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Rust OpenCV bindings
Experimental Rust bindings for OpenCV 3 and 4.
The API is usable but unstable and not very battle-tested; use at your own risk.
API
API Documentation is, to varying success, translated from OpenCV's doxygen docs. Most likely you'll want to refer to the official OpenCV C++ documentation as well.
OpenCV version support
The following OpenCV versions are supported at the moment:
- 3.2
- 3.4
- 4.1
You can choose the target OpenCV version with the following Cargo features:
opencv-32
opencv-34
(default)opencv-41
If you need support for contrib
modules, also enable contrib
feature.
Quickstart
Make sure the supported OpenCV version is installed in your system along with pkg_config
files or -dev
packages.
Update your Cargo.toml
= "0.24"
Select OpenCV version if different from default in Cargo.toml:
= { = "0.24", = false, = ["opencv-41"]}
And enable usage of contrib
modules:
= { = "0.24", = false, = ["opencv-41", "contrib"]}
Import prelude
use *;
Minimum rustc version
Generally you should use the latest stable rustc to compile this crate.
Platform support
Currently the main development and testing of the crate is performed on Linux, but other major platforms are also supported: Mac OS X and Windows.
Support for Windows is a bit tricky at the moment: you will need to set up OPENCV_LINK_LIBS
,
OPENCV_LINK_PATHS
, OPENCV_INCLUDE_PATHS
and potentially OPENCV_PYTHON3_BIN
environment
variables. Then build the crate with buildtime-bindgen
feature enabled. If you get linking
errors try also building with --release
flag.
Mac OS X build currently also requires buildtime-bindgen
feature enabled.
Also refer to the corresponding issue and Travis [build script] (https://github.com/twistedfall/opencv-rust/blob/master/ci/script.sh).
Features
opencv-32
- build against OpenCV 3.2.0, this feature is aimed primarily on stable Debian and Ubuntu users who can install OpenCV from the repository without having to compile it from the sourceopencv-34
(default) - build against OpenCV 3.4.xopencv-41
- build against OpenCV 4.1.xcontrib
- enable the usage of OpenCV contrib modules for corresponding OpenCV versionbuildtime-bindgen
- regenerate all bindings, should only be used during the crate development or when building on Windowsforce-3rd-party-libs-discovery
- legacy feature that enables some additional logic for discovery of dependent libs, should not be needed anymore
Functionality
Generally the crate tries to only wrap OpenCV API and provide some convenience functions to be able to use it in Rust easier. We try to avoid adding any functionality besides that.
Callbacks
Some API functions accept callbacks, e.g. set_mouse_callback. While currently
it's possible to successfully use those functions there are some limitations to
keep in mind. Current implementation of callback handling keeps hold of the
passed callback argument forever. That means that the closure used as a callback
will never be freed during the lifetime of a program and moreover Drop will
not be called for it (they are stored in global static Slab
).
There is a plan to implement possibility to be able to free at least some of the
closures.
Unsafety
Although crate tries to provide ergonomic Rust interface for OpenCV, don't expect
Rust safety guarantees at this stage. It's especially true for borrow checking and
shared mutable ownership. Notable example would be Mat
which is a reference counted
object in its essence. You can own a seemingly separate Mat
in Rust terms, but
it's going to be a mutable reference to the other Mat
under the hood. Treat safety
of the crate's API as you would treat one of C++, use clone()
when needed.
Getting Started
The following external dependencies are required:
- python3
- OpenCV 3.2.0, 3.4.8 or 4.1.2
OpenCV is a complicated dependency with a lot of different configurations that can break this crate since it relies on fragile header parsing. Try these strategies in order, continuing to the next if builds with this crate fail.
See if you already have the right version of OpenCV installed
if OpenCV is installed, its version can be checked with:
Install OpenCV
Install supported version of OpenCV. Check your platform's package manager or see the upstream OpenCV installation guides.
When your OpenCV is installed in a location that's not being picked up by build script you can try setting one or both of the following environment vars prior to trying to build the crate:
Path specified by PKG_CONFIG_PATH
must contain opencv.pc
or opencv4.pc
(for OpenCV 4.x).
