Digital watermarking of images in wavelet domain

• Main Author: Huang, Fu Jin.
• Other Authors: Ang, Yew Hock
• Format: Theses and Dissertations
• Published: 2008
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Computer hardware, software and systems
• Online Access: http://hdl.handle.net/10356/4393
• Institution: Nanyang Technological University

The explosive growth in the use of the Internet has made it an attractive medium for the distribution of multimedia material. However, it has become apparent that the digital nature of such material makes enforcement and proof of copyright ownership virtually impossible. Another problem with digital images is that undetectable modifications can be made with very simple and widely available equipment. The research is to identify and develop a digital watermarking scheme that embeds an invisible digital watermark onto a still image without significantly affecting its image quality. A method based on the spatial frequency domain using Wavelet Transform (WT) algorithm is developed as a part of this project. The proposed scheme takes the Human Visual System (HVS) into consideration to reduce the visual distortion of the watermarked image. Multiple watermarks are embedded into the host image to improve the resilience to attacks and also to improve the reliability of watermark detection. A maximum of 9 watermarks are embedded into the different quadrants of wavelet coefficients. The amount of data hidden in the watermarked image depends on the amount of significant coefficients and background coefficients. These watermarks are embedded into different areas of different frequency bands. Thus, the resilience to both spatial and frequency image processing are improved.