Public Watermarking Surviving General Scaling and Cropping: An Application for Print-and-Scan Process

Scaling and cropping are very common in today’s image processing software. When an image is printed-and-scanned, the final image is generally a cropped version of the rotated, scaled original image, with additional noises. The cropped image usually does not have the same aspect ratio as the original, so the DFT coefficients of the cropped image and the original would be quite different. In this paper, we propose an algorithm embedding spread spectrum watermarks in the DFT magnitudes of the log-log map magnitudes in the Fourier domain. These watermarks would be resistant to any aspect ratio of scaling and cropping and pixel value distortions as in the print-and-scan process.