Fix ICtCp chroma scaling in HDR tonemaps

SpecialKO · Jul 21, 2024 · 303ee96 · 303ee96
1 parent 04be0fc
commit 303ee96
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Showing 2 changed files with 43 additions and 10 deletions.
diff --git a/resources/shaders/imgui_pix_shader.hlsl b/resources/shaders/imgui_pix_shader.hlsl
@@ -323,8 +323,19 @@ float4 main (PS_INPUT input) : SV_Target
 
     if (Y_out + Y_in > 0.0)
     {
+      float I0      = ICtCp.x;
+      float I_scale = 0.0f;
+
       ICtCp.x *=
         max ((Y_out / Y_in), 0.0f);
+
+      if (ICtCp.x != 0.0f && I0 != 0.0f)
+      {
+        I_scale =
+          min (I0 / ICtCp.x, ICtCp.x / I0);
+      }
+
+      ICtCp.yz *= I_scale;
     }
 
     else
@@ -363,12 +374,4 @@ float4 main (PS_INPUT input) : SV_Target
     SanitizeFP (out_col);
 };
 
-#endif
-
-
-
-
-
-
-
-
+#endif
diff --git a/src/utility/image.cpp b/src/utility/image.cpp
@@ -1212,8 +1212,23 @@ SKIV_Image_TonemapToSDR (const DirectX::Image& image, DirectX::ScratchImage& fin
 
           if (Y_out + Y_in > 0.0f)
           {
+            float I0      = XMVectorGetX (ICtCp);
+            float I1      = 0.0f;
+            float I_scale = 0.0f;
+
             ICtCp.m128_f32 [0] *=
               std::max ((Y_out / Y_in), 0.0f);
+
+            I1 = XMVectorGetX (ICtCp);
+
+            if (I0 != 0.0f && I1 != 0.0f)
+            {
+              I_scale =
+                std::min (I0 / I1, I1 / I0);
+            }
+
+            ICtCp.m128_f32 [1] *= I_scale;
+            ICtCp.m128_f32 [2] *= I_scale;
           }
 
           value =
@@ -1405,8 +1420,23 @@ SKIV_Image_SaveToDisk_SDR (const DirectX::Image& image, const wchar_t* wszFileNa
 
           if (Y_out + Y_in > 0.0f)
           {
+            float I0      = XMVectorGetX (ICtCp);
+            float I1      = 0.0f;
+            float I_scale = 0.0f;
+
             ICtCp.m128_f32 [0] *=
               std::max ((Y_out / Y_in), 0.0f);
+
+            I1 = XMVectorGetX (ICtCp);
+
+            if (I0 != 0.0f && I1 != 0.0f)
+            {
+              I_scale =
+                std::min (I0 / I1, I1 / I0);
+            }
+
+            ICtCp.m128_f32 [1] *= I_scale;
+            ICtCp.m128_f32 [2] *= I_scale;
           }
 
           value =
@@ -1697,7 +1727,7 @@ SKIV_Image_CaptureDesktop (DirectX::ScratchImage& image, POINT point, int flags)
 
     // The list of supported formats should always contain DXGI_FORMAT_B8G8R8A8_UNORM,
     //   as this is the most common format for the desktop.
-    DXGI_FORMAT_B8G8R8A8_UNORM
+    //DXGI_FORMAT_B8G8R8A8_UNORM
   };
 
   static constexpr int num_sdr_formats = 4;