Cache bitmap on disk

I want to make thubmnail for performance issue.

The best way is that I cache the bitmap in disk, like memory cache.
Because the image size is matched to image view automatically.
So I make a way to cache bitmap on disk.

and

I remove bitmap.recycle() in BaseDiskCache. I need to reuse the bitmap after bitmapDiskCache.save(). I thinks it could be a bug.