OS	Arch	ABI	Build Status	Has Precompiled Library
Linux	x86_64	gnu		Yes
Linux	x86_64	musl		Yes
Linux	aarch64	gnu		Yes
Linux	aarch64	musl		Yes
Linux	armv6 (armhf)	gnueabihf		Yes
Linux	armv7l (armhf)	gnueabihf		Yes
Linux	ppc64le	gnu		Yes
Linux	s390x	gnu		Yes
Linux	riscv64	gnu		Yes
Linux	riscv64	musl		Yes
macOS 12 Monterey	x86_64	darwin		Yes
macOS 14 Sonoma	aarch64	darwin		Yes
Windows 2022	x86_64	msvc		Yes
Windows 2022	aarch64	msvc		Yes

Installation

In order to use evision, you will need Elixir installed. Then create an Elixir project via the mix build tool:

$ mix new my_app

Then you can add evision as a dependency in your mix.exs.

def deps do
  [
    {:evision, "~> 0.2"}
  ]
end

Use Precompiled Library (Default)

The following environment variables can be set based on your needs.

(Note that precompiled binaries do not use FFmpeg. If you'd like to use FFmpeg, please compile from source (please see instructions in the next section) and set corresponding environment variables. We're considering this option at the moment.)

Advanced Options

TARGET_ABI

Required if and only if the target is using musl libc.

# (for nerves project, this environment variable is set by nerves)
export TARGET_ABI=musl
## (for armv7l which uses hard-float ABI (armhf))
export TARGET_ABI=musleabihf

This variable will only be checked when identifying the musl libc ABI so that the correct precompiled binaries can be downloaded. Therefore,

1. You don't need to keep it in the runtime environment.
2. If you want to change it later, the directory _build/${MIX_ENV}/lib/evision needs to be deleted first.

The default value for the TARGET_ABI env var is obtained using the following elixir code

target_abi = List.last(String.split(to_string(:erlang.system_info(:system_architecture)), "-"))
target_abi =
  case target_abi do
    "darwin" <> _ -> "darwin"
    "win32" ->
      {compiler_id, _} = :erlang.system_info(:c_compiler_used)
      case compiler_id do
        :msc -> "msvc"
        _ -> to_string(compiler_id)
      end
    _ -> target_abi
  end

EVISION_PREFER_PRECOMPILED

# optional. 
# set this to "false" if you prefer :evision to be compiled from source
# 
# default value is "true", and :evision will prefer to use precompiled binaries (if available)
export EVISION_PREFER_PRECOMPILED=false

This variable will only be checked whenever the mix compile task is invoked directly (mix compile) or indirectly (mix test). And in the Makefile we would skip everything if _build/${MIX_ENV}/lib/evision/priv/evision.so is presented. Therefore,

1. You don't need to keep it in the runtime environment.
2. If you want to change it later, the directory _build/${MIX_ENV}/lib/evision needs to be deleted first.

If you found the precompiled binaries do not suit your needs (e.g., perhaps you need OpenCV to be compiled with FFmpeg to handle more video formats.), it's possible to override the behaviour by setting the environment variable EVISION_PREFER_PRECOMPILED to false, and then please delete _build/${MIX_ENV}/lib/evision and recompile evision

Also, for Linux users only, the precompiled binary is not compiled with GTK support, therefore functions like Evision.HighGui.imshow/2 will not work. However, you can either use Evision.Wx.imshow/2 (if Erlang on your system is compiled with wxWidgets), or set the environment variable EVISION_PREFER_PRECOMPILED to false so that OpenCV can detect available HighGui backend when compiling from source.

export EVISION_PREFER_PRECOMPILED=false

For livebook users,

Mix.install([
  {:evision, "~> 0.2"}
], system_env: [
  {"EVISION_PREFER_PRECOMPILED", "false"}
])

EVISION_ENABLE_CONTRIB

Set environment variable EVISION_ENABLE_CONTRIB to true to enable modules from opencv_contrib.

