// Copyright (c) Xenko contributors (https://xenko.com) and Silicon Studio Corp. (https://www.siliconstudio.co.jp)
// Distributed under the MIT license. See the LICENSE.md file in the project root for more information.
using System;
using System.Globalization;
using System.Runtime.InteropServices;
using System.Runtime.Serialization;

namespace math
{
    /// <summary>
    /// Represents a 32-bit color (4 bytes) in the form of BGRA (in byte order: B, G, R, A).
    /// </summary>
    [DataContract( Name = "ColorBGRA" )]
    [DataStyle( DataStyle.Compact )]
    [StructLayout( LayoutKind.Sequential, Size = 4 )]
    public partial struct ColorBGRA : IEquatable<ColorBGRA>, IFormattable
    {
        private const string ToStringFormat = "A:{0} R:{1} G:{2} B:{3}";

        /// <summary>
        /// The blue component of the color.
        /// </summary>
        [DataMember( Order = 0 )]
        public byte B;

        /// <summary>
        /// The green component of the color.
        /// </summary>
        [DataMember( Order = 1 )]
        public byte G;

        /// <summary>
        /// The red component of the color.
        /// </summary>
        [DataMember( Order = 2 )]
        public byte R;

        /// <summary>
        /// The alpha component of the color.
        /// </summary>
        [DataMember( Order = 3 )]
        public byte A;

        /// <summary>
        /// Initializes a new instance of the <see cref="ColorBGRA"/> struct.
        /// </summary>
        /// <param name="value">The value that will be assigned to all components.</param>
        public ColorBGRA( byte value )
        {
            A = R = G = B = value;
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="ColorBGRA"/> struct.
        /// </summary>
        /// <param name="value">The value that will be assigned to all components.</param>
        public ColorBGRA( float value )
        {
            A = R = G = B = ToByte( value );
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="ColorBGRA"/> struct.
        /// </summary>
        /// <param name="red">The red component of the color.</param>
        /// <param name="green">The green component of the color.</param>
        /// <param name="blue">The blue component of the color.</param>
        /// <param name="alpha">The alpha component of the color.</param>
        public ColorBGRA( byte red, byte green, byte blue, byte alpha )
        {
            R = red;
            G = green;
            B = blue;
            A = alpha;
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="ColorBGRA"/> struct.
        /// </summary>
        /// <param name="red">The red component of the color.</param>
        /// <param name="green">The green component of the color.</param>
        /// <param name="blue">The blue component of the color.</param>
        /// <param name="alpha">The alpha component of the color.</param>
        public ColorBGRA( float red, float green, float blue, float alpha )
        {
            R = ToByte( red );
            G = ToByte( green );
            B = ToByte( blue );
            A = ToByte( alpha );
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="ColorBGRA"/> struct.
        /// </summary>
        /// <param name="value">The red, green, blue, and alpha components of the color.</param>
        public ColorBGRA( Vec4 value )
        {
            R = ToByte( value.X );
            G = ToByte( value.Y );
            B = ToByte( value.Z );
            A = ToByte( value.W );
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="ColorBGRA"/> struct.
        /// </summary>
        /// <param name="value">The red, green, and blue components of the color.</param>
        /// <param name="alpha">The alpha component of the color.</param>
        public ColorBGRA( Vec3 value, float alpha )
        {
            R = ToByte( value.X );
            G = ToByte( value.Y );
            B = ToByte( value.Z );
            A = ToByte( alpha );
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="ColorBGRA"/> struct.
        /// </summary>
        /// <param name="bgra">A packed integer containing all four color components in BGRA order.</param>
        public ColorBGRA( uint bgra )
        {
            A = (byte)( ( bgra >> 24 ) & 255 );
            R = (byte)( ( bgra >> 16 ) & 255 );
            G = (byte)( ( bgra >> 8 ) & 255 );
            B = (byte)( bgra & 255 );
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="ColorBGRA"/> struct.
        /// </summary>
        /// <param name="bgra">A packed integer containing all four color components in BGRA.</param>
        public ColorBGRA( int bgra )
        {
            A = (byte)( ( bgra >> 24 ) & 255 );
            R = (byte)( ( bgra >> 16 ) & 255 );
            G = (byte)( ( bgra >> 8 ) & 255 );
            B = (byte)( bgra & 255 );
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="ColorBGRA"/> struct.
        /// </summary>
        /// <param name="values">The values to assign to the red, green, and blue, alpha components of the color. This must be an array with four elements.</param>
        /// <exception cref="ArgumentNullException">Thrown when <paramref name="values"/> is <c>null</c>.</exception>
        /// <exception cref="ArgumentOutOfRangeException">Thrown when <paramref name="values"/> contains more or less than four elements.</exception>
        public ColorBGRA( float[] values )
        {
            if( values == null )
                throw new ArgumentNullException( nameof( values ) );
            if( values.Length != 4 )
                throw new ArgumentOutOfRangeException( nameof( values ), "There must be four and only four input values for ColorBGRA." );

