chessboard_calibration¶
This script can be used to calibrate the kinect camera using a chessboard. calculates the intrinsic camera matrix and the distortion parameters.
Note
Usage:
- [q]: Stop the chessboard_calibration script.
- [s]: Save the frames/calibration results.
Source code¶
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import numpy as np
import cv2
import os
import sys
import copy
import datetime
from perception import Kinect2Sensor, CameraIntrinsics
# Panda_autograsp modules, msgs and srvs
from panda_autograsp import Logger
from panda_autograsp.functions import draw_axis
# Create Logger
script_logger = Logger.get_logger("chessboard_calibration.py")
#################################################
# Script settings ###############################
#################################################
# General settings
FULL_SCREEN = True # full screen
FACTORY = True # Use libfreenect2 factory camera parameters
# Calibration settings
criteria = (
cv2.TERM_CRITERIA_EPS + cv2.TERM_CRITERIA_MAX_ITER,
30,
0.001,
) # termination criteria
N_FRAMES = 10 # Take the mean over N_frames
N_ROWS = 5 # Inner chessboard rows
N_COLMNS = 7 # Inner chessboard columns
SQUARE_SIZE = 30 # [mm] The square size of a chessboard square
# Results save location
SAVE_PATH = os.path.abspath(
os.path.join(os.path.dirname(os.path.realpath(__file__)), "..", "data/calib")
) # Folder in which you want to save the calib results
#################################################
# Other script parameters #######################
#################################################
# Text default settings
font = cv2.FONT_HERSHEY_SIMPLEX
fontScale = 0.90
fontColor = (0, 0, 0)
lineType = 1
rectangle_bgr = (255, 255, 255)
#################################################
# Main script ###################################
#################################################
if __name__ == "__main__":
# set root logger format
root_logger = Logger.get_logger(
log_file=os.path.abspath(
os.path.join(
os.path.dirname(os.path.realpath(__file__)),
"..",
"logs/chessboard_calibration.log",
)
)
)
# Welcome message
print(
"\n== Chessboard calibration script ==\n"
"This script can be used to calibrate the "
"calculates the intrinsic camera matrix and "
"the distortion parameters.\n"
"\n"
"Usage:\n"
" [q]: Stop the chessboard_calibration script.\n"
" [s]: Save the frames/calibration results.\n"
)
#############################################
# Start Kinect sensor #######################
#############################################
sensor = Kinect2Sensor()
try:
sensor.start()
except IOError:
script_logger.warn(
"No kinect device detected make sure the kinect is connected."
)
script_logger.info("Shutting down chessboard_calibration script.")
sys.exit(0)
#############################################
# Get Intrinsic color matrix ###############
#############################################
# Setup results save name
time_str = datetime.datetime.now().strftime("%Y%m%d-%H%M%S")
NUMPY_SAVE = os.path.abspath(
os.path.join(SAVE_PATH, ("calib_intr_%s.npz" % time_str))
)
BERKLEY_SAVE = os.path.abspath(
os.path.join(SAVE_PATH, ("calib_intr_%s.intr" % time_str))
)
CAMERA_POSE_SAVE = os.path.abspath(
os.path.join(SAVE_PATH, ("calib_pose_%s.npz" % time_str))
)
# Prepare object points, like (0,0,0), (1,0,0), (2,0,0) ....,(6,5,0)
# Multiply with size of square to et the result in mm
objp = np.zeros((N_COLMNS * N_ROWS, 3), np.float32)
# Multiply by chessboard scale factor
objp[:, :2] = np.mgrid[0:N_ROWS, 0:N_COLMNS].T.reshape(-1, 2) * SQUARE_SIZE
# Arrays to store object points and image points from all the images.
objpoints = [] # 3d point in real world space
imgpoints = [] # 2d points in image plane.
axis = (
np.float32([[3, 0, 0], [0, 3, 0], [0, 0, -3]]).reshape(-1, 3) * SQUARE_SIZE
) # Coordinate axis
if not FACTORY:
# Start message
script_logger.info("--- Kinect2 camera calibration ---")
script_logger.info("Starting kinect2 calibration procedure.")
