatic basis functions that exhibit color opponency. Some of the basis
functions are non-orthogonal with respect to each other. Using these
basis functions, a source vector is calculated to provide a number of
coefficients, each coefficient associated with one basis function. The
source vector is compressed by selecting a subset of the calculated
coefficients, thereby providing an encoded vector. Because the method is
highly efficient, the image data is substantially represented by a small
number of coefficients. In some embodiments, the non-orthogonal basis
functions include two or more classes. A wavelet approach can also be
utilized.