Grabbing snapshots from webcams in ruby

Question

How can I take snapshots from a webcam in ruby? I know the webcam device is on /dev/video0, but how do I get a picture from it?

wedesoft · Accepted Answer · 2012-07-20T10:15:18.523

10

I'm the developer of Hornetseye. You can capture images with the V4L2-interface of HornetsEye as follows.

require 'rubygems'
require 'hornetseye_v4l2'
require 'hornetseye_xorg'
require 'hornetseye_rmagick'
include Hornetseye
input = V4L2Input.new '/dev/video0'
img = X11Display.show { input.read }
img.to_ubytergb.save_ubytergb 'test.png'

Currently supported colourspaces are UYVY, YUYV, YUV420, GREY, RGB24. Note that other colourspaces such as MJPEG are not supported at the moment.

edited Jul 20 '12 at 10:15

answered Feb 01 '10 at 14:41

wedesoft

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The gem is [`hornetseye-v4l2`](https://rubygems.org/gems/hornetseye-v4l2) – Dorian Oct 08 '16 at 21:42
But this doesn't work on macOS, and the OpenCV example works: http://stackoverflow.com/a/39938139/407213 – Dorian Oct 08 '16 at 22:44
@Dorian yes, that's correct. It only works under GNU/Linux. – wedesoft Oct 18 '16 at 21:36
This is a very interesting project. When I see efforts like this, I wish ruby hype train was still running. – nurettin Feb 12 '17 at 15:04
@nurettin Thanks – wedesoft Mar 21 '17 at 12:23

score 1 · Answer 2 · edited Apr 30 '21 at 16:11

1

I've never actually used it but hornetseye looks good. This question has also already been asked here

edited Apr 30 '21 at 16:11

wedesoft

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answered Jan 15 '10 at 00:52

Jamie

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I've been trying to use hornetseye, but it doesn't seem to fully work. – Malfist Jan 15 '10 at 17:30

score 0 · Answer 3 · answered Jan 14 '10 at 23:02

Since you're using Linux, try videodog. It's a small program, which does one thing and does that well: capturing a frame from your /dev/video0 device. From that point you can use any Ruby technique you want to process the JPEG image you got from videodog.

score 0 · Answer 4 · answered Jan 15 '10 at 01:29

The Video4Linux API involves sending special ioctls to the /dev/video* device, with data in packed structures; not something easy to do from Ruby. (It's not all that much fun from C, either.)

ruby-v4l is an extension library for capture pictures in Ruby using Video4Linux.

Orphaned in Debian because its maintainer hasn't been active since 2005, so if it doesn't work I don't think you'll be able to get much support.

A more modern solution would probably be to create proper libv4l binding for Ruby. However, I don't know of any present work on that.

score 0 · Answer 5 · answered Oct 10 '16 at 16:08

0

With the ruby-opencv gem:

require "opencv"

capture = OpenCV::CvCapture.open
sleep 1 # Warming up the webcam
capture.query.save("image.jpg")
capture.close

And to install OpenCV on macOS: brew install homebrew/science/opencv --HEAD.

answered Oct 10 '16 at 16:08

Dorian

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Chris Hasiński · Answer 6 · 2022-09-30T18:00:57.527

I've written a small wrapper-gem for the new OpenCV since ruby-opencv is stuck at OpenCV2, which isn't available on some modern systems. It should work on both macOS and Linux, provided OpenCV is installed.

Here it is: https://github.com/khasinski/framegrabber

In your case it would be:

Framegrabber.open(0) # 0 is the device id
image = Framegrabber.grab_image # Gets you a Magick::Image object
Framegrabber.release # turns off the webcam

Grabbing snapshots from webcams in ruby

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