            B = ToByte( values[0] );
            G = ToByte( values[1] );
            R = ToByte( values[2] );
            A = ToByte( values[3] );
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="ColorBGRA"/> struct.
        /// </summary>
        /// <param name="values">The values to assign to the red, green, and blue, alpha components of the color. This must be an array with four elements.</param>
        /// <exception cref="ArgumentNullException">Thrown when <paramref name="values"/> is <c>null</c>.</exception>
        /// <exception cref="ArgumentOutOfRangeException">Thrown when <paramref name="values"/> contains more or less than four elements.</exception>
        public ColorBGRA( byte[] values )
        {
            if( values == null )
                throw new ArgumentNullException( nameof( values ) );
            if( values.Length != 4 )
                throw new ArgumentOutOfRangeException( nameof( values ), "There must be four and only four input values for ColorBGRA." );

            B = values[0];
            G = values[1];
            R = values[2];
            A = values[3];
        }

        /// <summary>
        /// Gets or sets the component at the specified index.
        /// </summary>
        /// <value>The value of the alpha, red, green, or blue component, depending on the index.</value>
        /// <param name="index">The index of the component to access. Use 0 for the alpha component, 1 for the red component, 2 for the green component, and 3 for the blue component.</param>
        /// <returns>The value of the component at the specified index.</returns>
        /// <exception cref="System.ArgumentOutOfRangeException">Thrown when the <paramref name="index"/> is out of the range [0, 3].</exception>
        public byte this[int index]
        {
            get
            {
                switch( index )
                {
                    case 0:
                        return B;
                    case 1:
                        return G;
                    case 2:
                        return R;
                    case 3:
                        return A;
                }

                throw new ArgumentOutOfRangeException( nameof( index ), "Indices for ColorBGRA run from 0 to 3, inclusive." );
            }

            set
            {
                switch( index )
                {
                    case 0:
                        B = value;
                        break;
                    case 1:
                        G = value;
                        break;
                    case 2:
                        R = value;
                        break;
                    case 3:
                        A = value;
                        break;
                    default:
                        throw new ArgumentOutOfRangeException( nameof( index ), "Indices for ColorBGRA run from 0 to 3, inclusive." );
                }
            }
        }

        /// <summary>
        /// Converts the color into a packed integer.
        /// </summary>
        /// <returns>A packed integer containing all four color components.</returns>
        public int ToBgra()
        {
            int value = B;
            value |= G << 8;
            value |= R << 16;
            value |= A << 24;

            return value;
        }

        /// <summary>
        /// Converts the color into a packed integer.
        /// </summary>
        /// <returns>A packed integer containing all four color components.</returns>
        public int ToRgba()
        {
            int value = R;
            value |= G << 8;
            value |= B << 16;
            value |= A << 24;

            return value;
        }

        /// <summary>
        /// Converts the color into a three component vector.
        /// </summary>
        /// <returns>A three component vector containing the red, green, and blue components of the color.</returns>
        public Vec3 ToVector3()
        {
            return new Vec3( R / 255.0f, G / 255.0f, B / 255.0f );
        }

        /// <summary>
        /// Converts the color into a three component color.
        /// </summary>
        /// <returns>A three component color containing the red, green, and blue components of the color.</returns>
        public Color3 ToColor3()
        {
            return new Color3( R / 255.0f, G / 255.0f, B / 255.0f );
        }

        /// <summary>
        /// Converts the color into a four component vector.
        /// </summary>
        /// <returns>A four component vector containing all four color components.</returns>
        public Vec4 ToVector4()
        {
            return new Vec4( R / 255.0f, G / 255.0f, B / 255.0f, A / 255.0f );
        }

        /// <summary>
        /// Creates an array containing the elements of the color.
        /// </summary>
        /// <returns>A four-element array containing the components of the color in BGRA order.</returns>
        public byte[] ToArray()
        {
            return new[] { B, G, R, A };
        }

        /// <summary>
        /// Gets the brightness.
        /// </summary>
        /// <returns>The Hue-Saturation-Brightness (HSB) saturation for this <see cref="Color"/></returns>
        public float GetBrightness()
        {
            float r = R / 255.0f;
            float g = G / 255.0f;
            float b = B / 255.0f;

            float max, min;

            max = r;
            min = r;

            if( g > max )
                max = g;
            if( b > max )
                max = b;

            if( g < min )
                min = g;
            if( b < min )
                min = b;

            return ( max + min ) / 2;
        }

        /// <summary>
        /// Gets the hue.
        /// </summary>
        /// <returns>The Hue-Saturation-Brightness (HSB) saturation for this <see cref="Color"/></returns>
        public float GetHue()
        {
            if( R == G && G == B )
                return 0; // 0 makes as good an UNDEFINED value as any

