Merge "Added app context to smart screen brightness."

3 files changed, 589 insertions, 4 deletions

diff --git a/core/java/android/hardware/display/BrightnessConfiguration.java b/core/java/android/hardware/display/BrightnessConfiguration.java
index 7e52ca331f9f..be054297c769 100644
--- a/core/java/android/hardware/display/BrightnessConfiguration.java
+++ b/core/java/android/hardware/display/BrightnessConfiguration.java
@@ -19,26 +19,54 @@ package android.hardware.display;
 import android.annotation.Nullable;
 import android.annotation.SystemApi;
 import android.annotation.TestApi;
+import android.content.pm.ApplicationInfo;
 import android.os.Parcel;
 import android.os.Parcelable;
 import android.util.Pair;
 
 import com.android.internal.util.Preconditions;
+import com.android.internal.util.XmlUtils;
 
+import org.xmlpull.v1.XmlPullParser;
+import org.xmlpull.v1.XmlPullParserException;
+import org.xmlpull.v1.XmlSerializer;
+
+import java.io.IOException;
+import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
 import java.util.Objects;
 
 /** @hide */
 @SystemApi
 @TestApi
 public final class BrightnessConfiguration implements Parcelable {
+    private static final String TAG_BRIGHTNESS_CURVE = "brightness-curve";
+    private static final String TAG_BRIGHTNESS_POINT = "brightness-point";
+    private static final String TAG_BRIGHTNESS_CORRECTIONS = "brightness-corrections";
+    private static final String TAG_BRIGHTNESS_CORRECTION = "brightness-correction";
+    private static final String ATTR_LUX = "lux";
+    private static final String ATTR_NITS = "nits";
+    private static final String ATTR_DESCRIPTION = "description";
+    private static final String ATTR_PACKAGE_NAME = "package-name";
+    private static final String ATTR_CATEGORY = "category";
+
     private final float[] mLux;
     private final float[] mNits;
+    private final Map<String, BrightnessCorrection> mCorrectionsByPackageName;
+    private final Map<Integer, BrightnessCorrection> mCorrectionsByCategory;
     private final String mDescription;
 
-    private BrightnessConfiguration(float[] lux, float[] nits, String description) {
+    private BrightnessConfiguration(float[] lux, float[] nits,
+            Map<String, BrightnessCorrection> correctionsByPackageName,
+            Map<Integer, BrightnessCorrection> correctionsByCategory, String description) {
         mLux = lux;
         mNits = nits;
+        mCorrectionsByPackageName = correctionsByPackageName;
+        mCorrectionsByCategory = correctionsByCategory;
         mDescription = description;
     }
 
@@ -56,6 +84,38 @@ public final class BrightnessConfiguration implements Parcelable {
     }
 
     /**
+     * Returns a brightness correction by app, or null.
+     *
+     * @param packageName
+     *      The app's package name.
+     *
+     * @return The matching brightness correction, or null.
+     *
+     * @hide
+     */
+    @SystemApi
+    @Nullable
+    public BrightnessCorrection getCorrectionByPackageName(String packageName) {
+        return mCorrectionsByPackageName.get(packageName);
+    }
+
+    /**
+     * Returns a brightness correction by app category, or null.
+     *
+     * @param category
+     *      The app category.
+     *
+     * @return The matching brightness correction, or null.
+     *
+     * @hide
+     */
+    @SystemApi
+    @Nullable
+    public BrightnessCorrection getCorrectionByCategory(int category) {
+        return mCorrectionsByCategory.get(category);
+    }
+
+    /**
      * Returns description string.
      * @hide
      */
@@ -67,6 +127,20 @@ public final class BrightnessConfiguration implements Parcelable {
     public void writeToParcel(Parcel dest, int flags) {
         dest.writeFloatArray(mLux);
         dest.writeFloatArray(mNits);
+        dest.writeInt(mCorrectionsByPackageName.size());
+        for (Entry<String, BrightnessCorrection> entry : mCorrectionsByPackageName.entrySet()) {
+            final String packageName = entry.getKey();
+            final BrightnessCorrection correction = entry.getValue();
+            dest.writeString(packageName);
+            correction.writeToParcel(dest, flags);
+        }
+        dest.writeInt(mCorrectionsByCategory.size());
+        for (Entry<Integer, BrightnessCorrection> entry : mCorrectionsByCategory.entrySet()) {
+            final int category = entry.getKey();
+            final BrightnessCorrection correction = entry.getValue();
+            dest.writeInt(category);
+            correction.writeToParcel(dest, flags);
+        }
         dest.writeString(mDescription);
     }
 
