Fusion technique for grey-scale visible light and infrared images based on non-subsampled contourlet transform and intensity-hue-saturation transform

An adaptive fusion technique based on non-subsampled contourlet transform (NSCT) and intensity–hue–saturation (IHS) transform is presented. First, the grey-scale visible light image is colourised by utilising a reference image, and then, the values of components I, H and S can be obtained via IHS transform, which can separate intensity information from spectrum information of the image. Second, multi-scale and multi-directional decompositions of the infrared image and the component I of the grey-scale visible light image are performed by NSCT. By adopting certain fusion rules, the low-frequency and high-frequency components of the fused image can be achieved. Third, being the component I of the final fused image, the grey-scale fused image can be gained by the use of inverse NSCT. Finally, the red–green–blue colourised fused image is reconstructed by the inverse IHS. Experimental results show that the technique is effective.