raster drawing NO SVG changes all topGroup

this is the drawing program for raster drawing implmentation

by Nick Hulea

HTML

<script src="http://cdn.eyahuska.com/paper.js"></script>
<canvas resize="true" id="canvas-1" style="width:100%;"></canvas>
<script type="text/paperscript" canvas="canvas-1">
    var b, d, g, c, r, i, v, n, a, brush;
    var ebd = null;
    var iArray = [];
    var dArray = [],
        rArray = {},
        topGroup = new Group(),
        mousePath = null;
    var imagesArray = ['one.jpg', 'two.jpg', 'three.jpg', 'four.jpg', 'five.jpg'];

    var rastera = new Raster({
        source: 'http://cdn.eyahuska.com/six.jpg',
        // position: view.center,
        size: view.bounds
    });

    rastera.on('load', function() {
        loaded = true;
        onResize();
    });

    var rasterb = new Raster({
        source: 'http://cdn.eyahuska.com/two.jpg',
        position: view.center,
        size: view.bounds
    });

    rasterb.on('load', function() {
        loaded = true;
        onResize();
    });

    var brush_origin = new Path.Circle({
        radius: 50,
        strokeColor: 'red',
        strokeWeight: 10
    });

    brush = brush_origin.clone();

    topGroup = new Group([brush, rasterb]);
    topGroup.clipped = true;

    tool.fixedDistance = 20;

    function onMouseMove(event) {
        brush.position = event.point;
    }

    function onMouseDown(event) {

        brush = brush_origin.clone();

        var num = Math.floor(Math.random() * 5); // 0...6
        imagesrc = 'http://cdn.eyahuska.com/' + imagesArray[num];
        rasterb.source = imagesrc;
        console.log(imagesrc);


        topGroup.clipped = true;



        //normal array of all paths on canvas sweet!
        dArray.push(brush);
        //console.log(dArray);
        //

        //associative array of all paths on canvas sweet!
        rArray[brush.id] = 0;
        //console.log(rArray);
        //

        brush.position = event.point;
        mousePath = topGroup.children[0];
        addBrushStroke();

    }

    function onMouseDrag(event) {


        if (!mousePath) return;
 ...