There's a way to export the canvas image of your dataChart.

I'm currently doing this exporting the canvas images to base64 and sending the data to a web service wich deserializes the image and sends it to the user for download via browser.

To serialize the canvas image you can use this JQuery function on your client side JavaScript code: 

//This serializes your canvas image to base64

var img64 = $(yourCanvasObject).toDataURL("image/png");

Then you just have to send the img64 content to the web service.

There's my .ASMX web service code snippet, wich receives the string containing the serielized bas64 image, and a string to name the exported file, and is supposed to deserialize the image, convert it to a png file naming it as indicated, and getting it downloaded to the user via the browser:

I haven't tested this in much scenarios, but it's working fine for me. I hope it can help you as a workaround. (Conceptually, I don't think this is the best way to export a canvas HTML5 image. Using a web service to do this can sound a bit 'annoying', but I think it's even more elegant than making the user right click on the image, and clicking 'Save as..' option.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Services;
using System.Drawing;
using System.Security;
using System.IO;
using System.Text;

[WebMethod]
/// <summary>
/// This Service method provides a way to get base64 serialized img exported to .png format and
/// downloaded directly to the browser.
/// </summary>
/// <parameters>
/// base64Img:
/// A System.String representing the base64 serialized image.
/// </parameters>
/// <returns>
/// true if the image is correctly exported; otherwise, false.
/// </returns>
public bool ImageExporter(string base64Img, string fileName)
{
try
{
//check for empty string
if (!String.IsNullOrEmpty(base64Img))
{
//convert the serialized image to a Byte Array
Byte[] bitmapData = Convert.FromBase64String(base64Img);

//create a Stream
MemoryStream streamBitmap = new MemoryStream(bitmapData);

//generate a bitmap Image
Bitmap bitImage = new Bitmap((Bitmap)Image.FromStream(streamBitmap));

//send the image
SendImageForDownload(streamBitmap, fileName);

//everything went as expected
return true;
}
//no exportation done
return false;
}
catch (Exception ex)
{
string mes = ex.Message;
//error during exportation
return false;
}
}

[SecuritySafeCritical]
/// <summary>
/// This function modify the HttpResponse in order to get an image downloaded via browser.
/// </summary>
/// <parameters>
/// ms:
/// A System.IO.MemoryStream containing a deserialized image.
/// imageName:
/// A System.String with the file name the image will have when downloaded.
/// </parameters>
/// This function can throw some exceptions.
private void SendImageForDownload(MemoryStream ms, string imageName)
{
HttpContext.Current.Response.Clear();
HttpContext.Current.Response.AppendHeader("content-disposition",
String.Format("attachment; filename={0}.png", imageName));
HttpContext.Current.Response.ContentType = "image/png";
ms.Seek(0, SeekOrigin.Begin);
ms.CopyTo(HttpContext.Current.Response.OutputStream);
HttpContext.Current.Response.End();
}

So, resuming. Yo will need:

• JavaScript code to serialize the canvas image to base 64
• Ajax or other way to send the serialized image to the web service method
• A web service (mine is .asmx) wich deserializes the image, and sends it to the user via the Http Response.

Hope this helps.

Regards from Barcelona.