Question

I have four points which form a rectangle, and I am allowing the user to move any point and to rotate the rectangle by an angle (which rotates each point around the center point). It stays in near-perfect Rectangle shape (as far as PointF precision allows). Here’s an example of my “rectangle” drawn from four points:

However, I need to be able to get the width and height between the points. This is easy when the rectangle is not rotated, but once I rotate it my math returns the width and height shown by the red outline here:

Assuming I know the order of the points (clockwise from top-left for example), how do I retrieve the width and the height of the rectangle they represent?

Answer 1

If by “width” and “height”, you just mean the edge lengths, and you have your 4 PointF structures in a list or array, you can do:

double width = Math.Sqrt( Math.Pow(point[1].X - point[0].X, 2) + Math.Pow(point[1].Y - point[0].Y, 2));
double height = Math.Sqrt( Math.Pow(point[2].X - point[1].X, 2) + Math.Pow(point[2].Y - point[1].Y, 2));