android/graphics/Color.java

/*
 * Copyright (C) 2006 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.graphics;

import android.annotation.AnyThread;
import android.annotation.ColorInt;
import android.annotation.ColorLong;
import android.annotation.HalfFloat;
import android.annotation.IntRange;
import android.annotation.NonNull;
import android.annotation.Size;

import android.util.Half;
import com.android.internal.util.XmlUtils;

import java.util.Arrays;
import java.util.HashMap;
import java.util.Locale;
import java.util.function.DoubleUnaryOperator;

/**
 * {@usesMathJax}
 *
 * <p>The <code>Color</code> class provides methods for creating, converting and
 * manipulating colors. Colors have three different representations:</p>
 * <ul>
 *     <li>Color ints, the most common representation</li>
 *     <li>Color longs</li>
 *     <li><code>Color</code> instances</li>
 * </ul>
 * <p>The section below describe each representation in detail.</p>
 *
 * <h3>Color ints</h3>
 * <p>Color ints are the most common representation of colors on Android and
 * have been used since {@link android.os.Build.VERSION_CODES#BASE API level 1}.</p>
 *
 * <p>A color int always defines a color in the {@link ColorSpace.Named#SRGB sRGB}
 * color space using 4 components packed in a single 32 bit integer value:</p>
 *
 * <table summary="Color int definition">
 *     <tr>
 *         <th>Component</th><th>Name</th><th>Size</th><th>Range</th>
 *     </tr>
 *     <tr><td>A</td><td>Alpha</td><td>8 bits</td><td>\([0..255]\)</td></tr>
 *     <tr><td>R</td><td>Red</td><td>8 bits</td><td>\([0..255]\)</td></tr>
 *     <tr><td>G</td><td>Green</td><td>8 bits</td><td>\([0..255]\)</td></tr>
 *     <tr><td>B</td><td>Blue</td><td>8 bits</td><td>\([0..255]\)</td></tr>
 * </table>
 *
 * <p>The components in this table are listed in encoding order (see below),
 * which is why color ints are called ARGB colors.</p>
 *
 * <h4>Usage in code</h4>
 * <p>To avoid confusing color ints with arbitrary integer values, it is a
 * good practice to annotate them with the <code>@ColorInt</code> annotation
 * found in the Android Support Library.</p>
 *
 * <h4>Encoding</h4>
 * <p>The four components of a color int are encoded in the following way:</p>
 * <pre class="prettyprint">
 * int color = (A & 0xff) << 24 | (R & 0xff) << 16 | (G & 0xff) << 16 | (B & 0xff);
 * </pre>
 *
 * <p>Because of this encoding, color ints can easily be described as an integer
 * constant in source. For instance, opaque blue is <code>0xff0000ff</code>
 * and yellow is <code>0xffffff00</code>.</p>
 *
 * <p>To easily encode color ints, it is recommended to use the static methods
 * {@link #argb(int, int, int, int)} and {@link #rgb(int, int, int)}. The second
 * method omits the alpha component and assumes the color is opaque (alpha is 255).
 * As a convenience this class also offers methods to encode color ints from components
 * defined in the \([0..1]\) range: {@link #argb(float, float, float, float)} and
 * {@link #rgb(float, float, float)}.</p>
 *
 * <p>Color longs (defined below) can be easily converted to color ints by invoking
 * the {@link #toArgb(long)} method. This method performs a color space conversion
 * if needed.</p>
 *
 * <p>It is also possible to create a color int by invoking the method {@link #toArgb()}
 * on a color instance.</p>
 *
 * <h4>Decoding</h4>
 * <p>The four ARGB components can be individually extracted from a color int
 * using the following expressions:</p>
 * <pre class="prettyprint">
 * int A = (color >> 24) & 0xff; // or color >>> 24
 * int R = (color >> 16) & 0xff;
 * int G = (color >>  8) & 0xff;
 * int B = (color      ) & 0xff;
 * </pre>
 *
 * <p>This class offers convenience methods to easily extract these components:</p>
 * <ul>
 *     <li>{@link #alpha(int)} to extract the alpha component</li>
 *     <li>{@link #red(int)} to extract the red component</li>
 *     <li>{@link #green(int)} to extract the green component</li>
 *     <li>{@link #blue(int)} to extract the blue component</li>
 * </ul>
 *
 * <h3>Color longs</h3>
 * <p>Color longs are a representation introduced in
 * {@link android.os.Build.VERSION_CODES#O Android O} to store colors in different
 * {@link ColorSpace color spaces}, with more precision than color ints.</p>
 *
 * <p>A color long always defines a color using 4 components packed in a single
 * 64 bit long value. One of these components is always alpha while the other
 * three components depend on the color space's {@link ColorSpace.Model color model}.
 * The most common color model is the {@link ColorSpace.Model#RGB RGB} model in
 * which the components represent red, green and blue values.</p>
 *
 * <p class="note"><b>Component ranges:</b> the ranges defined in the tables
 * below indicate the ranges that can be encoded in a color long. They do not
 * represent the actual ranges as they may differ per color space. For instance,
 * the RGB components of a color in the {@link ColorSpace.Named#DISPLAY_P3 Display P3}
 * color space use the \([0..1]\) range. Please refer to the documentation of the
 * various {@link ColorSpace.Named color spaces} to find their respective ranges.</p>
 *
 * <p class="note"><b>Alpha range:</b> while alpha is encoded in a color long using
 * a 10 bit integer (thus using a range of \([0..1023]\)), it is converted to and
 * from \([0..1]\) float values when decoding and encoding color longs.</p>
 *
 * <p class="note"><b>sRGB color space:</b> for compatibility reasons and ease of
 * use, color longs encoding {@link ColorSpace.Named#SRGB sRGB} colors do not
 * use the same encoding as other color longs.</p>
 *
 * <table summary="Color long definition">
 *     <tr>
 *         <th>Component</th><th>Name</th><th>Size</th><th>Range</th>
 *     </tr>
 *     <tr><td colspan="4">{@link ColorSpace.Model#RGB RGB} color model</td></tr>
 *     <tr><td>R</td><td>Red</td><td>16 bits</td><td>\([-65504.0, 65504.0]\)</td></tr>
 *     <tr><td>G</td><td>Green</td><td>16 bits</td><td>\([-65504.0, 65504.0]\)</td></tr>
 *     <tr><td>B</td><td>Blue</td><td>16 bits</td><td>\([-65504.0, 65504.0]\)</td></tr>
 *     <tr><td>A</td><td>Alpha</td><td>10 bits</td><td>\([0..1023]\)</td></tr>
 *     <tr><td></td><td>Color space</td><td>6 bits</td><td>\([0..63]\)</td></tr>
 *     <tr><td colspan="4">{@link ColorSpace.Named#SRGB sRGB} color space</td></tr>
 *     <tr><td>A</td><td>Alpha</td><td>8 bits</td><td>\([0..255]\)</td></tr>
 *     <tr><td>R</td><td>Red</td><td>8 bits</td><td>\([0..255]\)</td></tr>
 *     <tr><td>G</td><td>Green</td><td>8 bits</td><td>\([0..255]\)</td></tr>
 *     <tr><td>B</td><td>Blue</td><td>8 bits</td><td>\([0..255]\)</td></tr>
 *     <tr><td>X</td><td>Unused</td><td>32 bits</td><td>\(0\)</td></tr>
 *     <tr><td colspan="4">{@link ColorSpace.Model#XYZ XYZ} color model</td></tr>
 *     <tr><td>X</td><td>X</td><td>16 bits</td><td>\([-65504.0, 65504.0]\)</td></tr>
 *     <tr><td>Y</td><td>Y</td><td>16 bits</td><td>\([-65504.0, 65504.0]\)</td></tr>
 *     <tr><td>Z</td><td>Z</td><td>16 bits</td><td>\([-65504.0, 65504.0]\)</td></tr>
 *     <tr><td>A</td><td>Alpha</td><td>10 bits</td><td>\([0..1023]\)</td></tr>
 *     <tr><td></td><td>Color space</td><td>6 bits</td><td>\([0..63]\)</td></tr>
 *     <tr><td colspan="4">{@link ColorSpace.Model#XYZ Lab} color model</td></tr>
