| 摘要 |
<p>PURPOSE:To secure the image quality of a restored image even in case of a high compression rate for image compression by dividing image data to blocks each of which consists of plural picture elements and subjects image data of each block to orthogonal transformation and assigning bits to only change points to compress data. CONSTITUTION:Image data photographed by an X-ray camera 3 is stored in an original image data memory 11 and is immediately read out and is divided into plural blocks by a block dividing part 12b. Each divided block is subjected to orthogonal transformation, for example, Fourier transformation by an orthogonal transforming part 13a. In a compressing part 14a, a feature detecting part 18 subjects transformed data to linear differentiation and quadratic differentiation to detect wave front values and change points as features. Bits are assigned to only wave front values and change points by a bit assigning part 19 to compress data. This compressed data is stored in an image data memory 16. Thus, an image having distinct edges is obtained though the compression rate is high.</p> |
