CIELChuv: measure hue in degrees, but add parameter to change this

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

5 files changed, 47 insertions, 11 deletions

diff --git a/doc/info/chap/colour-spaces.texinfo b/doc/info/chap/colour-spaces.texinfo
index a214feb..9455bbc 100644
--- a/doc/info/chap/colour-spaces.texinfo
+++ b/doc/info/chap/colour-spaces.texinfo
@@ -354,7 +354,7 @@ The wide-gamut RGB colour space, also known as
 Adobe Wide Gamut RGB.
 @end table
 
-Call @code{libcolour_proper(&c)} on a
+The call @code{libcolour_proper(&c)} on a
 @code{struct libcolour_rgb_t c} (done automatically for
 predefined colour spaces) sets @code{c.red.model},
 @code{c.green.model}, and @code{c.blue.model} to
@@ -521,7 +521,7 @@ The white point.
 CIE L*u*v* is not additive, since conversion from
 CIE 1931 XYZ is non-linear.
 
-Call @code{libcolour_proper(&c)} on a
+The call @code{libcolour_proper(&c)} on a
 @code{struct libcolour_cieluv_t c} sets
 @code{c.white.model} to @code{LIBCOLOUR_CIEXYZ}.
 Zero is always returned in this case.
@@ -555,15 +555,20 @@ The C*@sub{uv} value, the chroma.
 The h@sub{uv} value, the hue.
 @item struct libcolour_ciexyz white
 The white point.
+@item double one_revolution
+The value lowest positive values of @code{h} that is equivalent to 0.
+360 if the hue is measured in degrees, 400 if the hue is measured in
+gon, and 2 pi if the hue is measured radian. Any value can be used.
 @end table
 
 CIE LCh@sub{uv} is not additive. It is a cylindrical
 representation of CIE 1976 (L*, u*, v*).
 
-Call @code{libcolour_proper(&c)} on a
+The call @code{libcolour_proper(&c)} on a
 @code{struct libcolour_cielchuv_t c} sets
-@code{c.white.model} to @code{LIBCOLOUR_CIEXYZ}.
-Zero is always returned in this case.
+@code{c.white.model} to @code{LIBCOLOUR_CIEXYZ},
+and if @code{c.one_revolution} is 0, it is set
+to 360. Zero is always returned in this case.
 
 
 @node YIQ
diff --git a/src/convert.c b/src/convert.c
index 5a358c9..9a2c3d9 100644
--- a/src/convert.c
+++ b/src/convert.c
@@ -24,6 +24,8 @@
 
 
 #define WASDIV0(x)  (isinf(x) || isnan(x))
+#define PI          (3.14159265358979323846)
+#define PI2         (2 * PI)
 
 
 
@@ -598,11 +600,12 @@ static void cielchuv_to_cieluv(const libcolour_cielchuv_t* restrict from, libcol
     tmp.model = LIBCOLOUR_CIEXYZ;
     tmp2.model = LIBCOLOUR_CIELCHUV;
     tmp2.white = to->white;
+    tmp2.one_revolution = PI2;
     to_ciexyz((const libcolour_colour_t*)from, &tmp);
     to_cielchuv((const libcolour_colour_t*)&tmp, &tmp2);
     L = tmp2.L, C = tmp2.C, h = tmp2.h;
   } else {
-    L = from->L, C = from->C, h = from->h;
+    L = from->L, C = from->C, h = from->h * PI2 / from->one_revolution;
   }
   to->L = L;
   to->u = C * cos(h);
@@ -655,7 +658,7 @@ static void cieluv_to_cielchuv(const libcolour_cieluv_t* restrict from, libcolou
   }
   to->L = L;
   to->C = sqrt(u * u + v * v);
-  to->h = atan2(v, u);
+  to->h = atan2(v, u) / PI2 * to->one_revolution;
 }
 
 static void other_to_cielchuv(const libcolour_colour_t* restrict from, libcolour_cielchuv_t* restrict to)
@@ -669,6 +672,7 @@ static void other_to_cielchuv(const libcolour_colour_t* restrict from, libcolour
 
