Working bare minimum example illustrating integration of OpenCV with ReactNative in both iOS and Android.

Doc with all steps

OpenCV Version = 4.2.0 React Native Version = 0.63.2

In this repo, we've added a BlackAndWhite function to both iOS and Android native code which coverts an image into grayscale using OpenCV and the same is accessed in RN JavaScript using {NativeModules}

References: A great Tutorial