From 3cff39f02c54eb0f06835e1e0b6a2f6f02d0b5cb Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@gmail.com>
Date: Mon, 28 Nov 2011 21:15:44 -0500
Subject: Be more consistent about using sRGB in the client.

Also, expose the sRGB C and C^-1 functions.
---
 libdimension/color.c | 80 ++++++++++++++++++++++++++++++----------------------
 1 file changed, 47 insertions(+), 33 deletions(-)

(limited to 'libdimension/color.c')

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,
   };
-- 
cgit v1.2.3