How to lighten or darken a bitmap
<p>How do I take an existing bitmap, say</p>

<pre><code>Bitmap bm = BitmapFactory.decodeResource(getResources(), R.drawable.somebitmap);
</code></pre>

<p>and write a method that returns a darkened version of the bitmap?</p>

<pre><code>private Bitmap darkenBitMap(Bitmap bm) { }
</code></pre>

<p>I've been trying to use Paint and Canvas with no results so far.</p>