How to know if a line intersects a rectangle

Question

I have checked out this question, but the answer is very large for me:

How to know if a line intersects a plane in C#? - Basic 2D geometry

Is there any .NET

Answer 1

This code has better performance:

    public static bool SegmentIntersectRectangle(
        double rectangleMinX,
        double rectangleMinY,
        double rectangleMaxX,
        double rectangleMaxY,
        double p1X,
        double p1Y,
        double p2X,
        double p2Y)
    {
        // Find min and max X for the segment
        double minX = p1X;
        double maxX = p2X;

        if (p1X > p2X)
        {
            minX = p2X;
            maxX = p1X;
        }

        // Find the intersection of the segment's and rectangle's x-projections
        if (maxX > rectangleMaxX)
        {
            maxX = rectangleMaxX;
        }

        if (minX < rectangleMinX)
        {
            minX = rectangleMinX;
        }

        if (minX > maxX) // If their projections do not intersect return false
        {
            return false;
        }

        // Find corresponding min and max Y for min and max X we found before
        double minY = p1Y;
        double maxY = p2Y;

        double dx = p2X - p1X;

        if (Math.Abs(dx) > 0.0000001)
        {
            double a = (p2Y - p1Y)/dx;
            double b = p1Y - a*p1X;
            minY = a*minX + b;
            maxY = a*maxX + b;
        }

        if (minY > maxY)
        {
            double tmp = maxY;
            maxY = minY;
            minY = tmp;
        }

        // Find the intersection of the segment's and rectangle's y-projections
        if (maxY > rectangleMaxY)
        {
            maxY = rectangleMaxY;
        }

        if (minY < rectangleMinY)
        {
            minY = rectangleMinY;
        }

        if (minY > maxY) // If Y-projections do not intersect return false
        {
            return false;
        }

        return true;
    }

You can also check how it's work in JS demo: http://jsfiddle.net/77eej/2/

If you have two Points and Rect you can call this function like that:

    public static bool LineIntersectsRect(Point p1, Point p2, Rect r)
    {
        return SegmentIntersectRectangle(r.X, r.Y, r.X + r.Width, r.Y + r.Height, p1.X, p1.Y, p2.X, p2.Y);
    }