Draw polygons to input image. Output image to stdout. Can pipe to a file or image magick's display tool for example.

drawpoly.py

import sys
import itertools
import json
import argparse
from PIL import Image, ImageDraw

def parse_args():
    parser = argparse.ArgumentParser(usage="python3 drawpoly.py -p p1.json ... <input_image >out.jpg")
    parser.add_argument("-p", "--poly-jsons", type=str, required=True, nargs="+", help="""
        JSON file(s) path containing polygon to draw.
        Format: { points: [{x: int, y: int}, ...] }""")
    return parser.parse_args()

def poly(polyj):
    abs_points = polyj["points"]
    assert isinstance(abs_points, list) and len(abs_points) > 2, "invalid polygon"
    return [
        (p["x"], p["y"])
        for p in abs_points
    ]

def draw_poly(img, points, color):
    img2 = img.copy()
    draw = ImageDraw.Draw(img2)
    draw.polygon(points, fill = color)
    return Image.blend(img, img2, 0.5)

def main():
    args = parse_args()

    img = Image.open(sys.stdin.buffer).convert("RGBA")
    polys = []
    for poly_json in args.poly_jsons:
        with open(poly_json, encoding="utf-8") as polyf:
            polyj = json.load(polyf)
            points = poly(polyj)
            print("points", points, file=sys.stderr)
            polys.append(points)

    for points, color in zip(polys, itertools.cycle(COLORS)):
        img = draw_poly(img, points, color)
    img.save(sys.stdout, format="png")


COLORS = [
    "DarkSalmon",
    "ForestGreen",
    "AliceBlue",
    "Azure",
    "Blue",
    "AntiqueWhite",
    "Aquamarine",
    "Beige",
    "Brown",
    "BlanchedAlmond",
    "BlueViolet",
    "BurlyWood",
    "CadetBlue",
    "Chartreuse",
    "Chocolate",
    "Coral",
    "CornflowerBlue",
    "Cornsilk",
    "Crimson",
    "Cyan",
    "DarkBlue",
    "DarkCyan",
    "DarkGoldenRod",
    "DarkGray",
    "DarkGrey",
    "DarkGreen",
    "DarkKhaki",
    "DarkMagenta",
    "DarkOliveGreen",
    "DarkOrange",
    "DarkOrchid",
    "DarkRed",
    "DarkSeaGreen",
    "DarkSlateBlue",
    "DarkSlateGray",
    "DarkSlateGrey",
    "DarkTurquoise",
    "DarkViolet",
    "DeepPink",
    "DeepSkyBlue",
    "DimGray",
    "DimGrey",
    "DodgerBlue",
    "FireBrick",
    "FloralWhite",
    "Fuchsia",
    "Gainsboro",
    "GhostWhite",
    "Gold",
    "GoldenRod",
    "Gray",
    "Grey",
    "Green",
    "GreenYellow",
    "HoneyDew",
    "HotPink",
    "IndianRed",
    "Indigo",
    "Ivory",
    "Khaki",
    "Lavender",
    "LavenderBlush",
    "LawnGreen",
    "LemonChiffon",
    "LightBlue",
    "LightCoral",
    "LightCyan",
    "LightGoldenRodYellow",
    "LightGray",
    "LightGrey",
    "LightGreen",
    "LightPink",
    "LightSalmon",
    "LightSeaGreen",
    "LightSkyBlue",
    "LightSlateGray",
    "LightSlateGrey",
    "LightSteelBlue",
    "LightYellow",
    "Lime",
    "LimeGreen",
    "Linen",
    "Magenta",
    "Maroon",
    "MediumAquaMarine",
    "MediumBlue",
    "MediumOrchid",
    "MediumPurple",
    "MediumSeaGreen",
    "MediumSlateBlue",
    "MediumSpringGreen",
    "MediumTurquoise",
    "MediumVioletRed",
    "MidnightBlue",
    "MintCream",
    "MistyRose",
    "Moccasin",
    "NavajoWhite",
    "Navy",
    "OldLace",
    "Olive",
    "OliveDrab",
    "Orange",
    "OrangeRed",
    "Orchid",
    "PaleGoldenRod",
    "PaleGreen",
    "PaleTurquoise",
    "PaleVioletRed",
    "PapayaWhip",
    "PeachPuff",
    "Peru",
    "Pink",
    "Plum",
    "PowderBlue",
    "Purple",
    "RebeccaPurple",
    "Red",
    "RosyBrown",
    "RoyalBlue",
    "SaddleBrown",
    "Salmon",
    "SandyBrown",
    "SeaGreen",
    "SeaShell",
    "Sienna",
    "Silver",
    "SkyBlue",
    "SlateBlue",
    "SlateGray",
    "SlateGrey",
    "Snow",
    "SpringGreen",
    "SteelBlue",
    "Tan",
    "Teal",
    "Thistle",
    "Tomato",
    "Turquoise",
    "Violet",
    "Wheat",
    "White",
    "WhiteSmoke",
    "Yellow",
    "YellowGreen"
]

if __name__ == "__main__":
    main()