Digital Image Watermarking Based on Fractal Image Coding

Abstract

This chapter proposes a watermarking technique using Ridgelet and Discrete Wavelet Transform (DWT) techniques. A wavelet transform is the wavelet function representation. A wavelet is a mathematical function which divides a continuous time signal into different scale components, where each scale components is assigned with a frequency range. Wavelets represent objects with point singularities, while ridgelets represents objects with line singularities. The Ridgelet transform Technique is a multi-scale representation for functions on continuous spaces that are smooth away from discontinuities along lines. The proposed technique applies Ridgelet transform on the cover image to obtain ridgelet coefficients. These coefficients are transformed by using 2-level DWT to get low frequency sub-bands – LL1 and LL2. The mutual similarities between LL1 and LL2 sub-bands are considered for embedding watermark. The obtained watermarked image has better quality when compared to a few exiting methods.

Digital Watermarking Using Fractal Coding

“…A robust fractal color image watermarking algorithm [1] was proposed by Jian Lu, Yuru Zou, Chaoying Yang, and Lijing Wangis to achieve a better tradeoff between robustness and high visual quality of a host image. Rao and Prasad have presented a method based on ridgelets and discrete wavelet transform techniques [14]. They have applied fractal coding technique on watermark for embedding into ridgelet coefficients of original image.…”