在 iOS 上使用 ML Kit 辨識文字語言

你可以使用 ML Kit 辨識文字字串的語言。您可以查看字串最可能的語言，以及所有字串所有可用語言的可信度分數。

ML Kit 可辨識原生指令碼中超過 100 種語言的文字。此外，系統也可以辨識阿拉伯文、保加利亞文、中文、希臘文、北印度文、日文和俄文。查看支援語言和指令碼的完整清單。

立即體驗

事前準備

  1. 在 Podfile 中加入下列 ML Kit pod： 
    pod 'GoogleMLKit/LanguageID', '3.2.0'
  2. 安裝或更新專案的 Pod 後，請使用其 .xcworkspace 開啟 Xcode 專案。Xcode 12.4 以上版本支援 ML Kit。

辨別字串的語言

如要識別字串的語言，請取得 LanguageIdentification 的執行個體，然後將字串傳遞至 identifyLanguage(for:) 方法。

例如：

Swift

let languageId = NaturalLanguage.languageIdentification()

languageId.identifyLanguage(for: text) { (languageCode, error) in
  if let error = error {
    print("Failed with error: \(error)")
    return
  }
  if let languageCode = languageCode, languageCode != "und" {
    print("Identified Language: \(languageCode)")
  } else {
    print("No language was identified")
  }
}

Objective-C

MLKLanguageIdentification *languageId = [MLKLanguageIdentification languageIdentification];

[languageId identifyLanguageForText:text
                         completion:^(NSString * _Nullable languageCode,
                                      NSError * _Nullable error) {
                           if (error != nil) {
                             NSLog(@"Failed with error: %@", error.localizedDescription);
                             return;
                           }
                           if (![languageCode isEqualToString:@"und"] ) {
                             NSLog(@"Identified Language: %@", languageCode);
                           } else {
                             NSLog(@"No language was identified");
                           }
                         }];

如果呼叫成功，系統會將 BCP-47 語言代碼傳遞給完成處理常式，用來表示文字的語言。如果可以順利偵測到語言，則會傳遞 und (未判定) 程式碼。

根據預設，ML Kit 預設只會在確認具可信度值至少為 0.5 的語言時，傳回非 und 值。如要變更這個門檻，請將 LanguageIdentificationOptions 物件傳遞至 languageIdentification(options:)：

Swift

let options = LanguageIdentificationOptions(confidenceThreshold: 0.4)
let languageId = NaturalLanguage.languageIdentification(options: options)

Objective-C

MLKLanguageIdentificationOptions *options =
    [[MLKLanguageIdentificationOptions alloc] initWithConfidenceThreshold:0.4];
MLKLanguageIdentification *languageId =
    [MLKLanguageIdentification languageIdentificationWithOptions:options];

取得字串可能的語言

如要取得字串最可能語言的可信度值，請取得 LanguageIdentification 的執行個體，然後將字串傳遞至 identifyPossibleLanguages(for:) 方法。

例如：

Swift

let languageId = NaturalLanguage.languageIdentification()

languageId.identifyPossibleLanguages(for: text) { (identifiedLanguages, error) in
  if let error = error {
    print("Failed with error: \(error)")
    return
  }
  guard let identifiedLanguages = identifiedLanguages,
    !identifiedLanguages.isEmpty,
    identifiedLanguages[0].languageCode != "und"
  else {
    print("No language was identified")
    return
  }

  print("Identified Languages:\n" +
    identifiedLanguages.map {
      String(format: "(%@, %.2f)", $0.languageCode, $0.confidence)
      }.joined(separator: "\n"))
}

Objective-C

MLKLanguageIdentification *languageId = [MLKLanguageIdentification languageIdentification];

[languageId identifyPossibleLanguagesForText:text
                                  completion:^(NSArray * _Nonnull identifiedLanguages,
                                               NSError * _Nullable error) {
  if (error != nil) {
    NSLog(@"Failed with error: %@", error.localizedDescription);
    return;
  }
  if (identifiedLanguages.count == 1
      && [identifiedLanguages[0].languageCode isEqualToString:@"und"] ) {
    NSLog(@"No language was identified");
    return;
  }
  NSMutableString *outputText = [NSMutableString stringWithFormat:@"Identified Languages:"];
  for (MLKIdentifiedLanguage *language in identifiedLanguages) {
    [outputText appendFormat:@"\n(%@, %.2f)", language.languageCode, language.confidence];
  }
  NSLog(outputText);
}];

如果呼叫成功，系統會將 IdentifiedLanguage 物件清單傳遞至接續處理常式。您可以從每個物件取得語言的 BCP-47 程式碼，並確保字串以該語言顯示。請注意，這些值代表整個字串採用指定語言的信賴度，而 ML Kit 不會在單一字串中識別多種語言。

根據預設，ML Kit 只會傳回可信度值至少為 0.01 的語言。如要變更這個門檻，請將 LanguageIdentificationOptions 物件傳遞至 languageIdentification(options:)：

Swift

let options = LanguageIdentificationOptions(confidenceThreshold: 0.4)
let languageId = NaturalLanguage.languageIdentification(options: options)

Objective-C

MLKLanguageIdentificationOptions *options =
    [[MLKLanguageIdentificationOptions alloc] initWithConfidenceThreshold:0.4];
MLKLanguageIdentification *languageId =
    [MLKLanguageIdentification languageIdentificationWithOptions:options];

如果沒有語言符合此門檻，清單中會有一個項目，值為 und。