Up-scaling images.

I keep getting ads for Topaz up-scaling software, and have wondered if it is any good. Not that it matters, since I am running on Linux computers, and Topaz is Windows. But recently I found an open source up-scaler program names Upscayl, which runs on Linux, Windows, and Mac. So I installed it to do some testing. First thing I discovered is that my built in graphics card wasn’t powerful enough to run the software. So I had to buy a Nvidia GPU. I bought the least expensive one I could find, and it runs the software just fine.

My simple question is how does this software compare to scaling in Gimp. For example, if I take an image and scale it 400% in Gimp, how does that compare to scaling the image 400% in Upscayl.

So I took an image I have of a hummingbird.

I will upscale it and then crop it to the same dimensions, 1920×1080 pixels.

Here is the new image up-scaled by Gimp.

And here is the image up-scaled by Upscayl.

Upscayl did create a sharper image. Interestingly, the image it created is at a lower resolution, 300×300 ppi, where Gimp left the image at 350×350 ppi. But the Upscayl image is slightly larger, 1.3MB compared to 1.2MB

So let’s try 800%. Here is the file size before cropping.

Here is Gimp’s output cropped to 1920×1080.

Upscayl has a feature called “Double Upscayl” which runs the upscayl twice on the image. Running Upscayl takes longer that Gimp, especially if doing the double upscale. Here are it’s results. So first I left the scale factor at 4x and checked the “Double Upscayl” checkbox. This resulted in a much larger image, since it first did a 4x, and then another 4x. That is a 1600% scale factor. That isn’t what I wanted, but here is that result. First the uncropped image size.

And the cropped image. At this level of zoom you can see that the AI has sharpened the feathers too much.

Ok, now lets run Upscayl at 8x, without the doubling checkbox checked.

Here is the uncropped image size, it matches the 800% Gimp scaled image.

So what do I think? Well it certainly looks promising. Upscayl has different algorithms you can choose. I was using the ultrasharp. I also suspect that the image subject will make a difference. Does the image have blurry areas; how does it do with people; what about text in an image, etc.