Don't overdim SDR content in an HLG screenshot.
Aligning HLG and PQ to 1.0 == 203 nits made SDR assets in screenshots
too dim, since both the colorspace and the color transform applied
dimming. Removing dimming application from the color transform is a
larger change, so just compensate when configuring the screenshot in
SurfaceFlinger instead.
Bug: 280347733
Test: HwAccelerationTest
Test: Navigate in and out of recents
Change-Id: Idfdb74c0c3b977717b870b2bb9a469be37d27dc9
diff --git a/libs/shaders/shaders.cpp b/libs/shaders/shaders.cpp
index b8f2be1..c85517a 100644
--- a/libs/shaders/shaders.cpp
+++ b/libs/shaders/shaders.cpp
@@ -103,10 +103,14 @@
// tonemapping downstream.
// BT. 2100-2 operates on normalized luminances, so renormalize to the input to
// correctly adjust gamma.
+ // Note that following BT. 2408 for HLG OETF actually maps 0.75 == ~264.96 nits,
+ // rather than 203 nits, because 203 nits == OOTF(invOETF(0.75)), so even though
+ // we originally scaled by 203 nits we need to re-normalize to 264.96 nits when
+ // converting to the correct brightness range.
shader.append(R"(
float3 NormalizeLuminance(float3 xyz) {
float ootfGain = pow(xyz.y / 1000.0, -0.2 / 1.2);
- return xyz * ootfGain / 203.0;
+ return xyz * ootfGain / 264.96;
}
)");
break;