VNRecognizeTextRequest Supported Languages

I have no idea, but I suspect each language takes a lot of space on drive, and having "all languages" supported in one device is over-the-top expensive for most use cases. I'd suspect they would come out sooner or later with a "current locale langs" or "currenct keyoard langs" supported.

My implementation intersects between a Set of my wanted / suspected / expected languages and the VNRecognizeTextRequest's

supportedRecognitionLanguages

As mentioned, currently this seems to be only US english.

Literally billions of non-english speakers would benefit from an OCR service in their native language. English speakers would benefit from an OCR service when abroad.

Some apps' feasibility would depend on whether VNRecognizeTextRequest supports only the current locale lang or the current keyboards langs, or somwhow deduces langs from current location or something else. Having no langs but en-US at this stage would probably drive many developers to opt to use the googpetition or another cloudy OCR service from the get go and forsake VisionKit... I'm considering this.

Some OCR implementations would definetely benefit from having OCR languages support added / removed "by demand", so that LocationServices / user preferences / location by ip services could allow better chances at detecting texts for users WHEN ABROAD, which is... hmmm... a time where I suspect OCR / Translation would have many use cases and would be in high demand.

Despite the fact that we are now several beta versions further on... the problem has remained the same.

You can choose different languages but I don't really notice a difference.

For a long time I wondered why my app does not recognize German umlauts (e.g. Ü ö ä or a ß).

Now I found out that umlauts are only recognized if I set the .recognitionLevel= .fast and the .usesLanguageCorrection = false

Unfortunately, the .customWords seem not to work anymore and the quality of the text recognition is not good.

That would be nice if Apple could improve this or better explain what to do to get better results.

Code Block 
textRecognitionRequest = VNRecognizeTextRequest(completionHandler: recognizeTextHandler)
textRecognitionRequest.recognitionLevel = .accurate
textRecognitionRequest.recognitionLanguages = ["de-DE"]
textRecognitionRequest.usesLanguageCorrection = true

For those still looking for this info some years later the following chunk of code works for me.

import Vision

// Create a text recognition request
let textRecognitionRequest = VNRecognizeTextRequest()

// Retrieve the list of supported languages
do {
    let supportedLanguages = try textRecognitionRequest.supportedRecognitionLanguages()
    print("Supported languages: \(supportedLanguages)")
} catch {
    print("Failed to retrieve supported languages: \(error)")
}

Hope it helps!