| 摘要 |
PURPOSE: A method for extracting rotation and scale information by using the symmetry of auto-correlation is provided to increase the detection performance of a watermark by rapidly and accurately performing peak extraction for correcting the geometrical deformation. CONSTITUTION: A watermark signal is estimated from a geometrically deformed and watermarked image(S1), and autocorrelation is calculated(S21). A cross shift of a 4 quadrant is performed(S22). A candidate peaks having large energy value and a center peak from a 1 quadrant are extracted(S23). From the extracted peaks, the rotated angle and size-changed ratio are calculated. Therefore, geometrical deformation information is detected(S3). |
