Compute DWB compensation for luminance drop

Bug: 214402192
Test: atest FrameworksServicesTests:AmbientLuxTest
Change-Id: Id61d6521d68f75d45d20b3a9ea3d1fba89410e05

services/core/java/com/android/server/display/color/ColorDisplayService.java

@@ -1453,7 +1453,7 @@ public final class ColorDisplayService extends SystemService {
     /**
      * Local service that allows color transforms to be enabled from other system services.
      */
-    public final class ColorDisplayServiceInternal {
+    public class ColorDisplayServiceInternal {
 
         /**
          * Set the current CCT value for the display white balance transform, and if the transform
@@ -1472,6 +1472,11 @@ public final class ColorDisplayService extends SystemService {
             return false;
         }
 
+        /** Get the luminance of the current chromatic adaptation matrix. */
+        public float getDisplayWhiteBalanceLuminance() {
+            return mDisplayWhiteBalanceTintController.getLuminance();
+        }
+
         /**
          * Reset the CCT value for the display white balance transform to its default value.
          */

services/core/java/com/android/server/display/color/DisplayWhiteBalanceTintController.java

@@ -251,6 +251,18 @@ final class DisplayWhiteBalanceTintController extends TintController {
         }
     }
 
+    public float getLuminance() {
+        synchronized (mLock) {
+            if (mChromaticAdaptationMatrix != null && mChromaticAdaptationMatrix.length == 9) {
+                // Compute only the luminance (y) value of the xyz * [1 1 1] transform.
+                return 1 / (mChromaticAdaptationMatrix[1] + mChromaticAdaptationMatrix[4]
+                        + mChromaticAdaptationMatrix[7]);
+            } else {
+                return -1;
+            }
+        }
+    }
+
     private ColorSpace.Rgb makeRgbColorSpaceFromXYZ(float[] redGreenBlueXYZ, float[] whiteXYZ) {
         return new ColorSpace.Rgb(
                 "Display Color Space",

services/core/java/com/android/server/display/whitebalance/DisplayWhiteBalanceController.java

@@ -21,7 +21,6 @@ import android.util.Slog;
 import android.util.Spline;
 
 import com.android.internal.annotations.VisibleForTesting;
-import com.android.internal.util.Preconditions;
 import com.android.server.LocalServices;
 import com.android.server.display.color.ColorDisplayService.ColorDisplayServiceInternal;
 import com.android.server.display.utils.AmbientFilter;
@@ -455,6 +454,22 @@ public class DisplayWhiteBalanceController implements
         mLastAmbientColorTemperature = mAmbientColorTemperature;
     }
 
+    /**
+     * Calculate the adjusted brightness, in nits, due to the DWB color adaptation
+     *
+     * @param requestedBrightnessNits brightness the framework requires to be output
+     * @return the adjusted brightness the framework needs to output to counter the drop in
+     *         brightness due to DWB, or the requestedBrightnessNits if an adjustment cannot be made
+     */
+    public float calculateAdjustedBrightnessNits(float requestedBrightnessNits) {
+        float luminance = mColorDisplayServiceInternal.getDisplayWhiteBalanceLuminance();
+        if (luminance == -1) {
+            return requestedBrightnessNits;
+        }
+        float effectiveBrightness = requestedBrightnessNits * luminance;
+        return (requestedBrightnessNits - effectiveBrightness) + requestedBrightnessNits;
+    }
+
     /**
      * The DisplayWhiteBalanceController decouples itself from its parent (DisplayPowerController)
      * by providing this interface to implement (and a method to set its callbacks object), and

services/tests/servicestests/src/com/android/server/display/whitebalance/AmbientLuxTest.java

@@ -21,6 +21,7 @@ import static org.mockito.Matchers.any;
 import static org.mockito.Matchers.anyLong;
 import static org.mockito.Matchers.eq;
 import static org.mockito.Mockito.doAnswer;
+import static org.mockito.Mockito.doReturn;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.when;
@@ -37,7 +38,9 @@ import android.util.TypedValue;
 import androidx.test.InstrumentationRegistry;
 
 import com.android.internal.R;
+import com.android.server.LocalServices;
 import com.android.server.display.TestUtils;
+import com.android.server.display.color.ColorDisplayService;
 import com.android.server.display.utils.AmbientFilter;
 import com.android.server.display.utils.AmbientFilterStubber;
 
@@ -75,6 +78,7 @@ public final class AmbientLuxTest {
     @Mock private TypedArray mHighLightBiases;
     @Mock private TypedArray mAmbientColorTemperatures;
     @Mock private TypedArray mDisplayColorTemperatures;
+    @Mock private ColorDisplayService.ColorDisplayServiceInternal mColorDisplayServiceInternalMock;
 
     @Before
     public void setUp() throws Exception {
@@ -120,6 +124,18 @@ public final class AmbientLuxTest {
                 R.array.config_displayWhiteBalanceHighLightAmbientBiases))
                 .thenReturn(mHighLightBiases);
         mockThrottler();
+        LocalServices.removeServiceForTest(ColorDisplayService.ColorDisplayServiceInternal.class);
+        LocalServices.addService(ColorDisplayService.ColorDisplayServiceInternal.class,
+                mColorDisplayServiceInternalMock);
+    }
+
+    @Test
+    public void testCalculateAdjustedBrightnessNits() {
+        doReturn(0.9f).when(mColorDisplayServiceInternalMock).getDisplayWhiteBalanceLuminance();
+        DisplayWhiteBalanceController controller =
+                DisplayWhiteBalanceFactory.create(mHandler, mSensorManagerMock, mResourcesSpy);
+        final float adjustedNits = controller.calculateAdjustedBrightnessNits(500f);
+        assertEquals(/* expected= */ 550f, adjustedNits, /* delta= */ 0.001);
     }
 
     @Test