Color image watermarking in HSI space

For graylevel images, the histogram based watermarking approach considers the image histogram as its signature and, by exact histogram specification, images are marked accordingly. This paper extends to color images the histogram based watermarking. Image marking is performed in the hue, saturation, intensity (HSI) space by creating notches in the intensity component histogram. The number of notches and their locations are the features which define each watermark. The detection is blind and of considerably low complexity. Robustness of the proposed method is investigated-tests performed using StirMark show that marking with notches ensures high robustness against many attacks: JPEG compression, geometric distortions (cropping, scaling, rotation, row and column removal, translation, etc.,), linear and nonlinear filtering