Estimating the embedding capacity of a color image using Color Difference

Digital image watermarking has been widely applied to solve the copyright protection problems of the color image, related to illegal usage or distribution. The invisible image watermarking scheme is the type where the watermark is hidden in the cover image. Estimating the embedding capacity and maintaining perceptual quality of the cover image are the important issues in invisible watermarking. We propose a scheme for quantifying the embedding capacity of the color image considering Human Visual System (HVS). This scheme uses the threshold value of Just Noticeable Color Difference (JNCD) to estimate the number of bits that can be changed between the perceptual indistinguishable colors. The maximum change in the number of bits of a color is used to estimate tolerable embedding capacity of color. The watermark embedding capacity of image is calculated by summing the capacity of colors of an image.