Be more consistent about using sRGB in the client.

Also, expose the sRGB C and C^-1 functions.

3 files changed, 61 insertions, 44 deletions

diff --git a/libdimension/color.c b/libdimension/color.c
index efa4f4a..39f9b3d 100644
--- a/libdimension/color.c
+++ b/libdimension/color.c
@@ -97,69 +97,83 @@ const dmnsn_color dmnsn_cyan = {
   .trans  = 0.0,
 };
 
-/** Inverse function of sRGB's `C' function, for the reverse conversion. */
-static double
-dmnsn_sRGB_C_inv(double CsRGB)
+/* sRGB's `C' function. */
+static inline double
+dmnsn_sRGB_C(double Clinear)
 {
   /*
-   * If C represents R, G, and B, then the Clinear values are now found as
-   * follows:
+   * If C represents R, G, and B, then the sRGB values are now found as follows:
    *
-   *           { Csrgb/12.92,                  Csrgb <= 0.04045
-   * Clinear = {                        1/2.4
-   *           { ((Csrgb + 0.055)/1.055)     , Csrgb >  0.04045
+   *         { 12.92*Clinear,                Clinear <= 0.0031308
+   * Csrgb = {                1/2.4
+   *         { (1.055)*Clinear      - 0.055, Clinear >  0.0031308
    */
-  if (CsRGB == 1.0) {
+  if (Clinear == 1.0) {
     return 1.0; /* Map 1.0 to 1.0 instead of 0.9999999999999999 */
-  } else if (CsRGB <= 0.040449936) {
-    return CsRGB/12.92;
+  } else if (Clinear > 0.0031308) {
+    return 1.055*pow(Clinear, 1.0/2.4) - 0.055;
   } else {
-    return pow((CsRGB + 0.055)/1.055, 2.4);
+    return 12.92*Clinear;
   }
 }
 
-/* Convert from sRGB space */
+/* Export dmnsn_sRGB_C */
+double
+dmnsn_sRGB_gamma(double Clinear)
+{
+  return dmnsn_sRGB_C(Clinear);
+}
+
+/* Convert to sRGB space */
 dmnsn_color
-dmnsn_color_from_sRGB(dmnsn_color color)
+dmnsn_color_to_sRGB(dmnsn_color color)
 {
   dmnsn_color ret = {
-    .R = dmnsn_sRGB_C_inv(color.R),
-    .G = dmnsn_sRGB_C_inv(color.G),
-    .B = dmnsn_sRGB_C_inv(color.B),
+    .R = dmnsn_sRGB_C(color.R),
+    .G = dmnsn_sRGB_C(color.G),
+    .B = dmnsn_sRGB_C(color.B),
     .trans  = color.trans,
     .filter = color.filter,
   };
   return ret;
 }
 
-/** sRGB's `C' function. */
-static double
-dmnsn_sRGB_C(double Clinear)
+/* Inverse function of sRGB's `C' function, for the reverse conversion. */
+double
+dmnsn_sRGB_C_inv(double CsRGB)
 {
   /*
-   * If C represents R, G, and B, then the sRGB values are now found as follows:
+   * If C represents R, G, and B, then the Clinear values are now found as
+   * follows:
    *
-   *         { 12.92*Clinear,                Clinear <= 0.0031308
-   * Csrgb = {                1/2.4
-   *         { (1.055)*Clinear      - 0.055, Clinear >  0.0031308
+   *           { Csrgb/12.92,                  Csrgb <= 0.04045
+   * Clinear = {                        1/2.4
+   *           { ((Csrgb + 0.055)/1.055)     , Csrgb >  0.04045
    */
-  if (Clinear == 1.0) {
+  if (CsRGB == 1.0) {
     return 1.0; /* Map 1.0 to 1.0 instead of 0.9999999999999999 */
-  } else if (Clinear <= 0.0031308) {
-    return 12.92*Clinear;
+  } else if (CsRGB <= 0.040449936) {
+    return CsRGB/12.92;
   } else {
-    return 1.055*pow(Clinear, 1.0/2.4) - 0.055;
+    return pow((CsRGB + 0.055)/1.055, 2.4);
   }
 }
 
