Pixel-level image fusion, which is widely used in remote sensing, medical imaging, surveillance and etc., directly combines the original information in the source images. As a pixel-level method, multi-focus image fusion is designed to combine the partially focused images into one fully fused single image, which is expected to be more informative for human or machine perception. To achieve this purpose, an algorithm using spatial frequency (SF) measure and discrete wavelet transform (DWT) for multi-focus image fusion is proposed. In this work, the source images are decomposed into low frequency components and high frequency components by using DWT. Then the spatial frequency of the low frequency components is calculated. The spatial frequency is used to judge the focused regions, followed by the morphological filter and median filter. The fused low frequency can be obtained. And the high frequency components are fused using traditional method. Finally, the fused image is obtained by doing inverse discrete wavelet transform. To do the comparison, the proposed algorithm is compared with several existing fusion algorithms in qualitative and quantitative ways. Experimental results demonstrate that our method can be competitive or even outperforms the methods in comparison.
Because of the platform motion and system internal asymmetric structure, Satellite-borne infrared imaging system will generate image geometric distortions such as translation, rotation, distortion and scaling, which make the subsequent target detection result not accurate. Therefore, we propose an image distortion method and deeply analyze the influence of infrared image distortion on the SNR of infrared weak small targets, detection probability and false alarm probability. The simulation results show that the image distortion directly affects the subsequent performance of the infrared target detection and tracking algorithm by changing target geometric imaging and signal to noise ratio. The research result in this paper would have great application value in the satellite-borne infrared alarm/warning system.