Image processor and image processing method for decompressing progressive-coded compressed image data

An image processor for decompressing compressed image data, the compressed image data being obtained by dividing an original image into a plurality of blocks, dividing coefficient data obtained by performing orthogonal transformation for each block into a plurality of stages, and entropy-coding the coefficient data for each stage, the image processor comprising:

• a first processor having a compressed image memory for storing compressed image data;
• a second processor;
• and
• a common memory accessible from both the first processor and the second processor,
• wherein the first processor transfers compressed image data stored in the compressed image memory to the common memory,
• the second processor detects positions at which coded data at respective stages in a certain block are stored from the compressed image data transferred to the common memory,
• the first processor then transfers coded data at the respective stages from the compressed image memory to the common memory based on the positions detected by the second processor,
• and the second processor then entropy-decodes the coded data at the respective stages in the certain block transferred to the common memory, combines coefficient data at the respective stages in the certain block obtained by the entropy-decoding to form coefficient data for the certain block, performs inverse orthogonal transformation for the coefficient data, and determines if the plurality of blocks have been stored in a memory.