OpenCV on the Raspberry Pi with Arch Linux ARM

These are my notes on how I got OpenCV running on the Raspberry Pi today with a webcam. On this post you can find the Debian version that I did earlier.

  • Install Arch Linux ARM from image, use this guide.
  • Expand linux parition, also detailed on the same guide.
  • Configure copying arm224_start.elf to start.elf to get more memory for the apps
  • Configure networking: edit /etc/rc.conf and /etc/resolv.conf. Check this topic
  • Modify pacman configuration /etc/pacman.conf to use curl to download packages for my slow connection by uncommenting the line:
     XferCommand = /usr/bin/curl -C - -f %u > %o
  • I tried several times to update pacman and system using
    pacman -Syu

    but some errors about udev and libusb were found, and I finally gave up with this step. At last, everything worked except lxde which I don’t need, so I’ll check this back some other time.

  • Install lxde. I’m not sure if some libraries installed by this are useful to OpenCV.
    pacman -S lxde xorg-xinit xf86-video-fbdev
  • lxde didn’t worked: every time I tried to xinit, it throwed a error about not being found.
  • Install python2 (which was already installed but was updated), numpy, opencv and samples:
    pacman -S python2 python2-numpy opencv opencv-samples
  • Finally I run a simple test I use to open the webcam stream, take a frame and save it. It didn’t worked immediatly since I found that a Dell multimedia keyboard I had attached to a USB hub with my DIY USB powered cable with the webcam had some issues. But after solving it, the camera works and saves the image. The sample is this:
    import as cv
    import time
    #cv.NamedWindow("camera", 1)
    #capture = cv.CaptureFromCAM(-1)
    capture = cv.CreateCameraCapture(1)
    #cv.SetCaptureProperty(capture,cv.CV_CAP_PROP_FPS, 3)
    cv.SetCaptureProperty(capture,cv.CV_CAP_PROP_FRAME_WIDTH, 1280)
    cv.SetCaptureProperty(capture,cv.CV_CAP_PROP_FRAME_HEIGHT, 720)
    img = cv.QueryFrame(capture)
    print "Captured "