I'm afraid, no way around that. I mean, without A LOT of low-level hackery. IMAQ images have borders 3 pixels wide by default, whereas LabVIEW arrays don't have those. And not every VI from the Array palette works in-place, not producing a copy. Of course, you may read/write pixels data by its pointer using MoveBlock. Like this:
But I wouldn't expect more than that. You can always move the image processing into your DLL/SO and write everything in pure C/C++, C# et cetera.