On 08/09/2010 04:16 PM, Charlie De wrote: >> From Rupert: >> (as far as I can tell, the current Decompose Lab functions are >> broken, anyway). > > What makes you say that? And how severe is the problem? > > Right this minute I'm writing a script with LAB Decompose... Well, 'different' might have been nicer than 'broken' - The conversion doesn't account for gamma: http://www.brucelindbloom.com/index.html?Eqn_RGB_to_XYZ.html As a result, the L* channel is very light (check the histogram). I have no clue how that influences a* and b*. Also, it uses the conversion matrix for PAL/SECAM RGB. (Maybe PAL/SECAM has gamma 1.0? Then the missing gamma correction would be correct.) http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html Anyway, unless your image is in PAL/SECAM RGB, the conversion in Decompose is incorrect. _______________________________________________ Gimp-developer mailing list Gimp-developer@xxxxxxxxxxxxxxxxxxxxxx https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
