[Openexr-devel] DWA compression

[Larry Gritz]

The new compression modes are really great, thanks. I've been playing around 
with it and it performs very well, great compression while retaining visual 
quality.

But the numbers are confusing. Apologies if I missed prior discussion of this 
point, but does anybody have an explanation of what the value means?  I 
understand the basics -- higher is more compressed, below 100 gives nearly 
perfect visual fidelity -- but maybe because the scale is unbounded and highly 
nonlinear, I haven't been able to come up with an easy-to-explain description.  
In contrast, the 1-100 scale for JPEG quality has a more intuitive feel that, 
while still not linear, seems to be no trouble to wrap one's mind around (maybe 
because it reminds us of percentages?) and is much more amenable to putting 
into a UI slider. I'd love to find an equation that would map an intuitive 0-1 
or 0-100 scale inside an app to the dwaCompressionLevel in an analogous way.

--
Larry Gritz
address@hidden