Richard Gitschlag wrote: > Out of curiosity I looked through the C source for the decompose plugin and > noticed that the LAB > decomp actually performs a cube root (and offset) of its input values during > its calculations, > which is why a linear input gradient produces a nonlinear result.
> Perhaps there can be an additional L*a*b* color option added to the plugin > that incorporates the > gamma correction into its processing? Performing it manually after the > decomp does lose some > quality in the color channels for obvious reasons, but if it could be > included as part of the > plugin's execution then it would not. How about just implementing the conversion correctly ? To convert from RGB to L*a*b*, one has to convert from RGB to XYZ, then XYZ to L*a*b*. A typical working RGB space (like sRGB, AdobeRGB etc.) has a gamma encoding. So RGB to XYZ removes the gamma encoding (since XYZ is linear light), and then L*a*b* uses a 1/3 power which models perceptual linearity. Of course to display an L*a*b* value you have to convert it to XYZ and then to the display's RGB space. [And yes there are many possible avenues for optimising the performance of such conversions.] Graeme Gill. _______________________________________________ gimp-developer-list mailing list [email protected] http://mail.gnome.org/mailman/listinfo/gimp-developer-list
