On color-to-gray transformation for distributing color digital images

A new block embedding algorithm with a secret key is introduced for the Color-to-Gray and Back transformation. Color is embedded into the bit planes of the luminosity component of the YUV color space. We present an interface incorporated into Adobe Photoshop and consider a solution of the high quality digital image distribution problem. The solution is based on idea that the grayscale image with hidden color is a β version of a color original. Then a user could get a gray image before buying its color original he is interested. The proposed protocol has a secret key and can protect original images from unauthorized copying.