To download, head on over to the forum. I’m also in the process of adding this to the auto-updater.
This build has two big things going for it: 1) fixes to the Save Configuration dialog (sorta), and 2) some absolutely massive performance fixes to the main rendering engine when working with very large images.
Save Configuration dialog: Some folks have reported that they can’t get the Preview to work, even though saving and loading works fine. I don’t have a fix for this yet (AFAIK), but at least you’ll be able to see what the actual error is now so that you can send it to me. It will show up in the standard error dialog along with the almost useless "Preview: (error)" text that displays at the top.
Rendering engine: Before this update, Paint.NET has been very bad about handling very large images. I’m talking images that are on the order of 32,000 pixels large on either dimension (width or height). Zooming and panning often result in very long delays where the app just hangs until it figures itself out — and we’re talking 30, maybe even 60, seconds, even with a $1000 CPU like an overclocked Intel Core i9-7900X. I spent the last week optimizing this and replacing the data structures and work queue management code, and now this should all be working good. It’s not 60 FPS, so there’s still some work left when the time comes for it, but it’s very usable now! The worst delays might be on the order of 100-200ms, so they just feel like kind of a choppy framerate sometimes.
Changes since the previous alpha (build 7070):
- Fixed: Optimized rendering engine to remove huge lag spikes (30+ seconds) when zooming or panning very large images (e.g. 32K x 32K pixels).
- Improved: Added error reporting to the Save Configuration dialog. Instead of just saying "Preview: (error)", you’ll also get the standard error dialog that includes the exception which can used for troubleshooting.
Enjoy! 
paint.net blog 
What about a new feature for open images?
(Close all images except…)
(Close all images on the left.)
I don’t have any plans for that
What about either incorporating an Interlacing option for “Save as” dialog of JPG & PNG files (like JPEGTran & OptiPNG do) or, at the very least, make PDN remember if such a plugin was chosen last time so that it does not fall back to its JPG/PNG?
WIC does support interlaced PNG encoding, but I don’t see any option for interlaced or progressive encoding of JPEG.
What’s the appeal of interlaced PNG?
Having the image being shown in full on the first batch of bytes received, then getting more and more details with each new batch.
The default way only gives the first (couple of) lines, so the image’s full dimensions aren’t visible on first sight.
That’s the #1 reason for me to explicitly save each and every JPG/PNG image interlaced /progressive instead of “line by line” – the latter simply reminds me of those dark times of CRT monitors/TVs with their ugly scanlines.
Are you on a slow Internet connection?
That depends – not at home, but at work. As a developer, I’m asking for this feature for those that access my images from slow Internet connections.
Seems reasonable to me. I can add PNG interlacing very easily, so I’ll toss that in on the next update.
Progressive JPEG encoding, however, like I said is not supported by WIC. You’ll need to use an external tool for this.
Thanks a lot, Rick. I really appreciate your efforts! 🙂
Regarding WIC, I’ll try to convince Microsoft – if they’re as open and nice as you and/or as they state nowadays, I’m looking forward to get back to you after WIC offers progressive JPEG encoding. 😀