METHOD FOR TRANSFORMING SIZE OF IMAGE AT BLOCK DISCRETE COSINE TRANSFORM DOMAIN

摘要

PURPOSE: A method for transforming the size of an image at a block discrete cosine transform domain is provided to randomly transform the size of the image and remarkably reduce the amount of calculation by simplifying window functions. CONSTITUTION: In the case of downsampling, 8xM samples are made by inserting M-1 zeros in the back of each sample of a DCT(Discrete Cosine Transform) block formed of 8 samples. The adjacent 8xM samples are symmetrically convoluted with DCT coefficients of M window functions. Upper 8 samples of the M results of the symmetrical convolution are added with each other to make 8-sample DCT. In the case of upsampling, 8xL samples are made by inserting (L-1)x8 zeros after each sample of a DCT block formed of 8 samples. 8xL samples are symmetrically convoluted with DCT coefficients of L window functions. Every L sample is collected from the 8xL sample result value of the symmetrical convolution to make L 8-sample DCT block.