Re: [Gimp-user] Correcting grainy resolution?

2014-01-26 Thread john Culleton
On Fri, 24 Jan 2014 20:24:59 +0100
pfaoro for...@gimpusers.com 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?
 


You can't increase dot density in a bitmap file.
Facing that problem I would import the bitmap
file into Inkscape and then convert it to a
vector file. Then I would blow up the vector
file. You will lose some detail but at least it
won't be grainy. 


-- 
John Culleton
Wexford Press
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Re: [Gimp-user] Correcting grainy resolution?

2014-01-26 Thread Liam R E Quin
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

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