Un ejemplo:
http://disegnocentell.com.ar/test2.php Código PHP:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title></title>
</head>
<body>
<canvas id="pp" width="500" height ="350" onclick="window.open(this.toDataURL(),'','width=500,height=350');" style="cursor:pointer;">Acéptalo: Tu navegador es obsoleto :)</canvas>
<p>Click sobre la imagen</p>
<script>
var image=new Image();
image.src='arwen.jpg';
image.onload=function(){
var ctx = document.getElementById("pp").getContext("2d");
ctx.drawImage(image,0,0);
ctx.fillStyle = '#FFF';
ctx.font = 'bold 60px Verdana';
ctx.textBaseline = 'bottom';
ctx.fillText('¿Esto?', 130, 180);
}
</script>
</body>
</html>
Más info:
http://www.html5tutorial.info/html5-canvas-text.php