| 摘要 |
PROBLEM TO BE SOLVED: To provide a compression/expansion method for image data where a change in the image quality due to a change in image contents is reduced. SOLUTION: A coder 21 receives data as an original image. The coder 21 divides the image data into spatial frequencies (step 22), applies nonlinear conversion to selected frequency band images formed through the image data division (step 26) to change the data, applies quantization to the result (step 28) and compresses the data by compressing the quantized data into bit streams (step 30). Subsequently, the data are fed to a decoder, and the decoder executes the above processes in the reverse sequence. |
