你可以使用 Firebase ML 辨識圖片中的文字。Firebase ML 提供適用於辨識圖片文字 (例如路標文字) 的一般用途 API,以及用於辨識文件文字最佳化的 API。
事前準備
- 在 Xcode 中保持開啟應用程式專案,然後依序點選「File」>「Add Packages」。
- 在系統提示時,新增 Firebase Apple 平台 SDK 存放區:
- 選擇 Firebase ML 程式庫。
- 在目標建構設定的「Other Linker Flags」部分中新增
-ObjC
標記。 - 完成後,Xcode 會自動開始在背景解析並下載依附元件。
- 在應用程式中匯入 Firebase:
Swift
import FirebaseMLModelDownloader
Objective-C
@import FirebaseMLModelDownloader;
-
如果您尚未為專案啟用雲端式 API,請立即啟用:
- 開啟 Firebase 控制台的 Firebase ML API 頁面。
-
如果您尚未將專案升級至 Blaze 定價方案,按一下「升級」即可進行升級 (只有在專案未採用 Blaze 方案時,系統才會提示您升級)。
只有 Blaze 層級的專案可以使用以雲端為基礎的 API。
- 如果雲端型 API 尚未啟用,請點選「啟用雲端式 API」。
使用 Swift Package Manager 安裝及管理 Firebase 依附元件。
https://github.com/firebase/firebase-ios-sdk.git
接下來,進行一些應用程式內設定:
現在可以開始辨識圖片中的文字。
輸入圖片規範
-
為了讓 Firebase ML 準確辨識文字,輸入圖片必須包含以充足的像素資料表示的文字。理想情況下,拉丁文字的每個字元至少要有 16x16 像素。如果是中文、日文和韓文,則每個字元都必須是 24x24 像素。對於所有語言來說,大於 24x24 像素的字元通常沒有什麼助益。
舉例來說,640x480 的圖片可能適合掃描佔圖片整個寬度的名片,如要掃描印在正大尺寸紙上的文件,可能需要使用 720 x 1280 像素的圖片。
-
圖片焦點不佳可能會降低文字辨識的準確度。如果您仍未取得可接受的結果,請嘗試要求使用者重新拍攝圖片。
辨識圖片中的文字
如要辨識圖片中的文字,請按照下方說明執行文字辨識工具。
1. 執行文字辨識工具
將圖片做為UIImage
或 CMSampleBufferRef
傳遞至 VisionTextRecognizer
的 process(_:completion:)
方法:
- 呼叫
cloudTextRecognizer
取得VisionTextRecognizer
的例項:Swift
let vision = Vision.vision() let textRecognizer = vision.cloudTextRecognizer() // Or, to provide language hints to assist with language detection: // See https://cloud.google.com/vision/docs/languages for supported languages let options = VisionCloudTextRecognizerOptions() options.languageHints = ["en", "hi"] let textRecognizer = vision.cloudTextRecognizer(options: options)
Objective-C
FIRVision *vision = [FIRVision vision]; FIRVisionTextRecognizer *textRecognizer = [vision cloudTextRecognizer]; // Or, to provide language hints to assist with language detection: // See https://cloud.google.com/vision/docs/languages for supported languages FIRVisionCloudTextRecognizerOptions *options = [[FIRVisionCloudTextRecognizerOptions alloc] init]; options.languageHints = @[@"en", @"hi"]; FIRVisionTextRecognizer *textRecognizer = [vision cloudTextRecognizerWithOptions:options];
-
為了呼叫 Cloud Vision,圖片必須採用 Base64 編碼字串格式。如何處理
UIImage
:Swift
guard let imageData = uiImage.jpegData(compressionQuality: 1.0) else { return } let base64encodedImage = imageData.base64EncodedString()
Objective-C
NSData *imageData = UIImageJPEGRepresentation(uiImage, 1.0f); NSString *base64encodedImage = [imageData base64EncodedStringWithOptions:NSDataBase64Encoding76CharacterLineLength];
-
接著,將圖片傳遞至
process(_:completion:)
方法:Swift
textRecognizer.process(visionImage) { result, error in guard error == nil, let result = result else { // ... return } // Recognized text }
Objective-C
[textRecognizer processImage:image completion:^(FIRVisionText *_Nullable result, NSError *_Nullable error) { if (error != nil || result == nil) { // ... return; } // Recognized text }];
2. 從已辨識的文字區塊擷取文字
如果文字辨識作業成功,會傳回VisionText
物件。VisionText
物件包含圖片中可辨識的完整文字,以及零個或多個 VisionTextBlock
物件。
每個 VisionTextBlock
都代表矩形文字區塊,當中包含零或多個 VisionTextLine
物件。每個 VisionTextLine
物件都含有零或多個 VisionTextElement
物件,這些物件代表字詞和類似文字的實體 (日期、數字等)。
對於每個 VisionTextBlock
、VisionTextLine
和 VisionTextElement
物件,您可以取得在區域辨識的文字和該區域的定界座標。
例如:
Swift
