My Research
Detection of a digital watermark in images distorted by geometric transforms is made difficult by the so-called synchronization problem. Many watermarking methods have been developed to be robust against an affine transform. Based on such assumption, those methods fail under a more general projective transform. In this research, a method that is invariant to planar projective transform is presented. The method is based on a projective invariance property of the cross-ratio of four collinear points. Based on four coplanar points as obtained by extracting feature points from the host image, two sets of three collinear points are obtained. From each set of three collinear points, each watermark embed- ding location can be obtained through its cross-ratio relationship with those aforementioned three collinear points. The method to embed the watermark information by using alpha channel is also developed to increase the quality of embedded images.
Digital Watermarking Technique for Projective-Distorted Images Using Collinear Points
Publication
Natapon Pantuwong, Wiyada Yawai, and Nopporn Chotikakamthorn, “Digital Watermarking Technique for Projective-Distorted Images Using Collinear Points”, EUSIPCO 2005
Nopporn Chotikakamthorn, Natapon Pantuwong,and Wiyada Yawai, “Projective-Invariant Digital Image Watermarking Technique Using Four Co-Planar Feature Points”, IEEE ICIP 2005
Natapon Pantuwong and Nopporn Chotikakamthorn, “Cimparative Study of Two Projective-Invariant Digital Watermarking Methods Using Cross-Ratios and Line Intersections”, IEEE CIT 2005
Nopporn Chotikakamthorn and Natapon Pantuwong, “Attacks on Feature-Based Affine-Invariant Watermarking Method”, IEEE CIT 2005
Natapon Pantuwong and Nopporn Chotikakamthorn, “Line Watermark Embedding Method for Affine-Transformed Images”, ISSPA 2007
Natapon Pantuwong and Nopporn Chotikakamthorn, “Alpha Channel Digital Image Watermarking Method”, IEEE ICSP 2008
