This gist uses Pillow to get the boundary edges of an image and generate the polygon position of the draw inside. Im using this script to get the polygon of my games sprites to create the collisions mechanics using libgdx!

edge_detection_and_polygon_exporter.py

from PIL import Image, ImageFilter

filename = "dship1"

image = Image.open(filename + ".png")
image = image.filter(ImageFilter.FIND_EDGES)
image.save(filename + "_edge.png")
cols = image.width
rows = image.height
points = []
w = 1
h = 1
i = 0
for pixel in list(image.getdata()):
    if pixel[3] > 0:
        points.append((w, h))

    if i == cols:
        w = 0
        i = 0
        h += 1
    w += 1
    i += 1

with open(filename + "_points.txt", "wb") as nf:
    nf.write(',\n'.join('%s, %s' % x for x in points))