在RGB和HSB颜色值之间切换的算法

Question

我阅读了文章算法切换RGB和HSB颜色值

Type RGBColor
     Red As Byte
     Green As Byte
     Blue As Byte
End Type

Type HSBColor
     Hue As Double
     Saturation As Double
     Brightness As Double
End Type

Function RGBToHSB(rgb As RGBColor) As HSBColor
     Dim minRGB, maxRGB, Delta As Double
     Dim h, s, b As Double
     h = 0
     minRGB = Min(Min(rgb.Red, rgb.Green), rgb.Blue)
     maxRGB = Max(Max(rgb.Red, rgb.Green), rgb.Blue)
     Delta = (maxRGB - minRGB)
     b = maxRGB
     If (maxRGB <> 0) Then
          s = 255 * Delta / maxRGB
     Else
          s = 0
     End If
     If (s <> 0) Then
          If rgb.Red = maxRGB Then
               h = (CDbl(rgb.Green) - CDbl(rgb.Blue)) / Delta
          Else
               If rgb.Green = maxRGB Then
                    h = 2 + (CDbl(rgb.Blue) - CDbl(rgb.Red)) / Delta
               Else
                    If rgb.Blue = maxRGB Then
                         h = 4 + (CDbl(rgb.Red) - CDbl(rgb.Green)) / Delta
                    End If
               End If
          End If
     Else
          h = -1
     End If
     h = h * 60
     If h < 0 Then h = h + 360
     RGBToHSB.Hue = h
     RGBToHSB.Saturation = s * 100 / 255
     RGBToHSB.Brightness = b * 100 / 255
End Function

Function HSBToRGB(hsb As HSBColor) As RGBColor
     Dim maxRGB, Delta As Double
     Dim h, s, b As Double
     h = hsb.Hue / 60
     s = hsb.Saturation * 255 / 100
     b = hsb.Brightness * 255 / 100
     maxRGB = b
     If s = 0 Then
          HSBToRGB.Red = 0
          HSBToRGB.Green = 0
          HSBToRGB.Blue = 0
     Else
          Delta = s * maxRGB / 255
          If h > 3 Then
               HSBToRGB.Blue = CByte(Round(maxRGB))
               If h > 4 Then
                    HSBToRGB.Green = CByte(Round(maxRGB - Delta))
                    HSBToRGB.Red = CByte(Round((h - 4) * Delta)) + HSBToRGB.Green
               Else
                    HSBToRGB.Red = CByte(Round(maxRGB - Delta))
                    HSBToRGB.Green = CByte(HSBToRGB.Red - Round((h - 4) * Delta))
               End If
          Else
               If h > 1 Then
                    HSBToRGB.Green = CByte(Round(maxRGB))
                    If h > 2 Then
                         HSBToRGB.Red = CByte(Round(maxRGB - Delta))
                         HSBToRGB.Blue = CByte(Round((h - 2) * Delta)) + HSBToRGB.Red
                    Else
                         HSBToRGB.Blue = CByte(Round(maxRGB - Delta))
                         HSBToRGB.Red = CByte(HSBToRGB.Blue - Round((h - 2) * Delta))
                    End If
               Else
                    If h > -1 Then
                         HSBToRGB.Red = CByte(Round(maxRGB))
                         If h > 0 Then
                              HSBToRGB.Blue = CByte(Round(maxRGB - Delta))
                              HSBToRGB.Green = CByte(Round(h * Delta)) + HSBToRGB.Blue
                         Else
                              HSBToRGB.Green = CByte(Round(maxRGB - Delta))
                              HSBToRGB.Blue = CByte(HSBToRGB.Green - Round(h * Delta))
                         End If
                    End If
               End If
          End If
     End If
End Function

然后有人发布了一个错误,但没有详细说明

但我认为当h大于5时需要管理,例如颜色R:130 G:65 B:111

If h > 5 Then
    HSBToRGB.Red = CByte(Round(maxRGB))
If h > 6 Then
    HSBToRGB.Blue= CByte(Round(maxRGB - Delta))
    HSBToRGB.Green= CByte(Round((h - 6) * Delta)) HSBToRGB.Blue
Else
    HSBToRGB.Green= CByte(Round(maxRGB - Delta))
    HSBToRGB.Blue = CByte(HSBToRGB.Green- Round((h - 6) * Delta))
End If

我需要添加那段代码吗？我认为它应该进入HSB到RGB(在我的C#转换中)

...
if (s != 0) {
    delta = s * maxRGB / 255;
    if (h > 5)
        rgb.Red = Convert.ToByte(Math.Round(maxRGB));
    if (h > 6)
    {
        rgb.Green = Convert.ToByte(Math.Round(maxRGB - delta));
        rgb.Blue = Convert.ToByte(rgb.Green - Math.Round((h - 6) * delta));
    }
    if (h > 3)
    {
        ...

如果它像上面那样,或者

if (h > 6) { } 
else if (h > 3)  { }

Answer 1

使用.NET的Color对象中内置的方法是不可能的,因为正如几个答案所指出的那样,它们不支持反向(将HSB颜色转换为RGB).另外,Color.GetBrightness实际上返回亮度,而不是亮度/值.由于HSB/HSV和HSL颜色空间的相似性(维基百科),因此存在很多混淆.我看到很多颜色选择器最终使用了错误的算法和/或模型.