 *     <tr><td>L</td><td>L</td><td>16 bits</td><td>\([-65504.0, 65504.0]\)</td></tr>
 *     <tr><td>a</td><td>a</td><td>16 bits</td><td>\([-65504.0, 65504.0]\)</td></tr>
 *     <tr><td>b</td><td>b</td><td>16 bits</td><td>\([-65504.0, 65504.0]\)</td></tr>
 *     <tr><td>A</td><td>Alpha</td><td>10 bits</td><td>\([0..1023]\)</td></tr>
 *     <tr><td></td><td>Color space</td><td>6 bits</td><td>\([0..63]\)</td></tr>
 *     <tr><td colspan="4">{@link ColorSpace.Model#CMYK CMYK} color model</td></tr>
 *     <tr><td colspan="4">Unsupported</td></tr>
 * </table>
 *
 * <p>The components in this table are listed in encoding order (see below),
 * which is why color longs in the RGB model are called RGBA colors (even if
 * this doesn't quite hold for the special case of sRGB colors).</p>
 *
 * <p>The color long encoding relies on half-precision float values (fp16). If you
 * wish to know more about the limitations of half-precision float values, please
 * refer to the documentation of the {@link Half} class.</p>
 *
 * <h4>Usage in code</h4>
 * <p>To avoid confusing color longs with arbitrary long values, it is a
 * good practice to annotate them with the <code>@ColorLong</code> annotation
 * found in the Android Support Library.</p>
 *
 * <h4>Encoding</h4>
 *
 * <p>Given the complex nature of color longs, it is strongly encouraged to use
 * the various methods provided by this class to encode them.</p>
 *
 * <p>The most flexible way to encode a color long is to use the method
 * {@link #pack(float, float, float, float, ColorSpace)}. This method allows you
 * to specify three color components (typically RGB), an alpha component and a
 * color space. To encode sRGB colors, use {@link #pack(float, float, float)}
 * and {@link #pack(float, float, float, float)} which are the
 * equivalent of {@link #rgb(int, int, int)} and {@link #argb(int, int, int, int)}
 * for color ints. If you simply need to convert a color int into a color long,
 * use {@link #pack(int)}.</p>
 *
 * <p>It is also possible to create a color long value by invoking the method
 * {@link #pack()} on a color instance.</p>
 *
 * <h4>Decoding</h4>
 *
 * <p>This class offers convenience methods to easily extract the components
 * of a color long:</p>
 * <ul>
 *     <li>{@link #alpha(long)} to extract the alpha component</li>
 *     <li>{@link #red(long)} to extract the red/X/L component</li>
 *     <li>{@link #green(long)} to extract the green/Y/a component</li>
 *     <li>{@link #blue(long)} to extract the blue/Z/b component</li>
 * </ul>
 *
 * <p>The values returned by these methods depend on the color space encoded
 * in the color long. The values are however typically in the \([0..1]\) range
 * for RGB colors. Please refer to the documentation of the various
 * {@link ColorSpace.Named color spaces} for the exact ranges.</p>
 *
 * <h3>Color instances</h3>
 * <p>Color instances are a representation introduced in
 * {@link android.os.Build.VERSION_CODES#O Android O} to store colors in different
 * {@link ColorSpace color spaces}, with more precision than both color ints and
 * color longs. Color instances also offer the ability to store more than 4
 * components if necessary.</p>
 *
 * <p>Colors instances are immutable and can be created using one of the various
 * <code>valueOf</code> methods. For instance:</p>
 * <pre class="prettyprint">
 * // sRGB
 * Color opaqueRed = Color.valueOf(0xffff0000); // from a color int
 * Color translucentRed = Color.valueOf(1.0f, 0.0f, 0.0f, 0.5f);
 *
 * // Wide gamut color
 * {@literal @}ColorLong long p3 = pack(1.0f, 1.0f, 0.0f, 1.0f, colorSpaceP3);
 * Color opaqueYellow = Color.valueOf(p3); // from a color long
 *
 * // CIE L*a*b* color space
 * ColorSpace lab = ColorSpace.get(ColorSpace.Named.LAB);
 * Color green = Color.valueOf(100.0f, -128.0f, 128.0f, 1.0f, lab);
 * </pre>
 *
 * <p>Color instances can be converted to color ints ({@link #toArgb()}) or
 * color longs ({@link #pack()}). They also offer easy access to their various
 * components using the following methods:</p>
 * <ul>
 *     <li>{@link #alpha()}, returns the alpha component value</li>
 *     <li>{@link #red()}, returns the red component value (or first
 *     component value in non-RGB models)</li>
 *     <li>{@link #green()}, returns the green component value (or second
 *     component value in non-RGB models)</li>
 *     <li>{@link #blue()}, returns the blue component value (or third
 *     component value in non-RGB models)</li>
 *     <li>{@link #getComponent(int)}, returns a specific component value</li>
 *     <li>{@link #getComponents()}, returns all component values as an array</li>
 * </ul>
 *
 * <h3>Color space conversions</h3>
 * <p>You can convert colors from one color space to another using
 * {@link ColorSpace#connect(ColorSpace, ColorSpace)} and its variants. However,
 * the <code>Color</code> class provides a few convenience methods to simplify
 * the process. Here is a brief description of some of them:</p>
 * <ul>
 *     <li>{@link #convert(ColorSpace)} to convert a color instance in a color
 *     space to a new color instance in a different color space</li>
 *     <li>{@link #convert(float, float, float, float, ColorSpace, ColorSpace)} to
 *     convert a color from a source color space to a destination color space</li>
 *     <li>{@link #convert(long, ColorSpace)} to convert a color long from its
 *     built-in color space to a destination color space</li>
 *     <li>{@link #convert(int, ColorSpace)} to convert a color int from sRGB
 *     to a destination color space</li>
 * </ul>
 *
 * <p>Please refere to the {@link ColorSpace} documentation for more
 * information.</p>
 *
 * <h3>Alpha and transparency</h3>
 * <p>The alpha component of a color defines the level of transparency of a
 * color. When the alpha component is 0, the color is completely transparent.
 * When the alpha is component is 1 (in the \([0..1]\) range) or 255 (in the
 * \([0..255]\) range), the color is completely opaque.</p>
 *
 * <p>The color representations described above do not use pre-multiplied
 * color components (a pre-multiplied color component is a color component
 * that has been multiplied by the value of the alpha component).
 * For instance, the color int representation of opaque red is
 * <code>0xffff0000</code>. For semi-transparent (50%) red, the
 * representation becomes <code>0x80ff0000</code>. The equivalent color
 * instance representations would be <code>(1.0, 0.0, 0.0, 1.0)</code>
 * and <code>(1.0, 0.0, 0.0, 0.5)</code>.</p>
 */
@AnyThread
public class Color {
    @ColorInt public static final int BLACK       = 0xFF000000;
    @ColorInt public static final int DKGRAY      = 0xFF444444;
    @ColorInt public static final int GRAY        = 0xFF888888;
    @ColorInt public static final int LTGRAY      = 0xFFCCCCCC;
    @ColorInt public static final int WHITE       = 0xFFFFFFFF;
    @ColorInt public static final int RED         = 0xFFFF0000;
    @ColorInt public static final int GREEN       = 0xFF00FF00;
    @ColorInt public static final int BLUE        = 0xFF0000FF;
    @ColorInt public static final int YELLOW      = 0xFFFFFF00;
    @ColorInt public static final int CYAN        = 0xFF00FFFF;
    @ColorInt public static final int MAGENTA     = 0xFFFF00FF;
    @ColorInt public static final int TRANSPARENT = 0;

