Convert BrightnessUtils to use brightness as float

convertGammaToLinear needed to be constrained to 0-12, as sometimes ret
variable was 12.000001.

The first parameter for gammaToLinear_minValue_shouldReturnMin has been
changed - initally it used 1 (MIN_INT) but it should have been using 0
(GAMMA_SPACE_MIN). Since the function rounded the value at the end, the
result ended up the same.

The original functions cannot be removed yet since Car uses these methods.

Bug: 150671605

Test: m -j99 RunSettingsLibRoboTests ROBOTEST_FILTER="com.android.settingslib.display.BrightnessUtilsTest"

Change-Id: I4bba2ca0785f94597590c8f4bb3a7a8a834d6c83

2 files changed, 30 insertions, 20 deletions

diff --git a/packages/SettingsLib/src/com/android/settingslib/display/BrightnessUtils.java b/packages/SettingsLib/src/com/android/settingslib/display/BrightnessUtils.java
index 57d95942bcb9..4f86afaa995c 100644
--- a/packages/SettingsLib/src/com/android/settingslib/display/BrightnessUtils.java
+++ b/packages/SettingsLib/src/com/android/settingslib/display/BrightnessUtils.java
@@ -67,7 +67,7 @@ public class BrightnessUtils {
 
     /**
      * Version of {@link #convertGammaToLinear} that takes and returns float values.
-     * TODO: brightnessfloat Merge with above method later.
+     * TODO(flc): refactor Android Auto to use float version
      *
      * @param val The slider value.
      * @param min The minimum acceptable value for the setting.
@@ -83,9 +83,13 @@ public class BrightnessUtils {
             ret = MathUtils.exp((normalizedVal - C) / A) + B;
         }
 
-        // HLG is normalized to the range [0, 12], so we need to re-normalize to the range [0, 1]
+        // HLG is normalized to the range [0, 12], ensure that value is within that range,
+        // it shouldn't be out of bounds.
+        final float normalizedRet = MathUtils.constrain(ret, 0, 12);
+
+        // Re-normalize to the range [0, 1]
         // in order to derive the correct setting value.
-        return MathUtils.lerp(min, max, ret / 12);
+        return MathUtils.lerp(min, max, normalizedRet / 12);
     }
 
     /**
@@ -111,16 +115,7 @@ public class BrightnessUtils {
      * @return The corresponding slider value
      */
     public static final int convertLinearToGamma(int val, int min, int max) {
-        // For some reason, HLG normalizes to the range [0, 12] rather than [0, 1]
-        final float normalizedVal = MathUtils.norm(min, max, val) * 12;
-        final float ret;
-        if (normalizedVal <= 1f) {
-            ret = MathUtils.sqrt(normalizedVal) * R;
-        } else {
-            ret = A * MathUtils.log(normalizedVal - B) + C;
-        }
-
-        return Math.round(MathUtils.lerp(GAMMA_SPACE_MIN, GAMMA_SPACE_MAX, ret));
+        return convertLinearToGammaFloat((float) val, (float) min, (float) max);
     }
 
     /**
diff --git a/packages/SettingsLib/tests/robotests/src/com/android/settingslib/display/BrightnessUtilsTest.java b/packages/SettingsLib/tests/robotests/src/com/android/settingslib/display/BrightnessUtilsTest.java
index c0924d9a8b35..1b20f2c0a533 100644
--- a/packages/SettingsLib/tests/robotests/src/com/android/settingslib/display/BrightnessUtilsTest.java
+++ b/packages/SettingsLib/tests/robotests/src/com/android/settingslib/display/BrightnessUtilsTest.java
@@ -17,6 +17,7 @@
 package com.android.settingslib.display;
 
 import static com.android.settingslib.display.BrightnessUtils.GAMMA_SPACE_MAX;
+import static com.android.settingslib.display.BrightnessUtils.GAMMA_SPACE_MIN;
 
 import static com.google.common.truth.Truth.assertThat;
 
@@ -27,26 +28,40 @@ import org.robolectric.RobolectricTestRunner;
 @RunWith(RobolectricTestRunner.class)
 public class BrightnessUtilsTest {
 
-    private static final int MIN = 1;
-    private static final int MAX = 255;
+    private static final int MIN_INT = 1;
+    private static final int MAX_INT = 255;
+    private static final float MIN_FLOAT = 0.0f;
+    private static final float MAX_FLOAT = 1.0f;
 
     @Test
-    public void linearToGamma_minValue_shouldReturn0() {
-        assertThat(BrightnessUtils.convertLinearToGamma(MIN, MIN, MAX)).isEqualTo(0);
+    public void linearToGamma_minValue_shouldReturnMin() {
+        assertThat(BrightnessUtils.convertLinearToGamma(MIN_INT, MIN_INT, MAX_INT))
+                .isEqualTo(GAMMA_SPACE_MIN);
+        assertThat(BrightnessUtils.convertLinearToGammaFloat(MIN_FLOAT, MIN_FLOAT, MAX_FLOAT))
+                .isEqualTo(GAMMA_SPACE_MIN);
     }
 
     @Test
     public void linearToGamma_maxValue_shouldReturnGammaSpaceMax() {
-        assertThat(BrightnessUtils.convertLinearToGamma(MAX, MIN, MAX)).isEqualTo(GAMMA_SPACE_MAX);
+        assertThat(BrightnessUtils.convertLinearToGamma(MAX_INT, MIN_INT, MAX_INT))
+                .isEqualTo(GAMMA_SPACE_MAX);
+        assertThat(BrightnessUtils.convertLinearToGammaFloat(MAX_FLOAT, MIN_FLOAT, MAX_FLOAT))
+                .isEqualTo(GAMMA_SPACE_MAX);
     }
 
     @Test
     public void gammaToLinear_minValue_shouldReturnMin() {
-        assertThat(BrightnessUtils.convertGammaToLinear(MIN, MIN, MAX)).isEqualTo(MIN);
+        assertThat(BrightnessUtils.convertGammaToLinear(GAMMA_SPACE_MIN, MIN_INT, MAX_INT))
+                .isEqualTo(MIN_INT);
+        assertThat(BrightnessUtils.convertGammaToLinearFloat(GAMMA_SPACE_MIN, MIN_FLOAT, MAX_FLOAT))
+                .isEqualTo(MIN_FLOAT);
     }
 
     @Test
     public void gammaToLinear_gammaSpaceValue_shouldReturnMax() {
-        assertThat(BrightnessUtils.convertGammaToLinear(GAMMA_SPACE_MAX, MIN, MAX)).isEqualTo(MAX);
+        assertThat(BrightnessUtils.convertGammaToLinear(GAMMA_SPACE_MAX, MIN_INT, MAX_INT))
+                .isEqualTo(MAX_INT);
+        assertThat(BrightnessUtils.convertGammaToLinearFloat(GAMMA_SPACE_MAX, MIN_FLOAT, MAX_FLOAT))
+                .isEqualTo(MAX_FLOAT);
     }
 }