Detect QR codes in python on MacOS using CoreImage API via PyObjC

qrcodes.py

"""Uses CoreImage API via PyObjC to detect QR Codes in images on MacOS.  

This is a simple wrapper around the CIDetector API and only returns the text of the QR Code.
It does not return the location of the QR Code in the image.

Reference: https://developer.apple.com/documentation/coreimage/cidetector/detector_types?language=objc
"""

from typing import List

import objc
import Quartz
from Cocoa import NSURL
from Foundation import NSDictionary


def detect_qrcode(filepath: str) -> List[str]:
    """Detect QR Codes in images using CIDetector and return text of the found QR Codes"""
    with objc.autorelease_pool():
        context = Quartz.CIContext.contextWithOptions_(None)
        options = NSDictionary.dictionaryWithDictionary_(
            {"CIDetectorAccuracy": Quartz.CIDetectorAccuracyHigh}
        )
        detector = Quartz.CIDetector.detectorOfType_context_options_(
            Quartz.CIDetectorTypeQRCode, context, options
        )

        results = []
        input_url = NSURL.fileURLWithPath_(filepath)
        input_image = Quartz.CIImage.imageWithContentsOfURL_(input_url)
        features = detector.featuresInImage_(input_image)

        if not features:
            return []
        for idx in range(features.count()):
            feature = features.objectAtIndex_(idx)
            results.append(feature.messageString())
        return results


if __name__ == "__main__":
    import sys

    if len(sys.argv) < 2:
        print("Usage: qrcodes.py <image file>")
        sys.exit(1)

    print(detect_qrcode(sys.argv[1]))