函数1：pyrDown()
函数原型：
void pyrDown(InputArray src, OutputArray dst, const Size& dstsize=Size());
函数作用：
先对图像进行高斯平滑，然后再进行降采样（将图像尺寸行和列方向缩减一半）；
函数2：pyrUp()函数
函数原型：
void pyrUp(InputArray src, OutputArray dst, const Size& dstsize=Size());
函数作用：
先对图像进行升采样（将图像尺寸行和列方向增大一倍），然后再进行高斯平滑；
以及之前遗忘的一个知识点，一般进行二值化是对灰度图像进行二值化
//灰度图像二值化
threshold(gray,gray_B,125,255,THRESH_BINARY);
threshold(gray,gray_B_V,125,255,THRESH_BINARY_INV);
//灰度图像TOZERO变换
threshold(gray,gray_T,125,255,THRESH_TOZERO);
threshold(gray,gray_T_V,125,255,THRESH_TOZERO_INV);
//灰度图像TRUNC变换
threshold(gray,gray_TRUNC,125,255,THRESH_TRUNC);
//灰度图像大津法和三角法二值化
Mat img_Thr=imread("threshold.jpg",IMREAD_GRAYSCALE);
Mat img_Thr_0,img_Thr_T;
threshold(img_Thr,img_Thr_0,100,255,THRESH_BINARY|THRESH_OTSU);
threshold(img_Thr,img_Thr_T,125,255,THRESH_BINARY|THRESH_TRIANGLE);
//灰度图像自适应二值化
Mat adaptive_mean,adaptive_gauss; adaptiveThreshold(img_Thr,adaptive_mean,255,ADAPTIVE_THRESH_MEAN_C,THRESH_BINARY,55,0);
adaptiveThreshold(img_Thr,adaptive_gauss,255,ADAPTIVE_THRESH_GAUSSIAN_C,THRESH_BINARY,55,0);
