| 摘要 |
PROBLEM TO BE SOLVED: To provide the orthogonal transformation coding system in which prescribed excellent image quality is obtained for various input images and a high processing speed is attained. SOLUTION: N×M sets of picture element blocks are received from an input image and the picture element block is scanned by a zigzag scanning section 1, its output is orthogonally transformed by an orthogonal transformation section 2, its output is quantized by a quantization section 3 and its output is coded by an entropy coding section 4. A statistic variable arithmetic section 5 calculates a mean value, a variance and a standard deviation from the luminance of each picture element from the block from the zigzag scanning section 1, and a threshold level is decided based on the statistic variables. Picture elements whose luminance is regarded to be '0' less than the threshold level from each block picture element and stored in a picture element memory section. The processing is quickened by conducting orthogonal transformation, quantization and entropy coding based on the specification result of the picture elements. |