    @NonNull
    @Size(min = 4, max = 5)
    private final float[] mComponents;

    @NonNull
    private final ColorSpace mColorSpace;

    /**
     * Creates a new color instance set to opaque black in the
     * {@link ColorSpace.Named#SRGB sRGB} color space.
     *
     * @see #valueOf(float, float, float)
     * @see #valueOf(float, float, float, float)
     * @see #valueOf(float, float, float, float, ColorSpace)
     * @see #valueOf(float[], ColorSpace)
     * @see #valueOf(int)
     * @see #valueOf(long)
     */
    public Color() {
        // This constructor is required for compatibility with previous APIs
        mComponents = new float[] { 0.0f, 0.0f, 0.0f, 1.0f };
        mColorSpace = ColorSpace.get(ColorSpace.Named.SRGB);
    }

    /**
     * Creates a new color instance in the {@link ColorSpace.Named#SRGB sRGB}
     * color space.
     *
     * @param r The value of the red channel, must be in [0..1] range
     * @param g The value of the green channel, must be in [0..1] range
     * @param b The value of the blue channel, must be in [0..1] range
     * @param a The value of the alpha channel, must be in [0..1] range
     */
    private Color(float r, float g, float b, float a) {
        this(r, g, b, a, ColorSpace.get(ColorSpace.Named.SRGB));
    }

    /**
     * Creates a new color instance in the specified color space. The color space
     * must have a 3 components model.
     *
     * @param r The value of the red channel, must be in the color space defined range
     * @param g The value of the green channel, must be in the color space defined range
     * @param b The value of the blue channel, must be in the color space defined range
     * @param a The value of the alpha channel, must be in [0..1] range
     * @param colorSpace This color's color space, cannot be null
     */
    private Color(float r, float g, float b, float a, @NonNull ColorSpace colorSpace) {
        mComponents = new float[] { r, g, b, a };
        mColorSpace = colorSpace;
    }

    /**
     * Creates a new color instance in the specified color space.
     *
     * @param components An array of color components, plus alpha
     * @param colorSpace This color's color space, cannot be null
     */
    private Color(@Size(min = 4, max = 5) float[] components, @NonNull ColorSpace colorSpace) {
        mComponents = components;
        mColorSpace = colorSpace;
    }

    /**
     * Returns this color's color space.
     *
     * @return A non-null instance of {@link ColorSpace}
     */
    @NonNull
    public ColorSpace getColorSpace() {
        return mColorSpace;
    }

    /**
     * Returns the color model of this color.
     *
     * @return A non-null {@link ColorSpace.Model}
     */
    public ColorSpace.Model getModel() {
        return mColorSpace.getModel();
    }

    /**
     * Indicates whether this color color is in a wide-gamut color space.
     * See {@link ColorSpace#isWideGamut()} for a definition of a wide-gamut
     * color space.
     *
     * @return True if this color is in a wide-gamut color space, false otherwise
     *
     * @see #isSrgb()
     * @see ColorSpace#isWideGamut()
     */
    public boolean isWideGamut() {
        return getColorSpace().isWideGamut();
    }

    /**
     * Indicates whether this color is in the {@link ColorSpace.Named#SRGB sRGB}
     * color space.
     *
     * @return True if this color is in the sRGB color space, false otherwise
     *
     * @see #isWideGamut()
     */
    public boolean isSrgb() {
        return getColorSpace().isSrgb();
    }

    /**
     * Returns the number of components that form a color value according
     * to this color space's color model, plus one extra component for
     * alpha.
     *
     * @return An integer between 4 and 5
     */
    @IntRange(from = 4, to = 5)
    public int getComponentCount() {
        return mColorSpace.getComponentCount() + 1;
    }

    /**
     * Packs this color into a color long. See the documentation of this class
     * for a description of the color long format.
     *
     * @return A color long
     *
     * @throws IllegalArgumentException If this color's color space has the id
     * {@link ColorSpace#MIN_ID} or if this color has more than 4 components
     */
    @ColorLong
    public long pack() {
        return pack(mComponents[0], mComponents[1], mComponents[2], mComponents[3], mColorSpace);
    }

    /**
     * Converts this color from its color space to the specified color space.
     * The conversion is done using the default rendering intent as specified
     * by {@link ColorSpace#connect(ColorSpace, ColorSpace)}.
     *
     * @param colorSpace The destination color space, cannot be null
     *
     * @return A non-null color instance in the specified color space
     */
    @NonNull
    public Color convert(@NonNull ColorSpace colorSpace) {
        ColorSpace.Connector connector = ColorSpace.connect(mColorSpace, colorSpace);
        float[] color = new float[] {
                mComponents[0], mComponents[1], mComponents[2], mComponents[3]
        };
        connector.transform(color);
        return new Color(color, colorSpace);
    }

    /**
     * Converts this color to an ARGB color int. A color int is always in
     * the {@link ColorSpace.Named#SRGB sRGB} color space. This implies
     * a color space conversion is applied if needed.
     *
     * @return An ARGB color in the sRGB color space
     */
    @ColorInt
    public int toArgb() {
        if (mColorSpace.isSrgb()) {
            return ((int) (mComponents[3] * 255.0f + 0.5f) << 24) |
                   ((int) (mComponents[0] * 255.0f + 0.5f) << 16) |
                   ((int) (mComponents[1] * 255.0f + 0.5f) <<  8) |
                    (int) (mComponents[2] * 255.0f + 0.5f);
        }

        float[] color = new float[] {
                mComponents[0], mComponents[1], mComponents[2], mComponents[3]
        };
        // The transformation saturates the output
        ColorSpace.connect(mColorSpace).transform(color);

        return ((int) (color[3] * 255.0f + 0.5f) << 24) |
               ((int) (color[0] * 255.0f + 0.5f) << 16) |
               ((int) (color[1] * 255.0f + 0.5f) <<  8) |
                (int) (color[2] * 255.0f + 0.5f);
    }

    /**
     * <p>Returns the value of the red component in the range defined by this
     * color's color space (see {@link ColorSpace#getMinValue(int)} and
     * {@link ColorSpace#getMaxValue(int)}).</p>
     *
     * <p>If this color's color model is not {@link ColorSpace.Model#RGB RGB},
     * calling this method is equivalent to <code>getComponent(0)</code>.</p>
     *
     * @see #alpha()
     * @see #red()
     * @see #green
     * @see #getComponents()
     */
    public float red() {
        return mComponents[0];
    }

