Patent ID: 7751633

Claim:
A method for compressing an image, said method comprising: a) converting source data into a series of blocks each containing one or more colors, said series of blocks including a first block, intermediate blocks, and a last block; b) determining a baseline target block size based upon a target compression ratio for said source data; c) for each block in turn, selecting a compression mode from mode families, wherein the mode families comprise an n-color mode family, an interpolated mode family, a raw mode family, a BTC-VQ mode family, a lossless mode family, and a 4×4 transform mode family; d) for each block in turn, compressing the block using the compression mode selected in step c) to yield a corresponding compressed block; and wherein step c) further comprises, c)(1) determining whether the number of colors in said block is less than or equal to a maximum number of colors capable of being transmitted in an n-color mode, while remaining within a current number of available bytes; c)(2) determining whether a maximum color range of the RGB components in the block is one of below and above a predetermined threshold in response to the number of colors in said block exceeding the maximum number of colors; c)(3) determining whether a 4×4 transform mode is capable of being used to compress the block in response to the maximum color range being above the predetermined threshold; and wherein step d) further comprises compressing the block using the 4×4 transform family mode in response to a determination that the maximum color range of the RGB components in the block is below the predetermined threshold at step c)(2) and that the 4×4 transform mode is capable of being used at step c(3).