针对复杂背景及目标的分形特性差异, 提取图像四个方向的灰度梯度, 选择最小梯度大于阈值的区域进行平滑滤波, 最后对分维参数进行分段线性拉伸-Extraction of image in four directions of the gray gradient, minimum gradient is greater than the threshold area smoothing filter, the last on the fractal dimension parameters of p