Merge changes from topic "themesMay2322" into tm-dev

* changes:
  Update ColorScheme.toString() formatting
  Match latest variant spec; update hue rotation logic
  Match Android's colors to design intent
diff --git a/core/java/com/android/internal/graphics/cam/Cam.java b/core/java/com/android/internal/graphics/cam/Cam.java
index 1ac5e50..1df85c3 100644
--- a/core/java/com/android/internal/graphics/cam/Cam.java
+++ b/core/java/com/android/internal/graphics/cam/Cam.java
@@ -386,6 +386,13 @@
         // Yellows are very chromatic at L = 100, and blues are very chromatic at L = 0. All the
         // other hues are white at L = 100, and black at L = 0. To preserve consistency for users of
         // this system, it is better to simply return white at L* > 99, and black and L* < 0.
+        if (frame == Frame.DEFAULT) {
+            // If the viewing conditions are the same as the default sRGB-like viewing conditions,
+            // skip to using HctSolver: it uses geometrical insights to find the closest in-gamut
+            // match to hue/chroma/lstar.
+            return HctSolver.solveToInt(hue, chroma, lstar);
+        }
+
         if (chroma < 1.0 || Math.round(lstar) <= 0.0 || Math.round(lstar) >= 100.0) {
             return CamUtils.intFromLstar(lstar);
         }
diff --git a/core/java/com/android/internal/graphics/cam/CamUtils.java b/core/java/com/android/internal/graphics/cam/CamUtils.java
index 13dafdb..f541729 100644
--- a/core/java/com/android/internal/graphics/cam/CamUtils.java
+++ b/core/java/com/android/internal/graphics/cam/CamUtils.java
@@ -73,11 +73,123 @@
     // used. It was derived using Schlomer's technique of transforming the xyY
     // primaries to XYZ, then applying a correction to ensure mapping from sRGB
     // 1, 1, 1 to the reference white point, D65.
-    static final float[][] SRGB_TO_XYZ = {
-            {0.41233895f, 0.35762064f, 0.18051042f},
-            {0.2126f, 0.7152f, 0.0722f},
-            {0.01932141f, 0.11916382f, 0.95034478f}
-    };
+    static final double[][] SRGB_TO_XYZ =
+            new double[][] {
+                    new double[] {0.41233895, 0.35762064, 0.18051042},
+                    new double[] {0.2126, 0.7152, 0.0722},
+                    new double[] {0.01932141, 0.11916382, 0.95034478},
+            };
+
+    static final double[][] XYZ_TO_SRGB =
+            new double[][] {
+                    new double[] {
+                            3.2413774792388685, -1.5376652402851851, -0.49885366846268053,
+                    },
+                    new double[] {
+                            -0.9691452513005321, 1.8758853451067872, 0.04156585616912061,
+                    },
+                    new double[] {
+                            0.05562093689691305, -0.20395524564742123, 1.0571799111220335,
+                    },
+            };
+
+    /**
+     * The signum function.
+     *
+     * @return 1 if num > 0, -1 if num < 0, and 0 if num = 0
+     */
+    public static int signum(double num) {
+        if (num < 0) {
+            return -1;
+        } else if (num == 0) {
+            return 0;
+        } else {
+            return 1;
+        }
+    }
+
+    /**
+     * Converts an L* value to an ARGB representation.
+     *
+     * @param lstar L* in L*a*b*
+     * @return ARGB representation of grayscale color with lightness matching L*
+     */
+    public static int argbFromLstar(double lstar) {
+        double fy = (lstar + 16.0) / 116.0;
+        double fz = fy;
+        double fx = fy;
+        double kappa = 24389.0 / 27.0;
+        double epsilon = 216.0 / 24389.0;
+        boolean lExceedsEpsilonKappa = lstar > 8.0;
+        double y = lExceedsEpsilonKappa ? fy * fy * fy : lstar / kappa;
+        boolean cubeExceedEpsilon = fy * fy * fy > epsilon;
+        double x = cubeExceedEpsilon ? fx * fx * fx : lstar / kappa;
+        double z = cubeExceedEpsilon ? fz * fz * fz : lstar / kappa;
+        float[] whitePoint = WHITE_POINT_D65;
+        return argbFromXyz(x * whitePoint[0], y * whitePoint[1], z * whitePoint[2]);
+    }
+
+    /** Converts a color from ARGB to XYZ. */
+    public static int argbFromXyz(double x, double y, double z) {
+        double[][] matrix = XYZ_TO_SRGB;
+        double linearR = matrix[0][0] * x + matrix[0][1] * y + matrix[0][2] * z;
+        double linearG = matrix[1][0] * x + matrix[1][1] * y + matrix[1][2] * z;
+        double linearB = matrix[2][0] * x + matrix[2][1] * y + matrix[2][2] * z;
+        int r = delinearized(linearR);
+        int g = delinearized(linearG);
+        int b = delinearized(linearB);
+        return argbFromRgb(r, g, b);
+    }
+
+    /** Converts a color from linear RGB components to ARGB format. */
+    public static int argbFromLinrgb(double[] linrgb) {
+        int r = delinearized(linrgb[0]);
+        int g = delinearized(linrgb[1]);
+        int b = delinearized(linrgb[2]);
+        return argbFromRgb(r, g, b);
+    }
+
+    /** Converts a color from linear RGB components to ARGB format. */
+    public static int argbFromLinrgbComponents(double r, double g, double b) {
+        return argbFromRgb(delinearized(r), delinearized(g), delinearized(b));
+    }
+
+    /**
+     * Delinearizes an RGB component.
+     *
+     * @param rgbComponent 0.0 <= rgb_component <= 100.0, represents linear R/G/B channel
+     * @return 0 <= output <= 255, color channel converted to regular RGB space
+     */
+    public static int delinearized(double rgbComponent) {
+        double normalized = rgbComponent / 100.0;
+        double delinearized = 0.0;
+        if (normalized <= 0.0031308) {
+            delinearized = normalized * 12.92;
+        } else {
+            delinearized = 1.055 * Math.pow(normalized, 1.0 / 2.4) - 0.055;
+        }
+        return clampInt(0, 255, (int) Math.round(delinearized * 255.0));
+    }
+
+    /**
+     * Clamps an integer between two integers.
+     *
+     * @return input when min <= input <= max, and either min or max otherwise.
+     */
+    public static int clampInt(int min, int max, int input) {
+        if (input < min) {
+            return min;
+        } else if (input > max) {
+            return max;
+        }
+
+        return input;
+    }
+
+    /** Converts a color from RGB components to ARGB format. */
+    public static int argbFromRgb(int red, int green, int blue) {
+        return (255 << 24) | ((red & 255) << 16) | ((green & 255) << 8) | (blue & 255);
+    }
 
