RGB、HSB、HSL互相转换

参考：http://www.easyrgb.com/math.html
Public Type HSB
    Hue As Integer          
    Saturation As Integer   
    Brightness As Integer   
End Type

Public Type HSL
    Hue As Integer          
    Saturation As Integer   
    Luminance As Integer   
End Type

Public Type RGB
    Red As Integer          
    Green As Integer       
    Bue As Integer
End Type

' 转换RGB到HSB
Public Function RGB2HSB(ByVal R As Integer, ByVal G As Integer, ByVal B As Integer) As HSB
    Dim nH As Single, nS As Single, nV As Single
    Dim nR As Single, nG As Single, nB As Single
    Dim ndelR As Single, ndelG As Single, ndelB As Single
    Dim nmax As Single, nmin As Single, ndelMax As Single
 
    nR = R / 255
    nG = G / 255
    nB = B / 255
    nmax = Max(Max(nR, nG), nB)
    nmin = Min(Min(nR, nG), nB)
    ndelMax = nmax - nmin
    nV = nmax
    If (ndelMax = 0) Then
        nH = 0
        nS = 0
    Else
        nS = ndelMax / nmax
        ndelR = (((nmax - nR) / 6) + (ndelMax / 2)) / ndelMax
        ndelG = (((nmax - nG) / 6) + (ndelMax / 2)) / ndelMax
        ndelB = (((nmax - nB) / 6) + (ndelMax / 2)) / ndelMax
        If (nR = nmax) Then
            nH = ndelB - ndelG
        ElseIf (nG = nmax) Then
            nH = (1 / 3) + ndelR - ndelB
        ElseIf (nB = nmax) Then
            nH = (2 / 3) + ndelG - ndelR
        End If
        If (nH < 0) Then nH = nH + 1
        If (nH > 1) Then nH = nH - 1
    End If
    RGB2HSB.Hue = nH * 360
    RGB2HSB.Saturation = nS * 100
    RGB2HSB.Brightness = nV * 100
   
End Function

' 转换HSB到RGB
Public Function HSB2RGB(ByVal H As Integer, ByVal S As Integer, ByVal B As Integer) As RGB
    Dim nH As Single, nS As Single, nV As Single
    Dim nR As Single, nG As Single, nB As Single
    Dim hi As Single, f As Single, p As Single, q As Single, t As Single
   
    nH = H / 360
    nS = S / 100
    nV = B / 100
    If (S = 0) Then
        nR = nV * 255
        nG = nV * 255
        nB = nV * 255
    Else
        hi = nH * 6
        If (hi = 6) Then hi = 0
        f = Int(hi)
        p = nV * (1 - nS)
        q = nV * (1 - nS * (hi - f))
        t = nV * (1 - nS * (1 - (hi - f)))

        If (f = 0) Then
            nR = nV
            nG = t
            nB = p
        ElseIf (f = 1) Then
            nR = q
            nG = nV
            nB = p
        ElseIf (f = 2) Then
            nR = p
            nG = nV
            nB = t
        ElseIf (f = 3) Then
            nR = p
            nG = q
            nB = nV
        ElseIf (f = 4) Then
            nR = t
            nG = p
            nB = nV
        Else
            nR = nV
            nG = p
            nB = q
        End If
    End If
    HSB2RGB.Red = nR * 255
    HSB2RGB.Green = nG * 255
    HSB2RGB.Bue = nB * 255
   
End Function

' 转换RGB到HSL
Public Function RGB2HSL(ByVal R As Integer, ByVal G As Integer, ByVal B As Integer) As HSL
    Dim nH As Single, nS As Single, nL As Single
    Dim nR As Single, nG As Single, nB As Single
    Dim ndelR As Single, ndelG As Single, ndelB As Single
    Dim nmax As Single, nmin As Single, ndelMax As Single
   
    nR = (R / 255)
    nG = (G / 255)
    nB = (B / 255)
    nmax = Max(Max(nR, nG), nB)
    nmin = Min(Min(nR, nG), nB)
    ndelMax = nmax - nmin
    nL = (nmax + nmin) / 2
   
    If (ndelMax = 0) Then
        nH = 0
        nS = 0
    Else
        If (nL < 0.5) Then
            nS = ndelMax / (nmax + nmin)
        Else
            nS = ndelMax / (2 - nmax - nmin)
        End If
        ndelR = (((nmax - nR) / 6) + (ndelMax / 2)) / ndelMax
        ndelG = (((nmax - nG) / 6) + (ndelMax / 2)) / ndelMax
        ndelB = (((nmax - nB) / 6) + (ndelMax / 2)) / ndelMax
        If (nR = nmax) Then
            nH = ndelB - ndelG
        ElseIf (nG = nmax) Then
            nH = (1 / 3) + ndelR - ndelB
        ElseIf (nB = nmax) Then
            nH = (2 / 3) + ndelG - ndelR
        End If
        If (nH < 0) Then nH = nH + 1
        If (nH > 1) Then nH = nH - 1
    End If
    RGB2HSL.Hue = nH * 240
    RGB2HSL.Saturation = nS * 240
    RGB2HSL.Luminance = nL * 240
       
End Function

' 转换HSL到RGB
Public Function HSL2RGB(ByVal H As Integer, ByVal S As Integer, ByVal L As Integer) As RGB
    Dim nH As Single, nS As Single, nL As Single
    Dim nR As Single, nG As Single, nB As Single
    Dim p1 As Single, p2 As Single
   
    nH = H / 240
    nS = S / 240
    nL = L / 240
    If (nS = 0) Then
        nR = nL * 255
        nG = nL * 255
        nB = nL * 255
    Else
        If (nL < 0.5) Then
            p2 = Round(nL * (1 + nS), 2)
        Else
            p2 = Round((nL + nS) - (nS * nL), 2)
        End If
        p1 = Round(2 * nL - p2, 2)
        nR = 255 * Hue2RGB(p1, p2, nH + (1 / 3))
        nG = 255 * Hue2RGB(p1, p2, nH)
        nB = 255 * Hue2RGB(p1, p2, nH - (1 / 3))
    End If
    HSL2RGB.Red = nR
    HSL2RGB.Green = nG
    HSL2RGB.Bue = nB
   
End Function

Private Function Hue2RGB(ByVal p1 As Single, ByVal p2 As Single, ByVal Hue As Single) As Single
   
    If (Hue < 0) Then Hue = Hue + 1
    If (Hue > 1) Then Hue = Hue - 1
    If ((6 * Hue) < 1) Then
        Hue2RGB = (p1 + (p2 - p1) * 6 * Hue)
    ElseIf ((2 * Hue) < 1) Then
        Hue2RGB = p2
    ElseIf ((3 * Hue) < 2) Then
        Hue2RGB = p1 + (p2 - p1) * ((2 / 3) - Hue) * 6
    Else
        Hue2RGB = p1
    End If
   
End Function