Image scaling in the compressed domain

摘要

An efficient compressed-domain-based algorithm that works by combining the IDCT and pixel-domain averaging into a single compressed domain operation, where a part of the cost of even this simplified operation can be absorbed into the de-quantization process. The original image need not be decompressed fully, only to the point of extracting the transform coefficients. Compressed-domain scaling for all scales k/8 for 1<=k<=8, including 3/8, 5/8, ¾, 7/8, is provided. By chaining multiple operations, any scale factors of the form k₁k₂ . . . k_l/8^l for integers k_i's in the range [1,7] can be achieved.