How to convert RGB value to color name in Silverlight 4.0?

The code :

Dim myColor As Color = Colors.Red
Dim colorName As String = myColor.ToString()

Results in :

#FFFF0000

when printing colorName to screen.

Is it possible to get the color name in Sil开发者_如何学运维verlight without making a select case on the RGB values?

I developed a very useful ColorFromString class that does exactly that. You can get the code here ColorFromString for Silverlight or NET, or here:

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Windows.Media;

namespace ClassLibrary
{
    public static class ColorFromString
    {
        private static Dictionary<string, Color> namedColors =
        new Dictionary<string, Color>();

        // Extension for string
        public static Color ToColor(this string value)
        {
            if (value == null)
                return Colors.Red;

            // Named Colors
            string valueLower = value.ToLower();
            if (namedColors.ContainsKey(valueLower))
                return namedColors[valueLower];

            // #ARGB and #RGB Hex Colors
            if (value[0] == '#')
                value = value.Remove(0, 1);

            int length = value.Length;
            if ((length == 6 || length == 8) && IsHexColor(value))
            {
                if (length == 8)
                    return Color.FromArgb(
                    byte.Parse(value.Substring(0, 2), NumberStyles.HexNumber),
                    byte.Parse(value.Substring(2, 2), NumberStyles.HexNumber),
                    byte.Parse(value.Substring(4, 2), NumberStyles.HexNumber),
                    byte.Parse(value.Substring(6, 2), NumberStyles.HexNumber));

                if (length == 6)
                    return Color.FromArgb(0xff,
                    byte.Parse(value.Substring(0, 2), NumberStyles.HexNumber),
                    byte.Parse(value.Substring(2, 2), NumberStyles.HexNumber),
                    byte.Parse(value.Substring(4, 2), NumberStyles.HexNumber));
            }

            // A,R,G,B and R,G,B Colors
            string[] argb = value.Split(
            new char[] { ',', ' ' }, StringSplitOptions.RemoveEmptyEntries);
            if (argb != null)
            {
                if (argb.Length == 4)
                    return Color.FromArgb(
                    byte.Parse(argb[0]), byte.Parse(argb[1]), byte.Parse(argb[2]),
                    byte.Parse(argb[3]));

                if (argb.Length == 3)
                    return Color.FromArgb(0xff,
                    byte.Parse(argb[0]), byte.Parse(argb[1]), byte.Parse(argb[2]));
            }

            return Colors.Red;
        }

        private static bool IsHexColor(string value)
        {
            if (value == null)
                return false;

            foreach (char c in value.ToCharArray())
                if (!Uri.IsHexDigit(c))
                    return false;

