Fix handling of unencoded LMDB in Torch

[gheinrich]

Unencoded LMDB data are stored in BGR format so a
channel swap is required to have a consistent
representation of data across inputs, mean files,
etc.

[lukeyeager]

Oops. Do we need to backport this into digits-3.0? We should at least put it as a known issue in the release notes. Will you update the RC release notes to add a Known Issues section (like this)?

[lukeyeager]

Your implementation looked a little suspicious for grayscale images. I tried LeNet on grayscale images and got a different error than the one I was expecting:

2015-12-16 08:41:40 [FAIL] /home/lyeager/digits/tools/torch/main.lua:637: attempt to perform arithmetic on field 'batchSize' (a nil value)
DIGITS Lua Error
stack traceback:
/home/lyeager/digits/tools/torch/main.lua:637: in function 'Validation'
/home/lyeager/digits/tools/torch/main.lua:779: in main chunk
[C]: in function 'dofile'
/home/lyeager/digits/tools/torch/wrapper.lua:25: in function </home/lyeager/digits/tools/torch/wrapper.lua:25>
[C]: in function 'xpcall'
/home/lyeager/digits/tools/torch/wrapper.lua:25: in main chunk
[C]: in function 'dofile'
/usr/local/lib/luarocks/rocks/trepl/scm-1/bin/th:145: in main chunk
[C]: at 0x00406670

[gheinrich]

Thanks for spotting the bug on grayscale images! If have updated the code.
I have also added a reference to #477 on the 3.0 RC release notes. The fix should probably be backported into digits-3.0 for the next release candidate.