Use native sRGB support for blending

src/renderer/atlas/BackendD3D.cpp

@@ -265,7 +265,12 @@ void BackendD3D::_handleSettingsUpdate(const RenderingPayload& p)
     {
         wil::com_ptr<ID3D11Texture2D> buffer;
         THROW_IF_FAILED(p.swapChain.swapChain->GetBuffer(0, __uuidof(ID3D11Texture2D), reinterpret_cast<void**>(buffer.addressof())));
-        THROW_IF_FAILED(p.device->CreateRenderTargetView(buffer.get(), nullptr, _renderTargetView.put()));
+
+        static constexpr D3D11_RENDER_TARGET_VIEW_DESC desc{
+            .Format = DXGI_FORMAT_B8G8R8A8_UNORM_SRGB,
+            .ViewDimension = D3D11_RTV_DIMENSION_TEXTURE2D,
+        };
+        THROW_IF_FAILED(p.device->CreateRenderTargetView(buffer.get(), &desc, _renderTargetView.put()));
     }
 
     const auto fontChanged = _fontGeneration != p.s->font.generation();
@@ -547,7 +552,7 @@ void BackendD3D::_recreateBackgroundColorBitmap(const RenderingPayload& p)
         .Height = p.s->viewportCellCount.y,
         .MipLevels = 1,
         .ArraySize = 1,
-        .Format = DXGI_FORMAT_R8G8B8A8_UNORM,
+        .Format = DXGI_FORMAT_R8G8B8A8_UNORM_SRGB,
         .SampleDesc = { 1, 0 },
         .Usage = D3D11_USAGE_DYNAMIC,
         .BindFlags = D3D11_BIND_SHADER_RESOURCE,

src/renderer/atlas/dwrite.hlsl

@@ -35,6 +35,7 @@ float3 DWrite_EnhanceContrast3(float3 alpha, float k)
     return alpha * (k + 1.0f) / (alpha * k + 1.0f);
 }
 
+// dwrite vs. gamma 1.8: https://www.desmos.com/calculator/6wocsr6vcq
 float DWrite_ApplyAlphaCorrection(float a, float f, float4 g)
 {
     return a + a * (1 - a) * ((g.x * f + g.y) * a + (g.z * f + g.w));

src/renderer/atlas/shader_common.hlsl

@@ -27,7 +27,7 @@ struct PSData
     float4 position : SV_Position;
     float2 texcoord : texcoord;
     nointerpolation uint shadingType : shadingType;
-    nointerpolation uint2 renditionScale : renditionScale;
+    nointerpolation float2 renditionScale : renditionScale;
     nointerpolation float4 color : color;
 };
 

src/renderer/atlas/shader_ps.hlsl

@@ -44,27 +44,13 @@ Output main(PSData data) : SV_Target
     }
     case SHADING_TYPE_TEXT_GRAYSCALE:
     {
-        // These are independent of the glyph texture and could be moved to the vertex shader or CPU side of things.
-        const float4 foreground = premultiplyColor(data.color);
-        const float blendEnhancedContrast = DWrite_ApplyLightOnDarkContrastAdjustment(enhancedContrast, data.color.rgb);
-        const float intensity = DWrite_CalcColorIntensity(data.color.rgb);
-        // These aren't.
-        const float4 glyph = glyphAtlas[data.texcoord];
-        const float contrasted = DWrite_EnhanceContrast(glyph.a, blendEnhancedContrast);
-        const float alphaCorrected = DWrite_ApplyAlphaCorrection(contrasted, intensity, gammaRatios);
-        color = alphaCorrected * foreground;
+        color = glyphAtlas[data.texcoord].a * data.color;
         weights = color.aaaa;
         break;
     }
     case SHADING_TYPE_TEXT_CLEARTYPE:
     {
-        // These are independent of the glyph texture and could be moved to the vertex shader or CPU side of things.
-        const float blendEnhancedContrast = DWrite_ApplyLightOnDarkContrastAdjustment(enhancedContrast, data.color.rgb);
-        // These aren't.
-        const float4 glyph = glyphAtlas[data.texcoord];
-        const float3 contrasted = DWrite_EnhanceContrast3(glyph.rgb, blendEnhancedContrast);
-        const float3 alphaCorrected = DWrite_ApplyAlphaCorrection3(contrasted, data.color.rgb, gammaRatios);
-        weights = float4(alphaCorrected * data.color.a, 1);
+        weights = float4(glyphAtlas[data.texcoord].rgb * data.color.a, 1);
         color = weights * data.color;
         break;
     }
@@ -77,14 +63,14 @@ Output main(PSData data) : SV_Target
     case SHADING_TYPE_DOTTED_LINE:
     {
         const bool on = frac(data.position.x / (2.0f * underlineWidth * data.renditionScale.x)) < 0.5f;
-        color = on * premultiplyColor(data.color);
+        color = on * data.color;
         weights = color.aaaa;
         break;
     }
     case SHADING_TYPE_DASHED_LINE:
     {
         const bool on = frac(data.position.x / (backgroundCellSize.x * data.renditionScale.x)) < 0.5f;
-        color = on * premultiplyColor(data.color);
+        color = on * data.color;
         weights = color.aaaa;
         break;
     }
@@ -102,13 +88,13 @@ Output main(PSData data) : SV_Target
         const float s = sin(data.position.x * freq);
         const float d = abs(centerY - (s * amp) - data.position.y);
         const float a = 1 - saturate(d - strokeWidthHalf);
-        color = a * premultiplyColor(data.color);
+        color = a * data.color;
         weights = color.aaaa;
         break;
     }
     default:
     {
-        color = premultiplyColor(data.color);
+        color = data.color;
         weights = color.aaaa;
         break;
     }

src/renderer/atlas/shader_vs.hlsl

@@ -3,6 +3,8 @@
 
 #include "shader_common.hlsl"
 
+#pragma warning(disable: 3571) // pow(f, e) will not work for negative f, use abs(f) or conditionally handle negative values if you expect them
+
 cbuffer ConstBuffer : register(b0)
 {
     float2 positionScale;
@@ -13,7 +15,7 @@ PSData main(VSData data)
 // clang-format on
 {
     PSData output;
-    output.color = data.color;
+    output.color = float4(pow(data.color.rgb * data.color.a, 2.2), data.color.a);
     output.shadingType = data.shadingType;
     output.renditionScale = data.renditionScale;
     // positionScale is expected to be float2(2.0f / sizeInPixel.x, -2.0f / sizeInPixel.y). Together with the

src/tools/ColorTool/ColorTool/ColorTool.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net461</TargetFramework>
+    <TargetFramework>net472</TargetFramework>
     <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
     <LangVersion>latest</LangVersion>
   </PropertyGroup>