            return true;
        }

        static ColorFromString()
        {
            namedColors.Add("aliceblue", ToColor("#f0f8ff"));
            namedColors.Add("antiquewhite", ToColor("#faebd7"));
            namedColors.Add("aqua", ToColor("#00ffff"));
            namedColors.Add("aquamarine", ToColor("#7fffd4"));
            namedColors.Add("azure", ToColor("#f0ffff"));
            namedColors.Add("beige", ToColor("#f5f5dc"));
            namedColors.Add("bisque", ToColor("#ffe4c4"));
            namedColors.Add("black", ToColor("#000000"));
            namedColors.Add("blanchedalmond", ToColor("#ffebcd"));
            namedColors.Add("blue", ToColor("#0000ff"));
            namedColors.Add("blueviolet", ToColor("#8a2be2"));
            namedColors.Add("brown", ToColor("#a52a2a"));
            namedColors.Add("burlywood", ToColor("#deb887"));
            namedColors.Add("cadetblue", ToColor("#5f9ea0"));
            namedColors.Add("chartreuse", ToColor("#7fff00"));
            namedColors.Add("chocolate", ToColor("#d2691e"));
            namedColors.Add("coral", ToColor("#ff7f50"));
            namedColors.Add("cornflowerblue", ToColor("#6495ed"));
            namedColors.Add("cornsilk", ToColor("#fff8dc"));
            namedColors.Add("crimson", ToColor("#dc143c"));
            namedColors.Add("cyan", ToColor("#00ffff"));
            namedColors.Add("darkblue", ToColor("#00008b"));
            namedColors.Add("darkcyan", ToColor("#008b8b"));
            namedColors.Add("darkgoldenrod", ToColor("#b8860b"));
            namedColors.Add("darkgray", ToColor("#a9a9a9"));
            namedColors.Add("darkgreen", ToColor("#006400"));
            namedColors.Add("darkkhaki", ToColor("#bdb76b"));
            namedColors.Add("darkmagenta", ToColor("#8b008b"));
            namedColors.Add("darkolivegreen", ToColor("#556b2f"));
            namedColors.Add("darkorange", ToColor("#ff8c00"));
            namedColors.Add("darkorchid", ToColor("#9932cc"));
            namedColors.Add("darkred", ToColor("#8b0000"));
            namedColors.Add("darksalmon", ToColor("#e9967a"));
            namedColors.Add("darkseagreen", ToColor("#8fbc8f"));
            namedColors.Add("darkslateblue", ToColor("#483d8b"));
            namedColors.Add("darkslategray", ToColor("#2f4f4f"));
            namedColors.Add("darkturquoise", ToColor("#00ced1"));
            namedColors.Add("darkviolet", ToColor("#9400d3"));
            namedColors.Add("deeppink", ToColor("#ff1493"));
            namedColors.Add("deepskyblue", ToColor("#00bfff"));
            namedColors.Add("dimgray", ToColor("#696969"));
            namedColors.Add("dodgerblue", ToColor("#1e90ff"));
            namedColors.Add("firebrick", ToColor("#b22222"));
            namedColors.Add("floralwhite", ToColor("#fffaf0"));
            namedColors.Add("forestgreen", ToColor("#228b22"));
            namedColors.Add("fuchsia", ToColor("#ff00ff"));
            namedColors.Add("gainsboro", ToColor("#dcdcdc"));
            namedColors.Add("ghostwhite", ToColor("#f8f8ff"));
            namedColors.Add("gold", ToColor("#ffd700"));
            namedColors.Add("goldenrod", ToColor("#daa520"));
            namedColors.Add("gray", ToColor("#808080"));
            namedColors.Add("green", ToColor("#008000"));
            namedColors.Add("greenyellow", ToColor("#adff2f"));
            namedColors.Add("honeydew", ToColor("#f0fff0"));
            namedColors.Add("hotpink", ToColor("#ff69b4"));
            namedColors.Add("indianred", ToColor("#cd5c5c"));
            namedColors.Add("indigo", ToColor("#4b0082"));
            namedColors.Add("ivory", ToColor("#fffff0"));
            namedColors.Add("khaki", ToColor("#f0e68c"));
            namedColors.Add("lavender", ToColor("#e6e6fa"));
            namedColors.Add("lavenderblush", ToColor("#fff0f5"));
            namedColors.Add("lawngreen", ToColor("#7cfc00"));
            namedColors.Add("lemonchiffon", ToColor("#fffacd"));
            namedColors.Add("lightblue", ToColor("#add8e6"));
            namedColors.Add("lightcoral", ToColor("#f08080"));
            namedColors.Add("lightcyan", ToColor("#e0ffff"));
            namedColors.Add("lightgoldenrodyellow", ToColor("#fafad2"));
            namedColors.Add("lightgreen", ToColor("#90ee90"));
            namedColors.Add("lightgrey", ToColor("#d3d3d3"));
