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Radically reduced size of XCF file. What wrong with this idea?

Aug 6, 2011, 08:22 (This post was last modified: Aug 6, 2011 09:04 by ItDontMeanAThing.)
Post: #1
Radically reduced size of XCF file. What wrong with this idea?
I found a way to save a sub 1mb XCF file with a select saved as a channel and a layer of the image as a threshold. I can open the original jpg in gimp, select all, copy into new transparent layer in the tiny XCF file, do channel to selection, delete the threshold layer and I'm good to go. I went from a 27 mb xcf to a 0.5 mb xcf with the channel and layer for a 2 mb jpg.

At my low skill level the selects are usually the only XCF elements worth keeping. Everytime I've returned to a saved XCF weeks later because I knew more, I tossed it out and started over from the original jpg unless a select was involved. I could buy a larger HD, but I'm literally living out of 2 suitcases and expect to continue so indefinably. Keeping my pile of stuff small is a prime priority. Store them online? The only internet ISPs available here are rather slow.
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Aug 6, 2011, 09:49
Post: #2
RE: Radically reduced size of XCF file. What wrong with this idea?
The thing wrong with this idea is that each time you do a global change and save as JPEG, you lose something to compression. Not speaking of the risk of forgetting something important someday.

And often overlooked format is XCFBZ2. Instead of saving your image as foo.xcf, save it as foo.xcfbz2. Gimp will apply a ZIP-like, lossless compression algorithm to the image. Some parts of the image compress very well, like selection channels, or the alpha channel of many layers. My biggest XCF is 260M (a mix of photo and computer graphics: http://www.flickr.com/photos/ofnuts/5371081284/ , 6000x4000px), but as XCFBZ2 it's 57M.

And a "larger" HD will only be bigger inside, physically its the same size as your current one.

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Aug 6, 2011, 10:45
Post: #3
RE: Radically reduced size of XCF file. What wrong with this idea?
(Aug 6, 2011 09:49)ofnuts Wrote:  The thing wrong with this idea is that each time you do a global change and save as JPEG, you lose something to compression.
I'm not sure I undestand this. Only time I save to JPEG is after I'm done post processing (PP). That JPEG is used only for display. If I return to the image to PP it differently I would combine a copy of the original, unaltered JPEG and the selects saved in the XCF.

(Aug 6, 2011 09:49)ofnuts Wrote:  Not speaking of the risk of forgetting something important someday.
'Something important' meaning changes made during PP? Yes, that's a risk. I've saved the XCFs of the few images that are important to me and the PP was long and or complicated, at least to my rookie skills. I intend to keep doing so.
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Aug 6, 2011, 11:08
Post: #4
RE: Radically reduced size of XCF file. What wrong with this idea?
(Aug 6, 2011 10:45)ItDontMeanAThing Wrote:  
(Aug 6, 2011 09:49)ofnuts Wrote:  The thing wrong with this idea is that each time you do a global change and save as JPEG, you lose something to compression.
I'm not sure I undestand this. Only time I save to JPEG is after I'm done post processing (PP). That JPEG is used only for display. If I return to the image to PP it differently I would combine a copy of the original, unaltered JPEG and the selects saved in the XCF.
if you work that way, that means that 1) you can't improve on what you have already done and have to start over each time, and 2) you cannot save intermediate versions. Whatever suits you, but that will severely limit your workflow once you get more skilled with Gimp (start using layers, etc...). If you want to get tricky, you can even save your selections and masks as PNG. Then you can import them in some other image processing software, even if said software can't read XCF.
You may also find that as your skills improve, the selection you did 3 months ago eventually doesn't look that good and you can do much better now in much less time, and the benefits of saving the old selections start to fade.
(Aug 6, 2011 10:45)ItDontMeanAThing Wrote:  
(Aug 6, 2011 09:49)ofnuts Wrote:  Not speaking of the risk of forgetting something important someday.
'Something important' meaning changes made during PP? Yes, that's a risk. I've saved the XCFs of the few images that are important to me and the PP was long and or complicated, at least to my rookie skills. I intend to keep doing so.
That what the XCFBZ2 suggestion is for.

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