Abstract
M.Ing.
The objective of this research is to develop a new robust and efficient adaptive watermarking method for JPEG compressed images, in which the watermark can survive even if the watermarked image undergoes manipulations. In this thesis, we present two image watermarking methods: one based on the spatial domain and the other on the DCT-based domain. Both approaches, which embed meaningful information into images for copyright protection, are blind watermarking schemes. To illustrate the robustness and performance enhancement derived from Error Correction Codes (ECC) when applied to watermarking, we propose Method I based on the Direct Sequence Spread Spectrum (DSSS) technique in conjunction with Reed-Solomon codes for raw images in the spatial domain. As is evident from our results, the introduction of Reed-
Solomon codes improves the robustness of a watermark. Also, employing the properties of pseudo-noise (PN) to deal with cropping attacks is investigated for this method. Based on Method I, we propose Method II that takes into account the properties of JPEG images and exploits the advantages of error correction codes (ECC). Furthermore, some modifications are introduced in the basic Spread Spectrum watermarking to improve the accuracy of the watermark retrieval process. Several experimental results are provided to demonstrate the performance of the proposed schemes. In these experiments, JPEG compression, cropping, brightness/contrast
adjustment, median filtering and noise addition are used as watermark attacks to evaluate the robustness. The experimental results show that the proposed scheme (Method II) is very robust against common image processing attacks.