@@ -85,7 +159,14 @@ public final class BrightnessConfiguration implements Parcelable {
             }
             sb.append("(").append(mLux[i]).append(", ").append(mNits[i]).append(")");
         }
-        sb.append("], '");
+        sb.append("], {");
+        for (Entry<String, BrightnessCorrection> entry : mCorrectionsByPackageName.entrySet()) {
+            sb.append("'" + entry.getKey() + "': " + entry.getValue() + ", ");
+        }
+        for (Entry<Integer, BrightnessCorrection> entry : mCorrectionsByCategory.entrySet()) {
+            sb.append(entry.getKey() + ": " + entry.getValue() + ", ");
+        }
+        sb.append("}, '");
         if (mDescription != null) {
             sb.append(mDescription);
         }
@@ -98,6 +179,8 @@ public final class BrightnessConfiguration implements Parcelable {
         int result = 1;
         result = result * 31 + Arrays.hashCode(mLux);
         result = result * 31 + Arrays.hashCode(mNits);
+        result = result * 31 + mCorrectionsByPackageName.hashCode();
+        result = result * 31 + mCorrectionsByCategory.hashCode();
         if (mDescription != null) {
             result = result * 31 + mDescription.hashCode();
         }
@@ -114,6 +197,8 @@ public final class BrightnessConfiguration implements Parcelable {
         }
         final BrightnessConfiguration other = (BrightnessConfiguration) o;
         return Arrays.equals(mLux, other.mLux) && Arrays.equals(mNits, other.mNits)
+                && mCorrectionsByPackageName.equals(other.mCorrectionsByPackageName)
+                && mCorrectionsByCategory.equals(other.mCorrectionsByCategory)
                 && Objects.equals(mDescription, other.mDescription);
     }
 
@@ -123,7 +208,25 @@ public final class BrightnessConfiguration implements Parcelable {
             float[] lux = in.createFloatArray();
             float[] nits = in.createFloatArray();
             Builder builder = new Builder(lux, nits);
-            builder.setDescription(in.readString());
+
+            int n = in.readInt();
+            for (int i = 0; i < n; i++) {
+                final String packageName = in.readString();
+                final BrightnessCorrection correction =
+                        BrightnessCorrection.CREATOR.createFromParcel(in);
+                builder.addCorrectionByPackageName(packageName, correction);
+            }
+
+            n = in.readInt();
+            for (int i = 0; i < n; i++) {
+                final int category = in.readInt();
+                final BrightnessCorrection correction =
+                        BrightnessCorrection.CREATOR.createFromParcel(in);
+                builder.addCorrectionByCategory(category, correction);
+            }
+
+            final String description = in.readString();
+            builder.setDescription(description);
             return builder.build();
         }
 
@@ -133,11 +236,146 @@ public final class BrightnessConfiguration implements Parcelable {
     };
 
