I know - the title may sounds strange. Let me explain:

I created an image to show you, what I'm talking about:
![the problem](https://i.stack.imgur.com/yA1H3.png)

I got an image (Bitmap (1)), that as the size of 150w/200h.

Now I need to make the bitmap bigger ((2) 400w/400h), but the original image must have the same size. So that the image is embedded in white background.

I think one way to solve it is this:
\* create a big bitmap
\* create a canvas for it
\* draw the original bitmap on the canvas
\* draw the canvas
\* generate a bitmap of the canvas

The problem for me is, that it must be done in a background thread without drawing a view.
I hope you understand me.