Canvas drawImage example 1

function draw() {
        var ctx = document.getElementById('canvas').getContext('2d');
        var img = new Image();
        img.src = 'CanvasDrawImageExample1_fichiers/backdrop.png';
        img.onload = function(){
        ctx.drawImage(img,0,0);
        ctx.beginPath();
        ctx.moveTo(30,96);
        ctx.lineTo(70,66);
        ctx.lineTo(103,76);
        ctx.lineTo(170,15);
        ctx.stroke();
        }
        }