Move brightness color conversion from SysUI to settingslib
The color space conversion logic in BrightnessController is also needed
by Settings app to display brightness percentage correctly. This change
moves the conversion logic to settingslib so it can be shared by other
UIs such as Settings/VrSettings.
Bug: 73810208
Test: atest RunSettingsLibRoboTests
Change-Id: If92f0da2d930fec797902b5d1b3731100e1d0ea4
diff --git a/packages/SettingsLib/src/com/android/settingslib/display/BrightnessUtils.java b/packages/SettingsLib/src/com/android/settingslib/display/BrightnessUtils.java
new file mode 100644
index 0000000..55723f9
--- /dev/null
+++ b/packages/SettingsLib/src/com/android/settingslib/display/BrightnessUtils.java
@@ -0,0 +1,101 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settingslib.display;
+
+import android.util.MathUtils;
+
+public class BrightnessUtils {
+
+ public static final int GAMMA_SPACE_MAX = 1023;
+
+ // Hybrid Log Gamma constant values
+ private static final float R = 0.5f;
+ private static final float A = 0.17883277f;
+ private static final float B = 0.28466892f;
+ private static final float C = 0.55991073f;
+
+ /**
+ * A function for converting from the gamma space that the slider works in to the
+ * linear space that the setting works in.
+ *
+ * The gamma space effectively provides us a way to make linear changes to the slider that
+ * result in linear changes in perception. If we made changes to the slider in the linear space
+ * then we'd see an approximately logarithmic change in perception (c.f. Fechner's Law).
+ *
+ * Internally, this implements the Hybrid Log Gamma electro-optical transfer function, which is
+ * a slight improvement to the typical gamma transfer function for displays whose max
+ * brightness exceeds the 120 nit reference point, but doesn't set a specific reference
+ * brightness like the PQ function does.
+ *
+ * Note that this transfer function is only valid if the display's backlight value is a linear
+ * control. If it's calibrated to be something non-linear, then a different transfer function
+ * should be used.
+ *
+ * @param val The slider value.
+ * @param min The minimum acceptable value for the setting.
+ * @param max The maximum acceptable value for the setting.
+ * @return The corresponding setting value.
+ */
+ public static final int convertGammaToLinear(int val, int min, int max) {
+ final float normalizedVal = MathUtils.norm(0, GAMMA_SPACE_MAX, val);
+ final float ret;
+ if (normalizedVal <= R) {
+ ret = MathUtils.sq(normalizedVal / R);
+ } else {
+ 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]
+ // in order to derive the correct setting value.
+ return Math.round(MathUtils.lerp(min, max, ret / 12));
+ }
+
+ /**
+ * A function for converting from the linear space that the setting works in to the
+ * gamma space that the slider works in.
+ *
+ * The gamma space effectively provides us a way to make linear changes to the slider that
+ * result in linear changes in perception. If we made changes to the slider in the linear space
+ * then we'd see an approximately logarithmic change in perception (c.f. Fechner's Law).
+ *
+ * Internally, this implements the Hybrid Log Gamma opto-electronic transfer function, which is
+ * a slight improvement to the typical gamma transfer function for displays whose max
+ * brightness exceeds the 120 nit reference point, but doesn't set a specific reference
+ * brightness like the PQ function does.
+ *
+ * Note that this transfer function is only valid if the display's backlight value is a linear
+ * control. If it's calibrated to be something non-linear, then a different transfer function
+ * should be used.
+ *
+ * @param val The brightness setting value.
+ * @param min The minimum acceptable value for the setting.
+ * @param max The maximum acceptable value for the setting.
