There won’t be any new features this time around, of course, since it’s just a +0.0.1 release. There’s only 1 bug that I’ve found which I’ve decided to fix, which has to do with saving “large” 8-bit PNG/GIF/BMP images and is detailed over on the forum (summary: I was using 32-bit integer accumulators and they were overflowing; switching to 64-bit accumulators fixed it). Any plugin that makes use of the built-in quantization code will also be fixed.

So I’ve decided to add some more value to this release in the way of performance optimizations. The first optimization affects an admittedly small population of users: those who have Intel Atom-based nettops. The Intel Atom D510 and 330 chips are dual-core CPUs with HyperThreading and so they show up in Task Manager as 4 CPUs. Normally Paint.NET always uses multisampling to render the canvas. However, if the system has less than 4 CPUs it will use nearest neighbor while doing a zoom in/out with the mouse wheel. Since the Atom reports 4 cores, it was not benefitting from this, but it is now noticably zippier.

The second optimization is for everyone. One thing I’ve been wanting to do for awhile is to move some of the rendering kernels into C/C++ land. The reason for this is that the Visual C++ compiler can do a lot better static optimization than either the .NET JITter or NGEN.

With just a few hours of work today, I’ve managed to make Gaussian Blur about 42% faster. I’ve also applied this trick to the Normal, Multiply, and Overlay blend modes and am getting 15-20% faster performance. The “code” is almost exactly the same except with “uint” swapped for “unsigned __int32”, some marshalling logic, P/Invoke glue, etc. The bang-to-buck ratio here is great.

And of course, your mileage may vary (YMMV). These benchmarks were done on a quad-core Intel Core i7 at 4GHz running 64-bit Windows 7. I also ran them on my dual-core Atom 330, and the improvement was 35% for Gaussian Blur, and 30+% for the blend modes.

With v3.5.5 I will probably limit these optimizations to a few select areas in order to “test the waters.” If stability is good, as determined by the stream of crash logs I get (or don’t!), then I’ll bravely expand to other areas. I expect to release v3.5.5 by the middle of April.

Oh, yeah. On the Paint.NET v4.0 front, the decision has been made: it will require Win7/Vista minimum. I’ve already got most of the interop layer for Direct2D, DirectWrite, and Windows Imaging Component (WIC) written. The first feature to use these was a replacement of “my” super sampling code for WIC’s “Fant” resampling. This means that the quality of Image->Resize when shrinking an image has been greatly improved. I also have a version of the Curves adjustment that uses Direct2D instead of GDI+ for rendering its UI (this was mostly “prove to myself it actually works” code).

Please do remember that Paint.NET v4.0 probably won’t be available until late 2011 – you have plenty of time to enjoy XP with Paint.NET v3.5.x in the meantime if that’s the way you roll (and it’s not like I can delete it off your box once 4.0 ships, nor would I if I could). As a pre-emptive snark, in true Raymond Chen style: this was a decision I made after much deliberation with both quantitative and qualitative data, and spamming my comment box won’t change my mind. Your voice has already been heard. Thanks in advance.