在给出RGB颜色的情况下,原始代码在我计算色调值时错过了一些可能的场景.对我来说,按照你正在考虑的代码来添加它有点困难,但是第一件事就是跳出来(而你似乎没有暗示纠正)是当饱和度= 0时,你设置了色调为-1.当您稍后将色调乘以60时,最终得到-60,然后将其添加到360(If h < 0 Then h = h + 360),产生300的结果,这是不正确的.

我使用以下代码(在VB.NET中)在RGB和HSB(我称之为HSV)之间进行转换.结果已经过非常广泛的测试,结果几乎与Photoshop的颜色选择器相同(除了它对颜色配置文件的补偿).发布的代码和我的代码(除了计算色调的重要部分之外)的主要区别在于我更喜欢​​将RGB值归一化到0到1之间来进行计算,而不是使用0到255之间的原始值.这消除了您发布的原始代码中的一些低效率和多次转换.

Public Function RGBtoHSV(ByVal R As Integer, ByVal G As Integer, ByVal B As Integer) As HSV
     ''# Normalize the RGB values by scaling them to be between 0 and 1
     Dim red As Decimal = R / 255D
     Dim green As Decimal = G / 255D
     Dim blue As Decimal = B / 255D

     Dim minValue As Decimal = Math.Min(red, Math.Min(green, blue))
     Dim maxValue As Decimal = Math.Max(red, Math.Max(green, blue))
     Dim delta As Decimal = maxValue - minValue

     Dim h As Decimal
     Dim s As Decimal
     Dim v As Decimal = maxValue

     ''# Calculate the hue (in degrees of a circle, between 0 and 360)
     Select Case maxValue
        Case red
           If green >= blue Then
               If delta = 0 Then
                  h = 0
               Else
                  h = 60 * (green - blue) / delta
               End If
           ElseIf green < blue Then
               h = 60 * (green - blue) / delta + 360
           End If
        Case green
           h = 60 * (blue - red) / delta + 120
        Case blue
           h = 60 * (red - green) / delta + 240
     End Select

     ''# Calculate the saturation (between 0 and 1)
     If maxValue = 0 Then
        s = 0
     Else
        s = 1D - (minValue / maxValue)
     End If

     ''# Scale the saturation and value to a percentage between 0 and 100
     s *= 100
     v *= 100

  ''# Return a color in the new color space
  Return New HSV(CInt(Math.Round(h, MidpointRounding.AwayFromZero)), _
                 CInt(Math.Round(s, MidpointRounding.AwayFromZero)), _
                 CInt(Math.Round(v, MidpointRounding.AwayFromZero)))
End Function

您没有发布用于从HSB(我称之为HSV)颜色转换为RGB的代码,但这是我使用的代码,再次使用介于0和1之间的临时值:

Public Function HSVtoRGB(ByVal H As Integer, ByVal S As Integer, ByVal V As Integer) As RGB
     ''# Scale the Saturation and Value components to be between 0 and 1
     Dim hue As Decimal = H
     Dim sat As Decimal = S / 100D
     Dim val As Decimal = V / 100D

     Dim r As Decimal
     Dim g As Decimal
     Dim b As Decimal

     If sat = 0 Then
       ''# If the saturation is 0, then all colors are the same.
       ''# (This is some flavor of gray.)
        r = val
        g = val
        b = val
     Else
        ''# Calculate the appropriate sector of a 6-part color wheel
        Dim sectorPos As Decimal = hue / 60D
        Dim sectorNumber As Integer = CInt(Math.Floor(sectorPos))

        ''# Get the fractional part of the sector
        ''# (that is, how many degrees into the sector you are)
        Dim fractionalSector As Decimal = sectorPos - sectorNumber

        ''# Calculate values for the three axes of the color
        Dim p As Decimal = val * (1 - sat)
        Dim q As Decimal = val * (1 - (sat * fractionalSector))
        Dim t As Decimal = val * (1 - (sat * (1 - fractionalSector)))

        ''# Assign the fractional colors to red, green, and blue
        ''# components based on the sector the angle is in
        Select Case sectorNumber
           Case 0, 6
              r = val
              g = t
              b = p
           Case 1
              r = q
              g = val
              b = p
           Case 2
              r = p
              g = val
              b = t
           Case 3
              r = p
              g = q
              b = val
           Case 4
              r = t
              g = p
              b = val
           Case 5
              r = val
              g = p
              b = q
        End Select
     End If

     ''# Scale the red, green, and blue values to be between 0 and 255
     r *= 255
     g *= 255
     b *= 255

     ''# Return a color in the new color space
     Return New RGB(CInt(Math.Round(r, MidpointRounding.AwayFromZero)), _
                    CInt(Math.Round(g, MidpointRounding.AwayFromZero)), _
                    CInt(Math.Round(b, MidpointRounding.AwayFromZero)))
End Function

编辑:此代码与Richard J. Ross III在C中提供的代码非常相似.我在网上找到了尽可能多的不同算法,重写了大量代码,从每个代码中借用了最好的代码,并进行了大量测试以验证结果的准确性.我忽略了我从谁借来代码,因为这只是一个私人图书馆.也许VB版本会帮助那些不想从C转换的人.:-)