     static int intFromLstar(float lstar) {
         if (lstar < 1) {
@@ -126,9 +238,9 @@
         final float r = linearized(Color.red(argb));
         final float g = linearized(Color.green(argb));
         final float b = linearized(Color.blue(argb));
-        float[][] matrix = SRGB_TO_XYZ;
-        float y = (r * matrix[1][0]) + (g * matrix[1][1]) + (b * matrix[1][2]);
-        return y;
+        double[][] matrix = SRGB_TO_XYZ;
+        double y = (r * matrix[1][0]) + (g * matrix[1][1]) + (b * matrix[1][2]);
+        return (float) y;
     }
 
     @NonNull
@@ -137,19 +249,30 @@
         final float g = linearized(Color.green(argb));
         final float b = linearized(Color.blue(argb));
 
-        float[][] matrix = SRGB_TO_XYZ;
-        float x = (r * matrix[0][0]) + (g * matrix[0][1]) + (b * matrix[0][2]);
-        float y = (r * matrix[1][0]) + (g * matrix[1][1]) + (b * matrix[1][2]);
-        float z = (r * matrix[2][0]) + (g * matrix[2][1]) + (b * matrix[2][2]);
-        return new float[]{x, y, z};
+        double[][] matrix = SRGB_TO_XYZ;
+        double x = (r * matrix[0][0]) + (g * matrix[0][1]) + (b * matrix[0][2]);
+        double y = (r * matrix[1][0]) + (g * matrix[1][1]) + (b * matrix[1][2]);
+        double z = (r * matrix[2][0]) + (g * matrix[2][1]) + (b * matrix[2][2]);
+        return new float[]{(float) x, (float) y, (float) z};
     }
 
-    static float yFromLstar(float lstar) {
-        float ke = 8.0f;
+    /**
+     * Converts an L* value to a Y value.
+     *
+     * <p>L* in L*a*b* and Y in XYZ measure the same quantity, luminance.
+     *
+     * <p>L* measures perceptual luminance, a linear scale. Y in XYZ measures relative luminance, a
+     * logarithmic scale.
+     *
+     * @param lstar L* in L*a*b*
+     * @return Y in XYZ
+     */
+    public static double yFromLstar(double lstar) {
+        double ke = 8.0;
         if (lstar > ke) {
-            return (float) Math.pow(((lstar + 16.0) / 116.0), 3) * 100f;
+            return Math.pow((lstar + 16.0) / 116.0, 3.0) * 100.0;
         } else {
-            return lstar / (24389f / 27f) * 100f;
+            return lstar / (24389.0 / 27.0) * 100.0;
         }
     }
 
diff --git a/core/java/com/android/internal/graphics/cam/Frame.java b/core/java/com/android/internal/graphics/cam/Frame.java
index c422ad1..0ac7cbc 100644
--- a/core/java/com/android/internal/graphics/cam/Frame.java
+++ b/core/java/com/android/internal/graphics/cam/Frame.java
@@ -19,6 +19,8 @@
 import android.annotation.NonNull;
 import android.util.MathUtils;
 
+import com.android.internal.annotations.VisibleForTesting;
+
 /**
  * The frame, or viewing conditions, where a color was seen. Used, along with a color, to create a
  * color appearance model representing the color.
@@ -68,15 +70,18 @@
     private final float mFlRoot;
     private final float mZ;
 
-    float getAw() {
+    @VisibleForTesting
+    public float getAw() {
         return mAw;
     }
 
-    float getN() {
+    @VisibleForTesting
+    public float getN() {
         return mN;
     }
 
-    float getNbb() {
+    @VisibleForTesting
+    public float getNbb() {
         return mNbb;
     }
 
@@ -92,8 +97,9 @@
         return mNc;
     }
 
+    @VisibleForTesting
     @NonNull
-    float[] getRgbD() {
+    public float[] getRgbD() {
         return mRgbD;
     }
 
@@ -101,7 +107,9 @@
         return mFl;
     }
 
-    float getFlRoot() {
+    @VisibleForTesting
+    @NonNull
+    public float getFlRoot() {
         return mFlRoot;
     }
 
@@ -167,7 +175,7 @@
                 5.0 * adaptingLuminance));
 
         // Intermediate factor, ratio of background relative luminance to white relative luminance
-        float n = CamUtils.yFromLstar(backgroundLstar) / whitepoint[1];
+        float n = (float) CamUtils.yFromLstar(backgroundLstar) / whitepoint[1];
 
