Android :: Reduce Heap Size To Get Space For BitmapFactory.decodeFile

I learned from several discussions of this group that BitmapFactory.decodeFile() allocates heap memory outside of the "java heap". My app receives encrypted files from a remote server. Decoding those files needs a lot of heap space. After finishing this decoding step most of the allocated heap space will be freed by the GC. But the (total) heap size - as displayed by the DDM - remains large. In this situation there is not enough heap space outside of the "Java heap" to decode even medium sized image files using BitmapFactory.decodeFile(). At the moment I limit the size of encrypted files to ensure that the Java heap space never increases to more than 10 MB. This ensures that there is enough memory for BitmapFactory.decodeFile(). But this is not very elegant.

Is it possible to tell the dalvik-vm to reduce the (total) heap size to have more space for decoding images or is there another solution?