Infrared Image Enhancement Algorithms And Its DSP Implementation

With the development of infrared imaging technology, the infrared thermal imager has been widely used in many field of military and civilian. Since the infrared image have the ubiquitous shortcomings of edge blur, low contrast and noise, the enhancement algorithm for infrared image has been widely studied. Traditional algorithms mostly deal with image data of8-bit. But modern high performance infrared camera can output high dynamic range image data of12-16bit. In view of this, the author proposes a framework of algorithm based on image separating.The proposed framework is as follows:First, we use a filter to smooth the input raw image data to obtain the smoothed image data as the base layer; Secondly, we get the difference of the base layer and the raw data as the detail layer; Then, the base layer is compressed to a proper dynamic range for display and the detail layer is enhanced; Finally, we combine the processed detail layer and base layer and get the output image.This paper analyzes three smoothing filter (the Guided Image Filter, the Bilateral Filter and the Weighted Least Squares Filter) of their smoothing effect, noise suppression and the capacity of detail extraction and makes a detailed comparison of their feature and usage occasion. For the compression of base layer, the author focus on the gamma curve and histogram based algorithms. For the enhancement of the detail layer, a noise-suppression enhancement technique has been proposed based on human visual system.Based on the above analysis, this paper proposes a set of algorithm framework based on Guided Image Filter and improved histogram projection method and implements the algorithm on TMS320C6678DSP chip. Experimental result shows that the proposed method can effectively enhance the image detail, improve the overall contrast and suppress background noises. Since the algorithm have less computation amounts, it is suitable for engineering applications.