Color image watermarking based on self-embedded color permissibility with preserved high image quality and enhanced robustness

Semiblind copyright protection of color images based on a hybrid classified watermarking technique

“…As prescribed in Ref. 23, the extent of the perceptual redundancy of a color varies with the color space where it is represented. The perceptual redundancy of a color can be quantitatively measured by calculating the distance between that color and each of all possible colors that can be barely differentiated from it by visual perception.…”

“…(23), is owned to the fact that the PW-based watermarking includes only the three (out of four) largest DWT sub-bands.…”

“…Furthermore, if we are to describe the color content of an image, we would use terms such as red, dark yellow, or bright green (not RGB values), 23 since we tend to focus on and remember bright-saturated regions and large color regions present in an image.…”

“…23, the concept of color permissibility was introduced as a measure of the degree of color imperceptibility, where the strength of the watermark was controlled based on the allowable color permissibility. To achieve a high level of watermarking imperceptibility, the watermark was supposed to be embedded and detected in the chromaticity components in the DWT domain in a spread-spectrum fashion.…”

“…The watermark weights are generated based on the so-called "color permissibility" of the U and V planes of the color image under consideration. 23 It is expected, when combining the two algorithms (PW and SECP), to get a highly robust color image watermarking technique. This can be done, roughly speaking, by applying PW to the luminance component and SECP to the chrominance components of the RGB image.…”