Color transfer based on steerable pyramid and hot contrast for visible and infrared images

A color transfer scheme for visible and infrared images is presented. Two main procedures are included: image fusion using steerable pyramid in YUV color space, color transfer based on local mean value of infrared image to enhance hot contrast. Firstly, visible and infrared images are decomposed into 18 subband images with a 4-scale 4-oriatation steerable pyramid that contains one highpass subands, one lowpass subband and sixteen bandpass subbands. In each suband image, Y component of the fused image is formed by the pixels whose value is the larger one between the visible and infrared images. The weighted subtracting operations between visible and infrared constitute the U and V components. Then, during the process of color transfer, the local gray mean in the 5×5 window of the infrared image is concerned. The V component that represents the difference between luminance(Y) and red color is increased by the ratio of the local mean value to the global mean value. Therefore, the hot contrast of infrared is enhanced by rendering hot targets intense red color. Test results show that, the image fusion with the 4-scale 4-oriatation steerable pyramid multiples the paths to transfer the color and luminance of a target image into the fused images, thus, the transferred images are much more colorful, and synchronously reserve the two image's advantage that the visible image is good at situation awareness and the infrared image is superior in target detection.