In a previous post, I described how I could dynamically generate a continually evolving logo by masking and layering several different bitmaps.
This worked well enough, but failed to look convincing when the rendered texture was light. I overcame this by creating a halo effect, to make brightly textured emblems appear to luminesce. Again, the 2D rendering apis in Android made this very easy.
I start the process with the rendered texture in a Bitmap:
Using a Canvas over a tiny 3x3 Bitmap I produced a scaled copy of the texture.
Using the Bitmap.getPixels() method, I created a SweepGradient through the eight outermost colours.
Finally using a black-to-white-to-black RadialGradient applied with a PorterDuff.Mode of MULTIPLY a circular ring is of compatible colours is created:
This ring can then be overlayed separately onto the existing image, using the useful TransitionDrawable class to smoothly switch halos.
The final effect can be seen in this video