    /**
     * <p>Returns the value of the green component in the range defined by this
     * color's color space (see {@link ColorSpace#getMinValue(int)} and
     * {@link ColorSpace#getMaxValue(int)}).</p>
     *
     * <p>If this color's color model is not {@link ColorSpace.Model#RGB RGB},
     * calling this method is equivalent to <code>getComponent(1)</code>.</p>
     *
     * @see #alpha()
     * @see #red()
     * @see #green
     * @see #getComponents()
     */
    public float green() {
        return mComponents[1];
    }

    /**
     * <p>Returns the value of the blue component in the range defined by this
     * color's color space (see {@link ColorSpace#getMinValue(int)} and
     * {@link ColorSpace#getMaxValue(int)}).</p>
     *
     * <p>If this color's color model is not {@link ColorSpace.Model#RGB RGB},
     * calling this method is equivalent to <code>getComponent(2)</code>.</p>
     *
     * @see #alpha()
     * @see #red()
     * @see #green
     * @see #getComponents()
     */
    public float blue() {
        return mComponents[2];
    }

    /**
     * Returns the value of the alpha component in the range \([0..1]\).
     * Calling this method is equivalent to
     * <code>getComponent(getComponentCount())</code>.
     *
     * @see #red()
     * @see #green()
     * @see #blue()
     * @see #getComponents()
     * @see #getComponent(int)
     */
    public float alpha() {
        return mComponents[mComponents.length - 1];
    }

    /**
     * Returns this color's components as a new array. The last element of the
     * array is always the alpha component.
     *
     * @return A new, non-null array whose size is equal to {@link #getComponentCount()}
     *
     * @see #getComponent(int)
     */
    @NonNull
    @Size(min = 4, max = 5)
    public float[] getComponents() {
        return Arrays.copyOf(mComponents, mColorSpace.getComponentCount() + 1);
    }

    /**
     * <p>Returns the value of the specified component in the range defined by
     * this color's color space (see {@link ColorSpace#getMinValue(int)} and
     * {@link ColorSpace#getMaxValue(int)}).</p>
     *
     * <p>If the requested component index is {@link #getComponentCount()},
     * this method returns the alpha component, always in the range
     * \([0..1\).</p>
     *
     * @see #getComponents()
     *
     * @throws ArrayIndexOutOfBoundsException If the specified component index
     * is < 0 or >= {@link #getComponentCount()}
     */
    public float getComponent(@IntRange(from = 0, to = 4) int component) {
        return mComponents[component];
    }

    /**
     * <p>Returns the relative luminance of this color.</p>
     *
     * <p>Based on the formula for relative luminance defined in WCAG 2.0,
     * W3C Recommendation 11 December 2008.</p>
     *
     * @return A value between 0 (darkest black) and 1 (lightest white)
     *
     * @throws IllegalArgumentException If the this color's color space
     * does not use the {@link ColorSpace.Model#RGB RGB} color model
     */
    public float luminance() {
        if (mColorSpace.getModel() != ColorSpace.Model.RGB) {
            throw new IllegalArgumentException("The specified color must be encoded in an RGB " +
                    "color space. The supplied color space is " + mColorSpace.getModel());
        }

        DoubleUnaryOperator eotf = ((ColorSpace.Rgb) mColorSpace).getEotf();
        double r = eotf.applyAsDouble(mComponents[0]);
        double g = eotf.applyAsDouble(mComponents[1]);
        double b = eotf.applyAsDouble(mComponents[2]);

        return saturate((float) ((0.2126 * r) + (0.7152 * g) + (0.0722 * b)));
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        Color color = (Color) o;

        //noinspection SimplifiableIfStatement
        if (!Arrays.equals(mComponents, color.mComponents)) return false;
        return mColorSpace.equals(color.mColorSpace);
    }

    @Override
    public int hashCode() {
        int result = Arrays.hashCode(mComponents);
        result = 31 * result + mColorSpace.hashCode();
        return result;
    }

    /**
     * <p>Returns a string representation of the object. This method returns
     * a string equal to the value of:</p>
     *
     * <pre class="prettyprint">
     * "Color(" + r + ", " + g + ", " + b + ", " + a +
     *         ", " + getColorSpace().getName + ')'
     * </pre>
     *
     * <p>For instance, the string representation of opaque black in the sRGB
     * color space is equal to the following value:</p>
     *
     * <pre>
     * Color(0.0, 0.0, 0.0, 1.0, sRGB IEC61966-2.1)
     * </pre>
     *
     * @return A non-null string representation of the object
     */
    @Override
    @NonNull
    public String toString() {
        StringBuilder b = new StringBuilder("Color(");
        for (float c : mComponents) {
            b.append(c).append(", ");
        }
        b.append(mColorSpace.getName());
        b.append(')');
        return b.toString();
    }

    /**
     * Returns the color space encoded in the specified color long.
     *
     * @param color The color long whose color space to extract
     * @return A non-null color space instance. If the color long encodes
     * an unknown or invalid color space, the {@link ColorSpace.Named#SRGB sRGB}
     * color space is returned
     *
     * @see #red(long)
     * @see #green(long)
     * @see #blue(long)
     * @see #alpha(long)
     */
    @NonNull
    public static ColorSpace colorSpace(@ColorLong long color) {
        return ColorSpace.get((int) (color & 0x3fL));
    }

    /**
     * Returns the red component encoded in the specified color long.
     * The range of the returned value depends on the color space
     * associated with the specified color. The color space can be
     * queried by calling {@link #colorSpace(long)}.
     *
     * @param color The color long whose red channel to extract
     * @return A float value with a range defined by the specified color's
     * color space
     *
     * @see #colorSpace(long)
     * @see #green(long)
     * @see #blue(long)
     * @see #alpha(long)
     */
    public static float red(@ColorLong long color) {
        if ((color & 0x3fL) == 0L) return ((color >> 48) & 0xff) / 255.0f;
        return Half.toFloat((short) ((color >> 48) & 0xffff));
    }

    /**
     * Returns the green component encoded in the specified color long.
     * The range of the returned value depends on the color space
     * associated with the specified color. The color space can be
     * queried by calling {@link #colorSpace(long)}.
     *
     * @param color The color long whose green channel to extract
     * @return A float value with a range defined by the specified color's
     * color space
     *
     * @see #colorSpace(long)
     * @see #red(long)
     * @see #blue(long)
     * @see #alpha(long)
     */
    public static float green(@ColorLong long color) {
        if ((color & 0x3fL) == 0L) return ((color >> 40) & 0xff) / 255.0f;
        return Half.toFloat((short) ((color >> 32) & 0xffff));
    }

    /**
     * Returns the blue component encoded in the specified color long.
     * The range of the returned value depends on the color space
     * associated with the specified color. The color space can be
     * queried by calling {@link #colorSpace(long)}.
     *
     * @param color The color long whose blue channel to extract
     * @return A float value with a range defined by the specified color's
     * color space
     *
     * @see #colorSpace(long)
     * @see #red(long)
     * @see #green(long)
     * @see #alpha(long)
     */
    public static float blue(@ColorLong long color) {
        if ((color & 0x3fL) == 0L) return ((color >> 32) & 0xff) / 255.0f;
        return Half.toFloat((short) ((color >> 16) & 0xffff));
    }

