Myujth

I have a simple function that attempts to loop through all the pixels in a single channel cv::Mat. Its not functioning correctly. I'm running this in xcode on ios sim.

cv::Mat fillEdge(cv::Mat floated) 
 float currentColor = 255.0;
 cv::Size shape = floated.size();
 int h = shape.height;
 int w = shape.width;

 int count = 1;

 for(int y = 0; y!= h; y++) 
 for(int x = 0; x!= w; x++) 
 cv::Point2i p(y, x);
 floated.at<int>(p) = currentColor;
 
 
 std::cout << floated.channels() << std::endl;
 // prints 1


 std::cout << floated << std::endl;
 return floated;

For some reason it prints a striped image.

Here is what the output of the cv::Mat looks like before the function returns

[255, 0, 0, 0, 255, 0, 0, 0, 255, 0, 0, 0, 255, 0, 0, 0, 255,
0, 0, 0, 255, 0, 0, 0, 255, 0, 0, 0, 255, 0, 0, 0, 255, 0,
0, 0, 255, 0, 0, 0, 255, 0, 0, 0, 255, 0, 0, 0, 255, 0, 0,
0, 255, 0, 0, 0, 255, 0, 0, 0, 255, 0, 0, 0, 255, 0, 0, ...

Ok, I changed your for loops condition check, changed the definition of your Point2i and also changed the template type of your at method from int to float, to maintain type integrity.

This should work now:

cv::Mat fillEdge(cv::Mat floated) 
 float currentColor = 255.0;
 cv::Size shape = floated.size();
 int h = shape.height;
 int w = shape.width;

 int count = 1;

 for(int y = 0; y < h; y++) 
 for(int x = 0; x < w; x++) 
 cv:Point2i p = cv:Point2i(x,y);
 floated.at<float>(p) = currentColor;
 //floated.at<float>(y,x) = currentColor; //You could also replace the two lines above with direct indexing (be careful with the order of the axis, as pointed by @Micka in the comments)
 
 
 std::cout << floated.channels() << std::endl;
 // prints 1


 std::cout << floated << std::endl;
 return floated;

You should use setTo:

cv::Mat fillEdge(cv::Mat floated) 
 float currentColor = 255.0;
 floated.setTo(cv::Scalar(currentColor));
 return floated;