Hello, since you have data set of edge coordinate (x,y), you can:
(1) get the angle between this edge line and x-axis by doing linear fit.
Now you have the information of normal vector at well. The angle between normal vector and y-axis is same as angle between this edge line and x-axis.
(2) To rotate the image by θ, you can rotate every point (vector) by θ, then trigonometry states that the new coordinates (x', y') are
x' = x cos θ − y sin θ
y' = x sin θ + y cos θ
If you do not have data set of edge coordinate (x,y) at the very beginning, and you want to extract them from an image file, assuming that you have computer vision system toolbox, you can try detecting corners. Take a look at this page https://www.mathworks.com/help/vision/object-detectors.html, unfold "detect objects using point features".
