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docs (en): Update qr code scan instruction and script

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Arthur Golubtsov
2020-04-07 17:06:05 +03:00
parent c2d22ae12a
commit 6cbbb5580e
1 changed files with 16 additions and 17 deletions
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docs/en/camera.md
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@@ -94,40 +94,39 @@ The obtained images can be viewed using [web_video_server](web_video_server.md).
> **Hint** For high-speed recognition and positioning, it is better to use [ArUco markers](aruco.md).
To program actions of the copter upon detection of [QR codes](https://en.wikipedia.org/wiki/QR_code) you can use the [ZBar] library (http://zbar.sourceforge.net). It should be installed using pip:
To program actions of the copter upon detection of [QR codes](https://en.wikipedia.org/wiki/QR_code) you can use the [pyZBar](https://pypi.org/project/pyzbar/). It should be installed using pip:
```bash
sudo pip install zbar
sudo pip install pyzbar
```
QR codes recognition in Python:
```python
import cv2
import zbar
import rospy
from pyzbar import pyzbar
from cv_bridge import CvBridge
from sensor_msgs.msg import Image
bridge = CvBridge()
scanner = zbar.ImageScanner()
scanner.parse_config('enable')
rospy.init_node('barcode_test')
# Image subscriber callback function
def image_callback(data):
cv_image = bridge.imgmsg_to_cv2(data, 'bgr8') # OpenCV image
gray = cv2.cvtColor(cv_image, cv2.COLOR_BGR2GRAY, dstCn=0)
pil = ImageZ.fromarray(gray)
raw = pil.tobytes()
image = zbar.Image(320, 240, 'Y800', raw) # Image params
scanner.scan(image)
for symbol in image:
# print detected QR code
print 'decoded', symbol.type, 'symbol', '"%s"' % symbol.data
barcodes = pyzbar.decode(cv_image)
for barcode in barcodes:
b_data = barcode.data.encode("utf-8")
b_type = barcode.type
(x, y, w, h) = barcode.rect
xc = x + w/2
yc = y + h/2
print ("Found {} with data {} with center at x={}, y={}".format(b_type, b_data, xc, yc))
image_sub = rospy.Subscriber('main_camera/image_raw', Image, image_callback, queue_size=1)
rospy.spin()
```
The script will take up to 100% CPU capacity. To slow down the script artificially, you can use [throttling](http://wiki.ros.org/topic_tools/throttle) of frames from the camera, for example, at 5 Hz (`main_camera.launch`):