Image compression/decompression apparatus and method

An image compression method applicable to a compression apparatus composed of an image transformer, a context modeler composed of a context model template and a context model, and an encoder, for compressing a plurality of pixels of an image, in which each pixel is represented by at least a bit with a color value and location in said image;

• every said bits are located on different bit planes;
• said method comprises steps of:
• transforming all pixels of said image into a bit array comprising different bit planes each having a plurality of bits located in a same column;
• determining a number of column spacing of context model according to said number of bits of each pixel;
• determining a shape of context model correspondent to said context model template;
• covering a range of reference context bits in said bit array for a bit to be compressed;
• in the range, obtaining a plurality of reference context bits in a same bit plane of said bit to be compressed by using said context model;
• and
• encoding said bit to be compressed by using data of said reference context bits.