     /**
+     * Writes the configuration to an XML serializer.
+     *
+     * @param serializer
+     *      The XML serializer.
+     *
+     * @hide
+     */
+    public void saveToXml(XmlSerializer serializer) throws IOException {
+        serializer.startTag(null, TAG_BRIGHTNESS_CURVE);
+        if (mDescription != null) {
+            serializer.attribute(null, ATTR_DESCRIPTION, mDescription);
+        }
+        for (int i = 0; i < mLux.length; i++) {
+            serializer.startTag(null, TAG_BRIGHTNESS_POINT);
+            serializer.attribute(null, ATTR_LUX, Float.toString(mLux[i]));
+            serializer.attribute(null, ATTR_NITS, Float.toString(mNits[i]));
+            serializer.endTag(null, TAG_BRIGHTNESS_POINT);
+        }
+        serializer.endTag(null, TAG_BRIGHTNESS_CURVE);
+        serializer.startTag(null, TAG_BRIGHTNESS_CORRECTIONS);
+        for (Map.Entry<String, BrightnessCorrection> entry :
+                mCorrectionsByPackageName.entrySet()) {
+            final String packageName = entry.getKey();
+            final BrightnessCorrection correction = entry.getValue();
+            serializer.startTag(null, TAG_BRIGHTNESS_CORRECTION);
+            serializer.attribute(null, ATTR_PACKAGE_NAME, packageName);
+            correction.saveToXml(serializer);
+            serializer.endTag(null, TAG_BRIGHTNESS_CORRECTION);
+        }
+        for (Map.Entry<Integer, BrightnessCorrection> entry : mCorrectionsByCategory.entrySet()) {
+            final int category = entry.getKey();
+            final BrightnessCorrection correction = entry.getValue();
+            serializer.startTag(null, TAG_BRIGHTNESS_CORRECTION);
+            serializer.attribute(null, ATTR_CATEGORY, Integer.toString(category));
+            correction.saveToXml(serializer);
+            serializer.endTag(null, TAG_BRIGHTNESS_CORRECTION);
+        }
+        serializer.endTag(null, TAG_BRIGHTNESS_CORRECTIONS);
+    }
+
+    /**
+     * Read a configuration from an XML parser.
+     *
+     * @param parser
+     *      The XML parser.
+     *
+     * @throws IOException
+     *      The parser failed to read the XML file.
+     * @throws XmlPullParserException
+     *      The parser failed to parse the XML file.
+     *
+     * @hide
+     */
+    public static BrightnessConfiguration loadFromXml(XmlPullParser parser)
+            throws IOException, XmlPullParserException {
+        String description = null;
+        List<Float> luxList = new ArrayList<>();
+        List<Float> nitsList = new ArrayList<>();
+        Map<String, BrightnessCorrection> correctionsByPackageName = new HashMap<>();
+        Map<Integer, BrightnessCorrection> correctionsByCategory = new HashMap<>();
+        final int configDepth = parser.getDepth();
+        while (XmlUtils.nextElementWithin(parser, configDepth)) {
+            if (TAG_BRIGHTNESS_CURVE.equals(parser.getName())) {
+                description = parser.getAttributeValue(null, ATTR_DESCRIPTION);
+                final int curveDepth = parser.getDepth();
+                while (XmlUtils.nextElementWithin(parser, curveDepth)) {
+                    if (!TAG_BRIGHTNESS_POINT.equals(parser.getName())) {
+                        continue;
+                    }
+                    final float lux = loadFloatFromXml(parser, ATTR_LUX);
+                    final float nits = loadFloatFromXml(parser, ATTR_NITS);
+                    luxList.add(lux);
+                    nitsList.add(nits);
+                }
+            }
+            if (TAG_BRIGHTNESS_CORRECTIONS.equals(parser.getName())) {
+                final int correctionsDepth = parser.getDepth();
+                while (XmlUtils.nextElementWithin(parser, correctionsDepth)) {
+                    if (!TAG_BRIGHTNESS_CORRECTION.equals(parser.getName())) {
+                        continue;
+                    }
+                    final String packageName = parser.getAttributeValue(null, ATTR_PACKAGE_NAME);
+                    final String categoryText = parser.getAttributeValue(null, ATTR_CATEGORY);
+                    BrightnessCorrection correction = BrightnessCorrection.loadFromXml(parser);
+                    if (packageName != null) {
+                        correctionsByPackageName.put(packageName, correction);
+                    } else if (categoryText != null) {
+                        try {
+                            final int category = Integer.parseInt(categoryText);
+                            correctionsByCategory.put(category, correction);
+                        } catch (NullPointerException | NumberFormatException e) {
+                            continue;
+                        }
+                    }
+                }
+            }
+        }
+        final int n = luxList.size();
+        float[] lux = new float[n];
+        float[] nits = new float[n];
+        for (int i = 0; i < n; i++) {
+            lux[i] = luxList.get(i);
+            nits[i] = nitsList.get(i);
+        }
+        final BrightnessConfiguration.Builder builder = new BrightnessConfiguration.Builder(lux,
+                nits);
+        builder.setDescription(description);
+        for (Map.Entry<String, BrightnessCorrection> entry : correctionsByPackageName.entrySet()) {
+            final String packageName = entry.getKey();
+            final BrightnessCorrection correction = entry.getValue();
+            builder.addCorrectionByPackageName(packageName, correction);
+        }
+        for (Map.Entry<Integer, BrightnessCorrection> entry : correctionsByCategory.entrySet()) {
+            final int category = entry.getKey();
+            final BrightnessCorrection correction = entry.getValue();
+            builder.addCorrectionByCategory(category, correction);
+        }
+        return builder.build();
+    }
+
+    private static float loadFloatFromXml(XmlPullParser parser, String attribute) {
+        final String string = parser.getAttributeValue(null, attribute);
+        try {
+            return Float.parseFloat(string);
+        } catch (NullPointerException | NumberFormatException e) {
+            return Float.NaN;
+        }
+    }
+
+    /**
      * A builder class for {@link BrightnessConfiguration}s.
      */
     public static class Builder {
+        private static final int MAX_CORRECTIONS_BY_PACKAGE_NAME = 20;
+        private static final int MAX_CORRECTIONS_BY_CATEGORY = 20;
+
         private float[] mCurveLux;
         private float[] mCurveNits;
+        private Map<String, BrightnessCorrection> mCorrectionsByPackageName;
+        private Map<Integer, BrightnessCorrection> mCorrectionsByCategory;
         private String mDescription;
 
