''' Provides gamma factor corrections
'''

from PIL import Image

def correction( i, gf ) :
    ''' returns the gamma correction for gamma factor gf for value intensity i
    '''

    gc = int( 255 * ( i / 255 ) ** ( 1 / gf ) )

    return gc

def pixel( p, gf ) :
    ''' returns a new pixel whose RGB values are gamma corrections for gamma
        factor gf of the RGB values of pixel p
    '''

    r, g, b = p # a pixel is a tuple with three values: red, green, and blue

    # apply gamma correction to each individual color
    gr = correction(r, gf)
    gg = correction(g, gf)
    gb = correction(b, gf)

    gp = (gr, gg, gb) # reassembling the new pixel

    return gp

def create( original, gf ) :
    ''' Returns a new image whose dimensions match that of original, where a
        pixel in the new image is a gamma correction for gamma factor gf of
        the corresponding pixel in original
    '''

    ow, oh = original.size
    nw, nh = ow, oh
    new_image = Image.new( 'RGB', ( nw, nh ) )

    for nx in range( 0, nw ) :
        for ny in range( 0, nh ) :
            nspot = (nx, ny )
            ospot = nspot
            opixel = original.getpixel( ospot )

            npixel = pixel( opixel, gf )

            new_image.putpixel( nspot, npixel )
    return new_image



if ( __name__ == '__main__' ) :
    import url
    import gamma

    link = 'http://www.cs.virginia.edu/~cs1112/images/mandrill/full.png'
    reply = input( "Enter email id: " )
    id = reply.strip().lower()
    original = url.get_selfie( id )

    im = gamma.create( original, 0.25 )
    im.show()
    
    im = gamma.create( original, 2.00 )
    im.show()