| 摘要 |
PURPOSE:To suppress deterioration of picture quality of picture data and to attain efficient coding. CONSTITUTION:A character block discrimination hart 22 divides input color picture data into 8X8 picture element blocks and applies DCT transformation to obtain the absolute sum of 5 transformation coefficients belonging to a low frequency area among AC components of the transformation coefficients obtained through DCT transformation. When the sum is larger than a predetermined threshold level, the block is discriminated to be a character block and when it is smaller, the block is discriminated to be a natural picture block. Acoording to the result of discrimination, a linear quantization hart 24 selects an optimum coding table for an optimum quantization table by a Huffman coding hart 26 to execute quantization and coding. |
