How to change black background color of bitmap to transparent?

Question

I am creating Bitmap using following code:

Bitmap bm= Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);

But I want to change Background color from black to transparent because I want to use this object in another Activity also. I searched a lot but I am unable to find solution. Please help. Thanks in advance.

Answer 1

Of course the Bitmap created in mode ARGB_8888 supports transparency But the alpha channel is initially filled by 0xff, so bitmap is opaque. You have to clear the whole bitmap including the alpha channel like this:

Canvas c = new Canvas(bm);
c.drawColor(0, Mode.CLEAR);