Clear A Bitmap in .Net
<p>I'm using PictureBox control to draw complicated charts, and to optimize for performance i use a cache Bitmap for each layer of the drawing, and draw them on the control image, the upper layers have transparent backgrounds, i need to clear them and redraw on every change.</p>

<p>Assuming g instance of Graphics class of the Bitmap, using <code>g.Clear(Color.White)</code> draws a white rectangle over everything and so hiding lower layers, and <code>g.Clear(Color.Transparent)</code> draws Transparent rectangle over, what means doing nothing.</p>

<p>Isn't there a way to clear the Bitmap returning it to its original state?</p>