Android 9.0 亮度调节的变化(伽马曲线)

<activity
            android:name="Settings$DisplaySettingsActivity"
            android:label="@string/display_settings"
            android:icon="@drawable/ic_homepage_display"
            android:taskAffinity="com.android.settings"
            android:parentActivityName="Settings">
            <intent-filter android:priority="1">
                <action android:name="com.android.settings.DISPLAY_SETTINGS" />
                <action android:name="android.settings.DISPLAY_SETTINGS" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.DEFAULT" />
                <category android:name="android.intent.category.VOICE_LAUNCH" />
                <category android:name="com.android.settings.SHORTCUT" />
            </intent-filter>
            <intent-filter android:priority="7">
                <action android:name="com.android.settings.action.SETTINGS" />
            </intent-filter>
            <meta-data android:name="com.android.settings.category"
                android:value="com.android.settings.category.ia.homepage" />
            <meta-data android:name="com.android.settings.FRAGMENT_CLASS"
                android:value="com.android.settings.DisplaySettings" />
            <meta-data android:name="com.android.settings.PRIMARY_PROFILE_CONTROLLED"
                android:value="true" />
            <meta-data android:name="com.android.settings.summary"
                android:resource="@string/display_dashboard_summary"/>
        </activity>
        <!-- Keep compatibility with old shortcuts. -->
        <activity-alias android:name="DisplaySettings"
                android:label="@string/display_settings"
                android:exported="true"
                android:targetActivity="Settings$DisplaySettingsActivity">
            <meta-data android:name="com.android.settings.FRAGMENT_CLASS"
                android:value="com.android.settings.DisplaySettings" />
        </activity-alias>

public class DisplaySettings extends DashboardFragment {
    private static final String TAG = "DisplaySettings";
    public static final String KEY_DISPLAY_SIZE = "display_settings_screen_zoom";
    private static final String KEY_SCREEN_TIMEOUT = "screen_timeout";
    private static final String KEY_AMBIENT_DISPLAY = "ambient_display";
    private static final String KEY_AUTO_BRIGHTNESS = "auto_brightness_entry";
    private static final String KEY_NIGHT_DISPLAY = "night_display";
    private static final String KET_HDMI_SETTINGS = "hdmi_settings";
    @Override
    public int getMetricsCategory() {
        return MetricsEvent.DISPLAY;
    }
    @Override
    protected String getLogTag() {
        return TAG;
    }
    @Override
    protected int getPreferenceScreenResId() {
        return R.xml.display_settings;
    }
    //...
}

<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright (C) 2016 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.
-->
<PreferenceScreen
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:settings="http://schemas.android.com/apk/res-auto"
    android:key="display_settings_screen"
    android:title="@string/display_settings"
    settings:keywords="@string/keywords_display"
    settings:initialExpandedChildrenCount="4">
    <com.android.settingslib.RestrictedPreference
        android:key="brightness"
        android:title="@string/brightness"
        settings:keywords="@string/keywords_display_brightness_level"
        settings:useAdminDisabledSummary="true"
        settings:userRestriction="no_config_brightness">
        <intent android:action="com.android.intent.action.SHOW_BRIGHTNESS_DIALOG" />
    </com.android.settingslib.RestrictedPreference>
    ....

<activity
            android:name=".settings.BrightnessDialog"
            android:label="@string/quick_settings_brightness_dialog_title"
            android:theme="@*android:style/Theme.DeviceDefault.QuickSettings.Dialog"
            android:finishOnCloseSystemDialogs="true"
            android:launchMode="singleInstance"
            android:excludeFromRecents="true"
            android:exported="true">
            <intent-filter>
                <action android:name="com.android.intent.action.SHOW_BRIGHTNESS_DIALOG" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>

/*
 * Copyright (C) 2013 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.systemui.settings;
import android.app.Activity;
import android.os.Bundle;
import android.view.ContextThemeWrapper;
import android.view.Gravity;
import android.view.KeyEvent;
import android.view.LayoutInflater;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;
import android.widget.ImageView;
import com.android.internal.logging.MetricsLogger;
import com.android.internal.logging.nano.MetricsProto.MetricsEvent;
import com.android.systemui.R;
/** A dialog that provides controls for adjusting the screen brightness. */
public class BrightnessDialog extends Activity {
    private BrightnessController mBrightnessController;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        final Window window = getWindow();
        window.setGravity(Gravity.TOP);
        window.clearFlags(WindowManager.LayoutParams.FLAG_DIM_BEHIND);
        window.requestFeature(Window.FEATURE_NO_TITLE);
        // Use a dialog theme as the activity theme, but inflate the content as
        // the QS content.
        ContextThemeWrapper themedContext = new ContextThemeWrapper(this,
                com.android.internal.R.style.Theme_DeviceDefault_QuickSettings);
        View v = LayoutInflater.from(themedContext).inflate(
                R.layout.quick_settings_brightness_dialog, null);
        setContentView(v);
        final ImageView icon = findViewById(R.id.brightness_icon);
        final ToggleSliderView slider = findViewById(R.id.brightness_slider);
        mBrightnessController = new BrightnessController(this, icon, slider);
    }
    @Override
    protected void onStart() {
        super.onStart();
        mBrightnessController.registerCallbacks();
        MetricsLogger.visible(this, MetricsEvent.BRIGHTNESS_DIALOG);
    }
    @Override
    protected void onStop() {
        super.onStop();
        MetricsLogger.hidden(this, MetricsEvent.BRIGHTNESS_DIALOG);
        mBrightnessController.unregisterCallbacks();
    }
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_VOLUME_DOWN
                || keyCode == KeyEvent.KEYCODE_VOLUME_UP
                || keyCode == KeyEvent.KEYCODE_VOLUME_MUTE) {
            finish();
        }
        return super.onKeyDown(keyCode, event);
    }
}

