On 10/05/2010 01:20 AM, David Gowers (kampu) wrote:
> In that case it really is a bug. Neither the input colors or output
> colors contain 255.
> The output color series is:
> 008700 008d00 009300 009800 009d00 00a200 00a700 00ab00 00af00 00b300 00b600
But the outputs contain 0's. And that's not because they happened to
come out to exactly 0, but actually they should be <0 and thus are clipped.
So if expected clipping occurs, it's either to 0 or to 255. If no
component of the output is 0 or 255 then it wasn't clipped.
That said, the current algorithm has a limited precision. About 1.3% of
possible RGB values will be off by one after a RGB-Lab-RGB conversion,
0.003% will be off by two (bright cyans are worst). LCH conversion is
So far I haven't found a way to get perfect round-trips without being
I currently have a floating point version which is at least 4 times
slower. It gives perfect Lab roundtrips, and almost-perfect for LCH (off
by one for 0.00006% of RGB values). It still needs quite a bit of work,
but I am hoping to turn that into a viable babl candidate.
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