title: How to draw on Bitmap in android?
body: <p>I'm trying to figure out how to draw on a bitmap in android, and keep a copy of these changed bitmaps for an undo function.</p>
  
  <pre><code>Bitmap b = ...
  Paint p = new Paint();
  canvas.drawBitmap(b, new Matrix(), null);
  canvas.drawCircle(0,0,20,20);
  //does Bitmap b have the circle drawn on it next time?
  </code></pre>
  
  <p>Or how do I get the bitmap after its been drawn on with the canvas(I want to preserve a stack of bitmaps with the changes applied by canvas drawing)? Maybe I'm going about this entirely wrong.</p>