            namedColors.Add("lightpink", ToColor("#ffb6c1"));
            namedColors.Add("lightsalmon", ToColor("#ffa07a"));
            namedColors.Add("lightseagreen", ToColor("#20b2aa"));
            namedColors.Add("lightskyblue", ToColor("#87cefa"));
            namedColors.Add("lightslategray", ToColor("#778899"));
            namedColors.Add("lightsteelblue", ToColor("#b0c4de"));
            namedColors.Add("lightyellow", ToColor("#ffffe0"));
            namedColors.Add("lime", ToColor("#00ff00"));
            namedColors.Add("limegreen", ToColor("#32cd32"));
            namedColors.Add("linen", ToColor("#faf0e6"));
            namedColors.Add("magenta", ToColor("#ff00ff"));
            namedColors.Add("maroon", ToColor("#800000"));
            namedColors.Add("mediumaquamarine", ToColor("#66cdaa"));
            namedColors.Add("mediumblue", ToColor("#0000cd"));
            namedColors.Add("mediumorchid", ToColor("#ba55d3"));
            namedColors.Add("mediumpurple", ToColor("#9370db"));
            namedColors.Add("mediumseagreen", ToColor("#3cb371"));
            namedColors.Add("mediumslateblue", ToColor("#7b68ee"));
            namedColors.Add("mediumspringgreen", ToColor("#00fa9a"));
            namedColors.Add("mediumturquoise", ToColor("#48d1cc"));
            namedColors.Add("mediumvioletred", ToColor("#c71585"));
            namedColors.Add("midnightblue", ToColor("#191970"));
            namedColors.Add("mintcream", ToColor("#f5fffa"));
            namedColors.Add("mistyrose", ToColor("#ffe4e1"));
            namedColors.Add("moccasin", ToColor("#ffe4b5"));
            namedColors.Add("navajowhite", ToColor("#ffdead"));
            namedColors.Add("navy", ToColor("#000080"));
            namedColors.Add("oldlace", ToColor("#fdf5e6"));
            namedColors.Add("olive", ToColor("#808000"));
            namedColors.Add("olivedrab", ToColor("#6b8e23"));
            namedColors.Add("orange", ToColor("#ffa500"));
            namedColors.Add("orangered", ToColor("#ff4500"));
            namedColors.Add("orchid", ToColor("#da70d6"));
            namedColors.Add("palegoldenrod", ToColor("#eee8aa"));
            namedColors.Add("palegreen", ToColor("#98fb98"));
            namedColors.Add("paleturquoise", ToColor("#afeeee"));
            namedColors.Add("palevioletred", ToColor("#db7093"));
            namedColors.Add("papayawhip", ToColor("#ffefd5"));
            namedColors.Add("peachpuff", ToColor("#ffdab9"));
            namedColors.Add("peru", ToColor("#cd853f"));
            namedColors.Add("pink", ToColor("#ffc0cb"));
            namedColors.Add("plum", ToColor("#dda0dd"));
            namedColors.Add("powderblue", ToColor("#b0e0e6"));
            namedColors.Add("purple", ToColor("#800080"));
            namedColors.Add("red", ToColor("#ff0000"));
            namedColors.Add("rosybrown", ToColor("#bc8f8f"));
            namedColors.Add("royalblue", ToColor("#4169e1"));
            namedColors.Add("saddlebrown", ToColor("#8b4513"));
            namedColors.Add("salmon", ToColor("#fa8072"));
            namedColors.Add("sandybrown", ToColor("#f4a460"));
            namedColors.Add("seagreen", ToColor("#2e8b57"));
            namedColors.Add("seashell", ToColor("#fff5ee"));
            namedColors.Add("sienna", ToColor("#a0522d"));
            namedColors.Add("silver", ToColor("#c0c0c0"));
            namedColors.Add("skyblue", ToColor("#87ceeb"));
            namedColors.Add("slateblue", ToColor("#6a5acd"));
            namedColors.Add("slategray", ToColor("#708090"));
            namedColors.Add("snow", ToColor("#fffafa"));
            namedColors.Add("springgreen", ToColor("#00ff7f"));
            namedColors.Add("steelblue", ToColor("#4682b4"));
            namedColors.Add("tan", ToColor("#d2b48c"));
            namedColors.Add("teal", ToColor("#008080"));
            namedColors.Add("thistle", ToColor("#d8bfd8"));
            namedColors.Add("tomato", ToColor("#ff6347"));
            namedColors.Add("turquoise", ToColor("#40e0d0"));
            namedColors.Add("violet", ToColor("#ee82ee"));
            namedColors.Add("wheat", ToColor("#f5deb3"));
            namedColors.Add("white", ToColor("#ffffff"));
            namedColors.Add("whitesmoke", ToColor("#f5f5f5"));
            namedColors.Add("yellow", ToColor("#ffff00"));
            namedColors.Add("yellowgreen", ToColor("#9acd32"));
        }
    }
}

