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
- Render fullscreen or windowed video preview to HDMI and CSI displays
For specifics on the above features, please consult the Hex docs.
| 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 Raspbian 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 |
The package can be installed by adding picam to your list of dependencies in mix.exs:
def deps do
[{:picam, "~> 0.4.0"}]
endPicam 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
:okIf 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:
# lib/my_app/application.ex
children = [
worker(Picam.Camera, []),
# ...
]In order to facilitate running in dev and test modes on your development host, you can override the real Picam.Camera worker with Picam.FakeCamera by setting the :camera config option:
# config.exs
# ...
import_config "#{Mix.Project.config[:target]}.exs"# config/host.exs
use Mix.Config
config :picam, camera: Picam.FakeCameraThis will cause Picam to use the FakeCamera back-end instead of the real Camera back-end, which streams a static image of the specified size at approximately the specified fps rate (using a naïve sleep-based delay between frames).
In order for this to work, you will need to make sure you are staring the matching worker for your environment:
# lib/my_app/application.ex
camera = Application.get_env(:picam, :camera, Picam.Camera)
children = [
worker(camera, []),
# ...
]When using the FakeCamera, all the normal Picam API commands will be validated but silently ignored, with the following exceptions:
-
Picam.set_fps/1will set the desired frame rate (in frames per second) -
Picam.set_size/2only has static images built-in for the following resolutions:- 1920 x 1080
- 1280 x 720
- 640 x 480
If any other resolution is specified, the static image will default back to 1280 x 720. If you want to test with an image of a particular size or with specific image contents, you can specify your own image with
Picam.FakeCamera.set_image/1, which accepts a JPEG-encoded binary.For example:
"image.jpg" |> File.read!() |> Picam.FakeCamera.set_image()
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 |
- 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 (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.
React
Typescript
Django
Laravel
Facebook
Microsoft
Google
Alibaba
D3
Tencent