draw a bbox on an image

$ cat draw_bbox.py
import os
import cv2

label_dir = "./resize_label/"
image_dir = "./resize_img/"

for image in os.listdir(image_dir):
    #print(image)
    im = cv2.imread(image_dir+image)
    #im = cv2.cvtColor(im, cv2.COLOR_BGR2RGB)
    labels_file = label_dir + image.replace(".jpg",".txt")
    #print(labels_file)
    with open(labels_file,'r') as j:
         for line in j.readlines():
             label = line.strip()
             label = label.split(" ")
             for i in range( len(label)):

                  start=(int(float(label[4])), int(float(label[5])))
                  end=(int(float(label[6])), int(float(label[7])))
                  if label[0] != -1:
                      # Blue color in BGR
                      color = (255, 0, 0)

                      # Line thickness of 2 px
                      thickness = 2
                      image_bbox = cv2.rectangle(im, start, end, color, thickness)

             cv2.imwrite("processed_"+image, image_bbox)