# Create opencv window
if FULL_SCREEN:
cv2.namedWindow("Calibration", cv2.WND_PROP_FULLSCREEN)
cv2.setWindowProperty(
"Calibration", cv2.WND_PROP_FULLSCREEN, cv2.WINDOW_FULLSCREEN
)
# Get a number of images
images = []
frame = 0
while True:
if frame < N_FRAMES:
# Visualize current image
color_im, _, ir_im = sensor.frames(True)
gray = cv2.cvtColor(color_im.data, cv2.COLOR_BGR2GRAY)
# Find the chess board corners
ret, corners = cv2.findChessboardCorners(gray, (N_ROWS, N_COLMNS), None)
# If found, add object points, image points (after refining them)
if ret:
# Improve found corners ##
corners2 = cv2.cornerSubPix(
gray, corners, (11, 11), (-1, -1), criteria
)
# Draw and display the corners
img_detections = cv2.drawChessboardCorners(
color_im.data, (N_ROWS, N_COLMNS), corners2, ret
)
# Create screen display image #
screen_img = cv2.cvtColor(
copy.copy(img_detections), cv2.COLOR_RGB2BGR
)
# Write text on image
text_offset_x = 10
text_offset_y = 910
text_width = 550
text_height = 160
box_coords = (
(text_offset_x - 10, text_offset_y - 10),
(
text_offset_x + text_width + 10,
text_offset_y + text_height + 10,
),
)
cv2.rectangle(
screen_img,
box_coords[0],
box_coords[1],
rectangle_bgr,
cv2.FILLED,
)
cv2.putText(
screen_img,
"=Info=",
(text_offset_x, text_offset_y + 20),
font,
fontScale,
fontColor,
lineType,
)
cv2.putText(
screen_img,
"press s to save a calibration image",
(text_offset_x, text_offset_y + 55),
font,
fontScale,
fontColor,
lineType,
)
cv2.putText(
screen_img,
"press q to exit the calibration",
(text_offset_x, text_offset_y + 90),
font,
fontScale,
fontColor,
lineType,
)
cv2.putText(
screen_img,
"Computing intrinsic parameters",
(text_offset_x, text_offset_y + 125),
font,
fontScale,
(72, 193, 80),
lineType,
)
cv2.putText(
screen_img,
("%i of the %i images taken" % (frame, N_FRAMES)),
(text_offset_x, text_offset_y + 160),
font,
fontScale,
(255, 0, 0),
lineType,
)
# Show image
cv2.imshow("Calibration", screen_img)
else:
# Create screen display image
screen_img = cv2.cvtColor(
copy.copy(color_im.data), cv2.COLOR_RGB2BGR
)
# Write text on image
text_offset_x = 10
text_offset_y = 910
text_width = 550
text_height = 160
box_coords = (
(text_offset_x - 10, text_offset_y - 10),
(
text_offset_x + text_width + 10,
text_offset_y + text_height + 10,
),
)
cv2.rectangle(
screen_img,
box_coords[0],
box_coords[1],
rectangle_bgr,
cv2.FILLED,
)
cv2.putText(
screen_img,
"=Info=",
(text_offset_x, text_offset_y + 20),
font,
fontScale,
fontColor,
lineType,
)
cv2.putText(
screen_img,
"press s to save a calibration image",
(text_offset_x, text_offset_y + 55),
font,
fontScale,
fontColor,
lineType,
)
cv2.putText(
screen_img,
"press q to exit the calibration",
(text_offset_x, text_offset_y + 90),
font,
fontScale,
fontColor,
lineType,
)
cv2.putText(
screen_img,
"Computing intrinsic parameters",
(text_offset_x, text_offset_y + 125),
font,
fontScale,
(72, 193, 80),
lineType,
)
cv2.putText(
screen_img,
("%i of the %i images taken" % (frame, N_FRAMES)),
(text_offset_x, text_offset_y + 160),
font,
fontScale,
(255, 0, 0),
lineType,
)
# Show image
cv2.setWindowProperty(
"Calibration", cv2.WND_PROP_FULLSCREEN, cv2.WINDOW_FULLSCREEN
)
cv2.imshow("Calibration", screen_img)
# Process key events
key = cv2.waitKey(delay=1)
# Break if someone presses q or esc
if (key == 27) or (key == ord("q")):
sys.exit(0)
#################################
# save frames ###################
#################################
# Save frames to list if user clicks s
if key == ord("s"):
frame += 1
# Get color, depth and ir image frames
script_logger.info(
"%i of the %i calibration images taken. Click s to take "
"another image." % (frame, N_FRAMES)
)
if ret:
objpoints.append(objp)
imgpoints.append(corners2)
else:
script_logger.warning("No chessboard found please try again.")
else:
break
# Close all image windows
cv2.destroyAllWindows()
# Perform calibration
ret, color_mtx, dist, rvecs, tvecs = cv2.calibrateCamera(
objpoints, imgpoints, gray.shape[::-1], None, None
)
# Retrieve intr parameters out of camera matrix
f_x = color_mtx[0, 0] # x focal length
f_y = color_mtx[1, 1] # Y focal length
c_x = color_mtx[0, 2] # x optical center
c_y = color_mtx[1, 2] # y optical center
s = color_mtx[1, 0] # skew
# Unwrap distortion parameters
k_1 = dist[0][0] # First radial distortion coefficient
k_2 = dist[0][1] # Second ...
k_3 = dist[0][4] # Third ...
p_1 = dist[0][2] # First tangential distortion coefficient
p_2 = dist[0][3] # Second ..
