程序说明: //该函数用来对图像进行阈值变换。对于灰度值小于阈值的象素直接设置 灰度值为0；灰度值大于阈值的象素直接设置为255。-procedures : / / This function used to image transform threshold. For gray value less than the threshold value of the pixel intensity value directly set to 0; Gray value greater than the threshold value of the pixel is set to direct 255.