1

I'm using opencv2 and V4L2 driver on my pi and have managed to get a tiny picture out of the Raspberry Pi Camera Module with the following script:

#!/usr/bin/env python

import cv2


camera_port = 0

#Number of frames to throw away while the camera adjusts to light levels
ramp_frames = 60

# Now we can initialize the camera capture object with the cv2.VideoCapture class.
# All it needs is the index to a camera port.

camera = cv2.VideoCapture(camera_port)

# Captures a single image from the camera and returns it in PIL format
def get_image():

 # read is the easiest way to get a full image out of a VideoCapture object.
 retval, im = camera.read()
 return im

# Ramp the camera - these frames will be discarded and are only used to allow v4l2
# to adjust light levels, if necessary

for i in xrange(ramp_frames):
 temp = get_image()
print("Taking image...")

# Take the actual image we want to keep
camera_capture = get_image()

file = "test_image_1_from_open_cv2.jpg"

# A nice feature of the imwrite method is that it will automatically choose the
# correct format based on the file extension you provide. Convenient!

cv2.imwrite(file, camera_capture)


# You'll want to release the camera, otherwise you won't be able to create a new
# capture object until your script exits
del(camera)

I run the script from the directory that it's located by:

sudo ./videocaprure_opencv2.py

But the image is tiny!

How can I get a normal size picture?

  • I don't think opencv is using the v4l2 driver because when I do sudo service uv4l_raspicam stop and sudo ./videocaprure_opencv2.py the script still puts out a tiny image. followed by 14 lines of VIDIOC_QUERYMENU: Invalid argument – reggie Feb 23 '15 at 15:20
  • when i sudo service uv4l_raspicam start it prints out lots of lines of info but one is of interest <notice> [core] Registering device node /dev/video1, so I then do sudo dd if=/dev/video1 of=snapshot.jpeg bs=11M count=1 which gives me a full size picture using the driver. – reggie Feb 23 '15 at 15:24
0

You should set the image size before starting to capture, as by default the image is the smallest possible.

  • In the python script or elsewhere? iv tried v4l2-ctl --set-fmt-video=width=2592,height=1944,pixelformat=3 then sudo ./videocaprure_opencv2.py but no joy. – reggie Feb 23 '15 at 17:23
  • You should edit your question and provide a code example. – Steve Robillard Feb 23 '15 at 23:54
  • Hi Steve, I thought I did provided a code example above. I'm not sure how to specify the size in code. – reggie Feb 24 '15 at 14:56
  • http://raspberrypi.stackexchange.com/questions/24262/getting-image-data-from-raspberry-pi-camera-module-in-opencv-with-python has a very similar problem, but I don't seem to be able to use v4l2-ctl to configure the camera module as answer suggests, any ideas, I'm stuck. – reggie Mar 2 '15 at 20:35
  • I placed camera.set(3,800) camera.set(4,600) directly after camera = cv2.VideoCapture(camera_port) and it worked. I wasn't sure from the answer that adding code to the python script was the way to solve it, because the code I quoted in the first comment, was directed at the v4l2-ctl driver. – reggie Mar 3 '15 at 22:19

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.