Question

Some sample code about image processing using OpenCV give somethings like this:

for(i=0;i<height;i++)
{
      for(j=0;j<width;j++)
      {
          if(pointPolygonTest(Point(i,j),myPolygon))
          {
                 // do some processing
          }
      }
}

In the iteration, why we need to start from height and width? and also why the Point is store (height, width) so that is -> (y,x) ?

Answer 1

Actually here, the row/column convention is used to iterate over the whole image.

height = Number of Rows

width = Number of Columns

The image is being accessed row wise.The outer loop is iterating over rows of the image and the inner loop is iterating on columns. So basically i is the current row and j is the current column of the image.

The inner loop processes a complete row of the image.