content: /*
   * Copyright (C) 2021 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.anod.appwatcher.utils.color;
  
  import static androidx.annotation.RestrictTo.Scope.LIBRARY_GROUP;
  import static java.lang.Math.max;
  
  import androidx.annotation.RestrictTo;
  
  /**
   * CAM16, a color appearance model. Colors are not just defined by their hex code, but rather, a hex
   * code and viewing conditions.
   *
   * <p>CAM16 instances also have coordinates in the CAM16-UCS space, called J*, a*, b*, or jstar,
   * astar, bstar in code. CAM16-UCS is included in the CAM16 specification, and should be used when
   * measuring distances between colors.
   *
   * <p>In traditional color spaces, a color can be identified solely by the observer's measurement of
   * the color. Color appearance models such as CAM16 also use information about the environment where
   * the color was observed, known as the viewing conditions.
   *
   * <p>For example, white under the traditional assumption of a midday sun white point is accurately
   * measured as a slightly chromatic blue by CAM16. (roughly, hue 203, chroma 3, lightness 100)
   *
   * @hide
   */
  @RestrictTo(LIBRARY_GROUP)
  public final class Cam16 {
    // Transforms XYZ color space coordinates to 'cone'/'RGB' responses in CAM16.
    static final double[][] XYZ_TO_CAM16RGB = {
      {0.401288, 0.650173, -0.051461},
      {-0.250268, 1.204414, 0.045854},
      {-0.002079, 0.048952, 0.953127}
    };
  
    // Transforms 'cone'/'RGB' responses in CAM16 to XYZ color space coordinates.
    static final double[][] CAM16RGB_TO_XYZ = {
      {1.8620678, -1.0112547, 0.14918678},
      {0.38752654, 0.62144744, -0.00897398},
      {-0.01584150, -0.03412294, 1.0499644}
    };
  
    // CAM16 color dimensions, see getters for documentation.
    private final double hue;
    private final double chroma;
    private final double j;
    private final double q;
    private final double m;
    private final double s;
  
    // Coordinates in UCS space. Used to determine color distance, like delta E equations in L*a*b*.
    private final double jstar;
    private final double astar;
    private final double bstar;
  
    /**
     * CAM16 instances also have coordinates in the CAM16-UCS space, called J*, a*, b*, or jstar,
     * astar, bstar in code. CAM16-UCS is included in the CAM16 specification, and is used to measure
     * distances between colors.
     */
    double distance(Cam16 other) {
      double dJ = getJstar() - other.getJstar();
      double dA = getAstar() - other.getAstar();
      double dB = getBstar() - other.getBstar();
      double dEPrime = Math.sqrt(dJ * dJ + dA * dA + dB * dB);
      double dE = 1.41 * Math.pow(dEPrime, 0.63);
      return dE;
    }
  
    /** Hue in CAM16 */
    public double getHue() {
      return hue;
    }
  
    /** Chroma in CAM16 */
    public double getChroma() {
      return chroma;
    }
  
    /** Lightness in CAM16 */
    public double getJ() {
      return j;
    }
  
    /**
     * Brightness in CAM16.
     *
     * <p>Prefer lightness, brightness is an absolute quantity. For example, a sheet of white paper is
     * much brighter viewed in sunlight than in indoor light, but it is the lightest object under any
     * lighting.
     */
    public double getQ() {
      return q;
    }
  
    /**
     * Colorfulness in CAM16.
     *
     * <p>Prefer chroma, colorfulness is an absolute quantity. For example, a yellow toy car is much
     * more colorful outside than inside, but it has the same chroma in both environments.
     */
    public double getM() {
      return m;
    }
  
    /**
     * Saturation in CAM16.
     *
     * <p>Colorfulness in proportion to brightness. Prefer chroma, saturation measures colorfulness
     * relative to the color's own brightness, where chroma is colorfulness relative to white.
     */
    public double getS() {
      return s;
    }
  
    /** Lightness coordinate in CAM16-UCS */
    public double getJstar() {
      return jstar;
    }
  
    /** a* coordinate in CAM16-UCS */
    public double getAstar() {
      return astar;
    }
  
    /** b* coordinate in CAM16-UCS */
    public double getBstar() {
      return bstar;
    }
  
