| 摘要 |
<p>PROBLEM TO BE SOLVED: To select the image quality of a JPEG compressed image on the side of image expansion, while keeping compatibility with a general JPEG decoder by encoding differential data between source image data and image data, which are decoded by encoding the source image data through a JPEG base line system, and outputting the encoded differential data in addition to the encoded data of source images. SOLUTION: For this image compressing device 10, the JPEG code data are decoded by a JPEG decoder 13, and image data are provided. A differential computing element 12 compares the range of colors with image data V, and when the image data V are included in the range, the differential data between image data and encoded data are found. Since the difference can become a negative value, the half value of maximum gradation is added to the difference between image data and encoded data so that differential data can be provided. The differential data are inputted to a JPEG encoder 11, and JPEG encoded differential data 15 are outputted. If the image data lie out of the range, the value of differential data is made into half the value of the maximum gradation.</p> |