    /**
     * Returns the alpha component encoded in the specified color long.
     * The returned value is always in the range \([0..1]\).
     *
     * @param color The color long whose blue channel to extract
     * @return A float value in the range \([0..1]\)
     *
     * @see #colorSpace(long)
     * @see #red(long)
     * @see #green(long)
     * @see #blue(long)
     */
    public static float alpha(@ColorLong long color) {
        if ((color & 0x3fL) == 0L) return ((color >> 56) & 0xff) / 255.0f;
        return ((color >> 6) & 0x3ff) / 1023.0f;
    }

    /**
     * Indicates whether the specified color is in the
     * {@link ColorSpace.Named#SRGB sRGB} color space.
     *
     * @param color The color to test
     * @return True if the color is in the sRGB color space, false otherwise
     *
     * @see #isInColorSpace(long, ColorSpace)
     * @see #isWideGamut(long)
     */
    public static boolean isSrgb(@ColorLong long color) {
        return colorSpace(color).isSrgb();
    }

    /**
     * Indicates whether the specified color is in a wide-gamut color space.
     * See {@link ColorSpace#isWideGamut()} for a definition of a wide-gamut
     * color space.
     *
     * @param color The color to test
     * @return True if the color is in a wide-gamut color space, false otherwise
     *
     * @see #isInColorSpace(long, ColorSpace)
     * @see #isSrgb(long)
     * @see ColorSpace#isWideGamut()
     */
    public static boolean isWideGamut(@ColorLong long color) {
        return colorSpace(color).isWideGamut();
    }

    /**
     * Indicates whether the specified color is in the specified color space.
     *
     * @param color The color to test
     * @param colorSpace The color space to test against
     * @return True if the color is in the specified color space, false otherwise
     *
     * @see #isSrgb(long)
     * @see #isWideGamut(long)
     */
    public static boolean isInColorSpace(@ColorLong long color, @NonNull ColorSpace colorSpace) {
        return (int) (color & 0x3fL) == colorSpace.getId();
    }

    /**
     * Converts the specified color long to an ARGB color int. A color int is
     * always in the {@link ColorSpace.Named#SRGB sRGB} color space. This implies
     * a color space conversion is applied if needed.
     *
     * @return An ARGB color in the sRGB color space
     */
    @ColorInt
    public static int toArgb(@ColorLong long color) {
        if ((color & 0x3fL) == 0L) return (int) (color >> 32);

        float r = red(color);
        float g = green(color);
        float b = blue(color);
        float a = alpha(color);

        // The transformation saturates the output
        float[] c = ColorSpace.connect(colorSpace(color)).transform(r, g, b);

        return ((int) (a    * 255.0f + 0.5f) << 24) |
               ((int) (c[0] * 255.0f + 0.5f) << 16) |
               ((int) (c[1] * 255.0f + 0.5f) <<  8) |
                (int) (c[2] * 255.0f + 0.5f);
    }

    /**
     * Creates a new <code>Color</code> instance from an ARGB color int.
     * The resulting color is in the {@link ColorSpace.Named#SRGB sRGB}
     * color space.
     *
     * @param color The ARGB color int to create a <code>Color</code> from
     * @return A non-null instance of {@link Color}
     */
    @NonNull
    public static Color valueOf(@ColorInt int color) {
        float r = ((color >> 16) & 0xff) / 255.0f;
        float g = ((color >>  8) & 0xff) / 255.0f;
        float b = ((color      ) & 0xff) / 255.0f;
        float a = ((color >> 24) & 0xff) / 255.0f;
        return new Color(r, g, b, a, ColorSpace.get(ColorSpace.Named.SRGB));
    }

    /**
     * Creates a new <code>Color</code> instance from a color long.
     * The resulting color is in the same color space as the specified color long.
     *
     * @param color The color long to create a <code>Color</code> from
     * @return A non-null instance of {@link Color}
     */
    @NonNull
    public static Color valueOf(@ColorLong long color) {
        return new Color(red(color), green(color), blue(color), alpha(color), colorSpace(color));
    }

    /**
     * Creates a new opaque <code>Color</code> in the {@link ColorSpace.Named#SRGB sRGB}
     * color space with the specified red, green and blue component values. The component
     * values must be in the range \([0..1]\).
     *
     * @param r The red component of the opaque sRGB color to create, in \([0..1]\)
     * @param g The green component of the opaque sRGB color to create, in \([0..1]\)
     * @param b The blue component of the opaque sRGB color to create, in \([0..1]\)
     * @return A non-null instance of {@link Color}
     */
    @NonNull
    public static Color valueOf(float r, float g, float b) {
        return new Color(r, g, b, 1.0f);
    }

    /**
     * Creates a new <code>Color</code> in the {@link ColorSpace.Named#SRGB sRGB}
     * color space with the specified red, green, blue and alpha component values.
     * The component values must be in the range \([0..1]\).
     *
     * @param r The red component of the sRGB color to create, in \([0..1]\)
     * @param g The green component of the sRGB color to create, in \([0..1]\)
     * @param b The blue component of the sRGB color to create, in \([0..1]\)
     * @param a The alpha component of the sRGB color to create, in \([0..1]\)
     * @return A non-null instance of {@link Color}
     */
    @NonNull
    public static Color valueOf(float r, float g, float b, float a) {
        return new Color(saturate(r), saturate(g), saturate(b), saturate(a));
    }

    /**
     * Creates a new <code>Color</code> in the specified color space with the
     * specified red, green, blue and alpha component values. The range of the
     * components is defined by {@link ColorSpace#getMinValue(int)} and
     * {@link ColorSpace#getMaxValue(int)}. The values passed to this method
     * must be in the proper range.
     *
     * @param r The red component of the color to create
     * @param g The green component of the color to create
     * @param b The blue component of the color to create
     * @param a The alpha component of the color to create, in \([0..1]\)
     * @param colorSpace The color space of the color to create
     * @return A non-null instance of {@link Color}
     *
     * @throws IllegalArgumentException If the specified color space uses a
     * color model with more than 3 components
     */
    @NonNull
    public static Color valueOf(float r, float g, float b, float a, @NonNull ColorSpace colorSpace) {
        if (colorSpace.getComponentCount() > 3) {
            throw new IllegalArgumentException("The specified color space must use a color model " +
                    "with at most 3 color components");
        }
        return new Color(r, g, b, a, colorSpace);
    }

    /**
     * <p>Creates a new <code>Color</code> in the specified color space with the
     * specified component values. The range of the components is defined by
     * {@link ColorSpace#getMinValue(int)} and {@link ColorSpace#getMaxValue(int)}.
     * The values passed to this method must be in the proper range. The alpha
     * component is always in the range \([0..1]\).</p>
     *
     * <p>The length of the array of components must be at least
     * <code>{@link ColorSpace#getComponentCount()} + 1</code>. The component at index
     * {@link ColorSpace#getComponentCount()} is always alpha.</p>
     *
     * @param components The components of the color to create, with alpha as the last component
     * @param colorSpace The color space of the color to create
     * @return A non-null instance of {@link Color}
     *
     * @throws IllegalArgumentException If the array of components is smaller than
     * required by the color space
     */
    @NonNull
    public static Color valueOf(@NonNull @Size(min = 4, max = 5) float[] components,
            @NonNull ColorSpace colorSpace) {
        if (components.length < colorSpace.getComponentCount() + 1) {
            throw new IllegalArgumentException("Received a component array of length " +
                    components.length + " but the color model requires " +
                    (colorSpace.getComponentCount() + 1) + " (including alpha)");
        }
        return new Color(Arrays.copyOf(components, colorSpace.getComponentCount() + 1), colorSpace);
    }

