Improve L*a*b to RGB color conversion.

1 files changed, 11 insertions, 5 deletions

diff --git a/pdf/pdf_colorspace.c b/pdf/pdf_colorspace.c
index 11316fbe..a98e649b 100644
--- a/pdf/pdf_colorspace.c
+++ b/pdf/pdf_colorspace.c
@@ -39,19 +39,25 @@ static inline float invg(float x)
 }
 
 static void
-lab_to_xyz(fz_colorspace *cs, float *lab, float *xyz)
+lab_to_xyz(fz_colorspace *cs, float *lab, float *rgb)
 {
 	/* input is in range (0..100, -128..127, -128..127) not (0..1, 0..1, 0..1) */
-	float lstar, astar, bstar, l, m, n;
+	float lstar, astar, bstar, l, m, n, x, y, z, r, g, b;
 	lstar = lab[0];
 	astar = lab[1];
 	bstar = lab[2];
 	m = (lstar + 16) / 116;
 	l = m + astar / 500;
 	n = m - bstar / 200;
-	xyz[0] = fung(l);
-	xyz[1] = fung(m);
-	xyz[2] = fung(n);
+	x = fung(l);
+	y = fung(m);
+	z = fung(n);
+	r = (3.240449f * x + -1.537136f * y + -0.498531f * z) * 0.830026f;
+	g = (-0.969265f * x + 1.876011f * y + 0.041556f * z) * 1.05452f;
+	b = (0.055643f * x + -0.204026f * y + 1.057229f * z) * 1.1003f;
+	rgb[0] = sqrtf(CLAMP(r, 0, 1));
+	rgb[1] = sqrtf(CLAMP(g, 0, 1));
+	rgb[2] = sqrtf(CLAMP(b, 0, 1));
 }
 
 static void