-/* Convert to sRGB space */
+/* Export dmnsn_sRGB_C_inv */
+double
+dmnsn_sRGB_inverse_gamma(double CsRGB)
+{
+  return dmnsn_sRGB_C_inv(CsRGB);
+}
+
+/* Convert from sRGB space */
 dmnsn_color
-dmnsn_color_to_sRGB(dmnsn_color color)
+dmnsn_color_from_sRGB(dmnsn_color color)
 {
   dmnsn_color ret = {
-    .R = dmnsn_sRGB_C(color.R),
-    .G = dmnsn_sRGB_C(color.G),
-    .B = dmnsn_sRGB_C(color.B),
+    .R = dmnsn_sRGB_C_inv(color.R),
+    .G = dmnsn_sRGB_C_inv(color.G),
+    .B = dmnsn_sRGB_C_inv(color.B),
     .trans  = color.trans,
     .filter = color.filter,
   };
diff --git a/libdimension/dimension/color.h b/libdimension/dimension/color.h
index 8470957..295400b 100644
--- a/libdimension/dimension/color.h
+++ b/libdimension/dimension/color.h
@@ -85,10 +85,15 @@ dmnsn_color_saturate(dmnsn_color color)
 
 /* Perceptual color manipulation */
 
-/** Convert from sRGB space. */
-dmnsn_color dmnsn_color_from_sRGB(dmnsn_color color);
+/** Apply sRGB gamma */
+double dmnsn_sRGB_gamma(double Clinear);
 /** Convert to sRGB space. */
 dmnsn_color dmnsn_color_to_sRGB(dmnsn_color color);
+/** Remove sRGB gamma */
+double dmnsn_sRGB_inverse_gamma(double CsRGB);
+/** Convert from sRGB space. */
+dmnsn_color dmnsn_color_from_sRGB(dmnsn_color color);
+
 /** Greyscale color intensity. */
 double dmnsn_color_intensity(dmnsn_color color);
 /** Add two colors together. */
diff --git a/libdimension/tests/render.c b/libdimension/tests/render.c
index ae4a644..abd88d6 100644
--- a/libdimension/tests/render.c
+++ b/libdimension/tests/render.c
@@ -31,11 +31,7 @@ dmnsn_test_scene_set_defaults(dmnsn_scene *scene)
   default_finish->ambient = dmnsn_new_basic_ambient(
     dmnsn_color_from_sRGB(dmnsn_color_mul(0.1, dmnsn_white))
   );
-  default_finish->diffuse = dmnsn_new_lambertian(
-    dmnsn_color_intensity(
-      dmnsn_color_from_sRGB(dmnsn_color_mul(0.7, dmnsn_white))
-    )
-  );
+  default_finish->diffuse = dmnsn_new_lambertian(dmnsn_sRGB_inverse_gamma(0.7));
 }
 
 static void
@@ -130,9 +126,10 @@ dmnsn_test_scene_add_hollow_cube(dmnsn_scene *scene)
   cube->texture = dmnsn_new_texture();
   cube->texture->pigment = dmnsn_new_solid_pigment(cube_color);
 
-  dmnsn_color reflect = dmnsn_color_mul(0.5, dmnsn_white);
-  cube->texture->finish.reflection
-    = dmnsn_new_basic_reflection(dmnsn_black, reflect, 1.0);
+  dmnsn_color reflect =
+    dmnsn_color_from_sRGB(dmnsn_color_mul(0.5, dmnsn_white));
+  cube->texture->finish.reflection =
+    dmnsn_new_basic_reflection(dmnsn_black, reflect, 1.0);
 
   cube->interior = dmnsn_new_interior();
   cube->interior->ior = 1.1;
@@ -140,7 +137,8 @@ dmnsn_test_scene_add_hollow_cube(dmnsn_scene *scene)
   dmnsn_object *sphere = dmnsn_new_sphere();
   sphere->texture = dmnsn_new_texture();
   sphere->texture->pigment = dmnsn_new_solid_pigment(dmnsn_green);
-  sphere->texture->finish.specular = dmnsn_new_phong(0.2, 40.0);
+  sphere->texture->finish.specular =
+    dmnsn_new_phong(dmnsn_sRGB_inverse_gamma(0.2), 40.0);
   sphere->trans = dmnsn_scale_matrix(dmnsn_new_vector(1.25, 1.25, 1.25));
 
   dmnsn_object *hollow_cube = dmnsn_new_csg_difference(cube, sphere);