How good is the NanoPixel Export?

So I've kind of been taught that you should never upscale images due to potential loss of quality and that it's always better to start with as large a file as possible and then downscale as needed. I've been taught that even if an image looks okay on the computer, that there could be some pixelization that could affect the quality of a print.

However, I did a brief test exporting with NanoPixel at 4x and I compared that with the original image. When I zoomed in on both, the NanoPixel version actually looked less pixelated than the smaller original. So that makes me wonder if NanoPixel defies what I've previously been taught and it's actually fine for printing with, even on print-on-demand sites that specifically instruct against using upscaled images? Has anyone actually done any prints or printed on products such as shirts, mugs, etc. with art exported with NanoPixel? If so, I'd love to hear how the quality was.

If NanoPixel exported art is completely fine for printing and print-on-demand, I could see myself importing images made in other apps into Rebelle simply to use the NanoPixel export. This could be very useful to use with Flame Painter which can get slow and glitchy at times with larger canvases. Though I really hope that if Flame Painter is ever actually updated, that it will have NanoPixel built right in.

Hi

I don't use Nanopixel, but in case you like to compare.

Here is a download link to "Upscayl", a pretty good
open source upscaler (free)
https://upscayl.org/

By the way, I know the technique of painting bigger and
then scaling it down for print from comics and illustrations.
They use this technique to get better, smoother lines.

... Though I really hope that if Flame Painter is ever actually
updated, that it will have NanoPixel built right in ...

Apart from that, I am not sure if this will ever happen. I also
have very strong doubts that this will happen in my lifetime.
But I still have a nice life :)

Another Flamepainter lover

Thanks for the suggestion. I did see a good review for Upscayl on Youtube, so I guess it couldn't hurt to test it out. It seems that I couldn't even upscale as large as I'd want with Nanopixel anyway because it's limited by my graphics card which surprised me given that I do have a fairly high-end laptop. It would be interesting to compare Upscayl to both NanoPixel and various upscaling options within Photoshop.

Though it is disappointing if the NanoPixel option isn't as viable as I thought it could be due to size limitations. While I think Rebelle is amazing software, it lacks a couple of features that I'd need to really use it seriously in my work, which are seamless painting and symmetry painting with the former being the higher priority, and I can do both of those in Corel Painter and Flame Painter. If NanoPixel had been a good option for me, then I wouldn't feel like I'd wasted my money on it. I can definitely say that I won't be paying for any more Rebelle upgrades unless they add those features.

I can say that I was very impressed with the upscaling results
of “Upscalyl”. You can even set different modes. The limitations of
Nanopixel may come from how it works internally.

I agree with you that the features of Rebelles leave a lot to be
desired. The partly old-fashioned operation, that you can't use
the Transpose feature with Stencils and Paths and a few more
frustration things. In my opinion, there's a lot to work on first.
I don't know if they'll ever get it right.

I tested out Upscayl with the Digital Art model first. At first glance I thought it looked amazing, but then I noticed that it smoothed over some details in my art that I'm not sure I'm happy about. Beyond that, somehow it added new colors in a few spots. The art piece I tested it with is just black and shades of cyan and somehow the app gave it a few spots of dark red. The other annoying thing is that I fed it a 300 dpi image and the upscaled version it gave me back was only 72 dpi! Like I can easily change the DPI back in Photoshop, but I shouldn't have to. It's bad enough that it doesn't retain any of my metadata and I have to redo all of that.

I wanted to try the default "Real ESRGAN" model to see if I like that one better, but for whatever reason that one isn't working on my computer. It says that the upscale is successful but then never actually finishes processing it and it will just hang there forever. Have put in an email to support, and I hope I can get it working, otherwise I might need to pass on this app and consider if it's worth investing in something like Topaz GigaPixel.

that's a pity, for me Upscayl is great to use to
enlarge low-resolution images and to give them
smoother edges

I don't know if the issue is that in my case I'm not talking about images that are necessarily low-res. It's more my early digital art pieces that I made when I was exploring and experimenting and I had no idea what image sizes were often needed for things like making prints, especially if you want the option of doing really large prints. So they aren't low-res compared to like image thumbnails that you'd post online, but low-res for large printing purposes. And going forward it's more about the fact that I can only use a canvas so large before I start getting performance issues, even on a high-end laptop, so some upscaling might be needed there as well. Again, it would help so much in Flame Painter if I could just start out with a canvas size a quarter of what I wante the final version to be.

I played around with Upscayl a bit more, and I actually managed to get it to work on the "Fast Real ESRGAN" mode which is the 2nd option. For whatever reason it won't work with any model other than that or the Digital Art one. I think I like the results of this model better than the Digital Art one which is ironic given that it is a digital art piece. It didn't smooth over as many details and it didn't have as much of the weird issue of color changes (though I still noticed some tiny color changes when upscaling a ton). It still has the issue of not preserving my DPI settings or metadata. Though with the latter, I suppose that's mostly an issue for existing art pieces. Future art pieces I could simply not add any metadata until after the upscaling is complete.

I'm still rather frustrated that I'm unable to use most of the modes beause I don't know if one of the others would give me even better results. I've had no response yet to my support email and I'm a bit confused because I saw somewhere that posting on GitHub was the only way to get help, but why even have a support email listed then? I'd really prefer not to use GitHub because I'm not a developer and I've always found that site confusing to navigate.

I think I'm seriously going to download the demo version of Gigapixel to test it out. I'd rather not spend $99 on an upscaler, but the idea of being able to offer customers very large prints if they want them is pretty appealing. I also see it as a way to try to make my digital art as future proof as possible because who knows what new tech advances down the road might require larger image sizes.

Well, I just realized another problem with upscaling. I do digital art that is meant to be seamless so it can be tiled. I tried tiling the art I tested and the upscaling process altered my art enough that it was no longer seamless! I noticed issues regardless of whether it was upscaled with Nanopixel, Upscayl, or doing it natively in Photoshop with the Preserve details 2.0 option. In some cases it resulted in a line at the borders of each tile and other times things just didn't line up right. I mean if the piece is symmetrical and the upscaler has to add pixels to upscale it, you'd the it would apply the same changes to identical halves/quarters of the image, but apparently not...

I never have any issues with seamless art when I downscale... I don't know if there is an upscaler out there that won't have this problem. I haven't tested the Gigapixel yet, but I can't test whether the images are seamless or not on the demo version since it won't let you save files, so I'd have to shell out the $99 and then ask for a refund if it didn't work. I'm so disappointed because I was really loving the idea of being able to offer larger prints of my art. And I might still want a bit of tiling even on large prints to accomodate different aspect ratios.

here i every mode is working
i have a PC with Win 10