| 摘要 |
PROBLEM TO BE SOLVED: To provide a method to identify whether or not an image has so far been compressed in compliance with the JPEG. SOLUTION: In this method, an absolute value of differences between two pixels adjacent to each other in horizontal and vertical directions is calculated (S1) with respect to a prescribed number of pixels of an image. The results are classified into a 1st difference equivalent to that in a region I in crossing with a block border and a 2nd difference equivalent to that in a region II not in crossing with the block border, a histogram is calculated from samples in the regions I, II (S3), each histogram is normalized (S4), and whether or not the image is compressed is decided based on a difference between the two normalized histograms (S5, S6). |
