I am trying to show my picture as a negative, and I coded it, but it wont show the picture as a negative, did I do something wrong?
def negative(picButterfly2):
    for px in getPixels(picButterfly1):
        red=getRed(px)
        green=getGreen(px)
        blue=getBlue(px)
        negColor=makeColor(255-red, 255-green, 255-blue)
        setColor(px,negColor)
ALSO HOW DO I DRAW HORIZONTAL LINES? Thanks!