JavaScript实现水印

/** * js实现水印展示 * 精简版 * @param str */function addWaterMarker(str){  var canvas = document.createElement('canvas');  var body = document.body;  body.appendChild(canvas);  canvas.width=300;  canvas.height=200;  canvas.style.display='none';  var cans = canvas.getContext('2d');  cans.rotate(-20*Math.PI/180);  cans.font = "16px Microsoft JhengHei";  cans.fillStyle = "rgba(17, 17, 17, 0.50)";  cans.textAlign = 'left';  cans.textBaseline = 'Middle';  cans.fillText(str,canvas.width/3,canvas.height/2);  body.style.backgroundImage="url("+canvas.toDataURL("image/png")+")";}