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why is gimp's xcf files so large?

Mar 31, 2011, 23:07
Post: #1
why is gimp's xcf files so large?
I have multiple xcf files that I saved because I use the selected area in those pics in multiple photo edits... and you guys told me that xcf files store what is already selected... these xcf files of mine are anywhere between 20MB and 40MB... what are they so huge?
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Mar 31, 2011, 23:34
Post: #2
RE: why is gimp's xcf files so large?
Because they aren't compressed (at least not like JPEGs). Typically, you have 4 bytes per pixel in layers, and one byte per pixel in channels (saved selections...). So a 1000x1000 image with three layers and two saved selections can be 14MB. These figure mostly apply to photography, it will often be much less with computer graphics, because there is some optimization.

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Apr 1, 2011, 02:57
Post: #3
RE: why is gimp's xcf files so large?
You can also add in your own compression by zipping the files. Based on my totally unscientific tests, you can save roughly half the file size... but of course you add in the hassle of needing to always zip and unzip it in order to use it. Probably okay for archiving, but not for something you use frequently.

Also, most versions of Windows that use the NTFS file system (including 2k, XP, Vista, & 7) have a feature that lets you compress files or whole folders. Anything that goes into the folder is automatically compressed, and then if you open the file or take it out of the folder, its uncompressed on the fly... you don't need to do anything. Of course it does slow down access a little while Windows compresses or uncompresses it. You could try creating a compressed folder for your xcf files and see if the amount of space saved is worth the trade-off for however much it slows down access.

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Apr 1, 2011, 07:05
Post: #4
RE: why is gimp's xcf files so large?
No need to ZIP outside of Gimp. From Gimp, you can save using extensions .xcf.bz2, .xcfbz2 or .bz2 and Gimp will do a ZIP-like compression.

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Apr 1, 2011, 15:21
Post: #5
RE: why is gimp's xcf files so large?
(Apr 1, 2011 07:05)ofnuts Wrote:  No need to ZIP outside of Gimp. From Gimp, you can save using extensions .xcf.bz2, .xcfbz2 or .bz2 and Gimp will do a ZIP-like compression.
Interesting! I didn't know about that feature. I just tried it and it compressed my 21.5 MB .xcf down to 11.3 MB, just the same as Winzip did. Thanks!

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