On Fri, 24 Jan 2014 20:24:59 +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?

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
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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/
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