            float r = R / 255.0f;
            float g = G / 255.0f;
            float b = B / 255.0f;

            float max, min;
            float delta;
            float hue = 0.0f;

            max = r;
            min = r;

            if( g > max )
                max = g;
            if( b > max )
                max = b;

            if( g < min )
                min = g;
            if( b < min )
                min = b;

            delta = max - min;

            if( r == max )
            {
                hue = ( g - b ) / delta;
            }
            else if( g == max )
            {
                hue = 2 + ( b - r ) / delta;
            }
            else if( b == max )
            {
                hue = 4 + ( r - g ) / delta;
            }
            hue *= 60;

            if( hue < 0.0f )
            {
                hue += 360.0f;
            }
            return hue;
        }

        /// <summary>
        /// Gets the saturation.
        /// </summary>
        /// <returns>The Hue-Saturation-Brightness (HSB) saturation for this <see cref="Color"/></returns>
        public float GetSaturation()
        {
            float r = R / 255.0f;
            float g = G / 255.0f;
            float b = B / 255.0f;

            float max, min;
            float l, s = 0;

            max = r;
            min = r;

            if( g > max )
                max = g;
            if( b > max )
                max = b;

            if( g < min )
                min = g;
            if( b < min )
                min = b;

            // if max == min, then there is no color and
            // the saturation is zero.
            if( max != min )
            {
                l = ( max + min ) / 2;

                if( l <= .5 )
                {
                    s = ( max - min ) / ( max + min );
                }
                else
                {
                    s = ( max - min ) / ( 2 - max - min );
                }
            }
            return s;
        }

        /// <summary>
        /// Converts the color from a packed BGRA integer.
        /// </summary>
        /// <param name="color">A packed integer containing all four color components in BGRA order</param>
        /// <returns>A color.</returns>
        public static ColorBGRA FromBgra( int color )
        {
            return new ColorBGRA( color );
        }

        /// <summary>
        /// Converts the color from a packed BGRA integer.
        /// </summary>
        /// <param name="color">A packed integer containing all four color components in BGRA order</param>
        /// <returns>A color.</returns>
        public static ColorBGRA FromBgra( uint color )
        {
            return new ColorBGRA( color );
        }

        /// <summary>
        /// Converts the color from a packed RGBA integer.
        /// </summary>
        /// <param name="color">A packed integer containing all four color components in RGBA order</param>
        /// <returns>A color.</returns>
        public static ColorBGRA FromRgba( int color )
        {
            return new ColorBGRA( (byte)( color & 255 ), (byte)( ( color >> 8 ) & 255 ), (byte)( ( color >> 16 ) & 255 ), (byte)( ( color >> 24 ) & 255 ) );
        }

        /// <summary>
        /// Converts the color from a packed RGBA integer.
        /// </summary>
        /// <param name="color">A packed integer containing all four color components in RGBA order</param>
        /// <returns>A color.</returns>
        public static ColorBGRA FromRgba( uint color )
        {
            return FromRgba( unchecked((int)color) );
        }

        /// <summary>
        /// Adds two colors.
        /// </summary>
        /// <param name="left">The first color to add.</param>
        /// <param name="right">The second color to add.</param>
        /// <param name="result">When the method completes, completes the sum of the two colors.</param>
        public static void Add( ref ColorBGRA left, ref ColorBGRA right, out ColorBGRA result )
        {
            result.A = (byte)( left.A + right.A );
            result.R = (byte)( left.R + right.R );
            result.G = (byte)( left.G + right.G );
            result.B = (byte)( left.B + right.B );
        }

        /// <summary>
        /// Adds two colors.
        /// </summary>
        /// <param name="left">The first color to add.</param>
        /// <param name="right">The second color to add.</param>
        /// <returns>The sum of the two colors.</returns>
        public static ColorBGRA Add( ColorBGRA left, ColorBGRA right )
        {
            return new ColorBGRA( (byte)( left.R + right.R ), (byte)( left.G + right.G ), (byte)( left.B + right.B ), (byte)( left.A + right.A ) );
        }

        /// <summary>
        /// Subtracts two colors.
        /// </summary>
        /// <param name="left">The first color to subtract.</param>
        /// <param name="right">The second color to subtract.</param>
        /// <param name="result">WHen the method completes, contains the difference of the two colors.</param>
        public static void Subtract( ref ColorBGRA left, ref ColorBGRA right, out ColorBGRA result )
        {
            result.A = (byte)( left.A - right.A );
            result.R = (byte)( left.R - right.R );
            result.G = (byte)( left.G - right.G );
            result.B = (byte)( left.B - right.B );
        }

