Use Apple's Vision framework from Python to detect text in images

vision.py

""" Use Apple's Vision Framework via PyObjC to detect text in images """

import pathlib

import Quartz
import Vision
from Cocoa import NSURL
from Foundation import NSDictionary
# needed to capture system-level stderr
from wurlitzer import pipes


def image_to_text(img_path, lang="eng"):
    input_url = NSURL.fileURLWithPath_(img_path)

    with pipes() as (out, err):
    # capture stdout and stderr from system calls
    # otherwise, Quartz.CIImage.imageWithContentsOfURL_
    # prints to stderr something like:
    # 2020-09-20 20:55:25.538 python[73042:5650492] Creating client/daemon connection: B8FE995E-3F27-47F4-9FA8-559C615FD774
    # 2020-09-20 20:55:25.652 python[73042:5650492] Got the query meta data reply for: com.apple.MobileAsset.RawCamera.Camera, response: 0
        input_image = Quartz.CIImage.imageWithContentsOfURL_(input_url)

    vision_options = NSDictionary.dictionaryWithDictionary_({})
    vision_handler = Vision.VNImageRequestHandler.alloc().initWithCIImage_options_(
        input_image, vision_options
    )
    results = []
    handler = make_request_handler(results)
    vision_request = Vision.VNRecognizeTextRequest.alloc().initWithCompletionHandler_(handler)
    error = vision_handler.performRequests_error_([vision_request], None)

    return results

def make_request_handler(results):
    """ results: list to store results """
    if not isinstance(results, list):
        raise ValueError("results must be a list")

    def handler(request, error):
        if error:
            print(f"Error! {error}")
        else:
            observations = request.results()
            for text_observation in observations:
                recognized_text = text_observation.topCandidates_(1)[0]
                results.append([recognized_text.string(), recognized_text.confidence()])
    return handler


def main():
    import sys
    import pathlib

    img_path = pathlib.Path(sys.argv[1])
    if not img_path.is_file():
        sys.exit("Invalid image path")
    img_path = str(img_path.resolve())
    results = image_to_text(img_path)
    print(results)


if __name__ == "__main__":
    main()