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Color to HEX

TaggedCoding, Imaging, DotNet

It's not a huge deal anymore to use Hex values for colors in web pages, since Netscape3+ and IE both handle basically the same set of user-friendly color text values, but sometimes we need to feel like getting geeky helps cover the bases.

As with most things on the smithvoice.com sitelett, we found that we were typing this out by memory just often enough to make it tedious yet not often enough that our fingers could do it while we were watching TV. So we put it here for our future cut & pasting, and if it helps you too then so much the better.

 

Public Class rcsColorUtil
'The FromName will return a
'Color with an rgb value of 0 if
'the name you provide does not match any
'predefined names.
'so you don't have to check the IsNamedColor
'property for safety.  However, if you do want to check you
'have to iterate through a color array which is relatively intensive
Public Shared Function ColorToHex(ByVal Value As Color) As String
Return InternalColorToHex(Value)
End Function
 
Public Shared Function ColorToHex(ByVal Value As String) As String
Return InternalColorToHex(Color.FromName(Value))
End Function
 
Private Shared Function InternalColorToHex(ByVal Value As Color) As String
Dim hr, hb, hg, fr, fg, fb As String
hr = Hex(Value.R)
If Len(hr) = 1 Then
fr = "0" & hr
Else
fr = hr
End If
hg = Hex(Value.G)
If Len(hg) = 1 Then
fg = "0" & hg
Else
fg = hg
End If
hb = Hex(Value.B)
If Len(hb) = 1 Then
fb = "0" & hb
Else
fb = hb
End If
Return "#" & fr & fg & fb
End Function
 End Class

Pass in a Color or a KnownColor string and the correct overloaded function will pass off to the internal worker function. Because the entry functions are defined as Shared you don't have to instantiate an rcsColorUtil object to do the do. The following will suffice:

MsgBox(rcsColorUtil.ColorToHex("PaleGoldenrod"))
  
'or...
  
Dim c As Color = Color.SeaGreen
MsgBox(rcsColorUtil.ColorToHex(c))

As the comment says, there's no need to do a check of [Value].IsNamedColor because passing anything, including Nothing will not throw an exception. If you pass junk to IsNamedColor then the result will still be True and the values of the R, G and B will all be zero.

Personally we wish an exception would be raised for garbage input, making it a bit more logically consistant, but such is life in .Net-land :)

Hope it helps!

Robert Smith
Kirkland, WA



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