        /// <summary>
        /// Subtracts two colors.
        /// </summary>
        /// <param name="left">The first color to subtract.</param>
        /// <param name="right">The second color to subtract</param>
        /// <returns>The difference of the two colors.</returns>
        public static ColorBGRA Subtract( ColorBGRA left, ColorBGRA right )
        {
            return new ColorBGRA( (byte)( left.R - right.R ), (byte)( left.G - right.G ), (byte)( left.B - right.B ), (byte)( left.A - right.A ) );
        }

        /// <summary>
        /// Modulates two colors.
        /// </summary>
        /// <param name="left">The first color to modulate.</param>
        /// <param name="right">The second color to modulate.</param>
        /// <param name="result">When the method completes, contains the modulated color.</param>
        public static void Modulate( ref ColorBGRA left, ref ColorBGRA right, out ColorBGRA result )
        {
            result.A = (byte)( left.A * right.A / 255 );
            result.R = (byte)( left.R * right.R / 255 );
            result.G = (byte)( left.G * right.G / 255 );
            result.B = (byte)( left.B * right.B / 255 );
        }

        /// <summary>
        /// Modulates two colors.
        /// </summary>
        /// <param name="left">The first color to modulate.</param>
        /// <param name="right">The second color to modulate.</param>
        /// <returns>The modulated color.</returns>
        public static ColorBGRA Modulate( ColorBGRA left, ColorBGRA right )
        {
            return new ColorBGRA( (byte)( ( left.R * right.R ) / 255 ), (byte)( ( left.G * right.G ) / 255 ), (byte)( ( left.B * right.B ) / 255 ), (byte)( ( left.A * right.A ) / 255 ) );
        }

        /// <summary>
        /// Scales a color.
        /// </summary>
        /// <param name="value">The color to scale.</param>
        /// <param name="scale">The amount by which to scale.</param>
        /// <param name="result">When the method completes, contains the scaled color.</param>
        public static void Scale( ref ColorBGRA value, float scale, out ColorBGRA result )
        {
            result.A = (byte)( value.A * scale );
            result.R = (byte)( value.R * scale );
            result.G = (byte)( value.G * scale );
            result.B = (byte)( value.B * scale );
        }

        /// <summary>
        /// Scales a color.
        /// </summary>
        /// <param name="value">The color to scale.</param>
        /// <param name="scale">The amount by which to scale.</param>
        /// <returns>The scaled color.</returns>
        public static ColorBGRA Scale( ColorBGRA value, float scale )
        {
            return new ColorBGRA( (byte)( value.R * scale ), (byte)( value.G * scale ), (byte)( value.B * scale ), (byte)( value.A * scale ) );
        }

        /// <summary>
        /// Negates a color.
        /// </summary>
        /// <param name="value">The color to negate.</param>
        /// <param name="result">When the method completes, contains the negated color.</param>
        public static void Negate( ref ColorBGRA value, out ColorBGRA result )
        {
            result.A = (byte)( 255 - value.A );
            result.R = (byte)( 255 - value.R );
            result.G = (byte)( 255 - value.G );
            result.B = (byte)( 255 - value.B );
        }

        /// <summary>
        /// Negates a color.
        /// </summary>
        /// <param name="value">The color to negate.</param>
        /// <returns>The negated color.</returns>
        public static ColorBGRA Negate( ColorBGRA value )
        {
            return new ColorBGRA( (byte)( 255 - value.R ), (byte)( 255 - value.G ), (byte)( 255 - value.B ), (byte)( 255 - value.A ) );
        }

        /// <summary>
        /// Restricts a value to be within a specified range.
        /// </summary>
        /// <param name="value">The value to clamp.</param>
        /// <param name="min">The minimum value.</param>
        /// <param name="max">The maximum value.</param>
        /// <param name="result">When the method completes, contains the clamped value.</param>
        public static void Clamp( ref ColorBGRA value, ref ColorBGRA min, ref ColorBGRA max, out ColorBGRA result )
        {
            byte alpha = value.A;
            alpha = ( alpha > max.A ) ? max.A : alpha;
            alpha = ( alpha < min.A ) ? min.A : alpha;

            byte red = value.R;
            red = ( red > max.R ) ? max.R : red;
            red = ( red < min.R ) ? min.R : red;

            byte green = value.G;
            green = ( green > max.G ) ? max.G : green;
            green = ( green < min.G ) ? min.G : green;

            byte blue = value.B;
            blue = ( blue > max.B ) ? max.B : blue;
            blue = ( blue < min.B ) ? min.B : blue;

            result = new ColorBGRA( red, green, blue, alpha );
        }

        /// <summary>
        /// Restricts a value to be within a specified range.
        /// </summary>
        /// <param name="value">The value to clamp.</param>
        /// <param name="min">The minimum value.</param>
        /// <param name="max">The maximum value.</param>
        /// <returns>The clamped value.</returns>
        public static ColorBGRA Clamp( ColorBGRA value, ColorBGRA min, ColorBGRA max )
        {
            ColorBGRA result;
            Clamp( ref value, ref min, ref max, out result );
            return result;
        }