         /**
@@ -169,6 +407,88 @@ public final class BrightnessConfiguration implements Parcelable {
             checkMonotonic(nits, false /*strictly increasing*/, "nits");
             mCurveLux = lux;
             mCurveNits = nits;
+            mCorrectionsByPackageName = new HashMap<>();
+            mCorrectionsByCategory = new HashMap<>();
+        }
+
+        /**
+         * Returns the maximum number of corrections by package name allowed.
+         *
+         * @return The maximum number of corrections by package name allowed.
+         *
+         * @hide
+         */
+        @SystemApi
+        public int getMaxCorrectionsByPackageName() {
+            return MAX_CORRECTIONS_BY_PACKAGE_NAME;
+        }
+
+        /**
+         * Returns the maximum number of corrections by category allowed.
+         *
+         * @return The maximum number of corrections by category allowed.
+         *
+         * @hide
+         */
+        @SystemApi
+        public int getMaxCorrectionsByCategory() {
+            return MAX_CORRECTIONS_BY_CATEGORY;
+        }
+
+        /**
+         * Add a brightness correction by app package name.
+         * This correction is applied whenever an app with this package name has the top activity
+         * of the focused stack.
+         *
+         * @param packageName
+         *      The app's package name.
+         * @param correction
+         *      The brightness correction.
+         *
+         * @return The builder.
+         *
+         * @throws IllegalArgumentExceptions
+         *      Maximum number of corrections by package name exceeded (see
+         *      {@link #getMaxCorrectionsByPackageName}).
+         *
+         * @hide
+         */
+        @SystemApi
+        public Builder addCorrectionByPackageName(String packageName,
+                BrightnessCorrection correction) {
+            if (mCorrectionsByPackageName.size() >= getMaxCorrectionsByPackageName()) {
+                throw new IllegalArgumentException("Too many corrections by package name");
+            }
+            mCorrectionsByPackageName.put(packageName, correction);
+            return this;
+        }
+
+        /**
+         * Add a brightness correction by app category.
+         * This correction is applied whenever an app with this category has the top activity of
+         * the focused stack, and only if a correction by package name has not been applied.
+         *
+         * @param category
+         *      The {@link android.content.pm.ApplicationInfo#category app category}.
+         * @param correction
+         *      The brightness correction.
+         *
+         * @return The builder.
+         *
+         * @throws IllegalArgumentException
+         *      Maximum number of corrections by category exceeded (see
+         *      {@link #getMaxCorrectionsByCategory}).
+         *
+         * @hide
+         */
+        @SystemApi
+        public Builder addCorrectionByCategory(@ApplicationInfo.Category int category,
+                BrightnessCorrection correction) {
+            if (mCorrectionsByCategory.size() >= getMaxCorrectionsByCategory()) {
+                throw new IllegalArgumentException("Too many corrections by category");
+            }
+            mCorrectionsByCategory.put(category, correction);
+            return this;
         }
 
         /**
@@ -191,7 +511,8 @@ public final class BrightnessConfiguration implements Parcelable {
             if (mCurveLux == null || mCurveNits == null) {
                 throw new IllegalStateException("A curve must be set!");
             }
-            return new BrightnessConfiguration(mCurveLux, mCurveNits, mDescription);
+            return new BrightnessConfiguration(mCurveLux, mCurveNits, mCorrectionsByPackageName,
+                    mCorrectionsByCategory, mDescription);
         }
 
