Another minor update to SRGBAverage

2 files changed, 4 insertions, 2 deletions

diff --git a/Graphics/GraphicsTools/src/GraphicsUtilities.cpp b/Graphics/GraphicsTools/src/GraphicsUtilities.cpp
index 93e188fd..664749b2 100644
--- a/Graphics/GraphicsTools/src/GraphicsUtilities.cpp
+++ b/Graphics/GraphicsTools/src/GraphicsUtilities.cpp
@@ -149,7 +149,8 @@ ChannelType SRGBAverage(ChannelType c0, ChannelType c1, ChannelType c2, ChannelT
     float fLinearAverage = (FastSRGBToLinear(fc0) + FastSRGBToLinear(fc1) + FastSRGBToLinear(fc2) + FastSRGBToLinear(fc3)) * 0.25f;
     float fSRGBAverage   = FastLinearToSRGB(fLinearAverage) * MaxVal;
 
-    // Clamping by MaxVal is essential because fast SRGB math is imprecise
+    // Clamping on both ends is essential because fast SRGB math is imprecise
+    fSRGBAverage = std::max(fSRGBAverage, 0.f);
     fSRGBAverage = std::min(fSRGBAverage, MaxVal);
 
     return static_cast<ChannelType>(fSRGBAverage);
diff --git a/Tests/DiligentCoreTest/src/GraphicsAccessories/GraphicsUtilitiesTest.cpp b/Tests/DiligentCoreTest/src/GraphicsAccessories/GraphicsUtilitiesTest.cpp
index 50b4cb47..1aabca1c 100644
--- a/Tests/DiligentCoreTest/src/GraphicsAccessories/GraphicsUtilitiesTest.cpp
+++ b/Tests/DiligentCoreTest/src/GraphicsAccessories/GraphicsUtilitiesTest.cpp
@@ -488,7 +488,8 @@ TEST(GraphicsTools_CalculateMipLevel, sRGB)
                      FastSRGBToLinear(FineData[((x * 2 + 0) + (y * 2 + 1) * FineWidth) * NumChannels + c] / 255.f) +
                      FastSRGBToLinear(FineData[((x * 2 + 1) + (y * 2 + 1) * FineWidth) * NumChannels + c] / 255.f)) *
                     0.25f;
-                float fSRGB = FastLinearToSRGB(fLinearAverage);
+                fLinearAverage = std::min(std::max(fLinearAverage, 0.f), 255.f);
+                float fSRGB    = FastLinearToSRGB(fLinearAverage);
 
                 RefCoarseData[(x + y * CoarseWidth) * NumChannels + c] = static_cast<Uint8>(fSRGB * 255.f);
             }