GSdx: Add temperature setting. (#2989)

Ported libretro's white_point shader to GSdx.
Based on the work described here:
http://www.zombieprototypes.com/?p=210

bin/shaders/GSdx.fx

@@ -1937,6 +1937,42 @@ float4 ColorGrading(float4 color, float2 texcoord)
 }
 #endif
 
+
+/*------------------------------------------------------------------------------
+                           [COLOR_TEMPERATURE]
+------------------------------------------------------------------------------*/
+
+#if COLOR_TEMPERATURE == 1
+float4 TemperaturePass(float4 color, float2 texcoord)
+{
+   float temp = clamp(White_Point, 2000.0, 12000.0) / 100.0f;
+
+   // all calculations assume a scale of 255. We'll normalize this at the end
+   float3 wp = float3(255.0,255.0,255.0);
+
+   if (White_Point <= 6600.0) {
+       wp.r = 255.0;
+       wp.g = - 155.25485562709179 - 0.44596950469579133 * (temp - 2.0)  + 104.49216199393888 * log(temp - 2.0);
+       wp.b = White_Point <= 1900 ? 0.0 : - 254.76935184120902 + 0.8274096064007395 * (temp - 10.0) + 115.67994401066147 * log(temp - 10.0) ;
+   } else {
+       wp.r = 351.97690566805693 + 0.114206453784165 * (temp - 55.0) - 40.25366309332127 * log(temp - 55.0);
+       wp.g = 325.4494125711974  + 0.07943456536662342 * (temp - 50.0) - 28.0852963507957   * log(temp - 50.0);
+       wp.b = 255.0;
+   }
+
+   // clamp and normalize
+   wp.rgb = clamp(wp.rgb, 0.0, 255.0) / 255.0;
+
+   float3 adjusted = color.rgb * wp;
+   float3 base_luma = XYZtoYxy(RGBtoXYZ(color.rgb));
+   float3 adjusted_luma = XYZtoYxy(RGBtoXYZ(adjusted));
+   adjusted = adjusted_luma + (float3(base_luma.r,0.0,0.0) - float3(adjusted_luma.r,0.0,0.0));
+   color = float4(XYZtoRGB(YxytoXYZ(adjusted)), 1.0);
+
+   return color;
+}
+#endif
+
 /*------------------------------------------------------------------------------
                            [SCANLINES CODE SECTION]
 ------------------------------------------------------------------------------*/
@@ -2457,6 +2493,10 @@ PS_OUTPUT ps_main(VS_OUTPUT input)
     color = ContrastPass(color, texcoord);
     #endif
 
+    #if COLOR_TEMPERATURE == 1
+    color = TemperaturePass(color, texcoord);
+    #endif
+
     #if VIGNETTE == 1
     color = VignettePass(color, texcoord);
     #endif

bin/shaders/GSdx_FX_Settings.ini

@@ -44,6 +44,7 @@
 #define CURVE_CONTRAST              0      //# S-Curve Scene Contrast Enhancement. Locally adjusts contrast using a four-point cubic bezier spline.
 #define CEL_SHADING                 0      //# PX Cel Shading. Simulates the look of animation/toon. Typically best suited for animated style games.
 #define PAINT_SHADING               0      //# Paint Shading. Creates the effect of a painted scene. Adapted from ENB series, it's pretty performance heavy. 
+#define COLOR_TEMPERATURE           0      //# White Point Temperature. Changes the temperature of the image from D65 white point reference.
 
 //#[TV EMU TECHNIQUES]         [1=ON|0=OFF]  #READ: These can all be turned on & off independently of each other. These effects are typically used to simulated older TVs/CRT etc.
 #define LOTTES_CRT                  0     //# Timothy Lottes CRT emulation effect. Similar to scanlines, but with more control options. Ported by request.
@@ -128,6 +129,9 @@
 #define GradingStrength 0.25               //[0.00 to 1.00] The overall max strength of the colour grading effect. Raise to increase, lower to decrease the amount.
 #define Correlation 1.00                   //[0.10 to 1.00] Correlation between the base colour, and the grading influence. Lower = more of the scene is graded, Higher = less of the scene is graded.
 
+//##[COLOR TEMPERATURE]
+#define White_Point 6500.0                 //[2000.0 to 12000.0] Temperature value given in Kelvin. A typical CRT has a target white point temperature of D93 (9300K)
+
 //##[CEL SHADING]
 #define EdgeStrength 1.00                  //[0.00 to 4.00] Overall strength of the cel edge outline effect. Affects the overall density.  0.00: no outlines.
 #define EdgeFilter 0.75                    //[0.10 to 2.00] Filters out fainter cel edges. Use it for balancing the cel edge density. EG: for faces, foliage, etc.