commit 8b4ab814aed06a4afc22831390e0739c59f811ed
author Alec Mouri <alecmouri@google.com> Thu Nov 11 12:37:30 2021 -0800
committer Alec Mouri <alecmouri@google.com> Mon Nov 15 15:57:29 2021 -0800
tree 0b22bfd1780d83e8d96f5401ecc0788492c5bb4a
parent 465b2967f33f18e5e584dc8d18ce451b4590b331

Only scale SDR luminance by content max luminance for tonemapping

If color conversion is SDR->SDR, then scale luminance only by the
display luminance.

The use-case is for applying a color transform, which was defined to
occcur in linear space. Since uniform generation for tonemapping is (for
now) dataspace-agnostic, this means that scaling by the content
luminance should not be used since a tone-mapping operator may override
the one that is provided by applications.

Bug: 200310159
Test: builds, boots
Test: librenderengine_test
Change-Id: I2cc5860b6df064664c5e462674df20b589eae291

libs/renderengine/skia/filters/LinearEffect.cpp

diff --git a/libs/renderengine/skia/filters/LinearEffect.cpp b/libs/renderengine/skia/filters/LinearEffect.cpp
index 53136e4..c3a5a60 100644
--- a/libs/renderengine/skia/filters/LinearEffect.cpp
+++ b/libs/renderengine/skia/filters/LinearEffect.cpp
@@ -114,7 +114,8 @@
 }
 
 // Conversion from relative light to absolute light (maps from [0, 1] to [0, maxNits])
-static void generateLuminanceScalesForOOTF(ui::Dataspace inputDataspace, SkString& shader) {
+static void generateLuminanceScalesForOOTF(ui::Dataspace inputDataspace,
+                                           ui::Dataspace outputDataspace, SkString& shader) {
     switch (inputDataspace & HAL_DATASPACE_TRANSFER_MASK) {
         case HAL_DATASPACE_TRANSFER_ST2084:
             shader.append(R"(
@@ -131,12 +132,26 @@
                 )");
             break;
         default:
-            shader.append(R"(
-                    float3 ScaleLuminance(float3 xyz) {
-                        return xyz * in_libtonemap_inputMaxLuminance;
-                    }
-                )");
-            break;
+            switch (outputDataspace & HAL_DATASPACE_TRANSFER_MASK) {
+                case HAL_DATASPACE_TRANSFER_ST2084:
+                case HAL_DATASPACE_TRANSFER_HLG:
+                    // SDR -> HDR tonemap
+                    shader.append(R"(
+                            float3 ScaleLuminance(float3 xyz) {
+                                return xyz * in_libtonemap_inputMaxLuminance;
+                            }
+                        )");
+                    break;
+                default:
+                    // Input and output are both SDR, so no tone-mapping is expected so
+                    // no-op the luminance normalization.
+                    shader.append(R"(
+                                float3 ScaleLuminance(float3 xyz) {
+                                    return xyz * in_libtonemap_displayMaxLuminance;
+                                }
+                            )");
+                    break;
+            }
     }
 }
 
@@ -174,7 +189,7 @@
                                                           toAidlDataspace(outputDataspace))
                           .c_str());
 
-    generateLuminanceScalesForOOTF(inputDataspace, shader);
+    generateLuminanceScalesForOOTF(inputDataspace, outputDataspace, shader);
     generateLuminanceNormalizationForOOTF(outputDataspace, shader);
 
     shader.append(R"(