Color to gray and back: Color embedding into textured gray images

Abstract

We have developed a reversible method to convert color graphics and pictures to gray images. The method is based on mapping colors to low-visibility high-frequency textures that are applied onto the gray image. After receiving a monochrome textured image, the decoder can identify the textures and recover the color information. More specifically, the image is textured by carrying a sub-band (wavelet) transform and replacing band-pass sub-bands by the chrominance signals. The low-pass sub-band is the same as that of the luminance signal. The decoder performs a wavelet transform on the received gray image and recovers the chrominance channels. Registration problems are discussed and examples are presented.