Image content-based geometric transformation resistant watermarking approach

This paper presents a content-based RST (rotation, scaling, and translation) resistant image copyright protection method. The image content is represented by IFPs (important feature points) obtained by the robust Harris detector-based feature extraction method. These IFPs are further used by the acute triangle matching method to determine the possible geometric attacks for reducing synchronization errors. The spread-spectrum-based blind watermark embedding and retrieval scheme is applied in the DFT (discrete Fourier transform) domain of each perceptually highly textured sub-image. The multiplicative scheme is used to embed the blind watermark at highly secure mid-frequency positions generated by one-way hash functions. The watermark detection decision is based on the number of matched bits between the recovered and embedded watermarks in embedding sub-images. Experimental results demonstrate that our algorithm yields good perceptual invisibility, adaptability, and security. It is also more robust to geometric and common image processing attacks than other peer approaches.