         // Base exponential nonlinearity
         // note Schlomer 2018 has a typo and uses 1.58, the correct factor is 1.48
diff --git a/core/java/com/android/internal/graphics/cam/HctSolver.java b/core/java/com/android/internal/graphics/cam/HctSolver.java
new file mode 100644
index 0000000..d7a8691
--- /dev/null
+++ b/core/java/com/android/internal/graphics/cam/HctSolver.java
@@ -0,0 +1,721 @@
+/*
+ * Copyright (C) 2022 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.internal.graphics.cam;
+
+/**
+ * An efficient algorithm for determining the closest sRGB color to a set of HCT coordinates,
+ * based on geometrical insights for finding intersections in linear RGB, CAM16, and L*a*b*.
+ *
+ * Algorithm identified and implemented by Tianguang Zhang.
+ * Copied from //java/com/google/ux/material/libmonet/hct on May 22 2022.
+ * ColorUtils/MathUtils functions that were required were added to CamUtils.
+ */
+public class HctSolver {
+    private HctSolver() {}
+
+    // Matrix used when converting from linear RGB to CAM16.
+    static final double[][] SCALED_DISCOUNT_FROM_LINRGB =
+            new double[][] {
+                    new double[] {
+                            0.001200833568784504, 0.002389694492170889, 0.0002795742885861124,
+                    },
+                    new double[] {
+                            0.0005891086651375999, 0.0029785502573438758, 0.0003270666104008398,
+                    },
+                    new double[] {
+                            0.00010146692491640572, 0.0005364214359186694, 0.0032979401770712076,
+                    },
+            };
+
+    // Matrix used when converting from CAM16 to linear RGB.
+    static final double[][] LINRGB_FROM_SCALED_DISCOUNT =
+            new double[][] {
+                    new double[] {
+                            1373.2198709594231, -1100.4251190754821, -7.278681089101213,
+                    },
+                    new double[] {
+                            -271.815969077903, 559.6580465940733, -32.46047482791194,
+                    },
+                    new double[] {
+                            1.9622899599665666, -57.173814538844006, 308.7233197812385,
+                    },
+            };
+
+    // Weights for transforming a set of linear RGB coordinates to Y in XYZ.
+    static final double[] Y_FROM_LINRGB = new double[] {0.2126, 0.7152, 0.0722};
+
+    // Lookup table for plane in XYZ's Y axis (relative luminance) that corresponds to a given
+    // L* in L*a*b*. HCT's T is L*, and XYZ's Y is directly correlated to linear RGB, this table
+    // allows us to thus find the intersection between HCT and RGB, giving a solution to the
+    // RGB coordinates that correspond to a given set of HCT coordinates.
+    static final double[] CRITICAL_PLANES =
+            new double[] {
+                    0.015176349177441876,
+                    0.045529047532325624,
+                    0.07588174588720938,
+                    0.10623444424209313,
+                    0.13658714259697685,
+                    0.16693984095186062,
+                    0.19729253930674434,
+                    0.2276452376616281,
+                    0.2579979360165119,
+                    0.28835063437139563,
+                    0.3188300904430532,
+                    0.350925934958123,
+                    0.3848314933096426,
+                    0.42057480301049466,
+                    0.458183274052838,
+                    0.4976837250274023,
+                    0.5391024159806381,
+                    0.5824650784040898,
+                    0.6277969426914107,
+                    0.6751227633498623,
+                    0.7244668422128921,
+                    0.775853049866786,
+                    0.829304845476233,
+                    0.8848452951698498,
+                    0.942497089126609,
+                    1.0022825574869039,
+                    1.0642236851973577,
+                    1.1283421258858297,
+                    1.1946592148522128,
+                    1.2631959812511864,
+                    1.3339731595349034,
+                    1.407011200216447,
+                    1.4823302800086415,
+                    1.5599503113873272,
+                    1.6398909516233677,
+                    1.7221716113234105,
+                    1.8068114625156377,
+                    1.8938294463134073,
+                    1.9832442801866852,
+                    2.075074464868551,
+                    2.1693382909216234,
+                    2.2660538449872063,
+                    2.36523901573795,
+                    2.4669114995532007,
+                    2.5710888059345764,
+                    2.6777882626779785,
+                    2.7870270208169257,
+                    2.898822059350997,
+                    3.0131901897720907,
+                    3.1301480604002863,
+                    3.2497121605402226,
+                    3.3718988244681087,
+                    3.4967242352587946,
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+                    93.43925555268066,
+                    94.29903859396902,
+                    95.16341895893969,
+                    96.03240364439274,
+                    96.9059996312159,
+                    97.78421388448044,
+                    98.6670533535366,
+                    99.55452497210776,
+            };
+
+    /**
+     * Sanitizes a small enough angle in radians.
+     *
+     * @param angle An angle in radians; must not deviate too much from 0.
+     * @return A coterminal angle between 0 and 2pi.
+     */
+    static double sanitizeRadians(double angle) {
+        return (angle + Math.PI * 8) % (Math.PI * 2);
+    }
+
+    /**
+     * Delinearizes an RGB component, returning a floating-point number.
+     *
+     * @param rgbComponent 0.0 <= rgb_component <= 100.0, represents linear R/G/B channel
+     * @return 0.0 <= output <= 255.0, color channel converted to regular RGB space
+     */
+    static double trueDelinearized(double rgbComponent) {
+        double normalized = rgbComponent / 100.0;
+        double delinearized;
+        if (normalized <= 0.0031308) {
+            delinearized = normalized * 12.92;
+        } else {
+            delinearized = 1.055 * Math.pow(normalized, 1.0 / 2.4) - 0.055;
+        }
+        return delinearized * 255.0;
+    }
+
+    static double chromaticAdaptation(double component) {
+        double af = Math.pow(Math.abs(component), 0.42);
+        return CamUtils.signum(component) * 400.0 * af / (af + 27.13);
+    }
+
+    /**
+     * Returns the hue of a linear RGB color in CAM16.
+     *
+     * @param linrgb The linear RGB coordinates of a color.
+     * @return The hue of the color in CAM16, in radians.
+     */
+    static double hueOf(double[] linrgb) {
+        // Calculate scaled discount components using in-lined matrix multiplication to avoid
+        // an array allocation.
+        double[][] matrix = SCALED_DISCOUNT_FROM_LINRGB;
+        double[] row = linrgb;
+        double rD = linrgb[0] * matrix[0][0] + row[1] * matrix[0][1] + row[2] * matrix[0][2];
+        double gD = linrgb[0] * matrix[1][0] + row[1] * matrix[1][1] + row[2] * matrix[1][2];
+        double bD = linrgb[0] * matrix[2][0] + row[1] * matrix[2][1] + row[2] * matrix[2][2];
+
+        double rA = chromaticAdaptation(rD);
+        double gA = chromaticAdaptation(gD);
+        double bA = chromaticAdaptation(bD);
+        // redness-greenness
+        double a = (11.0 * rA + -12.0 * gA + bA) / 11.0;
+        // yellowness-blueness
+        double b = (rA + gA - 2.0 * bA) / 9.0;
+        return Math.atan2(b, a);
+    }
+
+    /**
+     * Cyclic order is the idea that 330° → 5° → 200° is in order, but, 180° → 270° → 210° is not.
+     * Visually, A B and C are angles, and they are in cyclic order if travelling from A to C
+     * in a way that increases angle (ex. counter-clockwise if +x axis = 0 degrees and +y = 90)
+     * means you must cross B.
+     * @param a first angle in possibly cyclic triplet
+     * @param b second angle in possibly cyclic triplet
+     * @param c third angle in possibly cyclic triplet
+     * @return true if B is between A and C
+     */
+    static boolean areInCyclicOrder(double a, double b, double c) {
+        double deltaAB = sanitizeRadians(b - a);
+        double deltaAC = sanitizeRadians(c - a);
+        return deltaAB < deltaAC;
+    }
+
+    /**
+     * Find an intercept using linear interpolation.
+     *
+     * @param source The starting number.
+     * @param mid The number in the middle.
+     * @param target The ending number.
+     * @return A number t such that lerp(source, target, t) = mid.
+     */
+    static double intercept(double source, double mid, double target) {
+        if (target == source) {
+            return target;
+        }
+        return (mid - source) / (target - source);
+    }
+
+    /**
+     * Linearly interpolate between two points in three dimensions.
+     *
+     * @param source three dimensions representing the starting point
+     * @param t the percentage to travel between source and target, from 0 to 1
+     * @param target three dimensions representing the end point
+     * @return three dimensions representing the point t percent from source to target.
+     */
+    static double[] lerpPoint(double[] source, double t, double[] target) {
+        return new double[] {
+                source[0] + (target[0] - source[0]) * t,
+                source[1] + (target[1] - source[1]) * t,
+                source[2] + (target[2] - source[2]) * t,
+        };
+    }
+
+    /**
+     * Intersects a segment with a plane.
+     *
+     * @param source The coordinates of point A.
+     * @param coordinate The R-, G-, or B-coordinate of the plane.
+     * @param target The coordinates of point B.
+     * @param axis The axis the plane is perpendicular with. (0: R, 1: G, 2: B)
+     * @return The intersection point of the segment AB with the plane R=coordinate, G=coordinate,
+     *     or B=coordinate
+     */
+    static double[] setCoordinate(double[] source, double coordinate, double[] target, int axis) {
+        double t = intercept(source[axis], coordinate, target[axis]);
+        return lerpPoint(source, t, target);
+    }
+
+    /** Ensure X is between 0 and 100. */
+    static boolean isBounded(double x) {
+        return 0.0 <= x && x <= 100.0;
+    }
+
+    /**
+     * Returns the nth possible vertex of the polygonal intersection.
+     *
+     * @param y The Y value of the plane.
+     * @param n The zero-based index of the point. 0 <= n <= 11.
+     * @return The nth possible vertex of the polygonal intersection of the y plane and the RGB cube
+     *     in linear RGB coordinates, if it exists. If the possible vertex lies outside of the cube,
+     *     [-1.0, -1.0, -1.0] is returned.
+     */
+    static double[] nthVertex(double y, int n) {
+        double kR = Y_FROM_LINRGB[0];
+        double kG = Y_FROM_LINRGB[1];
+        double kB = Y_FROM_LINRGB[2];
+        double coordA = n % 4 <= 1 ? 0.0 : 100.0;
+        double coordB = n % 2 == 0 ? 0.0 : 100.0;
+        if (n < 4) {
+            double g = coordA;
+            double b = coordB;
+            double r = (y - g * kG - b * kB) / kR;
+            if (isBounded(r)) {