    /**
     * All of the CAM16 dimensions can be calculated from 3 of the dimensions, in the following
     * combinations: - {j or q} and {c, m, or s} and hue - jstar, astar, bstar Prefer using a static
     * method that constructs from 3 of those dimensions. This constructor is intended for those
     * methods to use to return all possible dimensions.
     *
     * @param hue for example, red, orange, yellow, green, etc.
     * @param chroma informally, colorfulness / color intensity. like saturation in HSL, except
     *     perceptually accurate.
     * @param j lightness
     * @param q brightness; ratio of lightness to white point's lightness
     * @param m colorfulness
     * @param s saturation; ratio of chroma to white point's chroma
     * @param jstar CAM16-UCS J coordinate
     * @param astar CAM16-UCS a coordinate
     * @param bstar CAM16-UCS b coordinate
     */
    private Cam16(
        double hue,
        double chroma,
        double j,
        double q,
        double m,
        double s,
        double jstar,
        double astar,
        double bstar) {
      this.hue = hue;
      this.chroma = chroma;
      this.j = j;
      this.q = q;
      this.m = m;
      this.s = s;
      this.jstar = jstar;
      this.astar = astar;
      this.bstar = bstar;
    }
  
    /**
     * Create a CAM16 color from a color, assuming the color was viewed in default viewing conditions.
     *
     * @param argb ARGB representation of a color.
     */
    public static Cam16 fromInt(int argb) {
      return fromIntInViewingConditions(argb, ViewingConditions.DEFAULT);
    }
  
    /**
     * Create a CAM16 color from a color in defined viewing conditions.
     *
     * @param argb ARGB representation of a color.
     * @param viewingConditions Information about the environment where the color was observed.
     */
    // The RGB => XYZ conversion matrix elements are derived scientific constants. While the values
    // may differ at runtime due to floating point imprecision, keeping the values the same, and
    // accurate, across implementations takes precedence.
    @SuppressWarnings("FloatingPointLiteralPrecision")
    static Cam16 fromIntInViewingConditions(int argb, ViewingConditions viewingConditions) {
      // Transform ARGB int to XYZ
      int red = (argb & 0x00ff0000) >> 16;
      int green = (argb & 0x0000ff00) >> 8;
      int blue = (argb & 0x000000ff);
      double redL = ColorUtils.linearized(red);
      double greenL = ColorUtils.linearized(green);
      double blueL = ColorUtils.linearized(blue);
      double x = 0.41233895 * redL + 0.35762064 * greenL + 0.18051042 * blueL;
      double y = 0.2126 * redL + 0.7152 * greenL + 0.0722 * blueL;
      double z = 0.01932141 * redL + 0.11916382 * greenL + 0.95034478 * blueL;
  
      // Transform XYZ to 'cone'/'rgb' responses
      double[][] matrix = XYZ_TO_CAM16RGB;
      double rT = (x * matrix[0][0]) + (y * matrix[0][1]) + (z * matrix[0][2]);
      double gT = (x * matrix[1][0]) + (y * matrix[1][1]) + (z * matrix[1][2]);
      double bT = (x * matrix[2][0]) + (y * matrix[2][1]) + (z * matrix[2][2]);
  
      // Discount illuminant
      double rD = viewingConditions.getRgbD()[0] * rT;
      double gD = viewingConditions.getRgbD()[1] * gT;
      double bD = viewingConditions.getRgbD()[2] * bT;
  
      // Chromatic adaptation
      double rAF = Math.pow(viewingConditions.getFl() * Math.abs(rD) / 100.0, 0.42);
      double gAF = Math.pow(viewingConditions.getFl() * Math.abs(gD) / 100.0, 0.42);
      double bAF = Math.pow(viewingConditions.getFl() * Math.abs(bD) / 100.0, 0.42);
      double rA = Math.signum(rD) * 400.0 * rAF / (rAF + 27.13);
      double gA = Math.signum(gD) * 400.0 * gAF / (gAF + 27.13);
      double bA = Math.signum(bD) * 400.0 * bAF / (bAF + 27.13);
  
      // redness-greenness
      double a = (11.0 * rA + -12.0 * gA + bA) / 11.0;
      // yellowness-blueness
      double b = (rA + gA - 2.0 * bA) / 9.0;
  
