In this paper, an efficient and robust image fusion method is proposed to extract pixel intensity under the best exposure value directly from a low dynamic range of images with variable exposure values. Using this method, the HDR (high dynamic range) image can be computed and shown on the traditional display device without any prior information on a camera or scene. The proposed image fusion method is based on a mathematical model of a pixel intensity curve, established by a special robust curve fitting arithmetic criteria to evaluate the image quality of each pixel. The sufficient experimentations on various scenes indicate that the proposed method is more efficient than traditional HDRI (high dynamic range imaging) technologies and more robust when imaging noise, object movement, and small camera displacement simultaneously.