    /**
     * Converts the specified ARGB color int to an RGBA color long in the sRGB
     * color space. See the documentation of this class for a description of
     * the color long format.
     *
     * @param color The ARGB color int to convert to an RGBA color long in sRGB
     *
     * @return A color long
     */
    @ColorLong
    public static long pack(@ColorInt int color) {
        return (color & 0xffffffffL) << 32;
    }

    /**
     * Packs the sRGB color defined by the specified red, green and blue component
     * values into an RGBA color long in the sRGB color space. The alpha component
     * is set to 1.0. See the documentation of this class for a description of the
     * color long format.
     *
     * @param red The red component of the sRGB color to create, in \([0..1]\)
     * @param green The green component of the sRGB color to create, in \([0..1]\)
     * @param blue The blue component of the sRGB color to create, in \([0..1]\)
     *
     * @return A color long
     */
    @ColorLong
    public static long pack(float red, float green, float blue) {
        return pack(red, green, blue, 1.0f, ColorSpace.get(ColorSpace.Named.SRGB));
    }

    /**
     * Packs the sRGB color defined by the specified red, green, blue and alpha
     * component values into an RGBA color long in the sRGB color space. See the
     * documentation of this class for a description of the color long format.
     *
     * @param red The red component of the sRGB color to create, in \([0..1]\)
     * @param green The green component of the sRGB color to create, in \([0..1]\)
     * @param blue The blue component of the sRGB color to create, in \([0..1]\)
     * @param alpha The alpha component of the sRGB color to create, in \([0..1]\)
     *
     * @return A color long
     */
    @ColorLong
    public static long pack(float red, float green, float blue, float alpha) {
        return pack(red, green, blue, alpha, ColorSpace.get(ColorSpace.Named.SRGB));
    }

    /**
     * <p>Packs the 3 component color defined by the specified red, green, blue and
     * alpha component values into a color long in the specified color space. See the
     * documentation of this class for a description of the color long format.</p>
     *
     * <p>The red, green and blue components must be in the range defined by the
     * specified color space. See {@link ColorSpace#getMinValue(int)} and
     * {@link ColorSpace#getMaxValue(int)}.</p>
     *
     * @param red The red component of the color to create
     * @param green The green component of the color to create
     * @param blue The blue component of the color to create
     * @param alpha The alpha component of the color to create, in \([0..1]\)
     *
     * @return A color long
     *
     * @throws IllegalArgumentException If the color space's id is {@link ColorSpace#MIN_ID}
     * or if the color space's color model has more than 3 components
     */
    @ColorLong
    public static long pack(float red, float green, float blue, float alpha,
            @NonNull ColorSpace colorSpace) {
        if (colorSpace.isSrgb()) {
            int argb =
                    ((int) (alpha * 255.0f + 0.5f) << 24) |
                    ((int) (red   * 255.0f + 0.5f) << 16) |
                    ((int) (green * 255.0f + 0.5f) <<  8) |
                     (int) (blue  * 255.0f + 0.5f);
            return (argb & 0xffffffffL) << 32;
        }

        int id = colorSpace.getId();
        if (id == ColorSpace.MIN_ID) {
            throw new IllegalArgumentException(
                    "Unknown color space, please use a color space returned by ColorSpace.get()");
        }
        if (colorSpace.getComponentCount() > 3) {
            throw new IllegalArgumentException(
                    "The color space must use a color model with at most 3 components");
        }

        @HalfFloat short r = Half.toHalf(red);
        @HalfFloat short g = Half.toHalf(green);
        @HalfFloat short b = Half.toHalf(blue);

        int a = (int) (Math.max(0.0f, Math.min(alpha, 1.0f)) * 1023.0f + 0.5f);

        // Suppress sign extension
        return  (r & 0xffffL) << 48 |
                (g & 0xffffL) << 32 |
                (b & 0xffffL) << 16 |
                (a & 0x3ffL ) <<  6 |
                id & 0x3fL;
    }

    /**
     * Converts the specified ARGB color int from the {@link ColorSpace.Named#SRGB sRGB}
     * color space into the specified destination color space. The resulting color is
     * returned as a color long. See the documentation of this class for a description
     * of the color long format.
     *
     * @param color The sRGB color int to convert
     * @param colorSpace The destination color space
     * @return A color long in the destination color space
     */
    @ColorLong
    public static long convert(@ColorInt int color, @NonNull ColorSpace colorSpace) {
        float r = ((color >> 16) & 0xff) / 255.0f;
        float g = ((color >>  8) & 0xff) / 255.0f;
        float b = ((color      ) & 0xff) / 255.0f;
        float a = ((color >> 24) & 0xff) / 255.0f;
        ColorSpace source = ColorSpace.get(ColorSpace.Named.SRGB);
        return convert(r, g, b, a, source, colorSpace);
    }

    /**
     * <p>Converts the specified color long from its color space into the specified
     * destination color space. The resulting color is returned as a color long. See
     * the documentation of this class for a description of the color long format.</p>
     *
     * <p>When converting several colors in a row, it is recommended to use
     * {@link #convert(long, ColorSpace.Connector)} instead to
     * avoid the creation of a {@link ColorSpace.Connector} on every invocation.</p>
     *
     * @param color The color long to convert
     * @param colorSpace The destination color space
     * @return A color long in the destination color space
     */
    @ColorLong
    public static long convert(@ColorLong long color, @NonNull ColorSpace colorSpace) {
        float r = red(color);
        float g = green(color);
        float b = blue(color);
        float a = alpha(color);
        ColorSpace source = colorSpace(color);
        return convert(r, g, b, a, source, colorSpace);
    }

    /**
     * <p>Converts the specified 3 component color from the source color space to the
     * destination color space. The resulting color is returned as a color long. See
     * the documentation of this class for a description of the color long format.</p>
     *
     * <p>When converting multiple colors in a row, it is recommended to use
     * {@link #convert(float, float, float, float, ColorSpace.Connector)} instead to
     * avoid the creation of a {@link ColorSpace.Connector} on every invocation.</p>
     *
     * <p>The red, green and blue components must be in the range defined by the
     * specified color space. See {@link ColorSpace#getMinValue(int)} and
     * {@link ColorSpace#getMaxValue(int)}.</p>
     *
     * @param r The red component of the color to convert
     * @param g The green component of the color to convert
     * @param b The blue component of the color to convert
     * @param a The alpha component of the color to convert, in \([0..1]\)
     * @param source The source color space, cannot be null
     * @param destination The destination color space, cannot be null
     * @return A color long in the destination color space
     *
     * @see #convert(float, float, float, float, ColorSpace.Connector)
     */
    @ColorLong
    public static long convert(float r, float g, float b, float a,
            @NonNull ColorSpace source, @NonNull ColorSpace destination) {
        float[] c = ColorSpace.connect(source, destination).transform(r, g, b);
        return pack(c[0], c[1], c[2], a, destination);
    }

