opencv：USM锐化

USM：unsharp mask

对小的细节干扰小，对大的细节进行锐化

Mat dst;
Mat blur_image;
GaussianBlur(src, blur_image, Size(3, 3), 0);
Laplacian(src, dst, -1, 1, 1.0, 0, BORDER_DEFAULT);
imshow("Laplacian", dst);
Mat usm_image;
addWeighted(blur_image, 1.0, dst, -1.0, 0, usm_image);
imshow("usm filter", usm_image);