Re: [Gimp-user] Correcting "grainy" resolution?

[Liam R E Quin <liam holoweb net>]

On Fri, 2014-01-24 at 20:24 +0100, pfaoro wrote:
> Is there a (simple) way to blow up a snapshot originally take with a slow,
> cheap, disposable camera without having the result so grainy that it isn't
> usable?

What I do sometimes is use a step or staircase resize - there's one in
fx-foundry for example - to go twice or three times as big as I want.

Then do either gaussian blur or selective gausian blur (depends on the
image) and use filters->enhance->sharpen maybe to 80% (it will look
awful at this stage), then deal with (clone, erase, dodge burn) any
obvious problems, then scale down using the Cubic filter, which will
soften those oversharped edges...

Another approach (depends on the kind of noise in the image) is to
decompose into H S V layers and blur the H layer before scaling up, as
some cameras tend just to swap colours, they say. Mine doesn't.

There are more sophisticated approaches using fourier transform and
wavelet decomposition, and sometimes they get better results and
sometimes not.

If you want to print the photo, print at 72 or 144dpi, and use absorbent
paper (not glossy or extra smooth inkjet paper for example, but writing
paper), and the paper will mask a lot of the problems :D

Without seeing the picture it's hard to know, I'm afraid.

Liam

-- 
Liam Quin - XML Activity Lead, W3C, http://www.w3.org/People/Quin/
Pictures from old books: http://fromoldbooks.org/
Ankh: irc.sorcery.net irc.gnome.org freenode/#xml