Res: Port NSO-gba-colors shader (closes #2834)

CHANGES

@@ -52,6 +52,7 @@ Misc:
  - Qt: Remove maligned double-click-to-fullscreen shortcut (closes mgba.io/i/2632)
  - Qt: Pass logging context through to video proxy thread (fixes mgba.io/i/3095)
  - Qt: Show maker code and game version in ROM info
+ - Res: Port NSO-gba-colors shader (closes mgba.io/i/2834)
  - Scripting: Add `callbacks:oneshot` for single-call callbacks
  - Switch: Add bilinear filtering option (closes mgba.io/i/3111)
  - Vita: Add imc0 and xmc0 mount point support

res/shaders/nso-gba-color.shader/manifest.ini

@@ -0,0 +1,24 @@
+[shader]
+name=NSO GBA Color
+author=Pokefan531 and hunterk
+description=Shader that replicates the Nintendo Switch Online's GBA color filter.
+passes=1
+
+[pass.0]
+fragmentShader=nso-gba-color.fs
+vertexShader=nso-gba-color.vs
+blend=1
+width=-1
+height=-1
+
+[pass.0.uniform.darken_screen]
+type=float
+default=0.8
+readableName=Darken Screen
+
+[pass.0.uniform.color_mode]
+type=int
+default=1
+min=1
+max=3
+readableName=Color Profile (1=sRGB, 2=DCI, 3=Rec2020)

res/shaders/nso-gba-color.shader/nso-gba-color.fs

@@ -0,0 +1,21 @@
+// Shader that replicates the LCD Colorspace from Gameboy Advance --
+varying vec2 texCoord;
+varying mat4 profile;
+uniform sampler2D tex;
+uniform vec2 texSize;
+
+uniform float darken_screen;
+const float target_gamma = 2.2;
+const float display_gamma = 2.2;
+
+void main() {
+	// bring out our stored luminance value
+	float lum = profile[3].w;
+
+	// our adjustments need to happen in linear gamma
+	vec4 screen = pow(texture2D(tex, texCoord), vec4(target_gamma + darken_screen)).rgba;
+
+	screen = clamp(screen * lum, 0.0, 1.0);
+	screen = profile * screen;
+	gl_FragColor = pow(screen, vec4(1.0 / display_gamma));
+}

res/shaders/nso-gba-color.shader/nso-gba-color.vs

@@ -0,0 +1,34 @@
+uniform int color_mode;
+attribute vec4 position;
+varying vec2 texCoord;
+varying mat4 profile;
+
+const mat4 GBA_sRGB = mat4(
+	0.865, 0.0575, 0.0575, 0.0,  //red channel
+	0.1225, 0.925, 0.1225, 0.0,  //green channel
+	0.0125, 0.0125, 0.82, 0.0,  //blue channel
+	0.0,  0.0,  0.0,  1.0   //alpha channel
+);
+
+const mat4 GBA_DCI = mat4(
+	0.72, 0.0875, 0.0725, 0.0,  //red channel
+	0.2675, 0.9, 0.185, 0.0,  //green channel
+	0.0125, 0.0125, 0.7425, 0.0,  //blue channel
+	0.0,  0.0,  0.0,  1.0   //alpha channel
+);
+
+const mat4 GBA_Rec2020 = mat4(
+	0.57, 0.115, 0.0725, 0.0,  //red channel
+	0.3825, 0.8625, 0.195, 0.0,  //green channel
+	0.0475, 0.0225, 0.7325, 0.0,  //blue channel
+	0.0,  0.0,  0.0,  1.0   //alpha channel
+);
+
+void main() {
+	if (color_mode == 1) profile = GBA_sRGB;
+	else if (color_mode == 2) profile = GBA_DCI;
+	else if (color_mode == 3) profile = GBA_Rec2020;
+
+	gl_Position = position;
+	texCoord = (position.st + vec2(1.0, 1.0)) * vec2(0.5, 0.5);
+}