Fix low resolution images

[JoeCool59]

I'm a casual GIMP user. I have some old digital images shot or digitized in low resolution (pixelated). The one I'm currently working on was a jpeg from around 1990. I opened it and screenshot it and now it's a 600ppi png, but the image retains all the compression artifacts that are left over from its original life as a 70ppi jpeg. Is depixelating it an art? I recognize that GIMP is incapable of knowing what information should be in the image. I'm eager to learn new things in GIMP.

[denzjos]

I should load the original picture into gimp and use the G'Mic-Qt plugin :

- Repair / Unquantize [JPEG Smooth]
- Repair / Upscale [CNN2x]
Use gimp to optimise the result (Colours / Brightness-Contrast and others)