https://blog.csdn.net/oMoDao1/article/details/80324360
函数原型：
/** @brief Sets all or some of the array elements to the specified value.
This is an advanced variant of the Mat::operator=(const Scalar& s) operator.
@param value Assigned scalar converted to the actual array type.
@param mask Operation mask of the same size as \*this. Its non-zero elements indicate which matrix
elements need to be copied. The mask has to be of type CV_8U and can have 1 or multiple channels
*/
Mat& setTo(InputArray value, InputArray mask=noArray());
说明：
1、功能：把矩阵mask中元素不为0的点全部变为value值；
2、当默认不添加mask的时候，表明mask是一个与原图尺寸大小一致的且元素值全为非0的矩阵，因此不加mask的时候，
会将原矩阵的像素值全部赋值为value；
测试及验证：
1、mask元素全为0时
Mat src(3, 3, CV_8UC1);
Mat mask(3, 3, CV_8UC1, Scalar(0));
src.setTo(100, mask);
cout << src << endl;
输出结果：
[ 0, 0, 0;
0, 0, 0;
0, 0, 0]
2、mask元素全为非0时
Mat src(3, 3, CV_8UC1);
Mat mask(3, 3, CV_8UC1, Scalar(5));
src.setTo(100, mask);
cout << src << endl;
输出结果：
[100, 100, 100;
100, 100, 100;
100, 100, 100]
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作者：LoveWeeknd
来源：CSDN
原文：https://blog.csdn.net/oMoDao1/article/details/80324360?utm_source=copy
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