# enable opencv_contrib modules (default)
export EVISION_ENABLE_CONTRIB=true

# disable opencv_contrib modules
export EVISION_ENABLE_CONTRIB=false

This variable will only be checked whenever the mix compile task is invoked directly (mix compile) or indirectly (mix test). And in the Makefile we would skip everything if _build/${MIX_ENV}/lib/evision/priv/evision.so is presented. Therefore,

1. You don't need to keep it in the runtime environment.
2. If you want to change it later from false to true, you can delete the file _build/${MIX_ENV}/lib/evision/priv/evision.so, set EVISION_ENABLE_CONTRIB to true, and then execute mix compile.

Defaults to true because for precompiled binaries, including these "extra" modules only increases less than 20 MBs (tested on aarch64-apple-darwin) in size.

However, 20 MBs for Nerves users can be a huge deal (still depending on your device, for example, +20 MBs is often much more acceptable for RPIs as they are usually equipped with >= 8 GB microSD cards while being absolutely a luxury thing for some other embedded devices).

EVISION_ENABLE_CUDA

Set environment variable EVISION_ENABLE_CONTRIB to true to enable CUDA support from opencv_contrib. Defaults to false.

Note that EVISION_ENABLE_CONTRIB will need to be true as well.

# enable CUDA support
export EVISION_ENABLE_CUDA=true
## set a CUDA version that matches your local CUDA driver
## (this environment variable is only required for users who'd like to use precompiled binaries)
## available ones are 
## 11, for CUDA 11.x, built with CUDA 11.8.0
## 12, for CUDA 12.x, built with CUDA 12.5.0
export EVISION_CUDA_VERSION=11

## set a CUDNN version that matches your local CUDNN shared library
## (this environment variable is only required for users who'd like to use precompiled binaries)
## available ones are 
## 8, for CUDA 11.x or 12.x, built with CUDNN 8.9.7
## 9, for CUDA 11.x or 12.x, built with CUDNN 9.2.0
export EVISION_CUDNN_VERSION=9

## opencv_contrib modules is enabled by default
export EVISION_ENABLE_CONTRIB=true

# disable CUDA support (default) 
export EVISION_ENABLE_CUDA=false

IMPORTANT NOTE FOR WINDOWS USERS

If EVISION_ENABLE_CUDA is true, please also set CUDA runtime dir otherwise Evision will fail to load.

cmd

set EVISION_CUDA_RUNTIME_DIR=C:/PATH/TO/YOUR/CUDA/RUNTIME/BIN

Also, please don't quote even if there are spaces in the path

set EVISION_CUDA_RUNTIME_DIR=C:/PATH WITH SPACE/TO/YOUR/CUDA/RUNTIME/BIN

Powershell

$Env:EVISION_CUDA_RUNTIME_DIR="C:/PATH/TO/YOUR/CUDA/RUNTIME/BIN"
$Env:EVISION_CUDA_RUNTIME_DIR="C:/PATH WITH SPACE/TO/YOUR/CUDA/RUNTIME/BIN"

EVISION_PRECOMPILED_CACHE_DIR

# optional.
## set the cache directory for the precompiled archive file
export EVISION_PRECOMPILED_CACHE_DIR="$(pwd)/.cache"

Examples

Some examples are available in the examples directory.

Description

evision will pull OpenCV source code from GitHub, then parse and automatically generate corresponding OpenCV-Elixir bindings.

This project uses and modifies gen2.py and hdr_parser.py from the python module in the OpenCV repo so that they output header files that can be used in Elixir bindings.

We hope this project can largely reduce the work of manually porting OpenCV functions/modules to Elixir.

Compatible OpenCV versions:

• 4.5.3
• 4.5.4
• 4.5.5
• 4.6.0
• 4.7.0
• 4.8.0
• 4.9.0
• 4.10.0

by compatible, it means these versions can compile successfully, and I tested a small range of functions. Tons of tests should be written, and then we can have a list for tested OpenCV versions.

Docs

Online docs for the latest released version is available on Hex.pm, https://hexdocs.pm/evision/.

Useful links

• Installation
• Use Precompiled Library (Default)
• Compile evision from source
• Nerves Support
• Register Builtin Smart Cells
• Integration with Nx
• Access behaviour (Getting a sub-area of an image)

Acknowledgements

• gen2.py, hdr_parser.py, and c_src/erlcompat.hpp were directly copied from the python module in the OpenCV repo. Changes applied.
• Makefile, CMakeLists.txt, and c_src/nif_utils.hpp were also copied from the torchx module in the elixir-nx repo. Minor changes applied.