    /**
     * <p>Converts the specified color long from a color space to another using the
     * specified color space {@link ColorSpace.Connector connector}. The resulting
     * color is returned as a color long. See the documentation of this class for a
     * description of the color long format.</p>
     *
     * <p>When converting several colors in a row, this method is preferable to
     * {@link #convert(long, ColorSpace)} as it prevents a new connector from being
     * created on every invocation.</p>
     *
     * <p class="note">The connector's source color space should match the color long's
     * color space.</p>
     *
     * @param color The color long to convert
     * @param connector A color space connector, cannot be null
     * @return A color long in the destination color space of the connector
     */
    @ColorLong
    public static long convert(@ColorLong long color, @NonNull ColorSpace.Connector connector) {
        float r = red(color);
        float g = green(color);
        float b = blue(color);
        float a = alpha(color);
        return convert(r, g, b, a, connector);
    }

    /**
     * <p>Converts the specified 3 component color from a color space to another using
     * the specified color space {@link ColorSpace.Connector connector}. The resulting
     * color is returned as a color long. See the documentation of this class for a
     * description of the color long format.</p>
     *
     * <p>When converting several colors in a row, this method is preferable to
     * {@link #convert(float, float, float, float, ColorSpace, ColorSpace)} as
     * it prevents a new connector from being created on every invocation.</p>
     *
     * <p>The red, green and blue components must be in the range defined by the
     * source color space of the connector. See {@link ColorSpace#getMinValue(int)}
     * and {@link ColorSpace#getMaxValue(int)}.</p>
     *
     * @param r The red component of the color to convert
     * @param g The green component of the color to convert
     * @param b The blue component of the color to convert
     * @param a The alpha component of the color to convert, in \([0..1]\)
     * @param connector A color space connector, cannot be null
     * @return A color long in the destination color space of the connector
     *
     * @see #convert(float, float, float, float, ColorSpace, ColorSpace)
     */
    @ColorLong
    public static long convert(float r, float g, float b, float a,
            @NonNull ColorSpace.Connector connector) {
        float[] c = connector.transform(r, g, b);
        return pack(c[0], c[1], c[2], a, connector.getDestination());
    }

    /**
     * <p>Returns the relative luminance of a color.</p>
     *
     * <p>Based on the formula for relative luminance defined in WCAG 2.0,
     * W3C Recommendation 11 December 2008.</p>
     *
     * @return A value between 0 (darkest black) and 1 (lightest white)
     *
     * @throws IllegalArgumentException If the specified color's color space
     * does not use the {@link ColorSpace.Model#RGB RGB} color model
     */
    public static float luminance(@ColorLong long color) {
        ColorSpace colorSpace = colorSpace(color);
        if (colorSpace.getModel() != ColorSpace.Model.RGB) {
            throw new IllegalArgumentException("The specified color must be encoded in an RGB " +
                    "color space. The supplied color space is " + colorSpace.getModel());
        }

        DoubleUnaryOperator eotf = ((ColorSpace.Rgb) colorSpace).getEotf();
        double r = eotf.applyAsDouble(red(color));
        double g = eotf.applyAsDouble(green(color));
        double b = eotf.applyAsDouble(blue(color));

        return saturate((float) ((0.2126 * r) + (0.7152 * g) + (0.0722 * b)));
    }

    private static float saturate(float v) {
        return v <= 0.0f ? 0.0f : (v >= 1.0f ? 1.0f : v);
    }

    /**
     * Return the alpha component of a color int. This is the same as saying
     * color >>> 24
     */
    @IntRange(from = 0, to = 255)
    public static int alpha(int color) {
        return color >>> 24;
    }

    /**
     * Return the red component of a color int. This is the same as saying
     * (color >> 16) & 0xFF
     */
    @IntRange(from = 0, to = 255)
    public static int red(int color) {
        return (color >> 16) & 0xFF;
    }

    /**
     * Return the green component of a color int. This is the same as saying
     * (color >> 8) & 0xFF
     */
    @IntRange(from = 0, to = 255)
    public static int green(int color) {
        return (color >> 8) & 0xFF;
    }

    /**
     * Return the blue component of a color int. This is the same as saying
     * color & 0xFF
     */
    @IntRange(from = 0, to = 255)
    public static int blue(int color) {
        return color & 0xFF;
    }

    /**
     * Return a color-int from red, green, blue components.
     * The alpha component is implicitly 255 (fully opaque).
     * These component values should be \([0..255]\), but there is no
     * range check performed, so if they are out of range, the
     * returned color is undefined.
     *
     * @param red  Red component \([0..255]\) of the color
     * @param green Green component \([0..255]\) of the color
     * @param blue  Blue component \([0..255]\) of the color
     */
    @ColorInt
    public static int rgb(
            @IntRange(from = 0, to = 255) int red,
            @IntRange(from = 0, to = 255) int green,
            @IntRange(from = 0, to = 255) int blue) {
        return 0xff000000 | (red << 16) | (green << 8) | blue;
    }

    /**
     * Return a color-int from red, green, blue float components
     * in the range \([0..1]\). The alpha component is implicitly
     * 1.0 (fully opaque). If the components are out of range, the
     * returned color is undefined.
     *
     * @param red Red component \([0..1]\) of the color
     * @param green Green component \([0..1]\) of the color
     * @param blue Blue component \([0..1]\) of the color
     */
    @ColorInt
    public static int rgb(float red, float green, float blue) {
        return 0xff000000 |
               ((int) (red   * 255.0f + 0.5f) << 16) |
               ((int) (green * 255.0f + 0.5f) <<  8) |
                (int) (blue  * 255.0f + 0.5f);
    }

    /**
     * Return a color-int from alpha, red, green, blue components.
     * These component values should be \([0..255]\), but there is no
     * range check performed, so if they are out of range, the
     * returned color is undefined.
     * @param alpha Alpha component \([0..255]\) of the color
     * @param red Red component \([0..255]\) of the color
     * @param green Green component \([0..255]\) of the color
     * @param blue Blue component \([0..255]\) of the color
     */
    @ColorInt
    public static int argb(
            @IntRange(from = 0, to = 255) int alpha,
            @IntRange(from = 0, to = 255) int red,
            @IntRange(from = 0, to = 255) int green,
            @IntRange(from = 0, to = 255) int blue) {
        return (alpha << 24) | (red << 16) | (green << 8) | blue;
    }

    /**
     * Return a color-int from alpha, red, green, blue float components
     * in the range \([0..1]\). If the components are out of range, the
     * returned color is undefined.
     *
     * @param alpha Alpha component \([0..1]\) of the color
     * @param red Red component \([0..1]\) of the color
     * @param green Green component \([0..1]\) of the color
     * @param blue Blue component \([0..1]\) of the color
     */
    @ColorInt
    public static int argb(float alpha, float red, float green, float blue) {
        return ((int) (alpha * 255.0f + 0.5f) << 24) |
               ((int) (red   * 255.0f + 0.5f) << 16) |
               ((int) (green * 255.0f + 0.5f) <<  8) |
                (int) (blue  * 255.0f + 0.5f);
    }

