Re: [Openexr-devel] RE: proposed standard for .exr linear float fileexchange/filmout

[Kevin Wheatley]

Haarm-Pieter Duiker wrote:
>         xLin /= pdxWhiteReferenceLinear;
> 
>         if ( pdxBlackPoint != 0.0 )
>         {
>                 xLin = xLin*(whiteLin - blackLin) + blackLin;
>         }
>         xLog = log10( xLin ) pdxNegativeGamma/pdxDensityPerCodeValue + 
> pdxWhiteReference;

So in case anybody asks why the 'if' in our original, it comes from
being bitten by peopl assuming floating point maths in CPUs has
infinite precision whan it doesn't, we've seen examples where the
'defaults' don't work if you assume they are unchainging (e.g.
NVidia's control panel gamma settings for a start :-), it is kind of
an implementation detail, but I'd suggest anything that should be
unity at a particular setting should be skipped rather than calulated.
Of course the real idea woul be to hide this transform into the
OpenEXR distribution somewhere so everybody does the same. I don't
want to have to support 36 flavours of transform (can anybody say
TIFF).

Besides, maybe there are some smarter people than me out there and I
wouldn't want to miss anything :-)

> > Subject:      [Openexr-devel] exchanging exr's
> > Date:         Wed, 09 Jun 2004 10:33:03 +0100
> > From:         Ken McGaugh <address@hidden>
> >     xLog = pdxWhiteReference + log10( xLin )*siftGamma/siftStep

In case of any wonders:

siftGamma => pdxNegativeGamma
siftStep => pdxDensityPerCodeValue

sift was an earlier suggestion for attribute names prefix ...

Kevin

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