SwiftyTesseract

public class SwiftyTesseract

A class that performs optical character recognition with the open-source Tesseract library

Properties

  • Sets a String of characters that will only be recognized. This does not filter values.

    Example: setting a whiteList of “ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz” with an image containing digits may result in “1” being recognized as “I” and “2” being recognized as “Z”. Set this value only if it is 100% certain the characters that are defined will only be present during recognition.

    This may cause unpredictable recognition results if characters not defined in whiteList are present. If removal and not replacement is desired, filtering the recognition string is a better option.

    Declaration

    Swift

    public var whiteList: String? { get set }

  • Sets a String of characters that will not be recognized. This does not filter values.

    Example: setting a blackList of “0123456789” with an image containing digits may result in “1” being recognized as “I” and “2” being recognized as “Z”. Set this value only if it is 100% certain that the characters defined will not be present during recognition.

    This may cause unpredictable recognition results if characters defined in blackList are present. If removal and not replacement is desired, filtering the recognition string is a better option

    Declaration

    Swift

    public var blackList: String? { get set }

  • Preserve multiple interword spaces

    Declaration

    Swift

    public var preserveInterwordSpaces: Bool? { get set }

  • Minimum character height

    Declaration

    Swift

    public var minimumCharacterHeight: Int? { get set }

  • The current version of the underlying Tesseract library

    Declaration

    Swift

    lazy public private(set) var version: String? { get set }

Initialization

  • Creates an instance of SwiftyTesseract using standard RecognitionLanguages. The tessdata folder MUST be in your Xcode project as a folder reference (blue folder icon, not yellow) and be named “tessdata”

    Declaration

    Swift

    public convenience init(
  languages: [RecognitionLanguage],
  dataSource: LanguageModelDataSource = Bundle.main,
  engineMode: EngineMode = .lstmOnly
)

    Parameters

    languages

    Languages of the text to be recognized
    dataSource

    The LanguageModelDataSource that contains the tessdata folder - default is Bundle.main
    engineMode

    The tesseract engine mode - default is .lstmOnly

  • Convenience initializer for creating an instance of SwiftyTesseract with one language to avoid having to input an array with one value (e.g. [.english]) for the languages parameter

    Declaration

    Swift

    public convenience init(
  language: RecognitionLanguage,
  dataSource: LanguageModelDataSource = Bundle.main,
  engineMode: EngineMode = .lstmOnly
)

    Parameters

    language

    The language of the text to be recognized
    dataSource

    The LanguageModelDataSource that contains the tessdata folder - default is Bundle.main
    engineMode

    The tesseract engine mode - default is .lstmOnly

  • Declaration

    Swift

    public convenience init(
  language: RecognitionLanguage,
  bundle: Bundle = .main,
  engineMode: EngineMode = .lstmOnly
)

  • Declaration

    Swift

    public convenience init(
  languages: [RecognitionLanguage],
  bundle: Bundle = .main,
  engineMode: EngineMode = .lstmOnly
)
  • See more

    Declaration

    Swift

    public enum Error : Swift.Error

OCR

  • Takes a UIImage and passes resulting recognized UTF-8 text into completion handler

    Declaration

    Swift

    @available(*, deprecated, message: "use performOCR(on:﹚ or performOCRPublisher(on:﹚")
public func performOCR(on image: UIImage, completionHandler: (String?) -> ())

    Parameters

    image

    The image to perform recognition on
    completionHandler

    The action to be performed on the recognized string

  • Performs OCR on a UIImage

    Declaration

    Swift

    public func performOCR(on image: UIImage) -> Result<String, Swift.Error>

    Parameters

    image

    The image to perform recognition on

    Return Value

    A result containing the recognized Stringor an Error if recognition failed

  • Creates a cold publisher that performs OCR on a provided image upon subscription

    Declaration

    Swift

    @available(iOS 13.0, *)
public func performOCRPublisher(on image: UIImage) -> AnyPublisher<String, Swift.Error>

    Parameters

    image

    The image to perform recognition on

    Return Value

    A cold publisher that emits a single String on success or an Error on failure.

PDF Generation

  • Takes an array UIImages and returns the PDF as a Data object. If using PDFKit introduced in iOS 11, this will produce a valid PDF Document.

    Throws

    SwiftyTesseractError

    Declaration

    Swift

    public func createPDF(from images: [UIImage]) throws -> Data

    Parameters

    images

    Array of UIImages to perform OCR on

    Return Value

    PDF Data object

  • This method must be called after performOCR(on:). Otherwise calling this method will result in failure.

    Declaration

    Swift

    public func recognizedBlocks(for level: ResultIteratorLevel) -> Result<[RecognizedBlock], Swift.Error>

    Parameters

    level

    The level which corresponds to the granularity of the desired recognized block

    Return Value

    On success, an array of RecognizedBlocks in the coordinate space of the image.