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Module to perform feature matching using OpenCV

Image feature matching for Flutter

Pub License: MIT

Plugin to perform feature matching using OpenCV

An image comparison module written as an exercise in Flutter FFI and out of a need for that functionality. It is called PixelMatching, but it is actually a FeatureMatching module utilizing OpenCV. Isolate was utilized for asynchronous processing. For the internal functionality, it was written in C++.

The matching algorithm is using FLannBasedMatcher, and for the detector, Andorid uses SIFT iOS uses KAZE.

There is currently no method to change the algorithm, so if you want to change the algorithm and test it, please refer to ios/Classes/src/ImageProcessor.cpp and change it.

ImageProcessor::ImageProcessor() : stateCode(NotInitialized) {
#ifdef __ANDROID__
#elif __APPLE__

Demo Screenshots #

Demo Screenshot

Features #

  • Plugins utilizing OpenCV
  • Perform image comparisons on camera streams (mobile platforms only), image files.
  • Compares image features to calculate and return similarity

Supported platforms #

Flutter PixelMatching is available for Android and iOS.

  • Android (min SDK 24)
  • iOS (min iOS version 11.0)

flutter_pixelmatching is currently written to be available only on mobile and there are no plans for other platforms.

Getting started #

Installing dependencies #

flutter pub add flutter_pixelmatching


  flutter_pixelmatching: ^1.0.0


Symbolic errors in the archive when using the FFi module.
For this issue, check out the following link https://github.com/dart-lang/ffi/issues/41#issuecomment-645550964

Runner -> Build Settings -> Strip Style -> change from "All Symbols" to "Non-Global Symbols"


Usage #

For image data passed as parameters, we support CameraImage, Image from the Image plugin, and Uint8List of images.

final matching = PixelMatching();
// setup target image
await matching?.initialize(image: image);
// compare image 
final double? similarity = await matching?.similarity(cameraImage);

support CameraImage ImageFormatGroup

A list of currently supported ImageFormats for CameraImages. We added the YUV420 format due to issues with JPEG during recent development.

ImageFormatGroup Android iOS

⚠️ Issue #

Currently, for ease of use, the libopencv_java4.so binary file is included inside the plugin. I know it's not recommended, but it's there so you can try it out quickly. If you are using the OpenCV module in another plugin, it may cause conflicts. Please note that.

License #

MIT License. See LICENSE for details.