+                return new double[] {r, g, b};
+            } else {
+                return new double[] {-1.0, -1.0, -1.0};
+            }
+        } else if (n < 8) {
+            double b = coordA;
+            double r = coordB;
+            double g = (y - r * kR - b * kB) / kG;
+            if (isBounded(g)) {
+                return new double[] {r, g, b};
+            } else {
+                return new double[] {-1.0, -1.0, -1.0};
+            }
+        } else {
+            double r = coordA;
+            double g = coordB;
+            double b = (y - r * kR - g * kG) / kB;
+            if (isBounded(b)) {
+                return new double[] {r, g, b};
+            } else {
+                return new double[] {-1.0, -1.0, -1.0};
+            }
+        }
+    }
+
+    /**
+     * Finds the segment containing the desired color.
+     *
+     * @param y The Y value of the color.
+     * @param targetHue The hue of the color.
+     * @return A list of two sets of linear RGB coordinates, each corresponding to an endpoint of
+     *     the segment containing the desired color.
+     */
+    static double[][] bisectToSegment(double y, double targetHue) {
+        double[] left = new double[] {-1.0, -1.0, -1.0};
+        double[] right = left;
+        double leftHue = 0.0;
+        double rightHue = 0.0;
+        boolean initialized = false;
+        boolean uncut = true;
+        for (int n = 0; n < 12; n++) {
+            double[] mid = nthVertex(y, n);
+            if (mid[0] < 0) {
+                continue;
+            }
+            double midHue = hueOf(mid);
+            if (!initialized) {
+                left = mid;
+                right = mid;
+                leftHue = midHue;
+                rightHue = midHue;
+                initialized = true;
+                continue;
+            }
+            if (uncut || areInCyclicOrder(leftHue, midHue, rightHue)) {
+                uncut = false;
+                if (areInCyclicOrder(leftHue, targetHue, midHue)) {
+                    right = mid;
+                    rightHue = midHue;
+                } else {
+                    left = mid;
+                    leftHue = midHue;
+                }
+            }
+        }
+        return new double[][] {left, right};
+    }
+
+    static int criticalPlaneBelow(double x) {
+        return (int) Math.floor(x - 0.5);
+    }
+
+    static int criticalPlaneAbove(double x) {
+        return (int) Math.ceil(x - 0.5);
+    }
+
+    /**
+     * Finds a color with the given Y and hue on the boundary of the cube.
+     *
+     * @param y The Y value of the color.
+     * @param targetHue The hue of the color.
+     * @return The desired color, in linear RGB coordinates.
+     */
+    static int bisectToLimit(double y, double targetHue) {
+        double[][] segment = bisectToSegment(y, targetHue);
+        double[] left = segment[0];
+        double leftHue = hueOf(left);
+        double[] right = segment[1];
+        for (int axis = 0; axis < 3; axis++) {
+            if (left[axis] != right[axis]) {
+                int lPlane = -1;
+                int rPlane = 255;
+                if (left[axis] < right[axis]) {
+                    lPlane = criticalPlaneBelow(trueDelinearized(left[axis]));
+                    rPlane = criticalPlaneAbove(trueDelinearized(right[axis]));
+                } else {
+                    lPlane = criticalPlaneAbove(trueDelinearized(left[axis]));
+                    rPlane = criticalPlaneBelow(trueDelinearized(right[axis]));
+                }
+                for (int i = 0; i < 8; i++) {
+                    if (Math.abs(rPlane - lPlane) <= 1) {
+                        break;
+                    } else {
+                        int mPlane = (int) Math.floor((lPlane + rPlane) / 2.0);
+                        double midPlaneCoordinate = CRITICAL_PLANES[mPlane];
+                        double[] mid = setCoordinate(left, midPlaneCoordinate, right, axis);
+                        double midHue = hueOf(mid);
+                        if (areInCyclicOrder(leftHue, targetHue, midHue)) {
+                            right = mid;
+                            rPlane = mPlane;
+                        } else {
+                            left = mid;
+                            leftHue = midHue;
+                            lPlane = mPlane;
+                        }
+                    }
+                }
+            }
+        }
+        return CamUtils.argbFromLinrgbComponents((left[0] + right[0]) / 2,
+                (left[1] + right[1]) / 2, (left[2] + right[2]) / 2);
+    }
+
+    /** Equation used in CAM16 conversion that removes the effect of chromatic adaptation. */
+    static double inverseChromaticAdaptation(double adapted) {
+        double adaptedAbs = Math.abs(adapted);
+        double base = Math.max(0, 27.13 * adaptedAbs / (400.0 - adaptedAbs));
+        return CamUtils.signum(adapted) * Math.pow(base, 1.0 / 0.42);
+    }
+
+    /**
+     * Finds a color with the given hue, chroma, and Y.
+     *
+     * @param hueRadians The desired hue in radians.
+     * @param chroma The desired chroma.
+     * @param y The desired Y.
+     * @return The desired color as a hexadecimal integer, if found; 0 otherwise.
+     */
+    static int findResultByJ(double hueRadians, double chroma, double y) {
+        // Initial estimate of j.
+        double j = Math.sqrt(y) * 11.0;
+        // ===========================================================
+        // Operations inlined from Cam16 to avoid repeated calculation
+        // ===========================================================
+        Frame viewingConditions = Frame.DEFAULT;
+        double tInnerCoeff = 1 / Math.pow(1.64 - Math.pow(0.29, viewingConditions.getN()), 0.73);
+        double eHue = 0.25 * (Math.cos(hueRadians + 2.0) + 3.8);
+        double p1 = eHue * (50000.0 / 13.0) * viewingConditions.getNc()
+                * viewingConditions.getNcb();
+        double hSin = Math.sin(hueRadians);
+        double hCos = Math.cos(hueRadians);
+        for (int iterationRound = 0; iterationRound < 5; iterationRound++) {
+            // ===========================================================
+            // Operations inlined from Cam16 to avoid repeated calculation
+            // ===========================================================
+            double jNormalized = j / 100.0;
+            double alpha = chroma == 0.0 || j == 0.0 ? 0.0 : chroma / Math.sqrt(jNormalized);
+            double t = Math.pow(alpha * tInnerCoeff, 1.0 / 0.9);
+            double acExponent = 1.0 / viewingConditions.getC() / viewingConditions.getZ();
+            double ac = viewingConditions.getAw() * Math.pow(jNormalized, acExponent);
+            double p2 = ac / viewingConditions.getNbb();
+            double gamma = 23.0 * (p2 + 0.305) * t / (23.0 * p1 + 11 * t * hCos + 108.0 * t * hSin);
+            double a = gamma * hCos;
+            double b = gamma * hSin;
+            double rA = (460.0 * p2 + 451.0 * a + 288.0 * b) / 1403.0;
+            double gA = (460.0 * p2 - 891.0 * a - 261.0 * b) / 1403.0;
+            double bA = (460.0 * p2 - 220.0 * a - 6300.0 * b) / 1403.0;
+            double rCScaled = inverseChromaticAdaptation(rA);
+            double gCScaled = inverseChromaticAdaptation(gA);
+            double bCScaled = inverseChromaticAdaptation(bA);
+            double[][] matrix = LINRGB_FROM_SCALED_DISCOUNT;
+            double linrgbR = rCScaled * matrix[0][0] + gCScaled * matrix[0][1]
+                    + bCScaled * matrix[0][2];
+            double linrgbG = rCScaled * matrix[1][0] + gCScaled * matrix[1][1]
+                    + bCScaled * matrix[1][2];
+            double linrgbB = rCScaled * matrix[2][0] + gCScaled * matrix[2][1]
+                    + bCScaled * matrix[2][2];
+            // ===========================================================
+            // Operations inlined from Cam16 to avoid repeated calculation
+            // ===========================================================
+            if (linrgbR < 0 || linrgbG < 0 || linrgbB < 0) {
+                return 0;
+            }
+            double kR = Y_FROM_LINRGB[0];
+            double kG = Y_FROM_LINRGB[1];
+            double kB = Y_FROM_LINRGB[2];
+            double fnj = kR * linrgbR + kG * linrgbG + kB * linrgbB;
+            if (fnj <= 0) {
+                return 0;
+            }
+            if (iterationRound == 4 || Math.abs(fnj - y) < 0.002) {
+                if (linrgbR > 100.01 || linrgbG > 100.01 || linrgbB > 100.01) {
+                    return 0;
+                }
+                return CamUtils.argbFromLinrgbComponents(linrgbR, linrgbG, linrgbB);
+            }
+            // Iterates with Newton method,
+            // Using 2 * fn(j) / j as the approximation of fn'(j)
+            j = j - (fnj - y) * j / (2 * fnj);
+        }
+        return 0;
+    }
+
+    /**
+     * Finds an sRGB color with the given hue, chroma, and L*, if possible.
+     *
+     * @param hueDegrees The desired hue, in degrees.
+     * @param chroma The desired chroma.
+     * @param lstar The desired L*.
+     * @return A hexadecimal representing the sRGB color. The color has sufficiently close hue,
+     *     chroma, and L* to the desired values, if possible; otherwise, the hue and L* will be
+     *     sufficiently close, and chroma will be maximized.
+     */
+    public static int solveToInt(double hueDegrees, double chroma, double lstar) {
+        if (chroma < 0.0001 || lstar < 0.0001 || lstar > 99.9999) {
+            return CamUtils.argbFromLstar(lstar);
+        }
+        hueDegrees = sanitizeDegreesDouble(hueDegrees);
+        double hueRadians = Math.toRadians(hueDegrees);
+        double y = CamUtils.yFromLstar(lstar);
+        int exactAnswer = findResultByJ(hueRadians, chroma, y);
+        if (exactAnswer != 0) {
+            return exactAnswer;
+        }
+        return bisectToLimit(y, hueRadians);
+    }
+
+    /**
+     * Sanitizes a degree measure as a floating-point number.
+     *
+     * @return a degree measure between 0.0 (inclusive) and 360.0 (exclusive).
+     */
+    public static double sanitizeDegreesDouble(double degrees) {
+        degrees = degrees % 360.0;
+        if (degrees < 0) {
+            degrees = degrees + 360.0;
+        }
+        return degrees;
+    }
+
+    /**
+     * Finds an sRGB color with the given hue, chroma, and L*, if possible.
+     *
+     * @param hueDegrees The desired hue, in degrees.
+     * @param chroma The desired chroma.
+     * @param lstar The desired L*.
+     * @return An CAM16 object representing the sRGB color. The color has sufficiently close hue,
+     *     chroma, and L* to the desired values, if possible; otherwise, the hue and L* will be
+     *     sufficiently close, and chroma will be maximized.
+     */
+    public static Cam solveToCam(double hueDegrees, double chroma, double lstar) {
+        return Cam.fromInt(solveToInt(hueDegrees, chroma, lstar));
+    }
+}
diff --git a/core/tests/coretests/src/android/colormodel/CamTest.java b/core/tests/coretests/src/android/colormodel/CamTest.java
index a70ecd72..5bcc593 100644
--- a/core/tests/coretests/src/android/colormodel/CamTest.java
+++ b/core/tests/coretests/src/android/colormodel/CamTest.java
@@ -18,6 +18,9 @@
 
