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Merwanski/cv_bridge_alternative.py

Created February 23, 2022 23:06
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Alternative for the `cv_bridge` python library two most used functions.
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cv_bridge_alternative.py
# initial code from https://github.com/ros-perception/vision_opencv/blob/noetic/cv_bridge/python/cv_bridge/core.py
import cv2
import numpy as np
import sensor_msgs
def cv2_to_imgmsg(cvim, encoding="passthrough", header=None):
if not isinstance(cvim, (np.ndarray, np.generic)):
raise TypeError('Your input type is not a numpy array')
# prepare msg
img_msg = sensor_msgs.msg.Image()
img_msg.height = cvim.shape[0]
img_msg.width = cvim.shape[1]
if header is not None:
img_msg.header = header
# encoding handling
numpy_type_to_cvtype = {'uint8': '8U', 'int8': '8S', 'uint16': '16U',
'int16': '16S', 'int32': '32S', 'float32': '32F',
'float64': '64F'}
numpy_type_to_cvtype.update(dict((v, k) for (k, v) in numpy_type_to_cvtype.items()))
if len(cvim.shape) < 3:
cv_type = '{}C{}'.format(numpy_type_to_cvtype[cvim.dtype.name], 1)
else:
cv_type = '{}C{}'.format(numpy_type_to_cvtype[cvim.dtype.name], cvim.shape[2])
if encoding == "passthrough":
img_msg.encoding = cv_type
else:
img_msg.encoding = encoding
if cvim.dtype.byteorder == '>':
img_msg.is_bigendian = True
# img data to msg data
img_msg.data = cvim.tostring()
img_msg.step = len(img_msg.data) // img_msg.height
return img_msg
def imgmsg_to_cv2(img_msg, dtype=np.uint8):
# it should be possible to determine dtype from img_msg.encoding but there is many different cases to take into account
# original function args: imgmsg_to_cv2(img_msg, desired_encoding = "passthrough")
return np.frombuffer(img_msg.data, dtype=dtype).reshape(img_msg.height, img_msg.width, -1)
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