''' Purpose: support image black-and-white transformation
'''

def bw( opixel ) : 
    ''' Returns a new pixel whose RRB values are either (0, 0, 0) or
        (255, 255, 255).  
        
        Returns (0, 0, 0) if the average of RGB values for opixel is closer 
        to 0 than 255; otherwise, it returns (255, 255, 255)
    '''
    # if the color of opixel is closer to 0, then return (0,0,0)
    # else, return (255,255,255)

    # get the amount of red, green, and blue components from opixel
    red, green, blue = opixel

    # the amount of each color component is 0-255 inclusive
    # get the sum of the amount of red, green, and blue
    # then divide by 3 to get the average --> is this average closer to 0 or 255?
    average = ( red + green + blue ) / 3
    if ( average < 255 / 2 ):  # if the average is closer to 0 (less than half of 255)
        return (0, 0, 0)
    else: # otherwise, the average is closer to 255 if its at least halfway to 255
        return (255, 255, 255)


if ( __name__ == '__main__' ) :

    import url
    from manip import manip
    
    # get web image of interest
    link = "http://www.cs.virginia.edu/~cs1112/images/mandrill/full.png"

    original = url.get_image( link )

    new_image = manip( original, color=bw )

    new_image.show()