      // auxiliary components
      double u = (20.0 * rA + 20.0 * gA + 21.0 * bA) / 20.0;
      double p2 = (40.0 * rA + 20.0 * gA + bA) / 20.0;
  
      // hue
      double atan2 = Math.atan2(b, a);
      double atanDegrees = Math.toDegrees(atan2);
      double hue =
          atanDegrees < 0
              ? atanDegrees + 360.0
              : atanDegrees >= 360 ? atanDegrees - 360.0 : atanDegrees;
      double hueRadians = Math.toRadians(hue);
  
      // achromatic response to color
      double ac = p2 * viewingConditions.getNbb();
  
      // CAM16 lightness and brightness
      double j =
          100.0
              * Math.pow(
                  ac / viewingConditions.getAw(),
                  viewingConditions.getC() * viewingConditions.getZ());
      double q =
          4.0
              / viewingConditions.getC()
              * Math.sqrt(j / 100.0)
              * (viewingConditions.getAw() + 4.0)
              * viewingConditions.getFlRoot();
  
      // CAM16 chroma, colorfulness, and saturation.
      double huePrime = (hue < 20.14) ? hue + 360 : hue;
      double eHue = 0.25 * (Math.cos(Math.toRadians(huePrime) + 2.0) + 3.8);
      double p1 = 50000.0 / 13.0 * eHue * viewingConditions.getNc() * viewingConditions.getNcb();
      double t = p1 * Math.hypot(a, b) / (u + 0.305);
      double alpha =
          Math.pow(1.64 - Math.pow(0.29, viewingConditions.getN()), 0.73) * Math.pow(t, 0.9);
      // CAM16 chroma, colorfulness, saturation
      double c = alpha * Math.sqrt(j / 100.0);
      double m = c * viewingConditions.getFlRoot();
      double s =
          50.0 * Math.sqrt((alpha * viewingConditions.getC()) / (viewingConditions.getAw() + 4.0));
  
      // CAM16-UCS components
      double jstar = (1.0 + 100.0 * 0.007) * j / (1.0 + 0.007 * j);
      double mstar = 1.0 / 0.0228 * Math.log1p(0.0228 * m);
      double astar = mstar * Math.cos(hueRadians);
      double bstar = mstar * Math.sin(hueRadians);
  
      return new Cam16(hue, c, j, q, m, s, jstar, astar, bstar);
    }
  
    /**
     * @param j CAM16 lightness
     * @param c CAM16 chroma
     * @param h CAM16 hue
     */
    static Cam16 fromJch(double j, double c, double h) {
      return fromJchInViewingConditions(j, c, h, ViewingConditions.DEFAULT);
    }
  
    /**
     * @param j CAM16 lightness
     * @param c CAM16 chroma
     * @param h CAM16 hue
     * @param viewingConditions Information about the environment where the color was observed.
     */
    private static Cam16 fromJchInViewingConditions(
        double j, double c, double h, ViewingConditions viewingConditions) {
      double q =
          4.0
              / viewingConditions.getC()
              * Math.sqrt(j / 100.0)
              * (viewingConditions.getAw() + 4.0)
              * viewingConditions.getFlRoot();
      double m = c * viewingConditions.getFlRoot();
      double alpha = c / Math.sqrt(j / 100.0);
      double s =
          50.0 * Math.sqrt((alpha * viewingConditions.getC()) / (viewingConditions.getAw() + 4.0));
  
      double hueRadians = Math.toRadians(h);
      double jstar = (1.0 + 100.0 * 0.007) * j / (1.0 + 0.007 * j);
      double mstar = 1.0 / 0.0228 * Math.log1p(0.0228 * m);
      double astar = mstar * Math.cos(hueRadians);
      double bstar = mstar * Math.sin(hueRadians);
      return new Cam16(h, c, j, q, m, s, jstar, astar, bstar);
    }
  
    /**
     * Create a CAM16 color from CAM16-UCS coordinates.
     *
     * @param jstar CAM16-UCS lightness.
     * @param astar CAM16-UCS a dimension. Like a* in L*a*b*, it is a Cartesian coordinate on the Y
     *     axis.
     * @param bstar CAM16-UCS b dimension. Like a* in L*a*b*, it is a Cartesian coordinate on the X
     *     axis.
     */
    public static Cam16 fromUcs(double jstar, double astar, double bstar) {
  
      return fromUcsInViewingConditions(jstar, astar, bstar, ViewingConditions.DEFAULT);
    }
  
