opencv_dart 0.6.7

OpenCV4 bindings for Dart language and Flutter, using dart:ffi. The most complete OpenCV bindings for Dart!

opencv_dart

OpenCV Bindings for Dart Language.

!!!This package is experimental and APIs may change in the future!!!

WIP, contributions are welcome!

Platform	Supported	Tested	Prebuilt Binaries
Android	✅	☑️	x86_64, arm64-v8a, armeabi-v7a
iOS	✅	☑️	arm64, x64(Simulator)
Linux	✅	✅	x64
Windows	✅	✅	x64
macOS	✅	✅	x64, arm64

BREAKING CHANGES

The refactor of #13 bas been finished, since v1.0.0, nearly ALL APIs were changed to compitable with opencv-python, for example:

// old API
void cvtColor(Mat src, Mat dst, int code);
// new API
Mat cvtColor(Mat src, int code, {Mat? dst});

// then usage will be changed from:
cvtColor(src, dst, cv.COLOR_BGR2GRAY);
// to:
final dst = cvtColor(src, cv.COLOR_BGR2GRAY);
// or:
cvtColor(src, cv.COLOR_BGR2GRAY, dst: dst);

The New APIs will be published in v1.0.0, if you are still using the old APIs and do not want to upgrade, you can use the old versions less than v1.0.0.

The OLD APIs won't get any updates from maintainer since v0.6.7, if you really need to use the old APIs, you can open PRs.

IMPORTANT

Please run

dart run opencv_dart:setup <platform> --arch <arch>

to download prebuilt binaries.

• platform: auto android linux windows macos ios
• for Windows, arch: x64
• for Linux, arch: x64
• for macOS, arch: x64 arm64
• for IOS, arch: x64 arm64
• for Android, arch: x86_64 arm64-v8a armeabi-v7a
• run dart run opencv_dart:setup -h to see more options

Please use v0.3.0 and later version.

Example

Status

Core Modules

module	Binding status	Test status	description
core	✅	✅	Core module
calib3d	✅	✅	Calib3D module
dnn	✅	✅	DNN module
features2d	✅	✅	Features2D module
gapi	❌	❌	GAPI module
highgui	✅	✅	HighGUI module
imgcodecs	✅	✅	ImageCodecs module
imgproc	✅	✅	ImageProc module
ml	❌	❌	ML module
objdetect	✅	✅	Object Detection module
photo	✅	✅	Photo module
stitching	☑️	☑️	Stitching module
svd	✅	✅	SVD module
video	✅	✅	Video module
videoio	✅	✅	VideoIO module

Contrib Modules

module	Binding status	Test status	description
aruco	✅	✅	ArUco module
img_hash	✅	✅	Image hashing module
cuda	❌	❌
wechat_qrcode	❌	❌
bgsegm	❌	❌
superres	❌	❌
xfeatures2d	❌	❌
ximgproc	❌	❌
xobjdetect	❌	❌
xphoto	❌	❌

• ❌ : not finished
• ☑️ : partially supported
• ✅ : finished
• modules not in the above table are not considered, contributions are welcome
• videoio: cv.VideoCapture from file is not supported yet supported now.

Usage

import 'package:opencv_dart/opencv_dart.dart' as cv;

void main() {
  final img = cv.imread("test/images/lenna.png", flags: cv.IMREAD_COLOR);
  final gray = cv.Mat.empty();

  cv.cvtColor(img, gray, cv.COLOR_BGR2GRAY);
  print("${img.rows}, ${img.cols}");

  cv.imwrite("test_cvtcolor.png", gray);
}

More examples are on the way...

TODO

• ✅ compile libs for android, linux
• ✅ support for iOS, macOS
• ❌ add more examples
• ❌ documentation
• ✅ modify C wrapper to catch exceptions
• ❌ Native Assets
• ❌ async?
• ✅ directly include opencv source code, refactor cmakelists.txt

For Developers

This package is in heavy development, dynamic libraries for Windows and linux have been compiled, for other platforms, you need to compile it yourself.

How to compile

1. prepare a compiler.

   windows: Install Visual Studio 2019 or Later

   ubuntu: reference opencv official build guide to install

   sudo apt-get install build-essential libgtk-3-dev ffmpeg libavcodec-dev cmake \
      ninja-build ccache nasm libavformat-dev libavutil-dev libswscale-dev \
      libgflags-dev python3 libjpeg-dev libpng-dev libtiff-dev python3-pip
   

   macos:

   brew install --force --overwrite ninja ccache ffmpeg nasm cmake
   

   from v0.6.4, build system has been migrated to conan

      python3 -m pip install conan
      conan profile detect -f
   

2. clone this repo, git clone https://github.com/rainyl/opencv_dart.git

3. cd opencv_dart

4. compile

   for windows:

   conan build . -b missing -s compiler.cppstd=20
   

   for linux, macos:

   conan build . -b missing
   

   for android, you need to download android ndk and opencv for android sdk, extract opencv sdk and copy and rename OpenCV-android-sdk to build/opencv/android directory. NO need for opencv sdk now, will be compiled from source to enable contrib modules

   conan build . -b missing -pr:h profiles/android-<arch> -c tools.android:ndk_path="<ABSOLUTE path for ndk>"
   

   for ios:

   echo "tools.cmake.cmaketoolchain:user_toolchain=[\"`pwd`/profiles/ios.toolchain.cmake\"]" >> profiles/ios-<arch>
   conan build . -b missing -pr:h profiles/ios-<arch>
   

5. If you want to test using vscode, add dynamic library path to "dart.env" in settings.json

Acknowledgement

• gocv project: https://github.com/hybridgroup/gocv License: Apache-2.0

License

Apache-2.0 License