AS3: reading embedded metadata in flex - apache-flex

Question

I saw that you can embed meta-data into images very much like you can in mp3s, here.
Can someone point me to a tutorial of how to embed and read this sort of information w/ photoshop and flex together?
I really wouldn't know where to start... Tried googling but I'm not sure I have the right keywords down.
Thanks!

Answer 1

I've written a small snippet on the matter. this snippet is far from being proper tested, and is most definite not written in a clear and coherent way. But for now it seems to work. I'll update as I work on it.
private function init(event:Event):void
{
var ldr:Loader = new Loader();
ldr.contentLoaderInfo.addEventListener(Event.COMPLETE, imgLoaded);
var s:String = "link/to/asset.jpg";
ldr.load(new URLRequest(s));
}
private function imgLoaded(e:Event):void{
var info:LoaderInfo = e.target as LoaderInfo;
var xmpXML:XML = getXMP(info.bytes);
//trace(xmpXML);
var meta:XMPMeta = new XMPMeta(xmpXML);
}
private function trim(s:String):String{
return s.replace( /^([\s|\t|\n]+)?(.*)([\s|\t|\n]+)?$/gm, "$2" );
}
private function getXMP(ba:ByteArray):XML{
var LP:ByteArray = new ByteArray();
var PACKET:ByteArray = new ByteArray();
var l:int;
ba.readBytes(LP, 2, 2);
/*
http://www.adobe.com/devnet/xmp.html
read part 3: Storage in Files.
that will explain the -2 -29 and other things you see here.
*/
l = LP.readInt() - 2 -29;
ba.readBytes(PACKET, 33, l);
var p:String = trim(""+PACKET);
var i:int = p.search('<x:xmpmeta xmlns:x="adobe:ns:meta/"');
/* Delete all in front of the XMP XML */
p = p.substr(i);
/*
For some reason this left some rubbish in front, so I'll hardcode it out for now
TODO clean up
*/
var ar:Array = p.split('<');
var s:String = "";
var q:int;
var j:int = ar.length;
for(q=1;q<j;q++){
s += '<'+ar[q];
}
i = s.search('</x:xmpmeta>');
i += ('</x:xmpmeta>').length;
s = s.slice(0,i);
/* Delete all behind the XMP XML */
return XML(s);
}
Originally from http://snipplr.com/view/51037/xmp-metadata-from-jpg/

Answer 2

Photoshop (CS4+ I think) can also add XMP headers (XML style) which will be easier to parse than bytes but it contains different information.
http://code.google.com/p/exif-as3/
Here is a class that should do the job. It is non-commercial only but there is another option.
www.ultrashock.com/forums/server-side/extracting-metadata-from-photos-86065.html
Here is a php script that will do it that could be ported to as3 - it might be easier than creating one from scratch. If you did want php to read the info I would use the built in exif functions :)

Answer 3

Well AS3 don't have a built-in class to read jpg header.
BUT, if you are loading the image using URLLoader you can use the ByteArray to read if manually.
You can find the spec here:
http://www.obrador.com/essentialjpeg/HeaderInfo.htm
If you need some tutorial of using Bytearray you can start from here:
How to convert bytearray to image or image to bytearray ?
or here:
http://digitalmedia.oreilly.com/pub/a/oreilly/digitalmedia/helpcenter/flex3cookbook/chapter8.html?page=7
The principle is the same -read the bytes, convert them to readable data using the spec above and use it.
Good luck!

Answer 4

Yes, entirely possible. ByteArray is your friend.
You may want to give a read to this:
http://www.anttikupila.com/flash/getting-jpg-dimensions-with-as3-without-loading-the-entire-file/
This may also be of use, but I'd rather go with the first option:
http://download.macromedia.com/pub/developer/xmp/sdk/XMPLibrary-v1.0.zip