        /// <summary>
        /// Performs a linear interpolation between two colors.
        /// </summary>
        /// <param name="start">Start color.</param>
        /// <param name="end">End color.</param>
        /// <param name="amount">Value between 0 and 1 indicating the weight of <paramref name="end"/>.</param>
        /// <param name="result">When the method completes, contains the linear interpolation of the two colors.</param>
        /// <remarks>
        /// Passing <paramref name="amount"/> a value of 0 will cause <paramref name="start"/> to be returned; a value of 1 will cause <paramref name="end"/> to be returned.
        /// </remarks>
        public static void Lerp( ref ColorBGRA start, ref ColorBGRA end, float amount, out ColorBGRA result )
        {
            result.B = MathUtil.Lerp( start.B, end.B, amount );
            result.G = MathUtil.Lerp( start.G, end.G, amount );
            result.R = MathUtil.Lerp( start.R, end.R, amount );
            result.A = MathUtil.Lerp( start.A, end.A, amount );
        }

        /// <summary>
        /// Performs a linear interpolation between two colors.
        /// </summary>
        /// <param name="start">Start color.</param>
        /// <param name="end">End color.</param>
        /// <param name="amount">Value between 0 and 1 indicating the weight of <paramref name="end"/>.</param>
        /// <returns>The linear interpolation of the two colors.</returns>
        /// <remarks>
        /// Passing <paramref name="amount"/> a value of 0 will cause <paramref name="start"/> to be returned; a value of 1 will cause <paramref name="end"/> to be returned.
        /// </remarks>
        public static ColorBGRA Lerp( ColorBGRA start, ColorBGRA end, float amount )
        {
            ColorBGRA result;
            Lerp( ref start, ref end, amount, out result );
            return result;
        }

        /// <summary>
        /// Performs a cubic interpolation between two colors.
        /// </summary>
        /// <param name="start">Start color.</param>
        /// <param name="end">End color.</param>
        /// <param name="amount">Value between 0 and 1 indicating the weight of <paramref name="end"/>.</param>
        /// <param name="result">When the method completes, contains the cubic interpolation of the two colors.</param>
        public static void SmoothStep( ref ColorBGRA start, ref ColorBGRA end, float amount, out ColorBGRA result )
        {
            amount = MathUtil.SmoothStep( amount );
            Lerp( ref start, ref end, amount, out result );
        }

        /// <summary>
        /// Performs a cubic interpolation between two colors.
        /// </summary>
        /// <param name="start">Start color.</param>
        /// <param name="end">End color.</param>
        /// <param name="amount">Value between 0 and 1 indicating the weight of <paramref name="end"/>.</param>
        /// <returns>The cubic interpolation of the two colors.</returns>
        public static ColorBGRA SmoothStep( ColorBGRA start, ColorBGRA end, float amount )
        {
            ColorBGRA result;
            SmoothStep( ref start, ref end, amount, out result );
            return result;
        }

        /// <summary>
        /// Returns a color containing the smallest components of the specified colorss.
        /// </summary>
        /// <param name="left">The first source color.</param>
        /// <param name="right">The second source color.</param>
        /// <param name="result">When the method completes, contains an new color composed of the largest components of the source colorss.</param>
        public static void Max( ref ColorBGRA left, ref ColorBGRA right, out ColorBGRA result )
        {
            result.A = ( left.A > right.A ) ? left.A : right.A;
            result.R = ( left.R > right.R ) ? left.R : right.R;
            result.G = ( left.G > right.G ) ? left.G : right.G;
            result.B = ( left.B > right.B ) ? left.B : right.B;
        }

        /// <summary>
        /// Returns a color containing the largest components of the specified colorss.
        /// </summary>
        /// <param name="left">The first source color.</param>
        /// <param name="right">The second source color.</param>
        /// <returns>A color containing the largest components of the source colors.</returns>
        public static ColorBGRA Max( ColorBGRA left, ColorBGRA right )
        {
            ColorBGRA result;
            Max( ref left, ref right, out result );
            return result;
        }

        /// <summary>
        /// Returns a color containing the smallest components of the specified colors.
        /// </summary>
        /// <param name="left">The first source color.</param>
        /// <param name="right">The second source color.</param>
        /// <param name="result">When the method completes, contains an new color composed of the smallest components of the source colors.</param>
        public static void Min( ref ColorBGRA left, ref ColorBGRA right, out ColorBGRA result )
        {
            result.A = ( left.A < right.A ) ? left.A : right.A;
            result.R = ( left.R < right.R ) ? left.R : right.R;
            result.G = ( left.G < right.G ) ? left.G : right.G;
            result.B = ( left.B < right.B ) ? left.B : right.B;
        }

