Qt: Fix builtin post shaders

data/resources/shaders/simple-gamma.glsl

@@ -0,0 +1,33 @@
+/*
+[configuration]
+
+[OptionRangeFloat]
+GUIName = Gamma In
+OptionName = GAMMA_IN
+MinValue = 0.1
+MaxValue = 10.0
+StepAmount = 0.1
+DefaultValue = 2.2
+
+[OptionRangeFloat]
+GUIName = Gamma Out
+OptionName = GAMMA_OUT
+MinValue = 0.1
+MaxValue = 10.0
+StepAmount = 0.1
+DefaultValue = 2.2
+
+[/configuration]
+*/
+
+void main()
+{
+  float4 color = Sample();
+  float gamma_in = GetOption(GAMMA_IN);
+  float gamma_out = 1.0f / GetOption(GAMMA_OUT);
+
+  color.rgb = pow(color.rgb, float3(gamma_in, gamma_in, gamma_in));
+  color.rgb = pow(color.rgb, float3(gamma_out, gamma_out, gamma_out));
+
+  SetOutput(saturate(color));
+}