How can I override onDraw so that I take what would have been drawn (as a bitmap) and transform it?

Question

The method below works, but it unfortunately, this method involves creating a bitmap the size of the entire screen - not just the area that is drawn to. If I use this to dra

Answer 1

Have you tried changing the size of the bitmap you create, to be only equal to the clip bounds rather than the entire size of the given canvas? I don't know if this is the case with all Views, but I found that the onDraw method for some Views is given a canvas as big as the screen, regardless of the actual size of the content. It then clips the canvas, restricting it to the top left corner only, draws there and then translates that part to somewhere else on the screen when it's actually ready to display the whole layout. In other words, despite it having a canvas the size of the whole screen, it only actually uses a small piece of it. So what you could try doing is instead of using

Bitmap bitmap = Bitmap.createBitmap(canvas.getWidth(), canvas.getHeight(), ...)

you could try

Rect rect = canvas.getClipBounds();
int width = rect.width();
int height = rect.height();
Bitmap bitmap = Bitmap.createBitmap(width, height, ...); 

That way you reduce the overhead of working with a much larger bitmap than necessary. Note: I haven't actually tried doing this so it might not work, but it's worth trying.