Path specified by LD_LIBRARY_PATH
must contain libopencv_*.so
files.
Environment variables
-
OPENCV_HEADER_DIR
During crate build it uses opencv headers supplied inside the crate for binding generation. If you want to use your own (system) headers supplyOPENCV_HEADER_DIR
environment variable. The directory in that environment variable should containopencv2
dir, e.g./usr/include
for OpenCV-3.4.x or/usr/include/opencv4
for OpenCV-4.x. -
OPENCV_PKGCONFIG_NAME
In some cases you might want to override the pkgconfig package name, you can useOPENCV_PKGCONFIG_NAME
environment variable for that. If you set it pkgconfig will expect to find the file with that name and.pc
extension in the package directory. -
OPENCV_PYTHON3_BIN
During the build crate uses Python 3 to run header parsing and generation. The binary is usually autodiscovered, but you can useOPENCV_PYTHON3_BIN
to specify the full path to the binary to invoke. E.g. "/usr/bin/python3" or "C:\Python37\python.exe"
The following variables must be set when building without pkg_config
(e.g. on Windows msvc target):
-
OPENCV_LINK_LIBS
Comma separated list of library names to link to..lib
,.so
or.dylib
extension is optional. E.g. "opencv_world411". -
OPENCV_LINK_PATHS
Comma separated list of paths to search for libraries to link. E.g. "C:\tools\opencv\build\x64\vc14\lib". -
OPENCV_INCLUDE_PATHS
Comma separated list of paths to search for system include files during compilation. E.g. "C:\tools\opencv\build\include". One of the directories specified therein must contain "opencv2/core/version.hpp" file, it's used to detect the version of the headers.
You can also set them on other platforms, then pkg_config
usage will be disabled and the set values will
be used.
Compiling OpenCV
See the upstream guides for compiling OpenCV for your platform. Make sure to compile from the correct release tag! We recommend including opencv_contrib and configuring your build with the same flags the travis build uses:
Contrib modules
The following modules require opencv_contrib
installed:
- aruco
- bgsegm
- bioinspired
- ccalib
- cvv
- dpm
- freetype
- fuzzy
- hdf
- img_hash
- line_descriptor
- phase_unwrapping
- plot
- sfm
- shape
- structured_light
- superres
- videostab
- viz
- xfeatures2d
- xobjdetect
- xphoto
OpenCV 2 support
If you can't use OpenCV 3.x or higher, the (no longer maintained) 0.2.4
version of this crate is known to work with OpenCV 2.4.7.13
(and probably other 2.4 versions).
The binding strategy
This crate works following the model of python and java's OpenCV wrappers - it parses the OpenCV C++ headers, generates a C interface to the C++ api, and wraps the C interface in Rust.
All the major modules in the C++ API are merged together in a huge
cv::
namespace. We instead made one rust module for each major
OpenCV module. So, for example, C++ cv::Mat
is opencv::core::Mat
in this crate.
The methods and field names have been snake_cased. Methods arguments with default value lose these default values, but they are reported in the API documentation.
Overloaded methods have been — manually — given different names.
All methods return a Result to hack around C++ exception handling.
Most of the API is covered, but for various reasons several modules are not yet implemented. If a missing module is near and dear to you, file an issue (or better, open a pull request!)
Contributor's Guide
The crate itself, as imported by users, consists of generated rust
code in src committed to the repo. This way, users don't have
to handle the code generation overhead in their builds. When
developing this crate, you can test changes to the binding generation
using cargo build -vv --features buildtime-bindgen
. When changing
the codegen, be sure to push changes to the generated code!
hdr_parser.py
comes from OpenCV python/java generator. We've tried
not to mess too much with this file, but had to make a few changes.
gen_rust.py
is initially a copy of gen_java, also from the OpenCV
generators, but it has drifted significantly from the original.
The license for the original work is MIT.
Special thanks to ttacon for yielding the crate name.