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thecocce/PerspectiveImage.hx

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Created December 25, 2019 17:50
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  1. @andyli andyli created this gist Apr 9, 2010.
    66 changes: 66 additions & 0 deletions PerspectiveImage.hx
    View file
    Original file line number Diff line number Diff line change
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    //Ported from the work of Zeh:
    //http://zehfernando.com/2010/the-best-drawplane-distortimage-method-ever/

    import flash.display.BitmapData;
    import flash.display.Graphics;
    import flash.geom.Point;
    import flash.Vector;

    class PerspectiveImage {
    /**
    * @author zeh
    */
    static public function drawPlane(graphics:Graphics, bitmap:BitmapData, p1:Point, p2:Point, p3:Point, p4:Point) : Void {
    var pc:Point = getIntersection(p1, p4, p2, p3); // Central point

    // If no intersection between two diagonals, doesn't draw anything
    if (pc == null) return;

    // Lengths of first diagonal
    var ll1:Float = Point.distance(p1, pc);
    var ll2:Float = Point.distance(pc, p4);

    // Lengths of second diagonal
    var lr1:Float = Point.distance(p2, pc);
    var lr2:Float = Point.distance(pc, p3);

    // Ratio between diagonals
    var f:Float = (ll1 + ll2) / (lr1 + lr2);

    // Draws the triangle
    graphics.clear();
    graphics.beginBitmapFill(bitmap, null, false, true);

    graphics.drawTriangles(
    flash.Lib.vectorOfArray([p1.x, p1.y, p2.x, p2.y, p3.x, p3.y, p4.x, p4.y]),
    flash.Lib.vectorOfArray([0,1,2, 1,3,2]),
    flash.Lib.vectorOfArray([0,0,(1/ll2)*f, 1,0,(1/lr2), 0,1,(1/lr1), 1,1,(1/ll1)*f]) // Magic
    );
    }

    static private function getIntersection(p1:Point, p2:Point, p3:Point, p4:Point): Point {
    // Returns a point containing the intersection between two lines
    // http://keith-hair.net/blog/2008/08/04/find-intersection-point-of-two-lines-in-as3/
    // http://www.gamedev.pastebin.com/f49a054c1

    var a1:Float = p2.y - p1.y;
    var b1:Float = p1.x - p2.x;
    var a2:Float = p4.y - p3.y;
    var b2:Float = p3.x - p4.x;

    var denom:Float = a1 * b2 - a2 * b1;
    if (denom == 0) return null;

    var c1:Float = p2.x * p1.y - p1.x * p2.y;
    var c2:Float = p4.x * p3.y - p3.x * p4.y;

    var p:Point = new Point((b1 * c2 - b2 * c1)/denom, (a2 * c1 - a1 * c2)/denom);

    if (Point.distance(p, p2) > Point.distance(p1, p2)) return null;
    if (Point.distance(p, p1) > Point.distance(p1, p2)) return null;
    if (Point.distance(p, p4) > Point.distance(p3, p4)) return null;
    if (Point.distance(p, p3) > Point.distance(p3, p4)) return null;

    return p;
    }
    }