 import static org.junit.Assert.assertEquals;
 
+import android.platform.test.annotations.LargeTest;
+
+import org.junit.Assert;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
@@ -69,7 +72,7 @@
     public void camFromGreen() {
         Cam cam = Cam.fromInt(GREEN);
         assertEquals(79.331f, cam.getJ(), 0.001f);
-        assertEquals(108.409f, cam.getChroma(), 0.001f);
+        assertEquals(108.410f, cam.getChroma(), 0.001f);
         assertEquals(142.139f, cam.getHue(), 0.001f);
         assertEquals(85.587f, cam.getM(), 0.001f);
         assertEquals(78.604f, cam.getS(), 0.001f);
@@ -193,4 +196,32 @@
     public void deltaERedToBlue() {
         assertEquals(21.415f, Cam.fromInt(RED).distance(Cam.fromInt(BLUE)), 0.001f);
     }
+
+    @Test
+    public void viewingConditions_default() {
+        Frame vc = Frame.DEFAULT;
+
+        Assert.assertEquals(0.184, vc.getN(), 0.001);
+        Assert.assertEquals(29.981, vc.getAw(), 0.001);
+        Assert.assertEquals(1.016, vc.getNbb(), 0.001);
+        Assert.assertEquals(1.021, vc.getRgbD()[0], 0.001);
+        Assert.assertEquals(0.986, vc.getRgbD()[1], 0.001);
+        Assert.assertEquals(0.933, vc.getRgbD()[2], 0.001);
+        Assert.assertEquals(0.789, vc.getFlRoot(), 0.001);
+    }
+
+    @LargeTest
+    @Test
+    public void testHctReflexivity() {
+        for (int i = 0; i <= 0x00ffffff; i++) {
+            int color = 0xFF000000 | i;
+            Cam hct = Cam.fromInt(color);
+            int reconstructedFromHct = Cam.getInt(hct.getHue(), hct.getChroma(),
+                    CamUtils.lstarFromInt(color));
+
+            Assert.assertEquals("input was " + Integer.toHexString(color)
+                            + "; output was " + Integer.toHexString(reconstructedFromHct),
+                    reconstructedFromHct, reconstructedFromHct);
+        }
+    }
 }
diff --git a/packages/SystemUI/monet/src/com/android/systemui/monet/ColorScheme.kt b/packages/SystemUI/monet/src/com/android/systemui/monet/ColorScheme.kt
index 0c82022..beba0ee 100644
--- a/packages/SystemUI/monet/src/com/android/systemui/monet/ColorScheme.kt
+++ b/packages/SystemUI/monet/src/com/android/systemui/monet/ColorScheme.kt
@@ -21,8 +21,8 @@
 import android.graphics.Color
 import com.android.internal.graphics.ColorUtils
 import com.android.internal.graphics.cam.Cam
+import com.android.internal.graphics.cam.CamUtils
 import kotlin.math.absoluteValue
-import kotlin.math.max
 import kotlin.math.roundToInt
 
