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)

[sallyanne]

I'd like to know how you got it from such a low resolution to 600. You cannpt add pizels to an image unless of course you get ai to do it for you and then it will not be exact.
I'm sure Ofnuts has a document here about that but at the moment I cannot find it. If I do I will edit my reply with a link.

[denzjos]

(Yesterday, 07:33 AM)sallyanne Wrote: I'd like to know how you got it from such a low resolution to 600. You cannpt add pizels to an image unless of course you get ai to do it for you and then it will not be exact.
I'm sure Ofnuts has a document here about that but at the moment I cannot find it. If I do I will edit my reply with a link.

JoeCool took a screenshot and saved the image at 600 dpi, I think.

[zeuspaul]

First thing I would do is open the original JPEG in GIMP.  Then Image/Scale Image.  Then select Cubic as the method because it should give best results. Could try the other options and go with the best.

[rich2005]

Just my two euros worth.  In the dim-and-distant past taking a photograph of a photograph with the intention of enlargement was a valid method, but the quality of a photographic emulsion is way better than the pixel density of a computer monitor.  There are some improved scaling options these days, several in the gmic_qt plugin such as Upscale[Recursivex2] might actually give a small improvement as well as scaling.

IMHO it comes down to the type of image and the amount of user editing.
An old cartoon with solid colours, easy to color / fuzzy select and fill with colour.

   

Not so easy, an old digital from 25 years ago, plenty hand editing with clone and smudge tools.