As of image version 0.21.0 which I just published you can leverage the Evision.VideoCapture module to extract images from a video.
You can therefore use either the more idiomatic API in Image.Video or simply leverage the code that is there to use Evision directly.
Depending on the codec support of the OpenCV installation on your system I suspect you may not need to use the FFMEG CLI approach any more.
Example using Image
# Extract using a frame offset
iex> {:ok, video} = Image.Video.open("./test/support/video/video_sample.mp4")
iex> {:ok, _image} = Image.Video.image_from_video(video, frame: 0)
# Extract using a millisecond offset
iex> {:ok, _image} = Image.Video.image_from_video(video, millisecond: 0)
# Capturing images from a camera (note that seeking is not supported
# on image streams. On MacOS you will receive a prompt to permit the
# app to access the camera. You may need to restart the BEAM and/or
# your system if capturing fails immediately after granting permission.
iex> {:ok, video} = Image.Video.open(:default_camera)
iex> {:ok, _image} = Image.Video.image_from_video(video)
Example using Evision directly
# Extract by frame offset
video = Evision.VideoCapture.videoCapture(video_filename)
true = Evision.VideoCapture.set(video, Evision.cv_CAP_PROP_POS_FRAMES(), frame_offset),
cv_image = Evision.VideoCapture.read(video)
Using images in Nx
Both Image and Evision support zero-copy “export” of images to Nx. Just call Image.to_nx/1 or Evision.Mat.to_nx/1 as appropriate.
