[Image-SIG] 3 channel float images

Georg Mischler schorsch at schorsch.com
Thu Jul 13 18:43:32 CEST 2006

Georg Mischler wrote:

> I also experimented a bit with storing the data the same way
> Radiance does (RGBE: four ints, the mantissa of each RGB channel
> and a common exponent), which would save a lot of space at a
> slight computational expense. I don't remember why I didn't
> continue into that direction.

On checking, I just realized that my memory was faulty in more
than one sense.  My code actually stores RGBE values, and decodes
just where necessary (eg. in getpixel() etc.).

This has the advantage that it circumvents the storage issues
Fredrik mentioned (whichever those actually are), and that it
uses only a third of the memory.

It has the disadvantage that some of the internal filtering
operations won't give the expected result. You can't interpolate
by just taking averages, for example, because the exponent needs
to be treated differently. All operations that just copy pixels
around will work fine, though.


Georg Mischler  --  simulations developer  --  schorsch at schorsch com
+schorsch.com+  --  lighting design tools  --  http://www.schorsch.com/

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