[Python] Trouble when accessing camera (Arducam) on Raspberry PI 4

Question: I'm trying to capture an image using OpenCV and save it with both OpenCV and PIL on my Raspberry Pi 4. Here's my Python code:

import cv2
from PIL import Image

print("1")
cap = cv2.VideoCapture(0)
for i in range(100):
ret, frame = cap.read()

if not ret:
print("Failed to grab frame")
break

if i == 99:
print("3")
cv2.imshow("Captured Image", frame)
cv2.imwrite("captured_image.jpg", frame)
frame = cv2.resize(frame, (160, 90))
pil_image = Image.fromarray(frame)
pil_image.save("captured_image_pil.jpg")
print("4")


Problem:

1. cv2.imwrite() does not actually save the image — the file doesn't show up or is empty.
2. The image saved by PIL is completely black.
3. When I run libcamera-hello, the camera works fine and shows output.

What I tried:

• Verified camera works using libcamera-hello.
• Checked if the frames are being captured (they seem to be).

My question:

Why doesn't OpenCV save the image, and why is the PIL image black, even though the camera works with libcamera-hello? How can I fix this? My camera model is Arducam IMX 708

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