         private static void checkMonotonic(float[] vals, boolean strictlyIncreasing, String name) {
diff --git a/core/java/android/hardware/display/BrightnessCorrection.aidl b/core/java/android/hardware/display/BrightnessCorrection.aidl
new file mode 100644
index 000000000000..3abe29cc0076
--- /dev/null
+++ b/core/java/android/hardware/display/BrightnessCorrection.aidl
@@ -0,0 +1,19 @@
+/*
+ * 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 android.hardware.display;
+
+parcelable BrightnessCorrection;
diff --git a/core/java/android/hardware/display/BrightnessCorrection.java b/core/java/android/hardware/display/BrightnessCorrection.java
new file mode 100644
index 000000000000..c4e0e3b723cd
--- /dev/null
+++ b/core/java/android/hardware/display/BrightnessCorrection.java
@@ -0,0 +1,245 @@
+/*
+ * 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 android.hardware.display;
+
+import android.annotation.NonNull;
+import android.annotation.SystemApi;
+import android.os.Parcel;
+import android.os.Parcelable;
+import android.util.MathUtils;
+
+import com.android.internal.util.XmlUtils;
+
+import org.xmlpull.v1.XmlPullParser;
+import org.xmlpull.v1.XmlPullParserException;
+import org.xmlpull.v1.XmlSerializer;
+
+import java.io.IOException;
+
+/**
+ * BrightnessCorrection encapsulates a correction to the brightness, without comitting to the
+ * actual correction scheme.
+ * It is used by the BrightnessConfiguration, which maps context (e.g. the foreground app's package
+ * name and category) to corrections that need to be applied to the brightness within that context.
+ * Corrections are currently done by the app that has the top activity of the focused stack, either
+ * by its package name, or (if its package name is not mapped to any correction) by its category.
+ *
+ * @hide
+ */
+@SystemApi
+public final class BrightnessCorrection implements Parcelable {
+
+    private static final int SCALE_AND_TRANSLATE_LOG = 1;
+
+    private static final String TAG_SCALE_AND_TRANSLATE_LOG = "scale-and-translate-log";
+
+    private BrightnessCorrectionImplementation mImplementation;
+
+    // Parcelable classes must be final, and protected methods are not allowed in APIs, so we can't
+    // make this class abstract and use composition instead of inheritence.
+    private BrightnessCorrection(BrightnessCorrectionImplementation implementation) {
+        mImplementation = implementation;
+    }
+
+    /**
+     * Creates a BrightnessCorrection that given {@code brightness}, corrects it to be
+     * {@code exp(scale * log(brightness) + translate)}.
+     *
+     * @param scale
+     *      How much to scale the log brightness.
+     * @param translate
+     *      How much to translate the log brightness.
+     *
+     * @return A BrightnessCorrection that given {@code brightness}, corrects it to be
+     * {@code exp(scale * log(brightness) + translate)}.
+     *
+     * @throws IllegalArgumentException
+     *      - scale or translate are NaN.
+     */
+    @NonNull
+    public static BrightnessCorrection createScaleAndTranslateLog(float scale, float translate) {
+        BrightnessCorrectionImplementation implementation =
+                new ScaleAndTranslateLog(scale, translate);
+        return new BrightnessCorrection(implementation);
+    }
+
+    /**
+     * Applies the brightness correction to a given brightness.
+     *
+     * @param brightness
+     *      The brightness.
+     *
+     * @return The corrected brightness.
+     */
+    public float apply(float brightness) {
+        return mImplementation.apply(brightness);
+    }
+
+    /**
+     * Returns a string representation.
+     *
+     * @return A string representation.
+     */
+    public String toString() {
+        return mImplementation.toString();
+    }
+
+    public static final Creator<BrightnessCorrection> CREATOR =
+            new Creator<BrightnessCorrection>() {
+                public BrightnessCorrection createFromParcel(Parcel in) {
+                    final int type = in.readInt();
+                    switch (type) {
+                        case SCALE_AND_TRANSLATE_LOG:
+                            return ScaleAndTranslateLog.readFromParcel(in);
+                    }
+                    return null;
+                }
+
+                public BrightnessCorrection[] newArray(int size) {
+                    return new BrightnessCorrection[size];
+                }
+            };
+
+    @Override
+    public void writeToParcel(Parcel dest, int flags) {
+        mImplementation.writeToParcel(dest);
+    }
+
+    @Override
