Rectangle coordinates after transform

Question

I am currently drawing a rectangle with a transformation on his parent element (g). The resulting svg is this;

Answer 1

I found the solution myself;

var matrix = shape.getCTM();

// transform a point using the transformed matrix
var position = svg.createSVGPoint();
position.x = $(shape).attr("x");
position.y = $(shape).attr("y");
position = position.matrixTransform(matrix);