PerceptualHDR + Metal HDR Support

Data/Sys/Shaders/PerceptualHDR.glsl

@@ -0,0 +1,72 @@
+/*
+[configuration]
+
+[OptionRangeFloat]
+GUIName = Desaturation
+OptionName = DESATURATION
+MinValue = 0.0
+MaxValue = 1.0
+StepAmount = 0.1
+DefaultValue = 0.0
+
+[/configuration]
+*/
+
+/***** Linear <--> Oklab *****/
+
+const mat4 RGBtoLMS = mat4(
+    0.4122214708, 0.2119034982, 0.0883024619, 0.0000000000,
+    0.5363325363, 0.6806995451, 0.2817188376, 0.0000000000,
+    0.0514459929, 0.1073969566, 0.6299787005, 0.0000000000,
+    0.0000000000, 0.0000000000, 0.0000000000, 1.0000000000);
+
+const mat4 LMStoOklab = mat4(
+    0.2104542553, 1.9779984951, 0.0259040371, 0.0000000000,
+    0.7936177850, -2.4285922050, 0.7827717662, 0.0000000000,
+    -0.0040720468, 0.4505937099, -0.8086757660, 0.0000000000,
+    0.0000000000, 0.0000000000, 0.0000000000, 1.0000000000);
+
+float4 LinearRGBToOklab(float4 c)
+{
+    return LMStoOklab * pow(RGBtoLMS * c, float4(1.0 / 3.0));
+}
+
+const mat4 OklabtoLMS = mat4(
+    1.0000000000, 1.0000000000, 1.0000000000, 0.0000000000,
+    0.3963377774, -0.1055613458, -0.0894841775, 0.0000000000,
+    0.2158037573, -0.0638541728, -1.2914855480, 0.0000000000,
+    0.0000000000, 0.0000000000, 0.0000000000, 1.0000000000);
+
+const mat4 LMStoRGB = mat4(
+    4.0767416621, -1.2684380046, -0.0041960863, 0.0000000000,
+    -3.3077115913, 2.6097574011, -0.7034186147, 0.0000000000,
+    0.2309699292, -0.3413193965, 1.7076147010, 0.0000000000,
+    0.0000000000, 0.0000000000, 0.0000000000, 1.0000000000);
+
+float4 OklabToLinearRGB(float4 c)
+{
+    return max(LMStoRGB * pow(OklabtoLMS * c, float4(3.0)), 0.0);
+}
+
+void main()
+{
+    float4 color = Sample();
+
+    // Nothing to do here, we are in SDR
+    if (!OptionEnabled(hdr_output) || !OptionEnabled(linear_space_output)) {
+        SetOutput(color);
+        return;
+    }
+
+    const float hdr_paper_white = hdr_paper_white_nits / hdr_sdr_white_nits;
+    color.rgb /= hdr_paper_white;
+
+    float4 oklab_color = LinearRGBToOklab(color);
+
+    float lum = oklab_color.x;
+    oklab_color.z *= pow(hdr_paper_white, pow(oklab_color.x, DESATURATION) / 3.0);
+    oklab_color.y *= pow(hdr_paper_white, pow(oklab_color.x, DESATURATION) / 3.0);
+    oklab_color.x *= pow(hdr_paper_white, pow(oklab_color.x, 1.0) / 3.0);
+
+    SetOutput(OklabToLinearRGB(oklab_color));
+}

Source/Core/VideoBackends/Metal/MTLMain.mm

@@ -119,8 +119,13 @@ static bool WindowSystemTypeSupportsMetal(WindowSystemType type)
 
     MRCOwned<CAMetalLayer*> layer = MRCRetain(static_cast<CAMetalLayer*>(wsi.render_surface));
     [layer setDevice:adapter];
-    if (Util::ToAbstract([layer pixelFormat]) == AbstractTextureFormat::Undefined)
-      [layer setPixelFormat:MTLPixelFormatBGRA8Unorm];
+    [layer setWantsExtendedDynamicRangeContent:YES];
+    [layer setPixelFormat:MTLPixelFormatRGBA16Float];
+
+    const CFStringRef name = kCGColorSpaceExtendedLinearSRGB;
+    CGColorSpaceRef colorspace = CGColorSpaceCreateWithName(name);
+    [layer setColorspace:colorspace];
+    CGColorSpaceRelease(colorspace);
 
     ObjectCache::Initialize(std::move(adapter));
     g_state_tracker = std::make_unique<StateTracker>();

Source/Core/VideoBackends/Metal/MTLUtil.mm

@@ -77,6 +77,7 @@
   config->backend_info.bSupportsPartialMultisampleResolve = false;
   config->backend_info.bSupportsDynamicVertexLoader = true;
   config->backend_info.bSupportsVSLinePointExpand = true;
+  config->backend_info.bSupportsHDROutput = true;
 }
 
 void Metal::Util::PopulateBackendInfoAdapters(VideoConfig* config,