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Author: search.filters.author.Chotikakamthorn, NoppornSubject: search.filters.subject.Digital watermark

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    Printed Hypermedia Using Digital Watermarking Techniques
    (2002-12-01)
    Chotikakamthorn, Nopporn
    ;
    Kultrerattanarom, Siwaporn
    In this paper, a digital watermarking technique for image annotation has been applied for the purpose of turning a conventional printed medium into a hypermedia. By exploiting redundancy available in photographic images, hyperlink information can be invisibly embedded. To achieve the goal as stated, a spread spectrum-based watermarking method with high embedding capacity has been developed for the task at hand. In addition, by choosing image part for watermark embedding based on its spatial-hyperlink relationship, embedding of 'image map' coordinates is not needed. Computer experiments have been carried out to evaluated the proposed concept and the developed spread spectrum-based watermarking method.
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    Ring-shaped digital watermark for rotated and scaled images using random-phase sinusoidal function
    (2001-12-01)
    Chotikakamthorn, Nopporn
    ;
    Pholsomboon, Siriporn
    Digital watermarking for a still image is considered. A new spatial-domain watermarking method is presented. The method is applicable for rotated and scaled images. A watermark is constructed with a ring-shaped constraint. Sinusoidal function with random phase is used for generating each watermark ring. The method can not only be used for watermark detection in the presence of image rotation, but also for the estimation of the angle rotated, without the need for the original image. Practical method for construction of such a watermark is described. Results from experiments performed with images in electronic and printed forms, are provided.
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    Digital watermarking technique for image authentication by neighbouring block similarity measure
    (2001-12-01)
    Chotikakamthorn, Nopporn
    ;
    Sangiamkun, Wasin
    In this paper, the problem of image authentication by means of digital watermarking is considered. Inability of current solutions in dealing with identification of the authentic and altered image parts, under certain types of tampering and attacks, is identified. A new image verification scheme based on the test of relative similarity between neighbouring image blocks is proposed. Some relative similarity patterns are described. The method constructs the image signature such that it is block-wise dependent, and thus overcoming certain counterfeiting attacks suffered by previous methods. In addition, it can be used to identify cropping and block-shuffling types of attacks. Experimental results are included with concluding remarks.