 const val TAG = "ColorScheme"
@@ -43,13 +43,13 @@
      *    second item in the pair is a hue rotation that should be applied
      */
     fun getHueRotation(sourceHue: Float, hueAndRotations: List<Pair<Int, Int>>): Double {
-        for (i in 0..hueAndRotations.size) {
-            val previousIndex = if (i == 0) hueAndRotations.size - 1 else i - 1
-            val thisHue = hueAndRotations[i].first
-            val previousHue = hueAndRotations[previousIndex].first
-            if (ColorScheme.angleIsBetween(sourceHue, thisHue, previousHue)) {
-                return ColorScheme.wrapDegreesDouble(sourceHue.toDouble() +
-                        hueAndRotations[previousIndex].second)
+        val sanitizedSourceHue = (if (sourceHue < 0 || sourceHue >= 360) 0 else sourceHue).toFloat()
+        for (i in 0..hueAndRotations.size - 2) {
+            val thisHue = hueAndRotations[i].first.toFloat()
+            val nextHue = hueAndRotations[i + 1].first.toFloat()
+            if (thisHue <= sanitizedSourceHue && sanitizedSourceHue < nextHue) {
+                return ColorScheme.wrapDegreesDouble(sanitizedSourceHue.toDouble() +
+                        hueAndRotations[i].second)
             }
         }
 
