Convert base64 encode jpeg image to base64 encoded jpg/png/gif/tiff image?

Question

I am using this phonegap plugin called Screenshot and I am willing to upload the base64 encoded image to facebook. Unfortunately, I get an error from facebook saying that the available formats are only JPG, PNG, GIF and TIFF.

So I either have to find a way to change the java code of the plugin (I have never used java before) or come up with a javascript function in my application which converts it, although I don't really know if that is possible/worth it.

Here is the java code of the screenshot plugin which encodes the image:

else if (action.equals("getScreenshotAsURI")) {
    final Integer quality = (Integer) args.get(0);

    super.cordova.getActivity().runOnUiThread(new Runnable() {@Override
        public void run() {
            View view = webView.getRootView();
            try {
                view.setDrawingCacheEnabled(true);
                Bitmap bitmap = Bitmap.createBitmap(view.getDrawingCache());
                view.setDrawingCacheEnabled(false);

                ByteArrayOutputStream jpeg_data = new ByteArrayOutputStream();

                if (bitmap.compress(CompressFormat.JPEG, quality, jpeg_data)) {
                    byte[] code = jpeg_data.toByteArray();
                    byte[] output = Base64.encode(code, Base64.NO_WRAP);
                    String js_out = new String(output);
                    js_out = "data:image/jpeg;base64," + js_out;
                    JSONObject jsonRes = new JSONObject();
                    jsonRes.put("URI", js_out);
                    PluginResult result = new PluginResult(PluginResult.Status.OK, jsonRes);
                    callbackContext.sendPluginResult(result);

                    js_out = null;
                    output = null;
                    code = null;
                }

                jpeg_data = null;

            } catch (JSONException e) {
                callbackContext.error(e.getMessage());

            } catch (Exception e) {
                callbackContext.error(e.getMessage());

            }
        }
    });

    return true;
}

The entire code of the plugin can be found on the github repository in the beginning of my question. I tried changing CompressForma.JPEG to CompressForma.JPG, but had no luck ;(