ColorConverter for Silverlight

Silverlight 2.0 is missing a ColorConverter. There’s no easy and efficient way from code to convert from a HEX color format to a built in Color type. I like being able to paste standard web color formats into my source code without converting them to a Color.FromArgb byte format (as most web color selectors support that format).

I wrote this code to end this annoyance (but didn’t bother with a full-fledged TypeConverter):

public static class Extensions
{
    public static void SetFromHex ( this Color c, string hex )
    {
        Color c1 = ToColorFromHex(hex);

        c.A = c1.A;
        c.R = c1.R;
        c.G = c1.G;
        c.B = c1.B;                        
    }
public static Color ToColorFromHex ( string hex )
{
    if(string.IsNullOrEmpty(hex))
    {
        throw new ArgumentNullException("hex");
    }

    // remove any "#" characters
    while(hex.StartsWith("#"))
    {
        hex = hex.Substring(1);
    }

    int num = 0;
    // get the number out of the string 
    if(!Int32.TryParse(hex, System.Globalization.NumberStyles.HexNumber, null, out num))
    {
        throw new ArgumentException("Color not in a recognized Hex format.");
    }

    int[] pieces = new int[4];
    if(hex.Length > 7)
    {
        pieces[0] = ((num >> 24) & 0x000000ff);
        pieces[1] = ((num >> 16) & 0x000000ff);
        pieces[2] = ((num >> 8) & 0x000000ff);
        pieces[3] = (num & 0x000000ff);
    }
    else if(hex.Length > 5)
    {
        pieces[0] = 255;
        pieces[1] = ((num >> 16) & 0x000000ff);
        pieces[2] = ((num >> 8) & 0x000000ff);
        pieces[3] = (num & 0x000000ff);
    }
    else if(hex.Length == 3)
    {
        pieces[0] = 255;
        pieces[1] = ((num >> 8) & 0x0000000f);
        pieces[1] += pieces[1] * 16;
        pieces[2] = ((num >> 4) & 0x000000f);
        pieces[2] += pieces[2] * 16;
        pieces[3] = (num & 0x000000f);
        pieces[3] += pieces[3] * 16;
    }
    return Color.FromArgb((byte) pieces[0], (byte) pieces[1], (byte) pieces[2], (byte) pieces[3]);
}

}

 

It accepts 3 standard formats for colors:

  1. [ALPHA][RED][GREEN][BLUE] (alpha and all colors)
  2. [RED][GREEN][BLUE] (no alpha channel, automatically set to 255)
  3. Short hand [R][G][B] (takes the single digit hex number and adds it to the same number * 16, alpha set to 255);

To use the function:

Color c1 = Extensions.ToColorFromHex("#00B2D6E8");

Obviously the built in components, brushes, etc. support that format already, but there doesn’t seem to be any place that functionality is exposed.

4 Comments

  1. […] also used my ToColorFromHex function liberally (I used Kuler to make some colors and grabbed their hex values and directly […]

  2. dude you rock, thanks

  3. hey whats the code behind the smiley face with the shades on ???

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