The two colors may not look close, but there are only 140 "named" colors out of 16,777,216 possible combinations (256 * 256 * 256).

It is difficult to look at the RGB values and make any conclusions regarding the color matching.

'GetNearest...
'   http://social.msdn.microsoft.com/Forums/en-US/vbgeneral/thread/b2d491ac-4031-46d6-bccb-8bf9a46c2289
'   http://www.eggheadcafe.com/conversation.aspx?messageid=31472401&threadid=31472286

Imports System.Drawing
Imports System.Reflection
Imports System.Runtime.CompilerServices

Namespace Drawing

    <HideModuleName()> _
    Public Module ColorExtensions

        ''' <summary>
        ''' Gets the <see cref="System.Drawing.Color.Name">System.Drawing.Color.Name</see> of the closest matching color.
        ''' </summary>
        ''' <example>
        ''' <code>
        '''    Private Sub Example()
        '''        Dim oColor As Color = Color.FromName(GetNearestName(Color.FromArgb(255, 255, 255, 0)))
        '''        Debug.Assert(oColor.Name = "Yellow")
        '''    End Sub
        ''' </code>
        ''' </example>
        <Extension()> _
        Public Function GetNearestName(ByVal unknownColor As Color) As String

            'short-circut
            If unknownColor.IsNamedColor Then
                Return unknownColor.Name
            End If

            Dim oBestMatch As ColorName = GetNearestNameInternal(unknownColor)

            Return oBestMatch.Name
        End Function

        ''' <summary>
        ''' Gets the <see cref="System.Drawing.KnownColor">System.Drawing.KnownColor</see> of the closest matching known color.
        ''' </summary>
        ''' <example>
        ''' <code>
        '''    Private Sub Example()
        '''        Dim oColor As Color =  Color.FromKnownColor(GetNearestKnownColor(Color.FromArgb(255, 255, 255, 0)))
        '''        Debug.Assert(oColor.Name = "Yellow")
        '''    End Sub
        ''' </code>
        ''' </example>
        <Extension()> _
        Public Function GetNearestKnownColor(ByVal unknownColor As Color) As KnownColor

            'short-circut
            If unknownColor.IsKnownColor Then
                Return unknownColor.ToKnownColor
            End If

            Dim oBestMatch As ColorName = GetNearestKnownColorInternal(unknownColor)

            Return oBestMatch.Color.ToKnownColor
        End Function

        <DebuggerDisplay("Name={Color.Name}, Distance={Distance}, ARGB=({Color.A}, {Color.R}, {Color.G}, {Color.B})")> _
        Friend Structure ColorName

            Public Name As String
            Public Color As Color
            Public Distance As Double

            ''' <summary>
            ''' Returns RGB=(212,208,200)
            ''' </summary>
            Public Function ToRGBString() As String
                Return String.Format("RGB=({0},{1},{2})", Color.R, Color.G, Color.B)
            End Function

        End Structure

        Friend Function GetNearestNameInternal(ByVal unknownColor As Color) As ColorName

            Dim oBestMatch As ColorName = Nothing
            Dim nClosestDistance As Double = Double.MaxValue

            Dim oBindingFlags As BindingFlags = _
                BindingFlags.DeclaredOnly Or _
                BindingFlags.Public Or _
                BindingFlags.Static

            For Each oProperty As PropertyInfo In GetType(Color).GetProperties(oBindingFlags)

                Dim oNamedColor As Color = DirectCast(oProperty.GetValue(Nothing, Nothing), Color)
                Dim nDistance As Double

                nDistance = System.Math.Sqrt( _
                    (CInt(unknownColor.R) - oNamedColor.R) ^ 2 + _
                    (CInt(unknownColor.G) - oNamedColor.G) ^ 2 + _
                    (CInt(unknownColor.B) - oNamedColor.B) ^ 2)

                nDistance = System.Math.Sqrt(nDistance / 3)

                If nDistance < nClosestDistance Then
                    nClosestDistance = nDistance
                    oBestMatch.Name = oProperty.Name
                    oBestMatch.Distance = nDistance
                    oBestMatch.Color = oNamedColor
                End If

            Next

            Return oBestMatch
        End Function

        Friend Function GetNearestKnownColorInternal(ByVal unknownColor As Color) As ColorName

            Dim oBestMatch As ColorName = Nothing
            Dim nClosestDistance As Double = Double.MaxValue

            For Each sColorName As String In [Enum].GetNames(GetType(KnownColor))

