meanshift均值平移跟踪算法中核函数窗宽的自动选取代码，根据目标大小变化核窗宽，使得当目标出现大小变化时准确跟踪到目标中心-Meanshift mean shift tracking algorithm in the kernel function of window width automatically select code, according to the target size change window width, that when the target size cha