Android Bitmap Alpha Banding

Question

I have a png radial alpha gradient, so its edges are black and in the center completely transparent with a nice smooth gradient.

When I load a bitmap and display it on SurfaceView canvas, I get a bad alpha band. Instead of a nice smooth gradient, the alpha values ​​seem to jump down and produce large bands of all the same alpha values.

As far as I know, bitmaps with alpha channels should not be converted when loading or drawing. How to make png draw correctly on canvas?

Any help would be appreciated, thanks! = D