I know there is a resize function in gimp. In GMIC there are a couple I think. but are any of them really intended to make smaller photos larger and still be sharp?

Looking on the net I have found smilla enlarger may do this. Has any one here tried it and can you give a review please? Or have you you any other suggestions.

Thanks for replying Wallace, I hadn't heard of it before. I thought maybe someone here had since it is open source from source forge and runs using qt.
PUBLISHER'S DESCRIPTION
From Mischa Lusteck: SmillaEnlarger is a small graphical tool ( based on Qt ) to resize, especially magnify bitmaps in high quality. ( The used algorithm is an invention of my own )


But there hasn't been any reviews since 2016 and I think it was a beta version then - page has this years date on it.
Found an updated version on CNET 2017

Thank you Wallace. It may come in handy

Hi

I use the next G'mic Filter Xbr2X .
I Like it - it is a good effect.

Doron

For Windows users there is a free version of Reshade that can rescale images. MareroQ even wrote a plugin to make it easy to use from within gimp.

View it here:

viewtopic.php?f=9&t=14308&p=196572&hilit=reshade#p196572

It's very rare that I need to upscale an image, but when I do, I use the nnedi3 upscaler. It's the best I've seen yet, but you'll need to learn Avisynth to use it.

Here's a 4x upscale example. Unfortunately it's flattened also, but you can remove the black easy enough..

For windows I can recommend:

Waifu2x-caffe:
https://github.com/lltcggie/waifu2x-caffe/releases

It works very good with images like Wallaces avatar.

And Fitswork:
https://www.fitswork.de/software/softw_en.php
tutorial:
http://www.astrofriend.eu/astronomy/tut ... swork.html

try: Fitswork>Processing>Image Geometry>.........x2 hi-f sinc
Fitswork>Bearbeiten>Bildgeometrie>Bildgröße x2 hi-f sinc (german)

But you can try the other alternatives in that menu. (also with little neural networks).

@racer-x,

Your sugestion also works with a neural network solution I think?
Do you have a nice link to good tutorials for Avisynth?

Avisynth is a script based video editor. It's commandline. It's a Windows program, but it works under Wine too. I rarely use it anymore, so can't help with tutorials. I'm sure you can find some out there.

You'll need the nnedi3 filter. It can only upscale in multiples of 2. Example: 2x, 4x, 8x, 16x. Here is the command I used for 4x upscale:

SmillaEnlarger, a bit of a monster in Windows but a small download in linux . Looks like this:



I tried Smilla years ago and not all that impressed. Seems to generate artefacts and makes big file sizes.

A recommendation - ImageMagick

A long discussion and various algorithms here: https://www.imagemagick.org/Usage/filte ... upsampling

IMHO this one is as good as anything for enlarging and a little sharper.



but..whatever method used is still just guessing which pixels to add.

Thank you all.
I really wanted to find out if it could be done with photos. As far as I was aware - once a photo is shrunk you cannot enlarge it again. Tried one of them on a photo today and looks to me like if the information isn't there, enlarging doesn't make any difference.

@racer-x,

Thank you for information.

@sallyanne,

That is true. If an image is scaled-down, then the image lost pixels, therefore the image lost information.

Some neural network systems, like waifu2x, have good results, because the neural networks are trained on thousands of image pairs ( down-scaled and originals), so the neural network system based image scalers can better "guess" the information that is lost. But it isn't magic, the neural networks never recover the original information that is lost.