hardcoded_bridge.py

#!/usr/bin/env python3.9

import sys
import numpy as np
import rospy
from sensor_msgs.msg import Image

def imgmsg_to_cv2(img_msg):
    if img_msg.encoding != "rgb8":
        rospy.logerr("This Coral detect node has been hardcoded to the 'rgb8' encoding.  Come change the code if you're actually trying to implement a new camera")
    dtype = np.dtype("uint8") # Hardcode to 8 bits...
    dtype = dtype.newbyteorder('>' if img_msg.is_bigendian else '<')
    image_opencv = np.ndarray(shape=(img_msg.height, img_msg.width, 3), # and three channels of data. Since OpenCV works with bgr natively, we don't need to reorder the channels.
                    dtype=dtype, buffer=img_msg.data)
    image_opencv = np.array([image_opencv[:,:,2], image_opencv[:,:,1], image_opencv[:,:,0]])
    image_opencv = np.moveaxis(image_opencv, 0, -1)
    # If the byt order is different between the message and the system.
    if img_msg.is_bigendian == (sys.byteorder == 'little'):
        image_opencv = image_opencv.byteswap().newbyteorder()
    return image_opencv

def cv2_to_imgmsg(cv_image):
    img_msg = Image()
    img_msg.height = cv_image.shape[0]
    img_msg.width = cv_image.shape[1]
    img_msg.encoding = "rgb8"
    img_msg.is_bigendian = 0
    img_msg.data = cv_image.tostring()
    img_msg.step = len(img_msg.data) // img_msg.height # That double line is actually integer division, not a comment
    return img_msg