On 10/10/2014 05:01 PM, Simon Budig wrote:
Elle Stone (ellestone@xxxxxxxxxxxxxxxxxxxx) wrote:
You cannot get from "sRGB as PCS" to LAB without first converting from "sRGB
as PCS" to XYZ. LAB is a mathematical transform of XYZ, not sRGB.
This is the normal path from User_RGB to LAB: User_RGB -> XYZ -> LAB. Two
conversions.
You want to take this path, yes? User_RGB -> XYZ -> "sRGB as PCS" -> XYZ ->
LAB. Four conversions, going through XYZ twice.
[I am most likely talking about stuff that you already know, but it
might be worth reiterating to keep the discussion understandable for
people not that deep in the topic]
Note that - as long as we're talking about linear RGB spaces (which pure
sRGB is not, but AFAIK we're talking about "linear RGB with the sRGB
primaries" here) - all but the last conversions in your chain boil down
to applying a matrix to a vector. You can easily multiply these matrices
together to build a matrix that does the first three conversions in a
single operation.
Simon, my apologies. Pippin has pointed out that I didn't repond to your
email. Yes, I do realize that you can concantenate matrix conversions. I
acknowledged that in a reply to Pippin, but I should also have
acknowleged your input.
Again, my apologies. I didn't mean to ignore you.
Kind regards,
Elle Stone
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