[Gimp-user] xcf image corruption w/ Partha's 2.9.5 64-bit windows build

[Dave Bodenstab <dave_bodenstab comcast net>]

A bit more on the image corruption I'm seeing that I mentioned in my 
previous question about time-stamped backups.

What I'm doing:

I found a neat utility (Chunky) that displays nice maps of my Minecraft 
world. I'm using Gimp to stitch the pieces (approx. 1000 x 1000) 
together to make a larger map. As I explore further, I am adding to my map.

The maps are huge. I've already split them into two images. One is 
7200x14200 and the other is 10600x4800. A single 17000 x 18000 image is 
just too big to work with. :-)

I've got win7x64 with 16G memory and a 3GHz core i7. Perhaps my math is 
wrong, but I calculate that, with the alpha channel, the memory required 
for the larger should be on the order of 390MB. Even with a couple 
additional layers, it's perhaps pushing 1G memory usage. That is not 
that big really and my CPU is certainly capable of handling an image of 
that size.

As I mentioned, I've started with Partha's 64-bit build of v2.9.5 since 
I am just beginning to learn Gimp. If I could find a download link for 
2.9.6 that you just announced, I'd try that one.

Anyway, as suggested, I managed to "dock" the error console, however I 
suspect that I might have missed some error messages since I've always 
got the layers tab open. I've been saving much more frequently and, 
since I saw no errors, continued to work after saving to fileX.xcf where 
I bump X with each save. All seemed well until I started a new Gimp 
session and reloaded my latest image -- it was corrupted. I've now 
"undocked" the error console so hopefully I will see any errors immediately.

I wonder if the corruption occurs during my "layer merge down" 
operation. As I explore and expose a new map section, I've been 
stitching those segments into one larger map -- it's easier than trying 
to merge the individual segments into my main image due to constantly 
having to zoom in and out. When completed, I "Edit->copy" the layer and 
"Edit->paste as new layer" to my main image. I position the new layer 
and merge down to the background. (I've got other layers with text 
annotations and small images that I wish to keep separate). The "merge" 
does take significant time -- on the order of 30-60 seconds sometimes. 
If I saw any corruption I would stop, but I don't. It is only when I 
reload the xcf that I see it (although I think I saw it once when I 
switched back and forth between image tabs).

Q1: how different is 2.8.22 w.r.t. 2.9? I am leaning towards using the 
"stable" version to avoid losing any work even though I might have to 
relearn things for 2.9 and beyond.

Q2: can you give me step-by-step instructions for redirecting the error 
log a file (if it's possible on windows)? Perhaps I could send it as a 
bug report. Partha mentioned the log file written to %TEMP%, but since 
it's deleted at the start of my next session, it's gone when I notice 
the corruption.

Sorry for the long post.