Re: [Openexr-devel] Using Rgba interface for non-rgba files?

[Paul Schneider]

Making RgbaInputFile automatically read the "first three" channels

in the file might not be such a good idea.  If a file has more than

three channels, which ones are the first three?  Which channel maps

to R, G, and B respectively?  Assuming that we go by alphabetical

order, are "R", "G" and "B" an exception?  If you have an image

with channels "x", "y" and "z", and you add an "R" channel, does

RgbaInputFile read "R", "x" and "y"?

Another problem is that the Rgba interface (and the code that uses it) is expecting half data.  Other channels, especially XYZ, are likely to be float; would the Rgba interface automatically downsample the channels to half?  You'd also have to rely on the users being educated enough to change the dials in their software so that their XYZ images weren't gamma corrected or similar.

In a way, it's too bad that the Rgba interface exists and is so easy to use, because it encourages developers to only support a subset of the EXR images out there.  And I count myself among these lazy developers.

- Paul