let resultText = result.text for block in result.blocks { let blockText = block.text let blockConfidence = block.confidence let blockLanguages = block.recognizedLanguages let blockCornerPoints = block.cornerPoints let blockFrame = block.frame for line in block.lines { let lineText = line.text let lineConfidence = line.confidence let lineLanguages = line.recognizedLanguages let lineCornerPoints = line.cornerPoints let lineFrame = line.frame for element in line.elements { let elementText = element.text let elementConfidence = element.confidence let elementLanguages = element.recognizedLanguages let elementCornerPoints = element.cornerPoints let elementFrame = element.frame } } }
Objective-C
NSString *resultText = result.text; for (FIRVisionTextBlock *block in result.blocks) { NSString *blockText = block.text; NSNumber *blockConfidence = block.confidence; NSArray<FIRVisionTextRecognizedLanguage *> *blockLanguages = block.recognizedLanguages; NSArray<NSValue *> *blockCornerPoints = block.cornerPoints; CGRect blockFrame = block.frame; for (FIRVisionTextLine *line in block.lines) { NSString *lineText = line.text; NSNumber *lineConfidence = line.confidence; NSArray<FIRVisionTextRecognizedLanguage *> *lineLanguages = line.recognizedLanguages; NSArray<NSValue *> *lineCornerPoints = line.cornerPoints; CGRect lineFrame = line.frame; for (FIRVisionTextElement *element in line.elements) { NSString *elementText = element.text; NSNumber *elementConfidence = element.confidence; NSArray<FIRVisionTextRecognizedLanguage *> *elementLanguages = element.recognizedLanguages; NSArray<NSValue *> *elementCornerPoints = element.cornerPoints; CGRect elementFrame = element.frame; } } }
後續步驟
- 在部署至使用 Cloud API 的正式版應用程式之前,建議先採取一些額外步驟,預防及降低未經授權 API 存取所造成的影響。
辨識文件圖片中的文字
如要識別文件中的文字,請按照下列說明設定並執行文件文字辨識工具。
如下所述文件文字辨識 API 所提供的介面,讓您更輕鬆地處理文件的圖片。不過,如果您偏好使用稀疏文字 API 提供的介面,則可將雲端文字辨識工具設為使用密集文字模型,以便改用該介面掃描文件。
如何使用文件文字辨識 API:
1. 執行文字辨識工具
將圖片做為UIImage
或 CMSampleBufferRef
傳遞至 VisionDocumentTextRecognizer
的 process(_:completion:)
方法:
- 呼叫
cloudDocumentTextRecognizer
取得VisionDocumentTextRecognizer
的例項:Swift
let vision = Vision.vision() let textRecognizer = vision.cloudDocumentTextRecognizer() // Or, to provide language hints to assist with language detection: // See https://cloud.google.com/vision/docs/languages for supported languages let options = VisionCloudDocumentTextRecognizerOptions() options.languageHints = ["en", "hi"] let textRecognizer = vision.cloudDocumentTextRecognizer(options: options)
Objective-C
FIRVision *vision = [FIRVision vision]; FIRVisionDocumentTextRecognizer *textRecognizer = [vision cloudDocumentTextRecognizer]; // Or, to provide language hints to assist with language detection: // See https://cloud.google.com/vision/docs/languages for supported languages FIRVisionCloudDocumentTextRecognizerOptions *options = [[FIRVisionCloudDocumentTextRecognizerOptions alloc] init]; options.languageHints = @[@"en", @"hi"]; FIRVisionDocumentTextRecognizer *textRecognizer = [vision cloudDocumentTextRecognizerWithOptions:options];
-
為了呼叫 Cloud Vision,圖片必須採用 Base64 編碼字串格式。如何處理
UIImage
:Swift
guard let imageData = uiImage.jpegData(compressionQuality: 1.0) else { return } let base64encodedImage = imageData.base64EncodedString()
Objective-C
NSData *imageData = UIImageJPEGRepresentation(uiImage, 1.0f); NSString *base64encodedImage = [imageData base64EncodedStringWithOptions:NSDataBase64Encoding76CharacterLineLength];
-
接著,將圖片傳遞至
