from typing import Optional
from pyzbar import pyzbar
import asyncio
import cv2
from hermit.errors import InvalidSignatureRequest
from .format import decode_qr_code_data
from .utils import window_is_open
def read_qr_code() -> Optional[str]:
task = _capture_qr_code_async()
return asyncio.get_event_loop().run_until_complete(task)
async def _capture_qr_code_async() -> Optional[str]:
capture = _start_camera()
preview_dimensions = (640, 480)
decoded_data = None
encoded_data = None
window_name = "Signature Request QR Code Scanner"
cv2.namedWindow(window_name)
while window_is_open(window_name):
ret, frame = capture.read()
frame = cv2.resize(frame, preview_dimensions)
for qrcode in pyzbar.decode(frame):
# Extract the position & dimensions of box bounding the QR
# code
(x, y, w, h) = qrcode.rect
# Draw this bounding box on the image
cv2.rectangle(
frame,
(x, y),
(x + w, y + h),
(0, 0, 255),
2)
# Decode the QR code data
encoded_data = qrcode.data
try:
decoded_data = decode_qr_code_data(encoded_data)
except InvalidSignatureRequest as e:
print("Invalid signature request: {}".format(str(e)))
# Use the first QR code found
if decoded_data is not None:
break
# Preview the (reversed) frame
mirror = cv2.flip(frame, 1)
cv2.imshow(window_name, mirror)
# Break out of the loop if we found a valid QR code
if decoded_data:
break
await asyncio.sleep(0.01)
# Clean up windows before exiting.
capture.release()
cv2.destroyWindow(window_name)
return decoded_data
def _start_camera() -> cv2.VideoCapture:
capture = cv2.VideoCapture(0)
if not capture.isOpened():
raise IOError("Cannot open webcam")
return capture
