主要參考:https://www.geeksforgeeks.org/python-pil-imagedraw-draw-polygon-method/
主要是通過img1 = ImageDraw.Draw(img)使用ImageDraw.Draw來畫圖；需要注意的點就是保存的時候圖片應該爲png或bmp格式，如果是jpg格式，像素值會和自己定義的不太一樣，像素值具體參照rgb顏色表(https://tool.oschina.net/commons?type=3)；
from __future__ import division, print_function, absolute_import
import skimage
import cv2
import numpy as np
import os
import json
from PIL import Image,ImageDraw
color_code={}
color_code['yellow']='#FFFF00'
color_code['red']='#FF0000'
color_code['blue']='#0000FF'
color_code['green']='#00FF00'
color_code['magenta']='#FF00FF'
color_code['cyan']='#00FFFF'
dir='.../json_files/'
for file in os.listdir(dir):
json_file = dir + file
data = json.load(open(json_file))
img = Image.new('RGB', [640, 512], color_code['cyan'])
img1 = ImageDraw.Draw(img)
label_idx_list = list(np.arange(len(data['shapes'])))
for i in label_idx_list:
if data['shapes'][i]['label'] == 'lvw':
xy = []
for xy_tuple in data['shapes'][i]['points']:
xy += xy_tuple
img1.polygon(xy, fill=color_code['red'], outline=color_code['red'])
label_idx_list.remove(i)
for j in label_idx_list:
if data['shapes'][j]['label'] == 'lv':
xy = []
for xy_tuple in data['shapes'][j]['points']:
xy += xy_tuple
img1.polygon(xy, fill=color_code['yellow'], outline=color_code['yellow'])
if data['shapes'][j]['label'] == 'la':
xy = []
for xy_tuple in data['shapes'][j]['points']:
xy += xy_tuple
img1.polygon(xy, fill=color_code['blue'], outline=color_code['blue'])
if data['shapes'][j]['label'] == 'rv':
xy = []
for xy_tuple in data['shapes'][j]['points']:
xy += xy_tuple
img1.polygon(xy, fill=color_code['green'], outline=color_code['green'])
if data['shapes'][j]['label'] == 'ra':
xy = []
for xy_tuple in data['shapes'][j]['points']:
xy += xy_tuple
img1.polygon(xy, fill=color_code['magenta'], outline=color_code['magenta'])
img.save('.../json_label/'+ os.path.splitext(file)[0] + '.png')