android-34/com/android/systemui/monet/utils/ColorUtils.java

/*
 * Copyright (C) 2023 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.monet.utils;

/**
 * Color science utilities.
 *
 * <p>Utility methods for color science constants and color space conversions that aren't HCT or
 * CAM16.
 */
public class ColorUtils {
    private ColorUtils() {
    }

    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,
                    },
            };

    static final double[] WHITE_POINT_D65 = new double[]{95.047, 100.0, 108.883};

    /** 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);
    }

    /** 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);
    }

    /** Returns the alpha component of a color in ARGB format. */
    public static int alphaFromArgb(int argb) {
        return (argb >> 24) & 255;
    }

    /** Returns the red component of a color in ARGB format. */
    public static int redFromArgb(int argb) {
        return (argb >> 16) & 255;
    }

    /** Returns the green component of a color in ARGB format. */
    public static int greenFromArgb(int argb) {
        return (argb >> 8) & 255;
    }

    /** Returns the blue component of a color in ARGB format. */
    public static int blueFromArgb(int argb) {
        return argb & 255;
    }

    /** Returns whether a color in ARGB format is opaque. */
    public static boolean isOpaque(int argb) {
        return alphaFromArgb(argb) >= 255;
    }

    /** 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 XYZ to ARGB. */
    public static double[] xyzFromArgb(int argb) {
        double r = linearized(redFromArgb(argb));
        double g = linearized(greenFromArgb(argb));
        double b = linearized(blueFromArgb(argb));
        return MathUtils.matrixMultiply(new double[]{r, g, b}, SRGB_TO_XYZ);
    }

    /** Converts a color represented in Lab color space into an ARGB integer. */
    public static int argbFromLab(double l, double a, double b) {
        double[] whitePoint = WHITE_POINT_D65;
        double fy = (l + 16.0) / 116.0;
        double fx = a / 500.0 + fy;
        double fz = fy - b / 200.0;
        double xNormalized = labInvf(fx);
        double yNormalized = labInvf(fy);
        double zNormalized = labInvf(fz);
        double x = xNormalized * whitePoint[0];
        double y = yNormalized * whitePoint[1];
        double z = zNormalized * whitePoint[2];
        return argbFromXyz(x, y, z);
    }

    /**
     * Converts a color from ARGB representation to L*a*b* representation.
     *
     * @param argb the ARGB representation of a color
     * @return a Lab object representing the color
     */
    public static double[] labFromArgb(int argb) {
        double linearR = linearized(redFromArgb(argb));
        double linearG = linearized(greenFromArgb(argb));
        double linearB = linearized(blueFromArgb(argb));
        double[][] matrix = SRGB_TO_XYZ;
        double x = matrix[0][0] * linearR + matrix[0][1] * linearG + matrix[0][2] * linearB;
        double y = matrix[1][0] * linearR + matrix[1][1] * linearG + matrix[1][2] * linearB;
        double z = matrix[2][0] * linearR + matrix[2][1] * linearG + matrix[2][2] * linearB;
        double[] whitePoint = WHITE_POINT_D65;
        double xNormalized = x / whitePoint[0];
        double yNormalized = y / whitePoint[1];
        double zNormalized = z / whitePoint[2];
        double fx = labF(xNormalized);
        double fy = labF(yNormalized);
        double fz = labF(zNormalized);
        double l = 116.0 * fy - 16;
        double a = 500.0 * (fx - fy);
        double b = 200.0 * (fy - fz);
        return new double[]{l, a, b};
    }

    /**
     * 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 y = yFromLstar(lstar);
        int component = delinearized(y);
        return argbFromRgb(component, component, component);
    }

    /**
     * Computes the L* value of a color in ARGB representation.
     *
     * @param argb ARGB representation of a color
     * @return L*, from L*a*b*, coordinate of the color
     */
    public static double lstarFromArgb(int argb) {
        double y = xyzFromArgb(argb)[1];
        return 116.0 * labF(y / 100.0) - 16.0;
    }

    /**
     * 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) {
        return 100.0 * labInvf((lstar + 16.0) / 116.0);
    }

    /**
     * Converts a Y value to an L* 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 y Y in XYZ
     * @return L* in L*a*b*
     */
    public static double lstarFromY(double y) {
        return labF(y / 100.0) * 116.0 - 16.0;
    }

    /**
     * Linearizes an RGB component.
     *
     * @param rgbComponent 0 <= rgb_component <= 255, represents R/G/B channel
     * @return 0.0 <= output <= 100.0, color channel converted to linear RGB space
     */
    public static double linearized(int rgbComponent) {
        double normalized = rgbComponent / 255.0;
        if (normalized <= 0.040449936) {
            return normalized / 12.92 * 100.0;
        } else {
            return Math.pow((normalized + 0.055) / 1.055, 2.4) * 100.0;
        }
    }

    /**
     * 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 MathUtils.clampInt(0, 255, (int) Math.round(delinearized * 255.0));
    }

    /**
     * Returns the standard white point; white on a sunny day.
     *
     * @return The white point
     */
    public static double[] whitePointD65() {
        return WHITE_POINT_D65;
    }

    static double labF(double t) {
        double e = 216.0 / 24389.0;
        double kappa = 24389.0 / 27.0;
        if (t > e) {
            return Math.pow(t, 1.0 / 3.0);
        } else {
            return (kappa * t + 16) / 116;
        }
    }

    static double labInvf(double ft) {
        double e = 216.0 / 24389.0;
        double kappa = 24389.0 / 27.0;
        double ft3 = ft * ft * ft;
        if (ft3 > e) {
            return ft3;
        } else {
            return (116 * ft - 16) / kappa;
        }
    }
}