Which languages are available for text recognition in Vision framework?

Question

I'm trying to add the option to my app to allow for different languages when using Apple's Vision framework for recognising text.

There seems to be a function for programmatically returning the supported languages but I'm not sure if I'm calling it correctly because I'm only getting "en-US" back which I'm fairly sure isn't the only supported language?

Here's what I currently have:

// current revision number of Vision
let revision = VNRecognizeTextRequest.currentRevision
var possibleLanguages: Array<String> = []

do {
    possibleLanguages = try VNRecognizeTextRequest.supportedRecognitionLanguages(for: .accurate, 
                                                                            revision: revision)
} catch {
    print("Error getting the supported languages.")
}

print("Possible languages for revision \(revision):\n(possibleLanguages.joined(separator: "\n"))")

Any help would be much appreciated, thank you.

Necessary

I think the language has to be added in the device settings. What device of are running this on? Does that device only have English set in its setting? – Censure

Thanks, I like the thought but I’m on a device that is en-GB only. Just tried adding Russian language to my device and it still shows en-US only. – Necessary

@Necessary Did you find any solution for this. I have to add support for other languages as well. – Carbuncle

@Carbuncle I still haven't I'm afraid. Let me know if you come across a solution, thanks! – Necessary

Answer 1

iOS 15

In iOS 15 you can call the following instance method that returns the identifiers of the languages that the request (VNRecognizeTextRequest) supports:

func supportedRecognitionLanguages() throws -> [String]

You can use it this way:

print(try! request.supportedRecognitionLanguages())

A. Result (if you use .accurate recognitionLevel):

// ["en-US", "fr-FR", "it-IT", "de-DE", "es-ES", "pt-BR", "zh-Hans", "zh-Hant"]

B. Result (if you use .fast recognitionLevel):

// ["en-US", "fr-FR", "it-IT", "de-DE", "es-ES", "pt-BR"]

recognitionLanguages property

You can easily tell Vision framework which languages are needed for text recognition using recognitionLanguages instance property:

var recognitionLanguages: [String] { get set }

According to Apple documentation: recognitionLanguages defines the order in which languages are used during language processing and text recognition.Specify the languages as ISO language codes.

A real code may look like this:

import Vision

let recognizeTextRequest = VNRecognizeTextRequest()
recognizeTextRequest.minimumTextHeight = 0.05
recognizeTextRequest.recognitionLevel = .accurate

recognizeTextRequest.recognitionLanguages = ["en-US", "fr-FR", "zh-Hans"]

P.S.

In the beginning of 2020, Vision supported only English.

Astrolabe

Thanks for you answer, this is what I ended up having but I still couldn’t get any other languages to recognise. I went back and watched the WWDC video about it and there’s one quick moment where they say they only support En-US for the first version. I’m sure they’ll add more with iOS14. – Necessary

@mralexhay, you're right, it supports only English at the moment. – Astrolabe

Answer 2

As of iOS 14, VNRecognizeTextRequestRevision2 supports English, French, Italian, German, Spanish, Portuguese, and Chinese (both Simplified and Traditional) in the .accurate recognition level.

["en-US", "fr-FR", "it-IT", "de-DE", "es-ES", "pt-BR", "zh-Hans", "zh-Hant"]

The .fast recognition level supports English, French, Italian, German, Spanish, and Portuguese.

["en-US", "fr-FR", "it-IT", "de-DE", "es-ES", "pt-BR"]

You can check in Playground with this snippet:

try VNRecognizeTextRequest.supportedRecognitionLanguages(for: .fast, revision: 2)

Diaphragm

Answer 3

For iOS 16 release, this method for checking languages support

print(try! VNRecognizeTextRequest().supportedRecognitionLanguages())

returns the following list of languages:

["en-US", "fr-FR", "it-IT", "de-DE", "es-ES", "pt-BR", "zh-Hans", "zh-Hant", "yue-Hans", "yue-Hant", "ko-KR", "ja-JP", "ru-RU", "uk-UA"]

Szymanowski

Is this for .accurate only? – Lambart

VNRecognizeTextRequest() has recognitionLevel == .accurate by default, so yes, it is for .accurate case. – Szymanowski

in iOS 17 added support of "th-TH", "vi-VT" – Pugilism