Snap Matrix

//http://stackoverflow.com/questions/16359246/how-to-extract-position-rotation-and-scale-from-matrix-svg
function deltaTransformPoint(matrix, point)  {

        var dx = point.x * matrix.a + point.y * matrix.c + 0;
        var dy = point.x * matrix.b + point.y * matrix.d + 0;
        return { x: dx, y: dy };

}

function decomposeMatrix(matrix) {

        // @see https://gist.github.com/2052247

        // calculate delta transform point
        var px = deltaTransformPoint(matrix, { x: 0, y: 1 });
        var py = deltaTransformPoint(matrix, { x: 1, y: 0 });

        // calculate skew
        var skewX = ((180 / Math.PI) * Math.atan2(px.y, px.x) - 90);
        var skewY = ((180 / Math.PI) * Math.atan2(py.y, py.x));

        return {

            translateX: matrix.e,
            translateY: matrix.f,
            scaleX: Math.sqrt(matrix.a * matrix.a + matrix.b * matrix.b),
            scaleY: Math.sqrt(matrix.c * matrix.c + matrix.d * matrix.d),
            skewX: skewX,
            skewY: skewY,
            rotation: skewX // rotation is the same as skew x
        };
}

var s = Snap("#svgout");

var r1 = s.rect(0,0,100,100).attr({ fill: "red", opacity: "0.2", stroke: "black", strokeWidth: "2" });

var g1 = s.group( r1 ).transform("t100,100r10");
var g2 = s.group( g1 ).transform("t100,100r20");
var g3 = s.group( g2 ).transform("t100,100r30");

console.log( r1.transform() );
console.log( decomposeMatrix( r1.transform().globalMatrix ) ) ;

s.text( 100, 20, "rect1 localMatrix: " + r1.transform().localMatrix + "... rotation " + decomposeMatrix( r1.transform().localMatrix ).rotation );
s.text( 100, 40, "rect1 diffMatrix: " + r1.transform().diffMatrix  + "... rotation " + decomposeMatrix( r1.transform().diffMatrix ).rotation );
s.text( 100, 60, "rect1 globalTransform: " + r1.transform().globalMatrix + "... rotation " + decomposeMatrix( r1.transform().globalMatrix ).rotation );

s.text( 100, 100, "g1 localMatrix: " + g1.transform().localMatrix + "... rotation " + decomposeMatrix( g1.transform().localMatrix ).rotation ) ;
s.text( 100, 120, "g1 diffMatrix: " + g1.transform().diffMatrix + "... rotation " + decomposeMatrix( g1.transform().diffMatrix ).rotation  );
s.text( 100, 140, "g1 globalTransform: " + g1.transform().globalMatrix + "... rotation " + decomposeMatrix( g1.transform().globalMatrix ).rotation  );

s.text( 100, 180, "g2 localMatrix: " + g2.transform().localMatrix + "... rotation " + decomposeMatrix( g2.transform().localMatrix ).rotation);
s.text( 100, 200, "g2 diffMatrix: " + g2.transform().diffMatrix + "... rotation " + decomposeMatrix( g2.transform().diffMatrix ).rotation );
s.text( 100, 220, "g2 globalTransform: " + g2.transform().globalMatrix + "... rotation " + decomposeMatrix( g2.transform().globalMatrix ).rotation );

s.text( 100, 260, "g3 localMatrix: " + g3.transform().localMatrix + "... rotation " + decomposeMatrix( g3.transform().localMatrix ).rotation);
s.text( 100, 280, "g3 diffMatrix: " + g3.transform().diffMatrix + "... rotation " + decomposeMatrix( g3.transform().diffMatrix ).rotation );
s.text( 100, 300, "g3 globalTransform: " + g3.transform().globalMatrix + "... rotation " + decomposeMatrix( g3.transform().globalMatrix ).rotation );

   


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