A novel robust image watermarking using a chirp based technique

In this study, we propose a new spread spectrum image watermarking algorithm that embeds linear chirps as watermark messages. The slopes of the chirp on the time-frequency (TF) plane represent watermark messages such that each slope corresponds to a different message. We extract the watermark message using a line detection algorithm based on the Hough-Radon transform (HRT). The HRT detects the directional elements that satisfy a parametric constraint in the image of a TF plane. The proposed method not only detects the presence of watermark, but also extracts the embedded watermark bits and ensures the message is received correctly. The robustness of the proposed scheme has been evaluated using common image processing techniques such as JPEG compression and image cropping, and we found that the maximum bit error rate to be 19.03% which is zero after post processing using HRT.