@Override
    public void onChanged(ToggleSlider toggleSlider, boolean tracking, boolean automatic,
            int value, boolean stopTracking) {
        updateIcon(mAutomatic);
        if (mExternalChange) return;
        if (mSliderAnimator != null) {
            mSliderAnimator.cancel();
        }
        final int min;
        final int max;
        final int metric;
        final String setting;
        if (mIsVrModeEnabled) {
            metric = MetricsEvent.ACTION_BRIGHTNESS_FOR_VR;
            min = mMinimumBacklightForVr;
            max = mMaximumBacklightForVr;
            setting = Settings.System.SCREEN_BRIGHTNESS_FOR_VR;
        } else {
            metric = mAutomatic
                    ? MetricsEvent.ACTION_BRIGHTNESS_AUTO
                    : MetricsEvent.ACTION_BRIGHTNESS;
            min = mMinimumBacklight;
            max = mMaximumBacklight;
            setting = Settings.System.SCREEN_BRIGHTNESS;
        }
        final int val = convertGammaToLinear(value, min, max);
        if (stopTracking) {
            MetricsLogger.action(mContext, metric, val);
        }
        setBrightness(val);
        if (!tracking) {
            AsyncTask.execute(new Runnable() {
                    public void run() {
                        Settings.System.putIntForUser(mContext.getContentResolver(),
                                setting, val, UserHandle.USER_CURRENT);
                    }
                });
        }
        for (BrightnessStateChangeCallback cb : mChangeCallbacks) {
            cb.onBrightnessLevelChanged();
        }
    }

/*
 * 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;
    public static final boolean ENABLE_GAMMA = false;
    // 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));
    }
}

@@ -21,6 +21,7 @@ import android.util.MathUtils;
 public class BrightnessUtils {
     public static final int GAMMA_SPACE_MAX = 1023;
+    public static final boolean ENABLE_GAMMA = false;
     // Hybrid Log Gamma constant values
     private static final float R = 0.5f;
@@ -51,6 +52,11 @@ public class BrightnessUtils {
      * @return The corresponding setting value.
      */
     public static final int convertGammaToLinear(int val, int min, int max) {
+        if(!ENABLE_GAMMA){
+            float ratio = (float)val / GAMMA_SPACE_MAX;
+            return min + (int)(ratio * (max - min));
+        }
+        
         final float normalizedVal = MathUtils.norm(0, GAMMA_SPACE_MAX, val);
         final float ret;
         if (normalizedVal <= R) {
@@ -87,6 +93,11 @@ public class BrightnessUtils {
      * @return The corresponding slider value
      */
     public static final int convertLinearToGamma(int val, int min, int max) {
+        if(!ENABLE_GAMMA){
+            float ratio = (float)(val - min)/ (max - min);
+            return (int)(ratio * GAMMA_SPACE_MAX);
+        }
+

============================================
PLATFORM_VERSION_CODENAME=REL
PLATFORM_VERSION=9
TARGET_PRODUCT=rk3399
TARGET_BUILD_VARIANT=userdebug
TARGET_BUILD_TYPE=release
TARGET_ARCH=arm64
TARGET_ARCH_VARIANT=armv8-a
TARGET_CPU_VARIANT=cortex-a53
TARGET_2ND_ARCH=arm
TARGET_2ND_ARCH_VARIANT=armv7-a-neon
TARGET_2ND_CPU_VARIANT=cortex-a15
HOST_ARCH=x86_64
HOST_2ND_ARCH=x86
HOST_OS=linux
HOST_OS_EXTRA=Linux-4.4.0-142-generic-x86_64-Ubuntu-16.04.6-LTS
HOST_CROSS_OS=windows
HOST_CROSS_ARCH=x86
HOST_CROSS_2ND_ARCH=x86_64
HOST_BUILD_TYPE=release
BUILD_ID=PI
OUT_DIR=out
============================================
ninja: no work to do.
ninja: no work to do.
out/build-rk3399-_frameworks_base_packages_SystemUI_Android.mk-cleanspec.ninja is missing, regenerating...
out/build-rk3399-_frameworks_base_packages_SystemUI_Android.mk.ninja is missing, regenerating...
ninja: error: 'out/target/common/obj/JAVA_LIBRARIES/metrics-helper-lib_intermediates/classes-header.jar', needed by 'out/target/common/obj/APPS/SystemUISharedLibTests_intermediates/classes-full-debug.jar', missing and no known rule to make it
14:37:27 ninja failed with: exit status 1
#### failed to build some targets (59 seconds) ####