RGB->HSV and vice versa

[Lothar Pink]

I'm an idiot on that area.

How can I calculate H,S,V out of given R,G,B color values and vice versa?

Lothar

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[Dominic Sexton]

I have not tried it but the code here is quite easy to understand
http://cs.haifa.ac.il/hagit/courses/...t_convert.html

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Dominic
Manchester UK

[Trevor Ridley]

I adapted the following code for converting HSL to RGB from something I found on the internet a long while back, I don't remember where. I cannot vouch for its accuracy but it worked good enough for me.

It is in VBA but it should not be difficult to adapt for PB:

Sub HSLtoRGB(ByVal Hue As Integer, _
             ByVal Saturation As Integer, _
             ByVal Luminance As Integer, _
             ByRef RGBRed As Integer, _
             ByRef RGBGreen As Integer, _
             ByRef RGBBlue As Integer)

    Dim pHue As Single
    Dim pSat As Single
    Dim pLum As Single
    Dim pRed As Single
    Dim pGreen As Single
    Dim pBlue As Single
    Dim temp2 As Single
    Dim temp3() As Single
    Dim temp1 As Single
    Dim n As Integer

   ReDim temp3(0 To 2)
   
   pHue = Hue / 255
   pSat = Saturation / 255
   pLum = Luminance / 255

   If pSat = 0 Then
      pRed = pLum
      pGreen = pLum
      pBlue = pLum
   Else
      If pLum < 0.5 Then
         temp2 = pLum * (1 + pSat)
      Else
         temp2 = pLum + pSat - pLum * pSat
      End If
      temp1 = 2 * pLum - temp2
   
      temp3(0) = pHue + 1 / 3
      temp3(1) = pHue
      temp3(2) = pHue - 1 / 3
      
      For n = 0 To 2
         If temp3(n) < 0 Then temp3(n) = temp3(n) + 1
         If temp3(n) > 1 Then temp3(n) = temp3(n) - 1
      
         If 6 * temp3(n) < 1 Then
            temp3(n) = temp1 + (temp2 - temp1) * 6 * temp3(n)
         Else
            If 2 * temp3(n) < 1 Then
               temp3(n) = temp2
            Else
               If 3 * temp3(n%) < 2 Then
                  temp3(n%) = temp1 + (temp2 - temp1) _
                        * ((2 / 3) - temp3(n%)) * 6
               Else
                  temp3(n%) = temp1
                End If
             End If
          End If
       Next n%

       pRed = temp3(0)
       pGreen = temp3(1)
       pBlue = temp3(2)
    End If

    RGBRed = Int(pRed * 255)
    RGBGreen = Int(pGreen * 255)
    RGBBlue = Int(pBlue * 255)
    
End Sub

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Trevor