Re: [Openexr-user] EXR layer naming conventions

[jonathan . litt]

"Jim Hourihan" <address@hidden> wrote:
>> - For consistency, "<channel>" should, if possible, be chosen from  
>> the list of main channels: R/G/B/A/Z/Y/RY/BY. This works for layers  
>> that represent colors. Writers should be strict about using the  
>> recommended channel suffixes, but readers should recognize other reasonable
>> versions, like r/g/b/a, red/green/blue/alpha, etc..
> 
> This is what I was hoping to avoid in my code but cannot. Obviously  
> if you throw non-english languages possibly represented as UTF-8 or  
> possibly transliterated to ASCII in the mix you've got a lot of  
> permutations to deal with.

I'm not sure I follow ... just to recap my previous message, what I was 
suggesting is that full channel names beyond the standard ones be formatted 
"<layer>.<channel>" where "<layer>" could be freeform, including UTF-8 if 
desired (would be up to the application), but "<channel>" be rather strict, 
consisting of only R/G/B/A/Z/Y/RY/BY/AR/AG/AB (all previously defined in the 
spec except for Z) or plain integers. Readers could be flexible and also 
recognize lowercase or full words for "<channel>" (e.g. "red") or possibly 
other cases, but wouldn't be required to in order to be compliant. Do you think 
anything about a system like that would be unfriendly in regards to usage of 
UTF-8?

For example this is what the full channel names could look like for a file 
comprising main output, a diffuse layer, a spec layer saved as 
luminance/chrominance (a contrived example), a scalar noise layer, a uv layer, 
a normal layer, and then everything duplicated for a left-side stereo image:

R G B A Z
diff.R diff.G diff.B
spec.Y spec.RY spec.BY
noise.0
uv.0 uv.1
N.0 N.1 N.2
left.R left.G left.B left.A left.Z
left.diff.R left.diff.G left.diff.B
left.spec.Y left.spec.RY left.spec.BY
left.noise.0
left.uv.0 left.uv.1
left.N.0 left.N.1 left.N.2

The key idea here is the consistency of a) using <layer>.<channel> for all 
non-standard channels, even scalar channels and b) having the <channel> part in 
<layer>.<channel> conform to a standard.

-Jonathan