| 摘要 |
PURPOSE:To prevent increase in noise resulting from a DCT processing by limiting a band of an image signal to make compressed data quantity constant without increasing a compression rate of an image data compression section. CONSTITUTION:Image data are divided into plural blocks basically and orthogonal transformation is applied to each block and an orthogonal transformation coefficient is used for a quantization coefficient to quantize the data and a prescribed code is assigned to each of the quantized data to form quantization data. Concretely, a band characteristic control section 1 is used to limit a band characteristic to the image data and a DCT arithmetic operation section 2 sets a DCT coefficient. The DCT coefficient is divided by a quantization coefficient on a quantization table set in advance by a CPU 9 at a quantization section 3 and fractions are rounded off. The DCT coefficient obtained in this way is subject to run length coding and Huffman coding at a coding section 4 to compress the data. |
