Javascript ajax post of canvas.toDataURL(“image/jpeg”) to a asp.net web form

Question

javascript ajax code:

var dataURL = canvas.toDataURL("image/jpeg");
var xhr = new XMLHttpRequest();
xhr.open("POST", "myPage.aspx", true);
xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");

xhr.onreadystatechange = function () {
        if (xhr.readyState != 4) return;
        if (xhr.status != 200) {
            alert("Status: " + xhr.status);
        } else {
            alert(xhr.responseText);
        }
    };

xhr.send("imgData=" + dataURL);

c# server side code in myPage.aspx - page load:

// enctype="multipart/form-data"
string img = Server.UrlDecode(Request.Form["imgData"]);

img = Regex.Match(img, @"data:image/(?<type>.+?),(?<data>.+)").Groups["data"].Value;
//img = img.Replace("data:image/png;base64,", "");
img = img.Trim('\0');
//byte[] bytes = Encoding.UTF8.GetBytes(img);
byte[] bytes = Convert.FromBase64String(img);

The last server-side code is currently always raising an error.. Seems to be a base64 conversion error... "System.FormatException: 'Invalid length for a Base-64 char array or string.'" Any ideas? Thank you.

Answer 1

after test and trying, the problem was in javascript encoding... the right code is:

xhr.send("imgData=" + encodeURIComponent(dataURL));

Thank you all :-)