python中RGB和HSL的相互转换

大部分计算机软件支持的是RGB格式的颜色，但是HSL会更加人性化，下面的代码实现了rgb和hsl的相互转换

def HSL_to_RGB(h,s,l):
    ''' Converts HSL colorspace (Hue/Saturation/Value) to RGB colorspace.
        Formula from http://www.easyrgb.com/math.php?MATH=M19#text19
       
        Input:
            h (float) : Hue (0...1, but can be above or below
                              (This is a rotation around the chromatic circle))
            s (float) : Saturation (0...1)    (0=toward grey, 1=pure color)
            l (float) : Lightness (0...1)     (0=black 0.5=pure color 1=white)
       
        Ouput:
            (r,g,b) (integers 0...255) : Corresponding RGB values
       
        Examples:
            >>> print HSL_to_RGB(0.7,0.7,0.6)
            (110, 82, 224)
            >>> r,g,b = HSL_to_RGB(0.7,0.7,0.6)
            >>> print g
            82
    '''
    def Hue_2_RGB( v1, v2, vH ):
        while vH<0.0: vH += 1.0
        while vH>1.0: vH -= 1.0
        if 6*vH < 1.0 : return v1 + (v2-v1)*6.0*vH
        if 2*vH < 1.0 : return v2
        if 3*vH < 2.0 : return v1 + (v2-v1)*((2.0/3.0)-vH)*6.0
        return v1
   
    if not (0 <= s <=1): raise ValueError,"s (saturation) parameter must be between 0 and 1."
    if not (0 <= l <=1): raise ValueError,"l (lightness) parameter must be between 0 and 1."
   
    r,b,g = (l*255,)*3
    if s!=0.0:
       if l<0.5 : var_2 = l * ( 1.0 + s )
       else     : var_2 = ( l + s ) - ( s * l )
       var_1 = 2.0 * l - var_2
       r = 255 * Hue_2_RGB( var_1, var_2, h + ( 1.0 / 3.0 ) )
       g = 255 * Hue_2_RGB( var_1, var_2, h )
       b = 255 * Hue_2_RGB( var_1, var_2, h - ( 1.0 / 3.0 ) )
      
    return (int(round(r)),int(round(g)),int(round(b)))
def RGB_to_HSL(r,g,b):
    ''' Converts RGB colorspace to HSL (Hue/Saturation/Value) colorspace.
        Formula from http://www.easyrgb.com/math.php?MATH=M18#text18
       
        Input:
            (r,g,b) (integers 0...255) : RGB values
       
        Ouput:
            (h,s,l) (floats 0...1): corresponding HSL values
       
        Example:
            >>> print RGB_to_HSL(110,82,224)
            (0.69953051643192476, 0.69607843137254899, 0.59999999999999998)
            >>> h,s,l = RGB_to_HSL(110,82,224)
            >>> print s
            0.696078431373
    '''
    if not (0 <= r <=255): raise ValueError,"r (red) parameter must be between 0 and 255."
    if not (0 <= g <=255): raise ValueError,"g (green) parameter must be between 0 and 255."
    if not (0 <= b <=255): raise ValueError,"b (blue) parameter must be between 0 and 255."
   
    var_R = r/255.0
    var_G = g/255.0
    var_B = b/255.0
   
    var_Min = min( var_R, var_G, var_B )    # Min. value of RGB
    var_Max = max( var_R, var_G, var_B )    # Max. value of RGB
    del_Max = var_Max - var_Min             # Delta RGB value
   
    l = ( var_Max + var_Min ) / 2.0
    h = 0.0
    s = 0.0
    if del_Max!=0.0:
       if l<0.5: s = del_Max / ( var_Max + var_Min )
       else:     s = del_Max / ( 2.0 - var_Max - var_Min )
       del_R = ( ( ( var_Max - var_R ) / 6.0 ) + ( del_Max / 2.0 ) ) / del_Max
       del_G = ( ( ( var_Max - var_G ) / 6.0 ) + ( del_Max / 2.0 ) ) / del_Max
       del_B = ( ( ( var_Max - var_B ) / 6.0 ) + ( del_Max / 2.0 ) ) / del_Max
       if    var_R == var_Max : h = del_B - del_G
       elif  var_G == var_Max : h = ( 1.0 / 3.0 ) + del_R - del_B
       elif  var_B == var_Max : h = ( 2.0 / 3.0 ) + del_G - del_R
       while h < 0.0: h += 1.0
       while h > 1.0: h -= 1.0
      
    return (h,s,l)