| 摘要 |
PURPOSE:To control data quantity after compression so as to be a desired value by determining beforehand the data quantity function of every block of a divided picture, and executing successively data compression as changing a scale factor for every block so that the actual compressed data quantity follows the data quantity function. CONSTITUTION:Input picture data is divided into plural pXq-pieces of the blocks consisting of nXn-picture elements in a horizontal and a vertical direction per one block, and two-dimensional discrete cosine transformation (DCT) is applied. The cumulative distribution Bs of sum of square bs is obtained for every block, and the data quantity function Gs converted proportionally so that the maximum value of the cumulative distribution Bs corresponds to the prescribed data quantity after compression is obtained. Next, the DCT factor of a head block obtained by processing P1 is quantized by dividing it by a value obtained by multiplying every threshold of a quantize matrix consisting of nXn pieces of the thresholds by the initial value Sf0 of the scale factor Sf. Subsequently, the data quantity after compression of the picture data of a compressed one block portion is counted, and the adjustment of the scale factor Sf is executed. |
