Converting images to base64

brodyFile2DataURL.js

/**
 * To get a base64 encoded data uri from a local file
 *
 * @originalauthor brody at MozillaZine
 * @see http://forums.mozillazine.org/viewtopic.php?p=5091285#p5091285
 */
brodyFile2DataURL = {
	getFileFromURLSpec: function(aURL) {
		var ios = Components.classes["@mozilla.org/network/io-service;1"].getService(Components.interfaces.nsIIOService);
		var fph = ios.getProtocolHandler("file").QueryInterface(Components.interfaces.nsIFileProtocolHandler);
		try { return fph.getFileFromURLSpec(aURL).QueryInterface(Components.interfaces.nsILocalFile); }
		catch(ex) { }
		return null;
	},
	getDataURLFromIStream: function(aInputStream, aContentType) {
		var contentType = aContentType || "application/octet-stream";

		var binaryStream = Components.classes["@mozilla.org/binaryinputstream;1"].createInstance(Components.interfaces.nsIBinaryInputStream);
		binaryStream.setInputStream(aInputStream);
		var encoding = btoa(binaryStream.readBytes(binaryStream.available()));
		return "data:" + contentType + ";base64," + encoding;
	},
	getDataURLFromFile: function(aFile) {
		var contentType = Components.classes["@mozilla.org/mime;1"].getService(Components.interfaces.nsIMIMEService).getTypeFromFile(aFile);
		var inputStream = Components.classes["@mozilla.org/network/file-input-stream;1"].createInstance(Components.interfaces.nsIFileInputStream);
		inputStream.init(aFile,0x01,0600,0);
		
		return this.getDataURIFromIStream(inputStream, contentType);
	},
	asyncGetDataURLFromFile: function(aFile, aCallback) {
		Components.utils.import("resource://gre/modules/NetUtil.jsm");
		var contentType = Components.classes["@mozilla.org/mime;1"].getService(Components.interfaces.nsIMIMEService).getTypeFromFile(aFile);
		var self = this;
		NetUtil.asyncFetch(aFile, function (aInputStream, aAsyncFetchResult) {
			aCallback(self.getDataURIFromIStream(aInputStream, contentType));
		});
	},
};