Manipulating specific x,y values of a cv::Mat?

Question

What is the simplest way to modify a direct x,y location of a cv::Mat object? I have a cv::Mat called 'temp' which has an image in it, and what if I wanted to turn each pixel pink, one by one?

I tried something of the following:

for (int i = 0; i < temp.size().width; i++)
{
    for (int j = 0; j < temp.size().height; j++)
    {
        temp.at(cv::Point(i, j)) = 255;
        cv::waitKey();
    }
}

but that won't even compile..

Answer 1

The way to use at in this case is temp.at<unsigned char>(i, j). Here is an example :

 Mat H(100, 100, CV_64F);
 for(int i = 0; i < H.rows; i++)
    for(int j = 0; j < H.cols; j++)
        H.at<double>(i,j)=1./(i+j+1);

For the complete description look here: http://opencv.itseez.com/modules/core/doc/basic_structures.html#mat-at