FWIW the Accelerate framework[1] gives roughly comparable performance[2] for Lanczos resizing. Apple platforms only, but all Apple platforms, not limited to x86.
[1] vImageScale_ARGB8888( ).
[2] I don't have identical hardware available to time on, and it's doing an alpha channel as well, so this is slightly hand-wavy.
Accelerate is a really amazing and highly underrated framework. Sure the function names are, uh, sub optimal (I'm looking at you, vDSP). That said, having a framework guaranteed across all devices to implement algorithms and primitives in the fastest way for each new device as they come out is amazingly valuable.
I've built production systems over the last few years with it that really wouldnt have been possible without it.
Just to provide a little context for the vDSP function names, vecLib predates OS X--it was part of OS 9--and the vDSP interfaces descend from the SAL library at Mercury; like LAPACK and BLAS, they needed to be short for Fortran 77 compatibility.
[1] vImageScale_ARGB8888( ).
[2] I don't have identical hardware available to time on, and it's doing an alpha channel as well, so this is slightly hand-wavy.