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Grid-line watermarking: A novel method for creating a high-performance text-image watermark
(2013-01-01)
Yawai, Wiyada
;
Hiransakolwong, Nualsawat
This study aims to discover an effective method to watermark any text image in any language. The ultimate goal of this work is to generate invisible and more robust watermarks, increase the hiding capacity, and identify any change in the original text. Generally these are the limitations of most text-image watermarking methods. Using a grid of horizontal and vertical lines is one of the most effective methods to overcome these limitations. These grid lines run across textimage character-skeleton lines to finely mark and detect watermarks on these line-character intersection points; there is one intersection for one specific zero watermark pixel. Each intersection point is defined by one hiding bit of the watermark such that the more reference horizontal and vertical lines of grid pattern are plotted, the more points of intersection are obtained. This approach increases the hiding-bit capacity to watermark embedding, which is a disadvantage shared by many text-image watermarking methods. In addition, if all positions of all intersection points are collected, these points will act as the identity reference points of all original characters to verify their integrities after they are modified.
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Increase the hiding-bit capacity and strength for text watermarking with the line intersection on text image
(2012-10-08)
Yawai, Wiyada
;
Hiransakolwong, Nualsawat
This research presents how to use the intersection position of horizontal line, virtually run across text character skeleton line on a text image under the cross ratio applying, to be the marking point of zero watermark; means watermarking without any actual watermark, which consequently increase the remarkable watermark hiding-bit capacity and robustness. One point of intersection across one text character skeleton line is one specific pixel which defined as one hiding-bit of zero watermark; just only marking its pattern, so that the more reference horizontal lines plotting, the more points of intersection would be got and increasing the hiding-bit capacity for watermarking which generally is the most limitation of other text watermarking methods. The high capacity for hiding bits means more chance to make many sets of redundant encrypted watermark data, in case some parts of text document image have been modified or tampered with. In addition, intersection points for virtually embedding watermarks still have a great strength for identifying the point of text which has been modified if all positions of intersection points are collected. Moreover, these intersection positions also has been applied with the cross ratio of four collinear points, to build up its robustness in order to survive from possibly attacking. The testing proved that this watermarking method can be effectively used to hide more redundant data, verify its integrity, be robust and easily apply it to multi-language text images such as English, Thai, Chinese and Arabic languages. © 2012 AICIT.
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A robust image watermarking using multiresolution analysis of wavelet
(2005-12-01)
Temi, Chirawat
;
Choomchuay, Somsak
;
Lasakul, Attasit
Embedding watermark in the wavelet becomes more attractive to most researchers as it could provide better performance. In this paper present a method of embedding binary visualized image into the host image by modifying coefficients of wavelet domain in LL bands with appropriate strength factor in order to compromise between acceptable imperceptibility level and attacks' resistance. Qualified Significant Wavelet Tree (QSWT) is used in both to select locations where watermark data are to be embedded, and to find locations of watermark in the extraction process. Results show that the proposed method successfully achieves robustness level of various attacks such as image processing, rotation attack etc. © 2005 IEEE.
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Digital watermarking methods of still images using the wavelet transform
(2002-01-01)
Thitimajshima, Punya
Digital watermarking methods of still images can be placed under two categories based on whether they cast the watermark in the spatial domain or in the transform domain. It was found that the transform domain watermarking schemes are typically much more robust to image manipulation as compared to the spatial domain schemes. In this paper, we will present a watermarking method based on the wavelet transform which does not require the original image for watermark detection. In our method, the original image is decomposed using multi-stage discrete wavelet transform. The watermark, generated by pseudo-random sequence, is added to all high-frequency coefficients that are above a given threshold. The watermarked image is finally obtained by using the inverse discrete wavelet transform. For watermark detection, we calculate the correlation between the wavelet coefficients of a possibly corrupted watermarked image and the watermark. By comparing the correlation with a predefined threshold, the embedded watermark can be detected. Experimental results are given to illustrate the robustness against smoothing, cropping, and JPEG compression.

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