''' Purpose: support image mirroring transformation
'''

def mirror( nspot, nw, nh ) :
    ''' Returns the correspondent of nspot in its nw x ny image
        in the unmirrored original
    '''
    # nw and nh are the dimensions of the new image
    # since we're not changing the dimensions, they are also the dimensions for the original image

    nx, ny = nspot  # separate the x and y points of nspot (the spot in the new image we're looking at)
    # need to find ox, oy to get the ospot in the original image

    # ox is different because we've mirrored over the y-axis
    # so what is on the left side of the new image needs to be colored using
    # the pixels on the right side of the original image
    # how far are you from the width of the image/from the right side of the image
    # GOTCHA: the last index of nx is ALWAYS one less than the width of the image
    # so each spot from the right as we progress to the left of the original image is one less than we want
    ox = (nw - 1) - nx
    oy = ny  # the same y distance, did not change
    ospot = ( ox, oy )  # the coordinate of the spot in the original image that we want to look at
    return ospot

# we are going from the new image to the old image is because we are trying to create the new image.
# for each of the pixel in the new image, from left to right, top to bottom, we need to find the color at
# the corresponding position from the old image to paint the new spot.

# we could go from the original to the new image, but here, we will paint the new image and look back to the original


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, where=mirror )

    new_image.show()