Save MovieClip as PNG Example

25th Feb 2010

A couple of guys on Twitter asked me if I would write-up how I generate PNG files from MovieClips in my SWF, at run-time. So I put this example together and am sharing it here.

We use this technique in our virtual world WebbliWorld to save a PNG version of the users avatars after they have customised them. But there are all kinds of other reasons you may need this. My example includes two methods: Saving the PNG locally using the local file system, and Saving the PNG to a web server using AMFPHP.

This technique requires Flash Player 10 and the Adobe AS3 Core Lib.

Here’s a very simple example (included in the zip download below):

Essentially it all boils down to this:

1) When you are ready to save your image, create a Bitmap version of your MovieClip.

[as]
private function getMovieClipAsBitmap():Bitmap
{
var bounds:Rectangle = theMovieClip.getBounds(theMovieClip);

// The * 2 is because we’re scaling the clip up by a factor of two, to result in a larger PNG
// If you don’t need this, remove it and comment out the m.scale call below
var theBitmap:Bitmap = new Bitmap(new BitmapData(bounds.width * 2, bounds.height * 2, true, 0x0));

var m:Matrix = new Matrix(1, 0, 0, 1, -bounds.x, -bounds.y);

// Simply scale the matrix to make a bigger PNG. Here we are doubling it. Comment this out if you don’t need it.
m.scale(2, 2);

// Need to crop the PNG to a given size? Pass it a Rectangle as the 5th parameter to draw()
//var r:Rectangle = new Rectangle(0, 0, 50, 40);

theBitmap.bitmapData.draw(theMovieClip, m, null, null, null, true);

return theBitmap;
}
[/as]

2) Convert this Bitmap to a ByteArray.

[as]
private function getMovieClipAsByteArrayPNG():ByteArray
{
var data:Bitmap = getMovieClipAsBitmap();

var ba:ByteArray = PNGEncoder.encode(data.bitmapData);

return ba;
}
[/as]

3) Send this ByteArray to either the local filesystem, or AMFPHP.

[as]
// Uses FileReference to save the PNG locally to the hard drive (see “saveToServer” for an alternative)
private function saveLocalPNG(event:MouseEvent):void
{
var ba:ByteArray = getMovieClipAsByteArrayPNG();

file.save(ba, “BirdyNamNam.png”);
}
[/as]

Complete source code is included in the zip file including an AMFPHP PHP script for saving on a web server.

Hope someone finds this useful.

Download the Soure Code zip.