[Shotwell] storing original and modified photos

[Adam Dingle]

Shotwell friends/fans,

as you all know, Shotwell is a non-destructive photo editor.  If you 
edit a photo, then today Shotwell writes out a full-resolution JPEG 
including your changes only when you export.

We're considering enhancing Shotwell so that it generates a new 
full-resolution JPEG immediately after you make any edit (this would 
probably happen in the background, so the user interface wouldn't slow 
down due to this change).  This change would have several benefits. 
Since full-resolution modified copies would always be available, we'd 
easily be able to drag/drop to applications other than Nautilus 
(http://trac.yorba.org/ticket/1563).  Also, browsing through modified 
photos would be faster than it is today because we wouldn't need to 
apply your edits on the fly each time you move to a new photo.  Of 
course, Shotwell would still keep the original photos and remember all 
edits you've made, just like today.

If Shotwell does store modified copies of each photo, though, where 
should it keep them?  There are a few possibilities:

1. The original library directory (e.g. ~/Pictures) is unmodified.  
Shotwell keeps each modified photo in its own directory, e.g. 
~/.shotwell/modified_photos.

2. Whenever any photo has been modified, Shotwell moves the original 
photo to its own directory (e.g. ~/.shotwell/original_photos) and writes 
modified photos into the library directory (e.g. ~/Pictures) directly.  
When you revert to original, Shotwell moves the original photo back into 
the library directory.

3. Shotwell keeps original and modified photos side by side in the 
library directory.  We could either (a) keep the original photo 
DSC_001.JPG untouched, and create a new file DSC_001_MOD.JPG, or (b) 
rename the original photo to DSC_001_ORIG.JPG, and write the 
modifications into the original file DSC_001.JPG.

Note that Shotwell would also likely store tag and title data in IPTC or 
XMP tags in each modified photo file.

A potential advantage of (1) is that the original library is 
unmodified.  A potential advantage of (2) is that it might be easier to 
share the photo library with other photo applications: for example, 
photo edits made in Shotwell would show up in those applications 
immediately if they are also viewing the ~/Pictures library.

So, Shotwell users: which of the above approaches would you prefer for 
Shotwell to take?

adam