Matlab white pixels to line parameters

I have come as far as this picture below (it’s for placing a virtual ad in this football field) With my little knowledge of Matlab (at least for the image processing part) I need to determine for two sets of parallel lines their intersection points (vanishing points), but I am completely stuck…

Answer 1

[Matt J]

You can use HOUGHLINES to detect the different line segments in the image. As for auto-detecting which ones are world-parallel to each other, you could probably histogram the slopes/angles of the lines once you find them. It looks like any line segment up to 10 degrees part in the image would be world-parallel.