Picam

Picam is an Elixir library that provides a simple API for streaming MJPEG video and capturing JPEG stills using the camera module on Raspberry Pi devices running Linux.

Features currently supported by the API:

• Set sharpness, contrast, brightness, saturation, ISO, and shutter speed values
• Set the exposure, sensor, metering, and white balance modes
• Set image and color effects
• Rotate and flip the image vertically and horizontally
• Set the exposure compensation (EV) level
• Change the image size
• Adjust JPEG fidelity through quality level, restart intervals, and region of interest
• Enable or disable video stabilization
• Adjust the video framerate
• Display text annotations on the image frame(s)

For specifics on the above features, please consult the Hex docs.

Requirements

Requirement		Notes
Host Device	Raspberry Pi 1, 2, 3, Zero/W	Zero and Zero W require a special ribbon cable
Operating System	Linux	Works out of the box with Raspian and Nerves builds
Camera Module	V1, V2	Regular, NoIR. Note for V2 module, gpu_mem in /boot/config.txt must be set >= 192
C Libraries	Broadcom VideoCore	Located in /opt/vc by default. Override with VIDEOCORE_DIR

Installation

The package can be installed by adding picam to your list of dependencies in mix.exs:

def deps do
  [{:picam, "~> 0.1.0"}]
end

Usage

Picam uses a port application named raspijpgs that interfaces with the underlying Multi-Media Abstraction Layer (MMAL) API in VideoCore. The port is started by the Picam.Camera process.

For example, to write a JPEG still using the :sketch image effect to /tmp/frame.jpg:

iex(1)> Picam.Camera.start_link
{:ok, #PID<0.160.0>}

iex(2)> Picam.set_img_effect(:sketch)
:ok

iex(3)> Picam.set_size(640, 0) # 0 automatically calculates height
:ok

iex(4)> File.write!(Path.join(System.tmp_dir!, "frame.jpg"), Picam.next_frame)
:ok

iex(5)> Picam.set_img_effect(:none) # Disable the effect
:ok

If you receive an :unexpected_exit error immediately after starting the Picam.Camera process and you're using a V2 camera module, please check that you've set gpu_mem to a value >= 192 in /boot/config.txt. You can verify this has taken effect in your terminal using vcgencmd get_mem gpu.

More than likely you'll want to put the Picam.Camera process in your supervision tree rather than starting it manually:

children = [
  worker(Picam.Camera, []),
  # ...
]

Examples

The examples directory is where you can find other useful demos of Picam in action. More examples will be added over time.

Directory	Demo
picam_http	Streaming MJPEG video using plug

Limitations

• Currently only one camera is supported. If you intend to use more than one camera through an add-on compute module, please submit an issue.

Copyright and License

Copyright (c) 2013-2017, Broadcom Europe Ltd, Silvan Melchior, James Hughes, Frank Hunleth, Jeff Smith

Picam source code is licensed under the BSD 3-Clause License.