 static void to_cielchuv(const libcolour_colour_t* restrict from, libcolour_cielchuv_t* restrict to)
 {
+  double one_revolution;
   switch (from->model) {
   case LIBCOLOUR_CIELUV:
     cieluv_to_cielchuv(&from->cieluv, to);
@@ -677,7 +681,14 @@ static void to_cielchuv(const libcolour_colour_t* restrict from, libcolour_cielc
     if (to->white.X == from->cielchuv.white.X &&
 	to->white.Y == from->cielchuv.white.Y &&
 	to->white.Z == from->cielchuv.white.Z) {
-      *to = from->cielchuv;
+      if (to->one_revolution == from->cielchuv.one_revolution) {
+	*to = from->cielchuv;
+      } else {
+	one_revolution = to->one_revolution;
+	*to = from->cielchuv;
+	to->one_revolution = one_revolution;
+	to->h = to->h / from->cielchuv.one_revolution * one_revolution;
+      }
       break;
     }
     /* fall through */
diff --git a/src/libcolour.c b/src/libcolour.c
index 57f1e80..69014d3 100644
--- a/src/libcolour.c
+++ b/src/libcolour.c
@@ -121,6 +121,8 @@ int libcolour_proper(libcolour_colour_t* colour)
     break;
   case LIBCOLOUR_CIELCHUV:
     colour->cielchuv.white.model = LIBCOLOUR_CIEXYZ;
+    if (colour->cielchuv.one_revolution == 0.)
+      colour->cielchuv.one_revolution = 360.;
     break;
   case LIBCOLOUR_RGB:
     colour->rgb.red.model   = LIBCOLOUR_CIEXYY;
diff --git a/src/libcolour.h b/src/libcolour.h
index fe53a4e..6387151 100644
--- a/src/libcolour.h
+++ b/src/libcolour.h
@@ -232,6 +232,7 @@ typedef struct libcolour_cielchuv {
   double C;
   double h;
   struct libcolour_ciexyz white;
+  double one_revolution;
 } libcolour_cielchuv_t;
 
 typedef struct libcolour_rgb {
diff --git a/src/test.c b/src/test.c
index 7d5517c..795333f 100644
--- a/src/test.c
+++ b/src/test.c
@@ -94,8 +94,10 @@ static int test_convert_11(libcolour_colour_t* c1, libcolour_model_t model)
     if (r2 = test_convert(c1, &c2, &c3), r2 < 0)
       return -1;
     return r1 & r2;
-  case LIBCOLOUR_CIELUV:
   case LIBCOLOUR_CIELCHUV:
+    c2.cielchuv.one_revolution = 360.;
+    /* fall though */
+  case LIBCOLOUR_CIELUV:
     c2.cieluv.white.model = LIBCOLOUR_CIEXYZ;
     c2.cieluv.white.X = 1.0294;
     c2.cieluv.white.Y = 1;
@@ -119,8 +121,12 @@ static int test_convert_1n(libcolour_model_t model, const char* model_name, doub
   c1.model = model;
   switch (model) {
   case LIBCOLOUR_CIELAB:
-    c1.srgb.R = ch1 * 100, c1.srgb.G = ch2 * 100, c1.srgb.B = ch3 * 100;
+    c1.cielab.L = ch1 * 100, c1.cielab.a = ch2 * 100, c1.cielab.b = ch3 * 100;
     break;
+  case LIBCOLOUR_CIELCHUV:
+    if (ch3 > 0.9999)
+      return 1;
+    /* fall though */
   default:
     c1.srgb.R = ch1, c1.srgb.G = ch2, c1.srgb.B = ch3;
     break;
@@ -140,8 +146,11 @@ static int test_convert_1n(libcolour_model_t model, const char* model_name, doub
 	return rc;
       c1.srgb.with_gamma = run;
       break;
-    case LIBCOLOUR_CIELUV:
     case LIBCOLOUR_CIELCHUV:
+      c1.cielchuv.one_revolution = run < 2 ? 360. : 2 * 3.14159265358979323846;
+      c1.cielchuv.h *= c1.cielchuv.one_revolution;
+      /* fall through */
+    case LIBCOLOUR_CIELUV:
       c1.cieluv.white.model = LIBCOLOUR_CIEXYZ;
       if (run == 0) {
 	c1.cieluv.white.X = 1.0294;
@@ -151,6 +160,14 @@ static int test_convert_1n(libcolour_model_t model, const char* model_name, doub
 	c1.cieluv.white.X = 1.03;
 	c1.cieluv.white.Y = 0.8;
 	c1.cieluv.white.Z = 0.92;
+      } else if (run == 2 && model == LIBCOLOUR_CIELCHUV) {
+	c1.cieluv.white.X = 1.0294;
+	c1.cieluv.white.Y = 1;
+	c1.cieluv.white.Z = 0.9118;
+      } else if (run == 3 && model == LIBCOLOUR_CIELCHUV) {
+	c1.cieluv.white.X = 1.03;
+	c1.cieluv.white.Y = 0.8;
+	c1.cieluv.white.Z = 0.92;
       } else {
 	return rc;
       }