Use CIE XYZ instead of sRGB

Signed-off-by: Mattias Andrée <maandree@kth.se>

1 files changed, 41 insertions, 1 deletions

diff --git a/src/util.h b/src/util.h
index 3adc1b5..0dedf77 100644
--- a/src/util.h
+++ b/src/util.h
@@ -1,7 +1,11 @@
 /* See LICENSE file for copyright and license details. */
-
+#include <errno.h>
 #include <math.h>
 #include <stdio.h>
+#include <stdlib.h>
+
+#define D65_XYY_X 0.312726871026564878786047074755
+#define D65_XYY_Y 0.329023206641284038376227272238
 
 #define ELEMENTSOF(ARRAY) (sizeof(ARRAY) / sizeof(*(ARRAY)))
 
@@ -31,6 +35,21 @@ DEF_STR_TO_INT(toi, int, tolli, long long int)
 #define toju tollu
 #define toji tolli
 
+static inline int
+tolf(const char *s, double *out)
+{
+	char *end;
+	errno = 0;
+	*out = strtod(s, &end);
+	if (errno) {
+		return -1;
+	} else if (*end) {
+		errno = EINVAL;
+		return -1;
+	}
+	return 0;
+}
+
 int fshut(FILE *fp, const char *fname);
 void enfshut(int status, FILE *fp, const char *fname);
 void efshut(FILE *fp, const char *fname);
@@ -58,3 +77,24 @@ srgb_decode(double t)
 	t = t <= 0.0031306684425217108 * 12.92 ? t / 12.92 : pow((t + 0.055) / 1.055, 2.4);
 	return t * sign;
 }
+
+static inline void
+ciexyz_to_srgb(double x, double y, double z, double *r, double *g, double *b)
+{
+#define MULTIPLY(CX, CY, CZ)  ((CX) * x + (CY) * y + (CZ) * z)
+	*r = MULTIPLY(3.240446254647737500675930277794, -1.537134761820080575134284117667, -0.498530193022728718155178739835);
+	*g = MULTIPLY(-0.969266606244679751469561779231, 1.876011959788370209167851498933, 0.041556042214430065351304932619);
+	*b = MULTIPLY(0.055643503564352832235773149705, -0.204026179735960239147729566866, 1.057226567722703292062647051353);
+#undef MULTIPLY
+}
+
+static inline void
+srgb_to_ciexyz(double r, double g, double b, double *x, double *y, double *z)
+{
+#define MULTIPLY(CR, CG, CB) ((CR) * r + (CG) * g + (CB) * b)
+	*x = MULTIPLIY(0.412457445582367576708548995157, 0.357575865245515878143578447634, 0.180437247826399665973085006954);
+	*y = MULTIPLIY(0.212673370378408277403536885686, 0.715151730491031756287156895269, 0.072174899130559869164791564344);
+	*z = MULTIPLIY(0.019333942761673460208893260415, 0.119191955081838593666354597644, 0.950302838552371742508739771438);
+#undef MULTIPLY
+
+}