You can run the garbage collector from code by calling
RunGarbageCollector(). That does not, however, in my experience, free up graphics memory. How are you creating your roBitmaps? They will only be unloaded from memory, if you remove all references to them, so setting the original bitmap to invalid will only work if you haven't referenced that bitmap from any other object in your code. If you're not already, you may want to consider using the
roTextureManager to manage your bitmaps, as it does a lot of the caching, loading and unloading legwork for you.
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