                Dim oNamedColor As Color = Color.FromName(sColorName)
                Dim nDistance As Double

                nDistance = System.Math.Sqrt( _
                    (CInt(unknownColor.R) - oNamedColor.R) ^ 2 + _
                    (CInt(unknownColor.G) - oNamedColor.G) ^ 2 + _
                    (CInt(unknownColor.B) - oNamedColor.B) ^ 2)

                nDistance = System.Math.Sqrt(nDistance / 3)

                If nDistance < nClosestDistance Then
                    nClosestDistance = nDistance
                    oBestMatch.Name = oNamedColor.Name
                    oBestMatch.Distance = nDistance
                    oBestMatch.Color = oNamedColor
                End If

            Next

            Return oBestMatch
        End Function

#Region " Conditional Testing for GetNearest... Methods "

        <Conditional("DEBUG")> _
        Friend Sub TestGetNearest()

            'from immediate window
            '   ColorExtensions.Test
            '
            'Results based on "Windows XP" default theme, with the display name of "Windows XP style'.
            '
            'Windows XP style
            '   ActiveBorder, RGB=(212,208,200); LightGray, RGB=(211,211,211); ActiveBorder, RGB=(212,208,200)
            '   ActiveCaption, RGB=(0,84,227); RoyalBlue, RGB=(65,105,225); ActiveCaption, RGB=(0,84,227)
            '   ActiveCaptionText, RGB=(255,255,255); Transparent, RGB=(255,255,255); ActiveCaptionText, RGB=(255,255,255)
            '   AppWorkspace, RGB=(128,128,128); Gray, RGB=(128,128,128); AppWorkspace, RGB=(128,128,128)
            '   Control, RGB=(236,233,216); AntiqueWhite, RGB=(250,235,215); Control, RGB=(236,233,216)
            '   ControlDark, RGB=(172,168,153); DarkGray, RGB=(169,169,169); ControlDark, RGB=(172,168,153)
            '   ControlDarkDark, RGB=(113,111,100); DimGray, RGB=(105,105,105); ControlDarkDark, RGB=(113,111,100)
            '   ControlLight, RGB=(241,239,226); Beige, RGB=(245,245,220); ControlLight, RGB=(241,239,226)
            '   ControlLightLight, RGB=(255,255,255); Transparent, RGB=(255,255,255); ActiveCaptionText, RGB=(255,255,255)
            '   ControlText, RGB=(0,0,0); Black, RGB=(0,0,0); ControlText, RGB=(0,0,0)
            '   Desktop, RGB=(0,78,152); Teal, RGB=(0,128,128); Desktop, RGB=(0,78,152)
            '   GrayText, RGB=(172,168,153); DarkGray, RGB=(169,169,169); ControlDark, RGB=(172,168,153)
            '   Highlight, RGB=(49,106,197); RoyalBlue, RGB=(65,105,225); Highlight, RGB=(49,106,197)
            '   HighlightText, RGB=(255,255,255); Transparent, RGB=(255,255,255); ActiveCaptionText, RGB=(255,255,255)
            '   HotTrack, RGB=(0,0,128); Navy, RGB=(0,0,128); HotTrack, RGB=(0,0,128)
            '   InactiveBorder, RGB=(212,208,200); LightGray, RGB=(211,211,211); ActiveBorder, RGB=(212,208,200)
            '   InactiveCaption, RGB=(122,150,223); CornflowerBlue, RGB=(100,149,237); InactiveCaption, RGB=(122,150,223)
            '   InactiveCaptionText, RGB=(216,228,248); Lavender, RGB=(230,230,250); InactiveCaptionText, RGB=(216,228,248)
            '   Info, RGB=(255,255,225); LightYellow, RGB=(255,255,224); Info, RGB=(255,255,225)
            '   InfoText, RGB=(0,0,0); Black, RGB=(0,0,0); ControlText, RGB=(0,0,0)
            '   Menu, RGB=(255,255,255); Transparent, RGB=(255,255,255); ActiveCaptionText, RGB=(255,255,255)
            '   MenuText, RGB=(0,0,0); Black, RGB=(0,0,0); ControlText, RGB=(0,0,0)
            '   ScrollBar, RGB=(212,208,200); LightGray, RGB=(211,211,211); ActiveBorder, RGB=(212,208,200)
            '   Window, RGB=(255,255,255); Transparent, RGB=(255,255,255); ActiveCaptionText, RGB=(255,255,255)
            '   WindowFrame, RGB=(0,0,0); Black, RGB=(0,0,0); ControlText, RGB=(0,0,0)
            '   WindowText, RGB=(0,0,0); Black, RGB=(0,0,0); ControlText, RGB=(0,0,0)
            '   Transparent, RGB=(255,255,255); Transparent, RGB=(255,255,255); ActiveCaptionText, RGB=(255,255,255)
            '   Black, RGB=(0,0,0); Black, RGB=(0,0,0); ControlText, RGB=(0,0,0)
            '   Gray, RGB=(128,128,128); Gray, RGB=(128,128,128); AppWorkspace, RGB=(128,128,128)
            '   Navy, RGB=(0,0,128); Navy, RGB=(0,0,128); HotTrack, RGB=(0,0,128)
            '   White, RGB=(255,255,255); Transparent, RGB=(255,255,255); ActiveCaptionText, RGB=(255,255,255)
            '   ButtonFace, RGB=(236,233,216); AntiqueWhite, RGB=(250,235,215); Control, RGB=(236,233,216)
            '   ButtonHighlight, RGB=(255,255,255); Transparent, RGB=(255,255,255); ActiveCaptionText, RGB=(255,255,255)
            '   ButtonShadow, RGB=(172,168,153); DarkGray, RGB=(169,169,169); ControlDark, RGB=(172,168,153)
            '   GradientActiveCaption, RGB=(61,149,255); DodgerBlue, RGB=(30,144,255); GradientActiveCaption, RGB=(61,149,255)
            '   GradientInactiveCaption, RGB=(157,185,235); LightSteelBlue, RGB=(176,196,222); GradientInactiveCaption, RGB=(157,185,235)
            '   MenuBar, RGB=(236,233,216); AntiqueWhite, RGB=(250,235,215); Control, RGB=(236,233,216)
            '   MenuHighlight, RGB=(49,106,197); RoyalBlue, RGB=(65,105,225); Highlight, RGB=(49,106,197)
            '

