QR code reading in Raspberry Pi - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the library needed for QR code reading.

Raspberry Pi

import [1]

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Atime

Bnumpy

Ccv2

Dos

Attempts:

3 left

💡 Hint

Common Mistakes

Importing unrelated libraries like numpy or time.

Forgetting to import the QR code reading library.

The cv2 library (OpenCV) is used for image processing and QR code reading on Raspberry Pi.

2fill in blank

medium

Complete the code to initialize the QR code detector.

Raspberry Pi

detector = cv2.[1]()

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Aimread

BQRCodeDetector

CCascadeClassifier

DVideoCapture

Attempts:

3 left

💡 Hint

Common Mistakes

Using VideoCapture which is for camera input.

Using CascadeClassifier which is for face/object detection.

The QRCodeDetector() class in OpenCV is used to detect and decode QR codes.

3fill in blank

hard

Fix the error in the code to read a frame from the camera.

Raspberry Pi

ret, frame = cap.[1]()

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Aread

Bcapture

Cget

Dgrab

Attempts:

3 left

💡 Hint

Common Mistakes

Using capture() which does not exist.

Using get() which retrieves properties, not frames.

The read() method captures a frame from the video source and returns a success flag and the frame.

4fill in blank

hard

Fill both blanks to decode the QR code from the frame.

Raspberry Pi

data, bbox, _ = detector.[1](frame)
if data [2] "":
    print(f"QR Code data: {data}")

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AdetectAndDecode

B!=

C==

DdetectMultiScale

Attempts:

3 left

💡 Hint

Common Mistakes

Using detectMultiScale which is for object detection.

Checking if data equals empty string instead of not equals.

The detectAndDecode() method detects and decodes the QR code from the image. Checking if data != "" confirms a QR code was found.

5fill in blank

hard

Fill all three blanks to capture video, detect QR codes, and exit on pressing 'q'.

Raspberry Pi

cap = cv2.[1](0)
while True:
    ret, frame = cap.[2]()
    data, bbox, _ = detector.[3](frame)
    if data != "":
        print(f"QR Code: {data}")
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break
cap.release()
cv2.destroyAllWindows()

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AVideoCapture

Bread

CdetectAndDecode

Dimread

Attempts:

3 left

💡 Hint

Common Mistakes

Using imread which reads images from files, not camera.

Not releasing the camera or destroying windows.

VideoCapture(0) opens the default camera. read() captures frames. detectAndDecode() reads QR codes from frames. The loop exits when 'q' is pressed.