.TH LIBCOLOUR_DELTA_E 3 libcolour
.SH NAME
libcolour_delta_e - Calculate the delta E*_ab distance
.SH SYNOPSIS
.nf
#include <libcolour.h>

int \fBlibcolour_delta_e_f\fP(const libcolour_colour_f_t *\fIa\fP,
                        const libcolour_colour_f_t *\fIb\fP, float *\fIresult\fP);
int \fBlibcolour_delta_e_lf\fP(const libcolour_colour_lf_t *\fIa\fP,
                         const libcolour_colour_lf_t *\fIb\fP, double *\fIresult\fP);
int \fBlibcolour_delta_e_llf\fP(const libcolour_colour_llf_t *\fIa\fP,
                          const libcolour_colour_llf_t *\fIb\fP, long double *\fIresult\fP);

#define \fBlibcolour_delta_e\fP(\fIa\fP, \fIb\fP, \fIresult\fP)\\
	(_Generic((\fIa\fP),\\
	          const libcolour_colour_f_t *:   \fBlibcolour_delta_e_f\fP(\fIa\fP, \fIb\fP, \fIresult\fP),\\
	          const libcolour_colour_lf_t *:  \fBlibcolour_delta_e_lf\fP(\fIa\fP, \fIb\fP, \fIresult\fP),\\
	          const libcolour_colour_llf_t *: \fBlibcolour_delta_e_llf\fP(\fIa\fP, \fIb\fP, \fIresult\fP)))
.fi
.SH DESCRIPTION
.B libcolour_delta_e
and its non-generic functions calculate the delta E*_ab
.RB [ _
denotes that the following characters shall be subscripted]
(the distance in CIE L*a*b*) of two colours, and stores the
distance in
.IR *result .
.SH RETURN VALUES
Upon successful completion, the functions returns 0.
Otherwise the function return -1 with
.I errno
set to indicate the error.
.SH ERRORS
These functions fail if and only if
.BR libcolour_convert (3)
fails.
.SH SEE ALSO
.BR libcolour (7)
.SH AUTHORS
Mattias Andrée
.RI < maandree@kth.se >