MATLAB  对 OpenCV  转化图像对照表

1.**Best way to apply a function to each element of Mat**

```
for( i = ... )//through each row in Mat M
    for(j = ...)//through each column
        M.at<T>(i,j) = tanh( M.at<T>(i,j) );
```

```
//大概比之前的要快一倍
for (int i = 0; i < contSize.height; ++i)
{
    T* ptr = mat.ptr<T>(y);
    for (int j = 0; j < contSize.width; ++j)
    {
        ptr[j] = ...;
    }
}
```

```cpp
//效率并非最快
MatIterator_<double> it, end;
for( it = I.begin<double>(), end = I.end<double>(); it != end; ++it)
{
    //do something here
}
```

2. 类型转换，通过convertTo 赋值到本身上，通过copy，完成非指针的拷贝
3. 矩阵相乘和点乘点除是有区别的