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diff --git a/LIBCOLOUR_CIELAB.7 b/LIBCOLOUR_CIELAB.7 new file mode 100644 index 0000000..853a04f --- /dev/null +++ b/LIBCOLOUR_CIELAB.7 @@ -0,0 +1,70 @@ +.TH LIBCOLOUR_CIELAB 7 libcolour +.SH NAME +LIBCOLOUR_CIELAB - CIE L*a*b* +.SH DESCRIPTION +CIE L*a*b* +colours are presented with either of +.nf + + \fBtypedef struct libcolour_cielab_f libcolour_cielab_f_t;\fP + \fBtypedef struct libcolour_cielab_lf libcolour_cielab_lf_t;\fP + \fBtypedef struct libcolour_cielab_llf libcolour_cielab_llf_t;\fP + +.fi +These +.BR struct s +use +.BR float , +.BR double , +and +.BR long\ double , +respecitively, for the values stored in them, +and are otherwise identical. +.B struct libcolour_cielab_f +is defined as +.nf + + \fBstruct libcolour_cielab_f {\fP + \fBenum libcolour_model\fP \fImodel\fP\fB;\fP + \fBfloat\fP \fIL\fP\fB;\fP + \fBfloat\fP \fIa\fP\fB;\fP + \fBfloat\fP \fIb\fP\fB;\fP + \fB};\fP + +.fi +.I .model +shall be set to +.BR LIBCOLOUR_CIELAB . +In +.BR union\ libcolour_colour_f , +.BR union\ libcolour_colour_lf , +and +.BR union\ libcolour_colour_llf , +.I .cielab +is used for CIE L*a*b* colours. +.P +.IR .L , +.IR .a , +and +.I .b +hold the L*, a*, and b* values, respectively. +.P +L* is 0 in black and 100 in white. +Negative a* values are green, +positive a* values are red. +Negative b* values are blue, +positive b* values are yellow. +.P +CIE L*a*b* is not additive, since conversion from +CIE 1931 XYZ is non-linear. It’s white point is the +CIE Standard Illuminant D50. +.P +CIE L*a*b* approximates human colour perception with a +lightness parameter (L*) and two chromaticity parameters +(a* and b*), it is therefore useful in image +manipulation applications. +.SH SEE ALSO +.BR libcolour (7) +.SH AUTHORS +Mattias Andrée +.RI < maandree@kth.se > |