firefox 10.0.10esr 如何把整个网页保存为图片

截图扩展，截整个网页

如果玩鼠标手势Firegesture的话，代码：
var canvas = content.document.createElement("canvas");
canvas.width = content.document.body.clientWidth;
canvas.height = content.document.body.clientHeight;
var ctx = canvas.getContext("2d");
ctx.drawWindow(content, 0, 0, canvas.width, canvas.height, "rgb(255,255,255)");
saveImageURL(canvas.toDataURL(), content.document.title + ".png");