How to convert a byte array into an image?

Instead of calling the service with AJAX, use Javascript to build an image element and point it to the service directly...

var img = document.createElement("IMG");
img.src = "http://url/to/service";
img.alt = "ALT TEXT";
document.body.appendChild(img);

Just make sure the service sets the content type properly.

Here is JavaScript source to decode PNG, JPEG and GIF image bytes, using the Data URI scheme:

Images.decodeArrayBuffer = function(buffer, onLoad) {
    var mime;
    var a = new Uint8Array(buffer);
    var nb = a.length;
    if (nb < 4)
        return null;
    var b0 = a[0];
    var b1 = a[1];
    var b2 = a[2];
    var b3 = a[3];
    if (b0 == 0x89 && b1 == 0x50 && b2 == 0x4E && b3 == 0x47)
        mime = 'image/png';
    else if (b0 == 0xff && b1 == 0xd8)
        mime = 'image/jpeg';
    else if (b0 == 0x47 && b1 == 0x49 && b2 == 0x46)
        mime = 'image/gif';
    else
        return null;
    var binary = "";
    for (var i = 0; i < nb; i++)
        binary += String.fromCharCode(a[i]);
    var base64 = window.btoa(binary);
    var image = new Image();
    image.onload = onLoad;
    image.src = 'data:' + mime + ';base64,' + base64;
    return image;
}

I realize this is an old thread, but I managed to do this through an AJAX call on a web service and thought I'd share...

• I have an image in my page already:

   <img id="ItemPreview" src="" />
  

• AJAX:

  $.ajax({
          type: 'POST',
          contentType: 'application/json; charset=utf-8',
          dataType: 'json',
          timeout: 10000,
          url: 'Common.asmx/GetItemPreview',
          data: '{"id":"' + document.getElementById("AwardDropDown").value + '"}',
          success: function (data) {
              if (data.d != null) {
                  var results = jQuery.parseJSON(data.d);
                  for (var key in results) {
                      //the results is a base64 string.  convert it to an image and assign as 'src'
                      document.getElementById("ItemPreview").src = "data:image/png;base64," + results[key];
                  }
              }
          }
      });
  

My 'GetItemPreview' code queries a SQL server where I have an image stored as a base64 string and returns that field as the 'results':

     string itemPreview = DB.ExecuteScalar(String.Format("SELECT [avatarImage] FROM [avatar_item_template] WHERE [id] = {0}", DB.Sanitize(id)));
     results.Add("Success", itemPreview);
     return json.Serialize(results);

The magic is in the AJAX call at this line:

     document.getElementById("ItemPreview").src = "data:image/png;base64," + results[key];

Enjoy!