Hi

Looking at the Bitmap class, I presume (I've not tried) that when you
call Bitmap.createBitmap() with a buffer of pixel data, it's these
pixels that contain the alpha data (look at the Color class for the
layout of the 32 bit integer value of a pixel), and the Bitmap.Config
that you use to ensure that the alpha channel is not ignored (i.e. you
should use Bitmap.Config.ARGB_8888).

On Jan 12, 5:55 am, Stephen Lebed <srle...@gmail.com> wrote:
> I've created a bitmap that I'm overlaying over another bitmap.  I'd
> like to alter the transparency of sections of the overlaid bitmap,
> revealing the bitmap beneath.  I can't find a way to write only to the
> alpha channel of the overlaid bitmap.
>
> For example, I have a bitmap filled with red pixels, and an alpha that
> is 255, opaque.  A solid red bitmap.  How do I draw a circle on this
> map that would lower the alpha values toward 0, transparent?
>
> Any help would be greatly appreciated!
>
> Stephen
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