process(_:completion:)
方法:Swift
textRecognizer.process(visionImage) { result, error in guard error == nil, let result = result else { // ... return } // Recognized text }
Objective-C
[textRecognizer processImage:image completion:^(FIRVisionDocumentText *_Nullable result, NSError *_Nullable error) { if (error != nil || result == nil) { // ... return; } // Recognized text }];
2. 從已辨識的文字區塊擷取文字
如果文字辨識作業成功,會傳回VisionDocumentText
物件。VisionDocumentText
物件包含圖片中可辨識的完整文字,以及反映已辨識文件結構的物件階層:
對於每個 VisionDocumentTextBlock
、VisionDocumentTextParagraph
、VisionDocumentTextWord
和 VisionDocumentTextSymbol
物件,您可以取得區域中辨識的文字和該區域的定界座標。
例如:
Swift
let resultText = result.text for block in result.blocks { let blockText = block.text let blockConfidence = block.confidence let blockRecognizedLanguages = block.recognizedLanguages let blockBreak = block.recognizedBreak let blockCornerPoints = block.cornerPoints let blockFrame = block.frame for paragraph in block.paragraphs { let paragraphText = paragraph.text let paragraphConfidence = paragraph.confidence let paragraphRecognizedLanguages = paragraph.recognizedLanguages let paragraphBreak = paragraph.recognizedBreak let paragraphCornerPoints = paragraph.cornerPoints let paragraphFrame = paragraph.frame for word in paragraph.words { let wordText = word.text let wordConfidence = word.confidence let wordRecognizedLanguages = word.recognizedLanguages let wordBreak = word.recognizedBreak let wordCornerPoints = word.cornerPoints let wordFrame = word.frame for symbol in word.symbols { let symbolText = symbol.text let symbolConfidence = symbol.confidence let symbolRecognizedLanguages = symbol.recognizedLanguages let symbolBreak = symbol.recognizedBreak let symbolCornerPoints = symbol.cornerPoints let symbolFrame = symbol.frame } } } }
Objective-C
NSString *resultText = result.text; for (FIRVisionDocumentTextBlock *block in result.blocks) { NSString *blockText = block.text; NSNumber *blockConfidence = block.confidence; NSArray<FIRVisionTextRecognizedLanguage *> *blockRecognizedLanguages = block.recognizedLanguages; FIRVisionTextRecognizedBreak *blockBreak = block.recognizedBreak; CGRect blockFrame = block.frame; for (FIRVisionDocumentTextParagraph *paragraph in block.paragraphs) { NSString *paragraphText = paragraph.text; NSNumber *paragraphConfidence = paragraph.confidence; NSArray<FIRVisionTextRecognizedLanguage *> *paragraphRecognizedLanguages = paragraph.recognizedLanguages; FIRVisionTextRecognizedBreak *paragraphBreak = paragraph.recognizedBreak; CGRect paragraphFrame = paragraph.frame; for (FIRVisionDocumentTextWord *word in paragraph.words) { NSString *wordText = word.text; NSNumber *wordConfidence = word.confidence; NSArray<FIRVisionTextRecognizedLanguage *> *wordRecognizedLanguages = word.recognizedLanguages; FIRVisionTextRecognizedBreak *wordBreak = word.recognizedBreak; CGRect wordFrame = word.frame; for (FIRVisionDocumentTextSymbol *symbol in word.symbols) { NSString *symbolText = symbol.text; NSNumber *symbolConfidence = symbol.confidence; NSArray<FIRVisionTextRecognizedLanguage *> *symbolRecognizedLanguages = symbol.recognizedLanguages; FIRVisionTextRecognizedBreak *symbolBreak = symbol.recognizedBreak; CGRect symbolFrame = symbol.frame; } } } }
後續步驟
- 在部署至使用 Cloud API 的正式版應用程式之前,建議先採取一些額外步驟,預防及降低未經授權 API 存取所造成的影響。