An Effective Method for Transferring Color to Gray Scale Image Using Luminance Matching without Human Intervention

In this paper, we are proposing a fully automatic method for adding colors to grayscale images. In contrast to many previous computer-aided colorizing methods, which require intensive and accurate human intervention, this method needs only the user to provide a target gray level image for the process of 'colorization', a colorful image of the similar content as the grayscale image is automatically retrieved from the database of images, as an input source image. Then, the source and target image are both transformed into a perceptually de-correlated color space. In this color space a best matching source pixel is determined for each pixel of the target image. The matching criterion uses the first order statistics of the luminance distribution in a small window around the source and target pixels. Once a best matching source pixel is found, its chromaticity values are assigned (transferred) to the target pixel while the original luminance value of the target pixel is retained. The only requirement of the method is that the compositions of the source and target scenes resemble each other.