Re: [Openexr-devel] (no subject)

[Drew Hess]

Hi James,

Yes, you can export any channel as UINT.

How values are represented in a UINT channel is unspecified by the file
format; it's up to the application to decide that.  You should ask the
Splutterfish team about the method they use (or maybe they'll answer here,
I think they read this mailing list).

If you're using the 1.0.6 release of OpenEXR, the IlmImf library supports
automatic datatype conversion for InputFile objects, but it doesn't try to
be clever about scaling or normalization; it simply converts the data type
(modulo representation issues like infinities, etc.).  

So, for example, if the file has a UINT channel and a sample value of 255,
and you ask for a FLOAT channel in your frame buffer, readPixels will
convert that to 255.0 float.  If you want that to be mapped to 1.0, you'll
have to scale the float buffer after you get it back from readPixels ().


-dwh-





On Mon, 3 Nov 2003, James McPhail wrote:

> Hello
> 
> can one export, say, the Red channel in UINT format, or can these types 
> of channels only be FLOAT or HALF? I ask because the Splutterfish EXR 
> exporter for 3DSMax claims to be able to export RGBA as UINTs, although 
> upon doing so neither my own nor the ExrDisplay program can find these 
> channels in the file (they both just display solid black). Also, I tried 
> to enable my program to export to RGBA as UINTS, and I got strange 
> results. Does the UINT use 0-255 as the the black-white levels?
> 
> Thanks in advance!
> James
> 
> 
> 
> 
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