    /**
     * Create a CAM16 color from CAM16-UCS coordinates in defined viewing conditions.
     *
     * @param jstar CAM16-UCS lightness.
     * @param astar CAM16-UCS a dimension. Like a* in L*a*b*, it is a Cartesian coordinate on the Y
     *     axis.
     * @param bstar CAM16-UCS b dimension. Like a* in L*a*b*, it is a Cartesian coordinate on the X
     *     axis.
     * @param viewingConditions Information about the environment where the color was observed.
     */
    public static Cam16 fromUcsInViewingConditions(
        double jstar, double astar, double bstar, ViewingConditions viewingConditions) {
  
      double m = Math.hypot(astar, bstar);
      double m2 = Math.expm1(m * 0.0228) / 0.0228;
      double c = m2 / viewingConditions.getFlRoot();
      double h = Math.atan2(bstar, astar) * (180.0 / Math.PI);
      if (h < 0.0) {
        h += 360.0;
      }
      double j = jstar / (1. - (jstar - 100.) * 0.007);
      return fromJchInViewingConditions(j, c, h, viewingConditions);
    }
  
    /**
     * ARGB representation of the color. Assumes the color was viewed in default viewing conditions,
     * which are near-identical to the default viewing conditions for sRGB.
     */
    public int toInt() {
      return viewed(ViewingConditions.DEFAULT);
    }
  
    /**
     * ARGB representation of the color, in defined viewing conditions.
     *
     * @param viewingConditions Information about the environment where the color will be viewed.
     * @return ARGB representation of color
     */
    int viewed(ViewingConditions viewingConditions) {
      double alpha =
          (getChroma() == 0.0 || getJ() == 0.0) ? 0.0 : getChroma() / Math.sqrt(getJ() / 100.0);
  
      double t =
          Math.pow(
              alpha / Math.pow(1.64 - Math.pow(0.29, viewingConditions.getN()), 0.73), 1.0 / 0.9);
      double hRad = Math.toRadians(getHue());
  
      double eHue = 0.25 * (Math.cos(hRad + 2.0) + 3.8);
      double ac =
          viewingConditions.getAw()
              * Math.pow(getJ() / 100.0, 1.0 / viewingConditions.getC() / viewingConditions.getZ());
      double p1 = eHue * (50000.0 / 13.0) * viewingConditions.getNc() * viewingConditions.getNcb();
      double p2 = (ac / viewingConditions.getNbb());
  
      double hSin = Math.sin(hRad);
      double hCos = Math.cos(hRad);
  
      double gamma = 23.0 * (p2 + 0.305) * t / (23.0 * p1 + 11.0 * 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 rCBase = max(0, (27.13 * Math.abs(rA)) / (400.0 - Math.abs(rA)));
      double rC =
          Math.signum(rA) * (100.0 / viewingConditions.getFl()) * Math.pow(rCBase, 1.0 / 0.42);
      double gCBase = max(0, (27.13 * Math.abs(gA)) / (400.0 - Math.abs(gA)));
      double gC =
          Math.signum(gA) * (100.0 / viewingConditions.getFl()) * Math.pow(gCBase, 1.0 / 0.42);
      double bCBase = max(0, (27.13 * Math.abs(bA)) / (400.0 - Math.abs(bA)));
      double bC =
          Math.signum(bA) * (100.0 / viewingConditions.getFl()) * Math.pow(bCBase, 1.0 / 0.42);
      double rF = rC / viewingConditions.getRgbD()[0];
      double gF = gC / viewingConditions.getRgbD()[1];
      double bF = bC / viewingConditions.getRgbD()[2];
  
      double[][] matrix = CAM16RGB_TO_XYZ;
      double x = (rF * matrix[0][0]) + (gF * matrix[0][1]) + (bF * matrix[0][2]);
      double y = (rF * matrix[1][0]) + (gF * matrix[1][1]) + (bF * matrix[1][2]);
      double z = (rF * matrix[2][0]) + (gF * matrix[2][1]) + (bF * matrix[2][2]);
  
      return ColorUtils.argbFromXyz(x, y, z);
    }
  }