        /// <summary>
        /// Returns a color containing the smallest components of the specified colors.
        /// </summary>
        /// <param name="left">The first source color.</param>
        /// <param name="right">The second source color.</param>
        /// <returns>A color containing the smallest components of the source colors.</returns>
        public static ColorBGRA Min( ColorBGRA left, ColorBGRA right )
        {
            ColorBGRA result;
            Min( ref left, ref right, out result );
            return result;
        }

        /// <summary>
        /// Adjusts the contrast of a color.
        /// </summary>
        /// <param name="value">The color whose contrast is to be adjusted.</param>
        /// <param name="contrast">The amount by which to adjust the contrast.</param>
        /// <param name="result">When the method completes, contains the adjusted color.</param>
        public static void AdjustContrast( ref ColorBGRA value, float contrast, out ColorBGRA result )
        {
            result.A = value.A;
            result.R = ToByte( 0.5f + contrast * ( value.R / 255.0f - 0.5f ) );
            result.G = ToByte( 0.5f + contrast * ( value.G / 255.0f - 0.5f ) );
            result.B = ToByte( 0.5f + contrast * ( value.B / 255.0f - 0.5f ) );
        }

        /// <summary>
        /// Adjusts the contrast of a color.
        /// </summary>
        /// <param name="value">The color whose contrast is to be adjusted.</param>
        /// <param name="contrast">The amount by which to adjust the contrast.</param>
        /// <returns>The adjusted color.</returns>
        public static ColorBGRA AdjustContrast( ColorBGRA value, float contrast )
        {
            return new ColorBGRA(
                ToByte( 0.5f + contrast * ( value.R / 255.0f - 0.5f ) ),
                ToByte( 0.5f + contrast * ( value.G / 255.0f - 0.5f ) ),
                ToByte( 0.5f + contrast * ( value.B / 255.0f - 0.5f ) ),
                value.A );
        }

        /// <summary>
        /// Adjusts the saturation of a color.
        /// </summary>
        /// <param name="value">The color whose saturation is to be adjusted.</param>
        /// <param name="saturation">The amount by which to adjust the saturation.</param>
        /// <param name="result">When the method completes, contains the adjusted color.</param>
        public static void AdjustSaturation( ref ColorBGRA value, float saturation, out ColorBGRA result )
        {
            float grey = value.R / 255.0f * 0.2125f + value.G / 255.0f * 0.7154f + value.B / 255.0f * 0.0721f;

            result.A = value.A;
            result.R = ToByte( grey + saturation * ( value.R / 255.0f - grey ) );
            result.G = ToByte( grey + saturation * ( value.G / 255.0f - grey ) );
            result.B = ToByte( grey + saturation * ( value.B / 255.0f - grey ) );
        }

        /// <summary>
        /// Adjusts the saturation of a color.
        /// </summary>
        /// <param name="value">The color whose saturation is to be adjusted.</param>
        /// <param name="saturation">The amount by which to adjust the saturation.</param>
        /// <returns>The adjusted color.</returns>
        public static ColorBGRA AdjustSaturation( ColorBGRA value, float saturation )
        {
            float grey = value.R / 255.0f * 0.2125f + value.G / 255.0f * 0.7154f + value.B / 255.0f * 0.0721f;

            return new ColorBGRA(
                ToByte( grey + saturation * ( value.R / 255.0f - grey ) ),
                ToByte( grey + saturation * ( value.G / 255.0f - grey ) ),
                ToByte( grey + saturation * ( value.B / 255.0f - grey ) ),
                value.A );
        }

        /// <summary>
        /// Adds two colors.
        /// </summary>
        /// <param name="left">The first color to add.</param>
        /// <param name="right">The second color to add.</param>
        /// <returns>The sum of the two colors.</returns>
        public static ColorBGRA operator +( ColorBGRA left, ColorBGRA right )
        {
            return new ColorBGRA( (byte)( left.R + right.R ), (byte)( left.G + right.G ), (byte)( left.B + right.B ), (byte)( left.A + right.A ) );
        }

        /// <summary>
        /// Assert a color (return it unchanged).
        /// </summary>
        /// <param name="value">The color to assert (unchange).</param>
        /// <returns>The asserted (unchanged) color.</returns>
        public static ColorBGRA operator +( ColorBGRA value )
        {
            return value;
        }

        /// <summary>
        /// Subtracts two colors.
        /// </summary>
        /// <param name="left">The first color to subtract.</param>
        /// <param name="right">The second color to subtract.</param>
        /// <returns>The difference of the two colors.</returns>
        public static ColorBGRA operator -( ColorBGRA left, ColorBGRA right )
        {
            return new ColorBGRA( (byte)( left.R - right.R ), (byte)( left.G - right.G ), (byte)( left.B - right.B ), (byte)( left.A - right.A ) );
        }

        /// <summary>
        /// Negates a color.
        /// </summary>
        /// <param name="value">The color to negate.</param>
        /// <returns>A negated color.</returns>
        public static ColorBGRA operator -( ColorBGRA value )
        {
            return new ColorBGRA( -value.R, -value.G, -value.B, -value.A );
        }