            Debug.WriteLine(System.Windows.Forms.VisualStyles.VisualStyleInformation.DisplayName)

            For Each sKnownColorName As String In [Enum].GetNames(GetType(KnownColor))

                Dim oBaseColor As New ColorName

                oBaseColor.Name = sKnownColorName
                oBaseColor.Color = Color.FromName(sKnownColorName)

                Dim oTestColor As Color = Color.FromArgb(255, oBaseColor.Color.R, oBaseColor.Color.G, oBaseColor.Color.B)

                Dim oNearestNamed As ColorName = GetNearestNameInternal(oTestColor)
                Dim oNearestKnown As ColorName = GetNearestKnownColorInternal(oTestColor)

                'results will vary due to the current display theme properties

                If oNearestNamed.Name <> oNearestKnown.Name Then

                    Debug.Write("'   ")

                    Debug.Write(oBaseColor.Name)
                    Debug.Write(", ")
                    Debug.Write(oBaseColor.ToRGBString)
                    Debug.Write("; ")

                    Debug.Write(oNearestNamed.Name)
                    Debug.Write(", ")
                    Debug.Write(oNearestNamed.ToRGBString)
                    Debug.Write("; ")

                    Debug.Write(oNearestKnown.Name)
                    Debug.Write(", ")
                    Debug.Write(oNearestKnown.ToRGBString)

                    Debug.WriteLine("")

                End If

            Next

        End Sub

        ''' <summary>
        ''' Dump all the Is... Properties 
        ''' <example>
        ''' Current ActiveBorder is (255, 212, 208, 200)
        ''' Color.FromArgb(255, 212, 208, 200) 'ActiveBorder
        ''' Color.FromName("Yellow")           '255, 255, 0
        ''' Color.FromArgb(255, 255, 255, 0)   'Yellow
        ''' </example>
        ''' </summary>
        <Extension()> _
        <Conditional("DEBUG")> _
        Friend Sub BreakOnIsProperties(ByVal color As Color)

            Dim I As Color = color.FromArgb(color.A, color.R, color.G, color.B)

            If I.IsEmpty Then
                Stop
            End If

            If I.IsKnownColor Then
                Stop
            End If

            If I.IsNamedColor Then
                Stop
            End If

            If I.IsSystemColor Then
                Stop
            End If

        End Sub

#End Region

    End Module

End Namespace