Speaking on performance, be sure to check out this recent article on Flash 10.3 and AIR 2.6 performance:
http://blog.flexwiz.net/top-10-performance-killers-in-your-air-application/

http://stackoverflow.com/questions/2853257/using-pixelbender-to-double-the-size-of-a-bitmap

Any idea what the bottleneck is? I am guessing it is overhead of moving from as3 into pixelbender, but really have no idea. Would be super to understand why it is suffering and how to help.

I’ve been thinking of several scenarios that could cause the slowdowns for each type, but none have been really satisfactory or weren’t logical. The fact that I don’t have any insight on how _exactly_ data is passed to the kernel doesn’t help, either. One of those was the type of data the kernel would expect as straight memory chunks so it can easily receive screen buffer data for filters or blend modes (which are in fact relatively fast). But there has to be a conversion to float at some point, so for Vectors and ByteArrays it would mean doing 2 conversions. But such an implementation would not make sense in the context of Flash.

Conversion from BitmapData to float can be done using a simple mapping function with a lookup table. E.g. f(x) = t[x]; where t is initialized with t[i] = i / 255.0f for all i in [0,255].

For Vector. to float this is a different story. Something like ((float)x) might be done but that should not cause such a big difference.

Now what is really strange is that ByteArray is slower since no conversion is needed at all.

Thank you for the tests. For a new ImageProcessing framework I am using Vector.. But I will keep doing it since pre-multiplied alpha is a pain and I am shooting for high quality )