        /// <summary>
        /// Scales a color.
        /// </summary>
        /// <param name="scale">The factor by which to scale the color.</param>
        /// <param name="value">The color to scale.</param>
        /// <returns>The scaled color.</returns>
        public static ColorBGRA operator *( float scale, ColorBGRA value )
        {
            return new ColorBGRA( (byte)( value.R * scale ), (byte)( value.G * scale ), (byte)( value.B * scale ), (byte)( value.A * scale ) );
        }

        /// <summary>
        /// Scales a color.
        /// </summary>
        /// <param name="value">The factor by which to scale the color.</param>
        /// <param name="scale">The color to scale.</param>
        /// <returns>The scaled color.</returns>
        public static ColorBGRA operator *( ColorBGRA value, float scale )
        {
            return new ColorBGRA( (byte)( value.R * scale ), (byte)( value.G * scale ), (byte)( value.B * scale ), (byte)( value.A * scale ) );
        }

        /// <summary>
        /// Modulates two colors.
        /// </summary>
        /// <param name="left">The first color to modulate.</param>
        /// <param name="right">The second color to modulate.</param>
        /// <returns>The modulated color.</returns>
        public static ColorBGRA operator *( ColorBGRA left, ColorBGRA right )
        {
            return new ColorBGRA( (byte)( left.R * right.R / 255.0f ), (byte)( left.G * right.G / 255.0f ), (byte)( left.B * right.B / 255.0f ), (byte)( left.A * right.A / 255.0f ) );
        }

        /// <summary>
        /// Tests for equality between two objects.
        /// </summary>
        /// <param name="left">The first value to compare.</param>
        /// <param name="right">The second value to compare.</param>
        /// <returns><c>true</c> if <paramref name="left"/> has the same value as <paramref name="right"/>; otherwise, <c>false</c>.</returns>
        public static bool operator ==( ColorBGRA left, ColorBGRA right )
        {
            return left.Equals( right );
        }

        /// <summary>
        /// Tests for inequality between two objects.
        /// </summary>
        /// <param name="left">The first value to compare.</param>
        /// <param name="right">The second value to compare.</param>
        /// <returns><c>true</c> if <paramref name="left"/> has a different value than <paramref name="right"/>; otherwise, <c>false</c>.</returns>
        public static bool operator !=( ColorBGRA left, ColorBGRA right )
        {
            return !left.Equals( right );
        }

        /// <summary>
        /// Performs an explicit conversion from <see cref="ColorBGRA"/> to <see cref="Color3"/>.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns>The result of the conversion.</returns>
        public static explicit operator Color3( ColorBGRA value )
        {
            return new Color3( value.R, value.G, value.B );
        }

        /// <summary>
        /// Performs an explicit conversion from <see cref="ColorBGRA"/> to <see cref="Vec3"/>.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns>The result of the conversion.</returns>
        public static explicit operator Vec3( ColorBGRA value )
        {
            return new Vec3( value.R / 255.0f, value.G / 255.0f, value.B / 255.0f );
        }

        /// <summary>
        /// Performs an explicit conversion from <see cref="ColorBGRA"/> to <see cref="Vec4"/>.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns>The result of the conversion.</returns>
        public static explicit operator Vec4( ColorBGRA value )
        {
            return new Vec4( value.R / 255.0f, value.G / 255.0f, value.B / 255.0f, value.A / 255.0f );
        }

        /// <summary>
        /// Performs an explicit conversion from <see cref="ColorBGRA"/> to <see cref="Color4"/>.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns>The result of the conversion.</returns>
        public static explicit operator Color4( ColorBGRA value )
        {
            return new Color4( value.R / 255.0f, value.G / 255.0f, value.B / 255.0f, value.A / 255.0f );
        }

        /// <summary>
        /// Performs an explicit conversion from <see cref="Vec3"/> to <see cref="ColorBGRA"/>.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns>The result of the conversion.</returns>
        public static explicit operator ColorBGRA( Vec3 value )
        {
            return new ColorBGRA( value.X / 255.0f, value.Y / 255.0f, value.Z / 255.0f, 1.0f );
        }

        /// <summary>
        /// Performs an explicit conversion from <see cref="Color3"/> to <see cref="ColorBGRA"/>.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns>The result of the conversion.</returns>
        public static explicit operator ColorBGRA( Color3 value )
        {
            return new ColorBGRA( value.R, value.G, value.B, 1.0f );
        }

        /// <summary>
        /// Performs an explicit conversion from <see cref="Vec4"/> to <see cref="ColorBGRA"/>.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns>The result of the conversion.</returns>
        public static explicit operator ColorBGRA( Vec4 value )
        {
            return new ColorBGRA( value.X, value.Y, value.Z, value.W );
        }

