How to reduce an Image file size before uploading to a server

Lot of application allow sharing an image, which is picked from the gallery.

Do they upload the original image file? Which is like 1-3 mb? Or do they process?

In any case, how can I take the image from a filepath, reduce its size by lowering the resolution and save it some where else and the try to upload?

I tried:

Bitmap photo = decodeSampledBitmapFromFile(filePath, DESIRED_WIDTH,
                    DESIRED_HEIGHT);

FileOutputStream out = new FileOutputStream(filePath);
photo.compress(Bitmap.CompressFormat.JPEG, 100, out);

public static Bitmap decodeSampledBitmapFromFile(String path, int reqWidth,
        int reqHeight) {

    final BitmapFactory.Options options = new BitmapFactory.Options();
    options.inJustDecodeBounds = true;
    BitmapFactory.decodeFile(path, options);

    final int height = options.outHeight;
    final int width = options.outWidth;
    options.inPreferredConfig = Bitmap.Config.ARGB_8888;
    int inSampleSize = 1;

    if (height > reqHeight) {
        inSampleSize = Math.round((float) height / (float) reqHeight);
    }
    int expectedWidth = width / inSampleSize;

    if (expectedWidth > reqWidth) {
        inSampleSize = Math.round((float) width / (float) reqWidth);
    }
    options.inSampleSize = inSampleSize;
    options.inJustDecodeBounds = false;
    return BitmapFactory.decodeFile(path, options);
}

But is this they right way to do? Because I have seen answers suggesting compression operation takes rather big amount of time here

from How to reduce an Image file size before uploading to a server