OpenCV build for Mac Catalyst/iOS 13 iOS app on Mac support?

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I have managed to generate a universal XCFramework that can be used for Catalyst. There are probably more efficient ways but this is what worked for me:

1. Move to the working directory (where OpenCV has been cloned / downloaded).

2. Run the opencv/platforms/ios/build_framework.py script as instructed by the OpenCV documentation (https://docs.opencv.org/4.1.1/d5/da3/tutorial_ios_install.html). The script must be run twice so that two different opencv2.framework files can be generated: one for real iOS devices, one for the simulator (this is required to generate a universal XCFramework later on). The different frameworks can be obtained by editing the build_framework.py script and commenting out the unwanted targets (at the end of the script):

   • To generate the opencv2.framework for the simulator:

     # (iphoneos_archs, "iPhoneOS"),

     (iphonesimulator_archs, "iPhoneSimulator")

   • To generate the opencv2.framework for real iOS devices:

     (iphoneos_archs, "iPhoneOS")

     # (iphonesimulator_archs, "iPhoneSimulator")

3. Back up what has been generated, then delete the following build files:

   • <working_dir>/ios/build/build-x86_64-iphonesimulator/build/*
   • <working_dir>/ios/build/build-x86_64-iphonesimulator/lib/*
   • <working_dir>/ios/build/build-x86_64-iphonesimulator/3rdparty/lib/*

4. Open the following project with Xcode 11 or later:

   • <working_dir>/ios/build/build-x86_64-iphonesimulator/OpenCV.xcodeproj

5. Configure all targets for Catalyst:

   • Set "Target Device Family" to "Universal"
   • Set "Architectures" to "Standard"
   • Set "Build Active Architecture Only" to Yes
   • Set "Supports Mac Catalyst" to Yes

6. Build the "ALL_BUILD" scheme ("Release" configuration).

7. Locate the build products:

   • <working_dir>/ios/build/build-x86_64-iphonesimulator/lib/Release/*.a
   • <working_dir>/ios/build/build-x86_64-iphonesimulator/3rdparty/lib/Release/*.a

8. Merge the products as a single static library:

   • libtool -static -o <working_dir>/libopencv_merged_catalyst.a <all paths to *.a files from previous step>

9. Create the opencv2 framework binary:

   • lipo -create <working_dir>/libopencv_merged_catalyst.a -o <working_dir>/opencv2

10. Duplicate the opencv2.framework for iOS and substitute its binary with the new one for Catalyst (generated in the previous step).

11. Create a universal XCFramework:

    • xcodebuild -create-xcframework -framework path/to/ios/opencv2.framework -framework path/to/ios-simulator/opencv2.framework -framework path/to/catalyst/opencv2.framework -output <working_dir>/opencv.xcframework