    /**
     * Returns the relative luminance of a color.
     * <p>
     * Assumes sRGB encoding. Based on the formula for relative luminance
     * defined in WCAG 2.0, W3C Recommendation 11 December 2008.
     *
     * @return a value between 0 (darkest black) and 1 (lightest white)
     */
    public static float luminance(@ColorInt int color) {
        ColorSpace.Rgb cs = (ColorSpace.Rgb) ColorSpace.get(ColorSpace.Named.SRGB);
        DoubleUnaryOperator eotf = cs.getEotf();

        double r = eotf.applyAsDouble(red(color) / 255.0);
        double g = eotf.applyAsDouble(green(color) / 255.0);
        double b = eotf.applyAsDouble(blue(color) / 255.0);

        return (float) ((0.2126 * r) + (0.7152 * g) + (0.0722 * b));
    }

    /**
     * </p>Parse the color string, and return the corresponding color-int.
     * If the string cannot be parsed, throws an IllegalArgumentException
     * exception. Supported formats are:</p>
     *
     * <ul>
     *   <li><code>#RRGGBB</code></li>
     *   <li><code>#AARRGGBB</code></li>
     * </ul>
     *
     * <p>The following names are also accepted: <code>red</code>, <code>blue</code>,
     * <code>green</code>, <code>black</code>, <code>white</code>, <code>gray</code>,
     * <code>cyan</code>, <code>magenta</code>, <code>yellow</code>, <code>lightgray</code>,
     * <code>darkgray</code>, <code>grey</code>, <code>lightgrey</code>, <code>darkgrey</code>,
     * <code>aqua</code>, <code>fuchsia</code>, <code>lime</code>, <code>maroon</code>,
     * <code>navy</code>, <code>olive</code>, <code>purple</code>, <code>silver</code>,
     * and <code>teal</code>.</p>
     */
    @ColorInt
    public static int parseColor(@Size(min=1) String colorString) {
        if (colorString.charAt(0) == '#') {
            // Use a long to avoid rollovers on #ffXXXXXX
            long color = Long.parseLong(colorString.substring(1), 16);
            if (colorString.length() == 7) {
                // Set the alpha value
                color |= 0x00000000ff000000;
            } else if (colorString.length() != 9) {
                throw new IllegalArgumentException("Unknown color");
            }
            return (int)color;
        } else {
            Integer color = sColorNameMap.get(colorString.toLowerCase(Locale.ROOT));
            if (color != null) {
                return color;
            }
        }
        throw new IllegalArgumentException("Unknown color");
    }

    /**
     * Convert RGB components to HSV.
     * <ul>
     *   <li><code>hsv[0]</code> is Hue \([0..360[\)</li>
     *   <li><code>hsv[1]</code> is Saturation \([0...1]\)</li>
     *   <li><code>hsv[2]</code> is Value \([0...1]\)</li>
     * </ul>
     * @param red  red component value \([0..255]\)
     * @param green  green component value \([0..255]\)
     * @param blue  blue component value \([0..255]\)
     * @param hsv  3 element array which holds the resulting HSV components.
     */
    public static void RGBToHSV(
            @IntRange(from = 0, to = 255) int red,
            @IntRange(from = 0, to = 255) int green,
            @IntRange(from = 0, to = 255) int blue, @Size(3) float hsv[]) {
        if (hsv.length < 3) {
            throw new RuntimeException("3 components required for hsv");
        }
        nativeRGBToHSV(red, green, blue, hsv);
    }

    /**
     * Convert the ARGB color to its HSV components.
     * <ul>
     *   <li><code>hsv[0]</code> is Hue \([0..360[\)</li>
     *   <li><code>hsv[1]</code> is Saturation \([0...1]\)</li>
     *   <li><code>hsv[2]</code> is Value \([0...1]\)</li>
     * </ul>
     * @param color the argb color to convert. The alpha component is ignored.
     * @param hsv  3 element array which holds the resulting HSV components.
     */
    public static void colorToHSV(@ColorInt int color, @Size(3) float hsv[]) {
        RGBToHSV((color >> 16) & 0xFF, (color >> 8) & 0xFF, color & 0xFF, hsv);
    }

    /**
     * Convert HSV components to an ARGB color. Alpha set to 0xFF.
     * <ul>
     *   <li><code>hsv[0]</code> is Hue \([0..360[\)</li>
     *   <li><code>hsv[1]</code> is Saturation \([0...1]\)</li>
     *   <li><code>hsv[2]</code> is Value \([0...1]\)</li>
     * </ul>
     * If hsv values are out of range, they are pinned.
     * @param hsv  3 element array which holds the input HSV components.
     * @return the resulting argb color
    */
    @ColorInt
    public static int HSVToColor(@Size(3) float hsv[]) {
        return HSVToColor(0xFF, hsv);
    }

    /**
     * Convert HSV components to an ARGB color. The alpha component is passed
     * through unchanged.
     * <ul>
     *   <li><code>hsv[0]</code> is Hue \([0..360[\)</li>
     *   <li><code>hsv[1]</code> is Saturation \([0...1]\)</li>
     *   <li><code>hsv[2]</code> is Value \([0...1]\)</li>
     * </ul>
     * If hsv values are out of range, they are pinned.
     * @param alpha the alpha component of the returned argb color.
     * @param hsv  3 element array which holds the input HSV components.
     * @return the resulting argb color
     */
    @ColorInt
    public static int HSVToColor(@IntRange(from = 0, to = 255) int alpha, @Size(3) float hsv[]) {
        if (hsv.length < 3) {
            throw new RuntimeException("3 components required for hsv");
        }
        return nativeHSVToColor(alpha, hsv);
    }

    private static native void nativeRGBToHSV(int red, int greed, int blue, float hsv[]);
    private static native int nativeHSVToColor(int alpha, float hsv[]);

    /**
     * Converts an HTML color (named or numeric) to an integer RGB value.
     *
     * @param color Non-null color string.
     *
     * @return A color value, or {@code -1} if the color string could not be interpreted.
     *
     * @hide
     */
    @ColorInt
    public static int getHtmlColor(@NonNull String color) {
        Integer i = sColorNameMap.get(color.toLowerCase(Locale.ROOT));
        if (i != null) {
            return i;
        } else {
            try {
                return XmlUtils.convertValueToInt(color, -1);
            } catch (NumberFormatException nfe) {
                return -1;
            }
        }
    }

    private static final HashMap<String, Integer> sColorNameMap;
    static {
        sColorNameMap = new HashMap<>();
        sColorNameMap.put("black", BLACK);
        sColorNameMap.put("darkgray", DKGRAY);
        sColorNameMap.put("gray", GRAY);
        sColorNameMap.put("lightgray", LTGRAY);
        sColorNameMap.put("white", WHITE);
        sColorNameMap.put("red", RED);
        sColorNameMap.put("green", GREEN);
        sColorNameMap.put("blue", BLUE);
        sColorNameMap.put("yellow", YELLOW);
        sColorNameMap.put("cyan", CYAN);
        sColorNameMap.put("magenta", MAGENTA);
        sColorNameMap.put("aqua", 0xFF00FFFF);
        sColorNameMap.put("fuchsia", 0xFFFF00FF);
        sColorNameMap.put("darkgrey", DKGRAY);
        sColorNameMap.put("grey", GRAY);
        sColorNameMap.put("lightgrey", LTGRAY);
        sColorNameMap.put("lime", 0xFF00FF00);
        sColorNameMap.put("maroon", 0xFF800000);
        sColorNameMap.put("navy", 0xFF000080);
        sColorNameMap.put("olive", 0xFF808000);
        sColorNameMap.put("purple", 0xFF800080);
        sColorNameMap.put("silver", 0xFFC0C0C0);
        sColorNameMap.put("teal", 0xFF008080);

    }
}