Abstract: A method and system of encoding and decoding image data in images having less than 128 distinct colors. Eight bit data bytes representing the color of each pixel data are re-indexed for each pixel to seven or less bits, and a sub-palette stores the relationship between the re-indexed colors and the original eight-bit color values. The remaining bits in the byte store run lengths of pixels that have contiguous colors. Further data compression is achieved by grouping pixels into rows, eliminating any duplicate rows and identifying the pixel data by a series of row pointers. Still further compression is accomplished by dropping representations of transparent pixels from the end of rows and representing a number of transparent pixels at the beginning of rows with a single byte. The compressed data is efficiently decoded using the row pointers to expedite vertical clipping of the image and adjusting horizontal clipping for leading and trailing transparent pixels.

Abstract: A method and system of encoding image data in images having less than 128 distinct colors. Eight bit data bytes representing the color of each pixel data are re-indexed for each pixel to seven or less bits, and a sub-palette stores the relationship between the re-indexed colors and the original eight-bit color values. The remaining bits in the byte store run lengths of pixels that have contiguous colors. Further data compression is achieved by grouping pixels into rows, eliminating any duplicate rows and identifying the pixel data by a series of row pointers. Still further compression is accomplished by dropping representations of transparent pixels from the end of rows and representing a number of transparent pixels at the beginning of rows with a single byte.