[Lut shader] Fix gamma correction

to avoid color conversion, we de-gamma the image without changing the
primaries, after lut(s) shader being applied, we need to re-gamma it
back.

Bug: 329472856
Test: luts cts cases
Flag: android.hardware.flags.luts_api
Change-Id: I8c8a3b6d445d11efab4115c097d7eeb91d1be384

Author: Sally Qi

libs/renderengine/skia/SkiaRenderEngine.cpp

@@ -544,7 +544,8 @@ sk_sp<SkShader> SkiaRenderEngine::createRuntimeEffectShader(
     }
 
     if (graphicBuffer && parameters.layer.luts) {
-        shader = mLutShader.lutShader(shader, parameters.layer.luts);
+        shader = mLutShader.lutShader(shader, parameters.layer.luts,
+                                      toSkColorSpace(parameters.outputDataSpace));
     }
 
     if (parameters.requiresLinearEffect) {

libs/renderengine/skia/filters/LutShader.cpp

@@ -169,7 +169,8 @@ sk_sp<SkShader> LutShader::generateLutShader(sk_sp<SkShader> input,
 }
 
 sk_sp<SkShader> LutShader::lutShader(sk_sp<SkShader>& input,
-                                     std::shared_ptr<gui::DisplayLuts> displayLuts) {
+                                     std::shared_ptr<gui::DisplayLuts> displayLuts,
+                                     sk_sp<SkColorSpace> outColorSpace) {
     if (mBuilder == nullptr) {
         const static SkRuntimeEffect::Result instance = SkRuntimeEffect::MakeForShader(kShader);
         mBuilder = std::make_unique<SkRuntimeShaderBuilder>(instance.effect);
@@ -179,14 +180,11 @@ sk_sp<SkShader> LutShader::lutShader(sk_sp<SkShader>& input,
     if (fd.ok()) {
         // de-gamma the image without changing the primaries
         SkImage* baseImage = input->isAImage((SkMatrix*)nullptr, (SkTileMode*)nullptr);
-        if (baseImage) {
-            sk_sp<SkColorSpace> baseColorSpace =
-                    baseImage->colorSpace() ? baseImage->refColorSpace() : SkColorSpace::MakeSRGB();
-            sk_sp<SkColorSpace> gainmapMathColorSpace = baseColorSpace->makeLinearGamma();
-            auto colorXformSdrToGainmap =
-                    SkColorFilterPriv::MakeColorSpaceXform(baseColorSpace, gainmapMathColorSpace);
-            input = input->makeWithColorFilter(colorXformSdrToGainmap);
-        }
+        sk_sp<SkColorSpace> baseColorSpace = baseImage && baseImage->colorSpace()
+                ? baseImage->refColorSpace()
+                : SkColorSpace::MakeSRGB();
+        sk_sp<SkColorSpace> lutMathColorSpace = baseColorSpace->makeLinearGamma();
+        input = input->makeWithWorkingColorSpace(lutMathColorSpace);
 
         auto& offsets = displayLuts->offsets;
         auto& lutProperties = displayLuts->lutProperties;
@@ -223,16 +221,9 @@ sk_sp<SkShader> LutShader::lutShader(sk_sp<SkShader>& input,
                                       lutProperties[i].samplingKey);
         }
 
-        // re-gamma
-        baseImage = input->isAImage((SkMatrix*)nullptr, (SkTileMode*)nullptr);
-        if (baseImage) {
-            sk_sp<SkColorSpace> baseColorSpace =
-                    baseImage->colorSpace() ? baseImage->refColorSpace() : SkColorSpace::MakeSRGB();
-            sk_sp<SkColorSpace> gainmapMathColorSpace = baseColorSpace->makeLinearGamma();
-            auto colorXformGainmapToDst =
-                    SkColorFilterPriv::MakeColorSpaceXform(gainmapMathColorSpace, baseColorSpace);
-            input = input->makeWithColorFilter(colorXformGainmapToDst);
-        }
+        auto colorXformLutToDst =
+                SkColorFilterPriv::MakeColorSpaceXform(lutMathColorSpace, outColorSpace);
+        input = input->makeWithColorFilter(colorXformLutToDst);
     }
     return input;
 }

libs/renderengine/skia/filters/LutShader.h

@@ -28,8 +28,8 @@ namespace skia {
 
 class LutShader {
 public:
-    sk_sp<SkShader> lutShader(sk_sp<SkShader>& input,
-                              std::shared_ptr<gui::DisplayLuts> displayLuts);
+    sk_sp<SkShader> lutShader(sk_sp<SkShader>& input, std::shared_ptr<gui::DisplayLuts> displayLuts,
+                              sk_sp<SkColorSpace> outColorSpace);
 
 private:
     sk_sp<SkShader> generateLutShader(sk_sp<SkShader> input, const std::vector<float>& buffers,