How do I Pass an Image from Flash to ASP.NET? - asp.net

Question

Quick version:
How do I get an image that was generated on the users browser back to the server?
The current plan is this:
The Flash developer will convert the bitmap to JPEG
He will then POST the JPEG to a page on the site.
I'm thinking I can create a WebService which will use a StreamReader to read the post and save it as a file.
Would that work? Any existing code/samples for doing this?
I suppose we should be able to look at code for doing any file upload to ASP.NET.

Answer 1

In this example, I've created a Flash file with a button on the stage. When you click that button, the Flash sends the image of the button to an ASPX file which saves it out as a JPEG. As you'll see this is done by drawing the DisplayObject into a BitmapData object and as such, you can easily replace the reference to the button with anything that inherits from DisplayObject (including a movie clip that contains the canvas for a paint application etc).
I’ll walk you through the Flash element first and then the .NET backend.
Flash
To send a generated image like this from Flash to ASP.NET (or any other backend) you’re going to need a couple of 3rd party libraries. We’ll need a JPEG Encoder (which Flash doesn’t have, but recent versions of Flex do) which we can get from the AS3 Core Lib http://code.google.com/p/as3corelib/. We’ll also need a base64 encoder for sending the data over the wire. I’ll use the one from Dynamic Flash, available at http://dynamicflash.com/goodies/base64/.
Download these and extract them somewhere sensible on your hard disk (like a C:\lib folder).
I created a new AS3 Flash file and saved it as uploader.fla. I added a button component to the stage and named it btnUpload. Next I edited the ActionScript settings and added my c:\lib folder to the classpath. Then I gave the document a class name of Uploader and saved the file.
Next, I created an ActionScript file and added the following code to it:
package
{
import flash.display.BitmapData;
import flash.display.MovieClip;
import flash.events.MouseEvent;
import flash.net.URLLoader;
import flash.net.URLRequest;
import flash.net.URLRequestMethod;
import flash.net.URLVariables;
import flash.utils.ByteArray;
import fl.controls.Button;
import com.adobe.images.JPGEncoder;
import com.dynamicflash.util.Base64;
public class Uploader extends MovieClip
{
// Reference to the button on the stage
public var btnUpload:Button;
// Encoder quality
private var _jpegQuality:int = 100;
// Path to the upload script
private var _uploadPath:String = "/upload.aspx";
public function Uploader()
{
btnUpload.addEventListener(MouseEvent.CLICK, buttonClick);
}
private function buttonClick(e:MouseEvent):void
{
// Create a new BitmapData object the size of the upload button.
// We're going to send the image of the button to the server.
var image:BitmapData = new BitmapData(btnUpload.width, btnUpload.height);
// Draw the button into the BitmapData
image.draw(btnUpload);
// Encode the BitmapData into a ByteArray
var enc:JPGEncoder = new JPGEncoder(_jpegQuality);
var bytes:ByteArray = enc.encode(image);
// and convert the ByteArray to a Base64 encoded string
var base64Bytes:String = Base64.encodeByteArray(bytes);
// Add the string to a URLVariables object
var vars:URLVariables = new URLVariables();
vars.imageData = base64Bytes;
// and send it over the wire via HTTP POST
var url:URLRequest = new URLRequest(_uploadPath);
url.data = vars;
url.method = URLRequestMethod.POST;
var loader:URLLoader = new URLLoader();
loader.load(url);
}
}
}
I saved this file next to the FLA with the name Uploader.as.
I published the SWF into the root of my Asp.NET website.
This code assumes you want to upload the jpeg with a quality of 100% and that the script which will receive the data is called upload.aspx and is located in the root of the site.
ASP.NET
In the root of my website I created a WebForm named upload.aspx. In the .aspx file, i removed all the content apart from the page directive. It’s content look like this:
<%# Page Language="C#" AutoEventWireup="true" CodeFile="upload.aspx.cs" Inherits="upload" %>
Then in the CodeBehind, I added the following:
using System;
using System.IO;
public partial class upload : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
// Get the data from the POST array
string data = Request.Form["imageData"];
// Decode the bytes from the Base64 string
byte[] bytes = Convert.FromBase64String(data);
// Write the jpeg to disk
string path = Server.MapPath("~/save.jpg");
File.WriteAllBytes(path, bytes);
// Clear the response and send a Flash variable back to the URL Loader
Response.Clear();
Response.ContentType = "text/plain";
Response.Write("ok=ok");
}
}
There are obviously hard-coded values such as the save path but from this you should be able to create whatever system you require.

Answer 2

If you need to manipulate the image, as long as you can get a byte[] or a Stream of the POSTed file, you can create an image of it, e.g.
MemoryStream mstr = new MemoryStream(myByteArray);
Image myImage = Image.FromStream(mstr);

Answer 3

Have him post the files like a standard HTML form. You can access those files in the Page_Load event of the page he is posting to by using the following collection
Request.Files
This will return a collection of HttpPostedFiles just like what a FileUpload control does.