+    public int describeContents() {
+        return 0;
+    }
+
+    /**
+     * Writes the correction to an XML serializer.
+     *
+     * @param serializer
+     *      The XML serializer.
+     *
+     * @hide
+     */
+    public void saveToXml(XmlSerializer serializer) throws IOException {
+        mImplementation.saveToXml(serializer);
+    }
+
+    /**
+     * Read a correction from an XML parser.
+     *
+     * @param parser
+     *      The XML parser.
+     *
+     * @throws IOException
+     *      The parser failed to read the XML file.
+     * @throws XmlPullParserException
+     *      The parser failed to parse the XML file.
+     *
+     * @hide
+     */
+    public static BrightnessCorrection loadFromXml(XmlPullParser parser) throws IOException,
+            XmlPullParserException {
+        final int depth = parser.getDepth();
+        while (XmlUtils.nextElementWithin(parser, depth)) {
+            if (TAG_SCALE_AND_TRANSLATE_LOG.equals(parser.getName())) {
+                return ScaleAndTranslateLog.loadFromXml(parser);
+            }
+        }
+        return null;
+    }
+
+    private static float loadFloatFromXml(XmlPullParser parser, String attribute) {
+        final String string = parser.getAttributeValue(null, attribute);
+        try {
+            return Float.parseFloat(string);
+        } catch (NullPointerException | NumberFormatException e) {
+            return Float.NaN;
+        }
+    }
+
+    private interface BrightnessCorrectionImplementation {
+        float apply(float brightness);
+        String toString();
+        void writeToParcel(Parcel dest);
+        void saveToXml(XmlSerializer serializer) throws IOException;
+        // Package-private static methods:
+        // static BrightnessCorrection readFromParcel(Parcel in);
+        // static BrightnessCorrection loadFromXml(XmlPullParser parser) throws IOException,
+        //      XmlPullParserException;
+    }
+
+    /**
+     * A BrightnessCorrection that given {@code brightness}, corrects it to be
+     * {@code exp(scale * log(brightness) + translate)}.
+     */
+    private static class ScaleAndTranslateLog implements BrightnessCorrectionImplementation {
+        private static final float MIN_SCALE = 0.5f;
+        private static final float MAX_SCALE = 2.0f;
+        private static final float MIN_TRANSLATE = -0.6f;
+        private static final float MAX_TRANSLATE = 0.7f;
+
+        private static final String ATTR_SCALE = "scale";
+        private static final String ATTR_TRANSLATE = "translate";
+
+        private final float mScale;
+        private final float mTranslate;
+
+        ScaleAndTranslateLog(float scale, float translate) {
+            if (Float.isNaN(scale) || Float.isNaN(translate)) {
+                throw new IllegalArgumentException("scale and translate must be numbers");
+            }
+            mScale = MathUtils.constrain(scale, MIN_SCALE, MAX_SCALE);
+            mTranslate = MathUtils.constrain(translate, MIN_TRANSLATE, MAX_TRANSLATE);
+        }
+
+        @Override
+        public float apply(float brightness) {
+            return MathUtils.exp(mScale * MathUtils.log(brightness) + mTranslate);
+        }
+
+        @Override
+        public String toString() {
+            return "ScaleAndTranslateLog(" + mScale + ", " + mTranslate + ")";
+        }
+
+        @Override
+        public void writeToParcel(Parcel dest) {
+            dest.writeInt(SCALE_AND_TRANSLATE_LOG);
+            dest.writeFloat(mScale);
+            dest.writeFloat(mTranslate);
+        }
+
+        @Override
+        public void saveToXml(XmlSerializer serializer) throws IOException {
+            serializer.startTag(null, TAG_SCALE_AND_TRANSLATE_LOG);
+            serializer.attribute(null, ATTR_SCALE, Float.toString(mScale));
+            serializer.attribute(null, ATTR_TRANSLATE, Float.toString(mTranslate));
+            serializer.endTag(null, TAG_SCALE_AND_TRANSLATE_LOG);
+        }
+
+        static BrightnessCorrection readFromParcel(Parcel in) {
+            float scale = in.readFloat();
+            float translate = in.readFloat();
+            return BrightnessCorrection.createScaleAndTranslateLog(scale, translate);
+        }
+
+        static BrightnessCorrection loadFromXml(XmlPullParser parser) throws IOException,
+                XmlPullParserException {
+            final float scale = loadFloatFromXml(parser, ATTR_SCALE);
+            final float translate = loadFloatFromXml(parser, ATTR_TRANSLATE);
+            return BrightnessCorrection.createScaleAndTranslateLog(scale, translate);
+        }
+    }
+}