关于canvas下载二维码和图片加水印的方法

/*html*/<p id="qrcode">p><a href="javascript:;" download="二维码" id="down">下载二维码</a>/*js*/var canvas = document.getElementsByTagName(&#39;canvas&#39;)[0];var downImg = document.getElementById(&#39;down&#39;)img.href = document.getElementsByTagName(&#39;canvas&#39;)[0].toDataURL(&#39;image/png&#39;)

/*html*/<canvas id="canvas"></canvas>/*js*/var img = new Image();   // 创建img元素var canvas = document.getElementById(&#39;canvas&#39;)var ctx = canvas.getContext(&#39;2d&#39;);img.src = &#39;myImage.png&#39;;img.onload = function(){    ctx.drawImage(img, 0, 0);    ctx.font="30px yahei";   //设置水印文字    ctx.fillText("大前端", 1100, 260)}