@@ -79,7 +79,7 @@
 
 internal class HueVibrantSecondary() : Hue {
     val hueToRotations = listOf(Pair(0, 18), Pair(41, 15), Pair(61, 10), Pair(101, 12),
-            Pair(131, 15), Pair(181, 18), Pair(251, 15), Pair(301, 12))
+            Pair(131, 15), Pair(181, 18), Pair(251, 15), Pair(301, 12), Pair(360, 12))
     override fun get(sourceColor: Cam): Double {
         return getHueRotation(sourceColor.hue, hueToRotations)
     }
@@ -87,7 +87,7 @@
 
 internal class HueVibrantTertiary() : Hue {
     val hueToRotations = listOf(Pair(0, 35), Pair(41, 30), Pair(61, 20), Pair(101, 25),
-            Pair(131, 30), Pair(181, 35), Pair(251, 30), Pair(301, 25))
+            Pair(131, 30), Pair(181, 35), Pair(251, 30), Pair(301, 25), Pair(360, 25))
     override fun get(sourceColor: Cam): Double {
         return getHueRotation(sourceColor.hue, hueToRotations)
     }
@@ -95,7 +95,7 @@
 
 internal class HueExpressiveSecondary() : Hue {
     val hueToRotations = listOf(Pair(0, 45), Pair(21, 95), Pair(51, 45), Pair(121, 20),
-            Pair(141, 45), Pair(191, 90), Pair(271, 45), Pair(321, 45))
+            Pair(151, 45), Pair(191, 90), Pair(271, 45), Pair(321, 45), Pair(360, 45))
     override fun get(sourceColor: Cam): Double {
         return getHueRotation(sourceColor.hue, hueToRotations)
     }
@@ -103,7 +103,7 @@
 
 internal class HueExpressiveTertiary() : Hue {
     val hueToRotations = listOf(Pair(0, 120), Pair(21, 120), Pair(51, 20), Pair(121, 45),
-            Pair(141, 20), Pair(191, 15), Pair(271, 20), Pair(321, 120))
+            Pair(151, 20), Pair(191, 15), Pair(271, 20), Pair(321, 120), Pair(360, 120))
     override fun get(sourceColor: Cam): Double {
         return getHueRotation(sourceColor.hue, hueToRotations)
     }
@@ -111,34 +111,13 @@
 
 internal interface Chroma {
     fun get(sourceColor: Cam): Double
-
-    /**
-     * Given a hue, and a mapping of hues to hue rotations, find which hues in the mapping the
-     * hue fall betweens, and use the hue rotation of the lower hue.
-     *
-     * @param sourceHue hue of source color
-     * @param hueAndChromas list of pairs, where the first item in a pair is a hue, and the
-     *    second item in the pair is a chroma that should be applied
-     */
-    fun getSpecifiedChroma(sourceHue: Float, hueAndChromas: List<Pair<Int, Int>>): Double {
-        for (i in 0..hueAndChromas.size) {
-            val previousIndex = if (i == 0) hueAndChromas.size - 1 else i - 1
-            val thisHue = hueAndChromas[i].first
-            val previousHue = hueAndChromas[previousIndex].first
-            if (ColorScheme.angleIsBetween(sourceHue, thisHue, previousHue)) {
-                return hueAndChromas[i].second.toDouble()
-            }
-        }
-
-        // If this statement executes, something is wrong, there should have been a rotation
-        // found using the arrays.
-        return sourceHue.toDouble()
-    }
 }
 