# Print information
# NOTE: Skew is set to 0 in opencv2
print("=== Calibration results ==")
print("Reprojection error RMS: %f" % ret)
print("Distortion parameters:")
print(dist[0])
print("Camera matrix:")
print(color_mtx)
# Calculate re-projection error
tot_error = 0
for index, value in enumerate(objpoints):
imgpoints2, _ = cv2.projectPoints(
objpoints[index], rvecs[index], tvecs[index], color_mtx, dist
)
error = cv2.norm(imgpoints[index], imgpoints2, cv2.NORM_L2) / len(
imgpoints2
)
tot_error += error
print("Mean error: ", tot_error / len(objpoints))
##################################################
# Save camera matrix and distortion coefficients #
##################################################
# Save as numpy array
np.savez(NUMPY_SAVE, color_mtx=color_mtx, dist=dist, rvecs=rvecs, tvecs=tvecs)
# Save as berkeley format file
camera_intr_obj = CameraIntrinsics("none", f_x, f_y, c_x, c_y, s)
camera_intr_obj.save(BERKLEY_SAVE)
##################################################
# Get chessboard/world pose estimation ############
##################################################
# Get intrinsic parameters if factory is set
if FACTORY:
# Retrieve camera parameters
color_intr = sensor.color_intrinsics
ir_intr = sensor._device.getIrCameraParams()
color_mtx = color_intr.K
ir_mtx = [ir_intr.k1, ir_intr.k2, ir_intr.p1, ir_intr.p2, ir_intr.k3]
dist = np.array(ir_mtx)
else:
# Load camera parameters
try:
time_str = datetime.datetime.now().strftime("%Y%m%d-%H%M%S")
with np.load(NUMPY_SAVE) as X:
color_mtx, dist, _, _ = [
X[item] for item in ("color_mtx", "dist", "rvecs", "tvecs")
]
except IOError:
script_logger.warn("Camera parameters could not be loaded.")
# Print information
print(
"\nTo determine the camera/world external matrix put"
"the chessboard in the upper left corner of the robot"
"table. Following click [s] to save the calibration"
"results. You can click [q] to exit."
)
# Create opencv window
if FULL_SCREEN:
cv2.namedWindow("Pose", cv2.WND_PROP_FULLSCREEN)
cv2.setWindowProperty("Pose", cv2.WND_PROP_FULLSCREEN, cv2.WINDOW_FULLSCREEN)
# Show results
while True:
# Get color image
color_im, _, _ = sensor.frames(True)
gray = cv2.cvtColor(color_im.data, cv2.COLOR_BGR2GRAY)
# Create screen display image
# Needed since opencv uses BGR instead of BGR
screen_img = cv2.cvtColor(copy.copy(color_im.data), cv2.COLOR_RGB2BGR)
# Write text on image
text_offset_x = 10
text_offset_y = 970
text_width = 630
text_height = 100
box_coords = (
(text_offset_x - 10, text_offset_y - 10),
(text_offset_x + text_width + 10, text_offset_y + text_height + 10),
)
cv2.rectangle(
screen_img, box_coords[0], box_coords[1], rectangle_bgr, cv2.FILLED
)
cv2.putText(
screen_img,
"=Info=",
(text_offset_x, text_offset_y + 20),
font,
fontScale,
fontColor,
lineType,
)
cv2.putText(
screen_img,
"press s to save a camera/world translation",
(text_offset_x, text_offset_y + 55),
font,
fontScale,
fontColor,
lineType,
)
cv2.putText(
screen_img,
"press q to exit the calibration",
(text_offset_x, text_offset_y + 90),
font,
fontScale,
fontColor,
lineType,
)
# Find the chess board corners
ret, corners = cv2.findChessboardCorners(gray, (N_ROWS, N_COLMNS), None)
if ret:
corners2 = cv2.cornerSubPix(gray, corners, (11, 11), (-1, -1), criteria)
# Find the rotation and translation vectors.
_, rvecs, tvecs, inliers = cv2.solvePnPRansac(
objp, corners2, color_mtx, dist
)
# project 3D points to image plane
imgpts, jac = cv2.projectPoints(axis, rvecs, tvecs, color_mtx, dist)
# Show image
screen_img = draw_axis(screen_img, corners2, imgpts)
cv2.imshow("Pose", screen_img)
# Check for user commands
key = cv2.waitKey(delay=1)
if key == ord("s"):
# Save rotation and transformation matrix
script_logger.info(
"Saving chessboard calibration results at %s." % (CAMERA_POSE_SAVE)
)
np.savez(
CAMERA_POSE_SAVE,
mtx=color_mtx,
dst=dist,
rvecs=rvecs,
tvecs=tvecs,
inliers=inliers,
)
# Close figure
script_logger.info("Closing aruco pose estimation script.")
sys.exit(0)
# Break if someone presses q or esc
if (key == 27) or (key == ord("q")):
script_logger.info("Closing aruco pose estimation script.")
sys.exit(0)
cv2.destroyAllWindows()
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