Canvas drawImage(canvas) example

function canvasReady() {
  draw(document.getElementById('canvas').getContext('2d'),
       document.getElementById('canvas2').getContext('2d'));
}
function draw(ctx, ctx2) {
  var img = new Image();
  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();

    ctx2.globalAlpha = 0.5;
    ctx2.shadowColor = "red";
    ctx2.shadowBlur = 3;
    ctx2.fillStyle = "green";
    ctx2.fillRect(0, 0, ctx2.canvas.width, ctx2.canvas.height);
    ctx2.drawImage(ctx.canvas, 10, 10);
    ctx2.drawImage(ctx.canvas, 30, 30, 100, 130);
    ctx2.drawImage(ctx.canvas, 10, 10, 40, 40, 60, 100, 80, 80);

    // prevent IE6 memory leak
    img = null;
  }
  img.src = '../img/backdrop.png';
}
      

Source image