-internal class ChromaMinimum(val chroma: Double) : Chroma {
+internal class ChromaMaxOut : Chroma {
     override fun get(sourceColor: Cam): Double {
-        return max(sourceColor.chroma.toDouble(), chroma)
+        // Intentionally high. Gamut mapping from impossible HCT to sRGB will ensure that
+        // the maximum chroma is reached, even if lower than this constant.
+        return 130.0
     }
 }
 
@@ -192,11 +171,11 @@
             n2 = TonalSpec(HueSource(), ChromaConstant(8.0))
     )),
     VIBRANT(CoreSpec(
-            a1 = TonalSpec(HueSource(), ChromaMinimum(48.0)),
+            a1 = TonalSpec(HueSource(), ChromaMaxOut()),
             a2 = TonalSpec(HueVibrantSecondary(), ChromaConstant(24.0)),
             a3 = TonalSpec(HueVibrantTertiary(), ChromaConstant(32.0)),
-            n1 = TonalSpec(HueSource(), ChromaConstant(12.0)),
-            n2 = TonalSpec(HueSource(), ChromaConstant(14.0))
+            n1 = TonalSpec(HueSource(), ChromaConstant(8.0)),
+            n2 = TonalSpec(HueSource(), ChromaConstant(12.0))
     )),
     EXPRESSIVE(CoreSpec(
             a1 = TonalSpec(HueAdd(240.0), ChromaConstant(40.0)),
@@ -229,7 +208,7 @@
 }
 
 class ColorScheme(
-    @ColorInt seed: Int,
+    @ColorInt val seed: Int,
     val darkTheme: Boolean,
     val style: Style = Style.TONAL_SPOT
 ) {
@@ -293,12 +272,14 @@
 
     override fun toString(): String {
         return "ColorScheme {\n" +
-                "  neutral1: ${humanReadable(neutral1)}\n" +
-                "  neutral2: ${humanReadable(neutral2)}\n" +
-                "  accent1: ${humanReadable(accent1)}\n" +
-                "  accent2: ${humanReadable(accent2)}\n" +
-                "  accent3: ${humanReadable(accent3)}\n" +
+                "  seed color: ${stringForColor(seed)}\n" +
                 "  style: $style\n" +
+                "  palettes: \n" +
+                "  ${humanReadable("PRIMARY", accent1)}\n" +
+                "  ${humanReadable("SECONDARY", accent2)}\n" +
+                "  ${humanReadable("TERTIARY", accent3)}\n" +
+                "  ${humanReadable("NEUTRAL", neutral1)}\n" +
+                "  ${humanReadable("NEUTRAL VARIANT", neutral2)}\n" +
                 "}"
     }
 
@@ -416,13 +397,6 @@
             return seeds
         }
 
-        internal fun angleIsBetween(angle: Float, a: Int, b: Int): Boolean {
-            if (a < b) {
-                return a <= angle && angle <= b
-            }
-            return a <= angle || angle <= b
-        }
-
         private fun wrapDegrees(degrees: Int): Int {
             return when {
                 degrees < 0 -> {
@@ -455,8 +429,20 @@
             return 180f - ((a - b).absoluteValue - 180f).absoluteValue
         }
 
-        private fun humanReadable(colors: List<Int>): String {
-            return colors.joinToString { "#" + Integer.toHexString(it) }
+        private fun stringForColor(color: Int): String {
+            val width = 4
+            val hct = Cam.fromInt(color)
+            val h = "H${hct.hue.roundToInt().toString().padEnd(width)}"
+            val c = "C${hct.chroma.roundToInt().toString().padEnd(width)}"
+            val t = "T${CamUtils.lstarFromInt(color).roundToInt().toString().padEnd(width)}"
+            val hex = Integer.toHexString(color).replaceRange(0, 2, "").uppercase()
+            return "$h$c$t = #$hex"
+        }
+
+        private fun humanReadable(paletteName: String, colors: List<Int>): String {
+            return "$paletteName\n" + colors.map {
+                stringForColor(it)
+            }.joinToString(separator = "\n") { it }
         }
 
         private fun score(cam: Cam, proportion: Double): Double {
diff --git a/packages/SystemUI/tests/src/com/android/systemui/monet/ColorSchemeTest.java b/packages/SystemUI/tests/src/com/android/systemui/monet/ColorSchemeTest.java
index 890e4de..63dca3b 100644
--- a/packages/SystemUI/tests/src/com/android/systemui/monet/ColorSchemeTest.java
+++ b/packages/SystemUI/tests/src/com/android/systemui/monet/ColorSchemeTest.java
@@ -69,7 +69,7 @@
         // Expressive applies hue rotations to the theme color. The input theme color has hue
         // 117, ensuring the hue changed significantly is a strong signal styles are being applied.
         ColorScheme colorScheme = new ColorScheme(wallpaperColors, false, Style.EXPRESSIVE);
-        Assert.assertEquals(Cam.fromInt(colorScheme.getAccent1().get(6)).getHue(), 357.46, 0.1);
+        Assert.assertEquals(357.77, Cam.fromInt(colorScheme.getAccent1().get(6)).getHue(), 0.1);
     }