# Author: Arah J. Leonard
# Copyright 01AUG09
# Original source: http://www.insanit.net/computer-programming/red-green-blue-to-red-yellow-blue-part-2/
# Distributed under the LGPL - http://www.gnu.org/copyleft/lesser.html
# ALSO distributed under the The MIT License from the Open Source Initiative (OSI) - http://www.opensource.org/licenses/mit-license.php
# You may use EITHER of these licenses to work with / distribute this source code.
# Enjoy!

# Convert a red-green-blue system to a red-yellow-blue system.
def rgb2ryb(r, g, b):
    t = type(r)
    
    # Remove the whiteness from the color.
    w = float(min(r, g, b))
    r = float(r) - w
    g = float(g) - w
    b = float(b) - w
    
    mg = max(r, g, b)
    
    # Get the yellow out of the red+green.
    y = min(r, g)
    r -= y
    g -= y
    
    # If this unfortunate conversion combines blue and green, then cut each in half to preserve the value's maximum range.
    if b and g:
        b /= 2.0
        g /= 2.0
    
    # Redistribute the remaining green.
    y += g
    b += g
    
    # Normalize to values.
    my = max(r, y, b)
    if my:
        n = mg / my
        r *= n
        y *= n
        b *= n
    
    # Add the white back in.
    r += w
    y += w
    b += w
    
    # And return back the ryb typed accordingly.
    return t(r), t(y), t(b)

# Convert a red-yellow-blue system to a red-green-blue system.
def ryb2rgb(r, y, b):
    t = type(r)
    
    # Remove the whiteness from the color.
    w = float(min(r, y, b))
    r = float(r) - w
    y = float(y) - w
    b = float(b) - w
    
    my = max(r, y, b)
    
    # Get the green out of the yellow and blue
    g = min(y, b)
    y -= g
    b -= g
    
    if b and g:
        b *= 2.0
        g *= 2.0
    
    # Redistribute the remaining yellow.
    r += y
    g += y
    
    # Normalize to values.
    mg = max(r, g, b)
    if mg:
        n = my / mg
        r *= n
        g *= n
        b *= n
    
    # Add the white back in.
    r += w
    g += w
    b += w
    
    # And return back the ryb typed accordingly.
    return t(r), t(g), t(b)

# Return the complementary color values for a given color.  You must also give it the upper limit of the color values, typically 255 for GUIs, 1.0 for OpenGL.
def complimentary(r, g, b, limit=255):
    return limit - r, limit - g, limit - b

# Debugging test code.  Not intended to be used as an application.
if __name__=="__main__":
    red = (255, 0, 0)
    green = (0, 255, 0)
    blue = (0, 0, 255)
    cyan = (0, 255, 255)
    magenta = (255, 0, 255)
    yellow = (255, 255, 0)
    black = (0, 0, 0)
    white = (255, 255, 255)
    orange = (255, 128, 0)
    darkgreen = (0, 128, 0)
    tests = [red, green, blue, cyan, magenta, yellow, black, white, orange, darkgreen, (255, 128, 64), (255, 64, 128), (64, 255, 128), (128, 255, 64), (64, 128, 255), (128, 64, 255)]
    for test in tests:
        ryb = rgb2ryb(test[0], test[1], test[2])
        rgb = ryb2rgb(ryb[0], ryb[1], ryb[2])
        cryb = complimentary(ryb[0], ryb[1], ryb[2])
        crgb = ryb2rgb(cryb[0], cryb[1], cryb[2])
        print test, "rgb2ryb", ryb, "ryb2rgb", rgb
        print "complimentary rgb", complimentary(rgb[0], rgb[1], rgb[2])
        print "complimentary ryb", cryb, "to rgb", crgb
        print