METHOD AND APPARATUS FOR EXTRACTING PIXEL VALUES

摘要

The invention provides a method and apparatus for extracting the luminance and chrominance values of pixels encoded according to MPEG or JPEG encoding using a forward discrete cosine transform (DCT). The invention applies theoretical work to mathematically analyse the forward DCT used in MPEG encoding to derive a set of equations which directly relate a pixel value in an encoded image to one or more of the DCT coefficients obtained via the forward DCT transform in the usual image encoding process. These predetermined equations are used in the invention to allow for extremely fast and computationally efficient extraction of pixel values directly from the DCT coefficients of an encoded pixel block, without having to undergo an inverse DCT transform. The invention is expected to be of use in any application where it is desirable to extract original images from MPEG and JPEG encoded versions in a fast and efficient manner.