        /// <summary>
        /// Performs an explicit conversion from <see cref="Color4"/> to <see cref="ColorBGRA"/>.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns>The result of the conversion.</returns>
        public static explicit operator ColorBGRA( Color4 value )
        {
            return new ColorBGRA( value.R, value.G, value.B, value.A );
        }

        /// <summary>
        /// Performs an implicit conversion from <see cref="Color"/> to <see cref="ColorBGRA"/>.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns>The result of the conversion.</returns>
        public static implicit operator ColorBGRA( Color value )
        {
            return new ColorBGRA( value.R, value.G, value.B, value.A );
        }

        /// <summary>
        /// Performs an implicit conversion from <see cref="ColorBGRA"/> to <see cref="Color"/>.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns>The result of the conversion.</returns>
        public static implicit operator Color( ColorBGRA value )
        {
            return new Color( value.R, value.G, value.B, value.A );
        }

        /// <summary>
        /// Performs an explicit conversion from <see cref="ColorBGRA"/> to <see cref="int"/>.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns>
        /// The result of the conversion.
        /// </returns>
        public static explicit operator int( ColorBGRA value )
        {
            return value.ToBgra();
        }

        /// <summary>
        /// Performs an explicit conversion from <see cref="int"/> to <see cref="ColorBGRA"/>.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns>
        /// The result of the conversion.
        /// </returns>
        public static explicit operator ColorBGRA( int value )
        {
            return new ColorBGRA( value );
        }

        /// <summary>
        /// Returns a <see cref="string"/> that represents this instance.
        /// </summary>
        /// <returns>
        /// A <see cref="string"/> that represents this instance.
        /// </returns>
        public override string ToString()
        {
            return ToString( CultureInfo.CurrentCulture );
        }

        /// <summary>
        /// Returns a <see cref="string"/> that represents this instance.
        /// </summary>
        /// <param name="format">The format to apply to each channel (byte).</param>
        /// <returns>
        /// A <see cref="string"/> that represents this instance.
        /// </returns>
        public string ToString( string format )
        {
            return ToString( format, CultureInfo.CurrentCulture );
        }

        /// <summary>
        /// Returns a <see cref="string"/> that represents this instance.
        /// </summary>
        /// <param name="formatProvider">The format provider.</param>
        /// <returns>
        /// A <see cref="string"/> that represents this instance.
        /// </returns>
        public string ToString( IFormatProvider formatProvider )
        {
            return string.Format( formatProvider, ToStringFormat, A, R, G, B );
        }

        /// <summary>
        /// Returns a <see cref="string"/> that represents this instance.
        /// </summary>
        /// <param name="format">The format to apply to each channel (byte).</param>
        /// <param name="formatProvider">The format provider.</param>
        /// <returns>
        /// A <see cref="string"/> that represents this instance.
        /// </returns>
        public string ToString( string format, IFormatProvider formatProvider )
        {
            if( format == null )
                return ToString( formatProvider );

            return string.Format( formatProvider, ToStringFormat,
                                 A.ToString( format, formatProvider ),
                                 R.ToString( format, formatProvider ),
                                 G.ToString( format, formatProvider ),
                                 B.ToString( format, formatProvider ) );
        }

        /// <summary>
        /// Returns a hash code for this instance.
        /// </summary>
        /// <returns>
        /// A hash code for this instance, suitable for use in hashing algorithms and data structures like a hash table.
        /// </returns>
        public override int GetHashCode()
        {
            return A.GetHashCode() + R.GetHashCode() + G.GetHashCode() + B.GetHashCode();
        }

        /// <summary>
        /// Determines whether the specified <see cref="ColorBGRA"/> is equal to this instance.
        /// </summary>
        /// <param name="other">The <see cref="ColorBGRA"/> to compare with this instance.</param>
        /// <returns>
        /// <c>true</c> if the specified <see cref="ColorBGRA"/> is equal to this instance; otherwise, <c>false</c>.
        /// </returns>
        public bool Equals( ColorBGRA other )
        {
            return R == other.R && G == other.G && B == other.B && A == other.A;
        }

        /// <summary>
        /// Determines whether the specified <see cref="object"/> is equal to this instance.
        /// </summary>
        /// <param name="value">The <see cref="object"/> to compare with this instance.</param>
        /// <returns>
        /// <c>true</c> if the specified <see cref="object"/> is equal to this instance; otherwise, <c>false</c>.
        /// </returns>
        public override bool Equals( object value )
        {
            if( value == null )
                return false;

            if( !ReferenceEquals( value.GetType(), typeof( ColorBGRA ) ) )
                return false;

            return Equals( (ColorBGRA)value );
        }

        private static byte ToByte( float component )
        {
            var value = (int)( component * 255.0f );
            return (byte)( value < 0 ? 0 : value > 255 ? 255 : value );
        }
    }
}