キャンバスを使ってWeChatアバターなしの招待状ポスターを生成する

If (!string.IsNullOrEmpty(Request.QueryString["data"].ToString()))
{
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Request.QueryString["data"].ToString());
    Request.Timeout = 3000;
    WebResponse response = request.GetResponse();
    Stream stream = response.GetResponseStream();
    Bitmap image = new Bitmap(stream);
    //Save as PNG to the memory stream 
    MemoryStream ms = new MemoryStream();
    image.Save(ms, ImageFormat.Png);
    //re-export the header image
    BinaryWrite(ms.GetBuffer());
    Response.End();
    ms.Close();
    Response.Close();
    stream.Close();
}

<script type="text/javascript">
window.onload = function ()
{
    var IMAGE_URL;
    function takeScreenshot(){
        var shareContent = document.getElementById('shareMember');// the (native) DOM object of the package that needs to be screenshot
        var width = shareContent.offsetWidth; //Get the dom width
        var height = shareContent.offsetHeight; //Get the height of the dom
        var canvas = document.createElement("canvas"); //create a canvas node
       var scale = 1; //define any magnification support fractional
        canvas.width = width * scale; //define canvas width * scale
        canvas.height = height * scale; //define the height of the canvas * scale
        canvas.getContext("2d").scale(scale, scale); //get context, set scale
       //var rect = shareContent.getBoundingClientRect();//get the offset of the element relative to the inspection
        //canvas.getContext("2d").translate(-rect.left, -rect.top);//set the context position, the value is the negative offset relative to the viewport, let the image reset
        var opts = {
            scale:scale, // the added scale parameter
            canvas:canvas, // custom canvas
            logging: true, // logging switch
            width:width, // original width of the dom
            height:height, // the original height of the dom
            backgroundColor: 'transparent',
        };
        html2canvas(shareContent, opts,{useCORS:true,logging:true}).then(function (canvas)
        {
            IMAGE_URL = canvas.toDataURL("image/png");
            $('.copyImage').attr('src',IMAGE_URL);
        })
    }
    takeScreenshot();
}
</script>

    <div class="shareBox" id="shareMember">
        <div class="top">
            <div class="logo"><img src="wxheadimg.aspx?data=WeChathead URL"/></div>
        </div>
        <div class="middle">
            <img src="makeQRCode.aspx?data=2dimensional code content" class="qrcode" />
        </div>
        <img src="" class="copyImage">
    </div>
jpg.shareBox{position:relative}
.shareBox .copyImage{position:absolute;top:0px;left:0px;z-index:999;opacity:0;height:666px;width:666px;}