Better ACES tonemapping function

Also, use it in the oklch example as this allows for regression testing 
of the visual output, but also because the example just looks better 
with ACES tonemapping.

docs/windows.md

@@ -641,11 +641,11 @@ of each pixel. Default is `0`.
 adjustments, Values less than 1 will lighten the output image and values
 greater than 1 will darken it.
 
-`tonemap=` [ `:aces` | `:reinhard` ]
+`tonemap=` [ `:reinhard` | `:aces` ]
 : If specified, then a tone-mapping function will be applied to map high
 dynamic range images into the $[0,1]$ range. The supported tone-mapping
-functions are: (an approximation of) the ACES filmic curve, and the Reinhard
-curve. Default is no tone-mapping.
+functions are: the Reinhard curve function, and a (close approximation of) the
+ACES filmic function. Default is no tone-mapping.
 
 If `tonemap=:reinhard` then an additional attribute is supported:
 

examples/oklch.fl

@@ -5,11 +5,12 @@ let M=50
 
 !window size=1080
     !record filename=OUTPUT
-        !canvas3d
-            !light color=0.5 direction=0;0;-1
-            !transform rotate_x=t/30 rotate_z=-t/12 scale=2.5
-                for c in ..M
-                    !transform translate=0;0;200*c/M-100
-                        for h in ..N
-                            !transform rotate_z=-h/N translate=0;50;0
-                                !sphere size=25 color=oklch(1;0.4*c/M;h/N)
+        !adjust tonemap=:aces
+            !canvas3d
+                !light color=1 direction=0;0;-1
+                !transform rotate_x=t/30 rotate_z=-t/12 scale=2.5
+                    for c in ..M
+                        !transform translate=0;0;200*c/M-100
+                            for h in ..N
+                                !transform rotate_z=-h/N translate=0;50;0
+                                    !sphere size=25 color=oklch(1;0.4*c/M;h/N)

src/flitter/render/window/glsl/color_functions.glsl

@@ -16,6 +16,11 @@ vec3 tonemap_reinhard(vec3 c, float whitepoint) {
     return cd;
 }
 
-vec3 tonemap_aces(vec3 c) {
-    return c * (2.51 * c + 0.03) / (c * (2.43 * c + 0.59) + 0.14);
+vec3 tonemap_aces(vec3 color)
+{
+    // This function based on https://github.com/TheRealMJP/BakingLab/blob/master/BakingLab/ACES.hlsl
+    //
+    color = mat3(0.59719, 0.076, 0.0284, 0.35458, 0.90834, 0.13383, 0.04823, 0.01566, 0.83777) * color;
+    color = (color * (color + 0.0245786) - 0.000090537) / (color * (0.983729 * color + 0.4329510) + 0.238081);
+    return mat3(1.60475, -0.10208, -0.00327, -0.53108, 1.10813, -0.07276, -0.07367, -0.00605, 1.07602) * color;
 }