Area of intersection between circle and rectangle

Question

I\'m looking for a fast way to determine the area of intersection between a rectangle and a circle (I need to do millions of these calculations).

A specific property

Answer 1

Here is another solution for the problem:

public static bool IsIntersected(PointF circle, float radius, RectangleF rectangle)
{

        var rectangleCenter = new PointF((rectangle.X +  rectangle.Width / 2),
                                         (rectangle.Y + rectangle.Height / 2));

        var w = rectangle.Width  / 2;
        var h = rectangle.Height / 2;

        var dx = Math.Abs(circle.X - rectangleCenter.X);
        var dy = Math.Abs(circle.Y - rectangleCenter.Y);

        if (dx > (radius + w) || dy > (radius + h)) return false;


        var circleDistance = new PointF
                                 {
                                     X = Math.Abs(circle.X - rectangle.X - w),
                                     Y = Math.Abs(circle.Y - rectangle.Y - h)
                                 };


        if (circleDistance.X <= (w))
        {
            return true;
        }

        if (circleDistance.Y <= (h))
        {
            return true;
        }

        var cornerDistanceSq = Math.Pow(circleDistance.X - w, 2) + 
                    Math.Pow(circleDistance.Y - h, 2);

        return (cornerDistanceSq <= (Math.Pow(radius, 2)));
}