change_color.py

def color_change1(original, new_color):
    """
    Change a color in a single-color transparent PNG.

    @type im: PIL.Image
    @type new_color: tuple
    """
    # get the data for the image as a sequence of tuples
    # carve out memory for the converted image data
    converted = []
    # instead of making a new tuple for the same data,
    # index by alpha channel with a tuple for the color
    tups = {}

    for pixel in original.getdata():
        alpha = pixel[3]
        if alpha not in tups:
            # record a tuple for this alpha level
            tups[alpha] = new_color + (alpha,)
        # add color to new image data
        converted.append(tups[alpha])

    im2 = Image.new(original.mode, original.size)
    im2.putdata(converted)
    return im2