''' Purpose: support image inverse transformation
'''

def size( original ) :
    ''' Purpose: return the size of the new image when performing a inverse
            transformation
    '''

    nw, nh = original.size

    return (nw, nh)

def color( opixel ) :
    ''' Purpose: return the new pixel when performing an inverse transformation
            of opixel, that is (255 - r, 255 - g, 255 - b), where r, g, and b
            are are the RGB values of opixel
    '''

    # Return the negative color based on the opixel r,g,b we pass in
    r,g,b = opixel  # Extract r,g,b from opixel
    # Modify the red, green, and blue values for the inverse pixel (npixel)
    nr = 255 - r
    ng = 255 - g
    nb = 255 - b
    npixel = ( nr, ng, nb )
    return npixel

    # Could've also just done
    # r,g,b = opixel
    # return (255 - r, 255 - g, 255 - b)

def where( nspot, original = None ) :
    ''' Purpose: return the correspondent of nspot in the original when
            performing a inverse transformation
    '''

    ospot = nspot

    return ospot

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 )

    original.show()

    new_image = manip( original, size, color, where )

    new_image.show()