+ * @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(0, GAMMA_SPACE_MAX, ret));
+ }
+}
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
new file mode 100644
index 0000000..eb7ad6d
--- /dev/null
+++ b/packages/SettingsLib/tests/robotests/src/com/android/settingslib/display/BrightnessUtilsTest.java
@@ -0,0 +1,52 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settingslib.display;
+
+import static com.android.settingslib.display.BrightnessUtils.GAMMA_SPACE_MAX;
+import static com.google.common.truth.Truth.assertThat;
+
+import com.android.settingslib.SettingsLibRobolectricTestRunner;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+@RunWith(SettingsLibRobolectricTestRunner.class)
+public class BrightnessUtilsTest {
+
+ private static final int MIN = 1;
+ private static final int MAX = 255;
+
+ @Test
+ public void linearToGamma_minValue_shouldReturn0() {
+ assertThat(BrightnessUtils.convertLinearToGamma(MIN, MIN, MAX)).isEqualTo(0);
+ }
+
+ @Test
+ public void linearToGamma_maxValue_shouldReturnGammaSpaceMax() {
+ assertThat(BrightnessUtils.convertLinearToGamma(MAX, MIN, MAX)).isEqualTo(GAMMA_SPACE_MAX);
+ }
+
+ @Test
+ public void gammaToLinear_minValue_shouldReturnMin() {
+ assertThat(BrightnessUtils.convertGammaToLinear(MIN, MIN, MAX)).isEqualTo(MIN);
+ }
+
+ @Test
+ public void gammaToLinear_gammaSpaceValue_shouldReturnMax() {
+ assertThat(BrightnessUtils.convertGammaToLinear(GAMMA_SPACE_MAX, MIN, MAX)).isEqualTo(MAX);
+ }
+}
diff --git a/packages/SystemUI/src/com/android/systemui/settings/BrightnessController.java b/packages/SystemUI/src/com/android/systemui/settings/BrightnessController.java
index 1736f38..be0aa11 100644
--- a/packages/SystemUI/src/com/android/systemui/settings/BrightnessController.java
+++ b/packages/SystemUI/src/com/android/systemui/settings/BrightnessController.java
@@ -16,6 +16,10 @@
package com.android.systemui.settings;
+import static com.android.settingslib.display.BrightnessUtils.GAMMA_SPACE_MAX;
+import static com.android.settingslib.display.BrightnessUtils.convertGammaToLinear;
+import static com.android.settingslib.display.BrightnessUtils.convertLinearToGamma;
+
import android.animation.ValueAnimator;
import android.content.ContentResolver;
import android.content.Context;
@@ -24,7 +28,6 @@
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Handler;
-import android.os.IPowerManager;
import android.os.Looper;
import android.os.Message;
import android.os.PowerManager;
@@ -36,7 +39,6 @@
import android.service.vr.IVrManager;
import android.service.vr.IVrStateCallbacks;
import android.util.Log;
-import android.util.MathUtils;
import android.widget.ImageView;
import com.android.internal.logging.MetricsLogger;
@@ -50,15 +52,8 @@
private static final String TAG = "StatusBar.BrightnessController";
private static final boolean SHOW_AUTOMATIC_ICON = false;
- private static final int SLIDER_MAX = 1023;
private static final int SLIDER_ANIMATION_DURATION = 3000;
- // Hybrid Log Gamma constant values
- private static final float R = 0.5f;
- private static final float A = 0.17883277f;
- private static final float B = 0.28466892f;
- private static final float C = 0.55991073f;
-
private static final int MSG_UPDATE_ICON = 0;
private static final int MSG_UPDATE_SLIDER = 1;
private static final int MSG_SET_CHECKED = 2;
@@ -273,7 +268,7 @@
mContext = context;
mIcon = icon;
mControl = control;
- mControl.setMax(SLIDER_MAX);
+ mControl.setMax(GAMMA_SPACE_MAX);
mBackgroundHandler = new Handler((Looper) Dependency.get(Dependency.BG_LOOPER));
mUserTracker = new CurrentUserTracker(mContext) {
@Override
@@ -481,76 +476,4 @@
mSliderAnimator.start();
}
- /**
- * A function for converting from the linear space that the setting works in to the
- * gamma space that the slider works in.
- *
- * The gamma space effectively provides us a way to make linear changes to the slider that
- * result in linear changes in perception. If we made changes to the slider in the linear space
- * then we'd see an approximately logarithmic change in perception (c.f. Fechner's Law).
- *
- * Internally, this implements the Hybrid Log Gamma opto-electronic transfer function, which is
- * a slight improvement to the typical gamma transfer function for displays whose max
- * brightness exceeds the 120 nit reference point, but doesn't set a specific reference
- * brightness like the PQ function does.
- *
- * Note that this transfer function is only valid if the display's backlight value is a linear
- * control. If it's calibrated to be something non-linear, then a different transfer function
- * should be used.
- *
- * @param val The brightness setting value.
- * @param min The minimum acceptable value for the setting.
- * @param max The maximum acceptable value for the setting.
- *
- * @return The corresponding slider value
- */
- private 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(0, SLIDER_MAX, ret));
- }
-
- /**
- * A function for converting from the gamma space that the slider works in to the
- * linear space that the setting works in.
- *
- * The gamma space effectively provides us a way to make linear changes to the slider that
- * result in linear changes in perception. If we made changes to the slider in the linear space
- * then we'd see an approximately logarithmic change in perception (c.f. Fechner's Law).
- *
- * Internally, this implements the Hybrid Log Gamma electro-optical transfer function, which is
- * a slight improvement to the typical gamma transfer function for displays whose max
- * brightness exceeds the 120 nit reference point, but doesn't set a specific reference
- * brightness like the PQ function does.
- *
- * Note that this transfer function is only valid if the display's backlight value is a linear
- * control. If it's calibrated to be something non-linear, then a different transfer function
- * should be used.
- *
- * @param val The slider value.
- * @param min The minimum acceptable value for the setting.
- * @param max The maximum acceptable value for the setting.
- *
- * @return The corresponding setting value.
- */
- private static final int convertGammaToLinear(int val, int min, int max) {
- final float normalizedVal = MathUtils.norm(0, SLIDER_MAX, val);
- final float ret;
- if (normalizedVal <= R) {
- ret = MathUtils.sq(normalizedVal/R);
- } else {
- 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]
- // in order to derive the correct setting value.
- return Math.round(MathUtils.lerp(min, max, ret / 12));
- }
}