MLKitDigitalInkRecognition Framework Reference

  • MLKDigitalInkRecognitionContext provides information about the context in which ink has been drawn, improving recognition quality when passed to a DigitalInkRecognizer along with the ink.

  • It includes properties like preContext, representing preceding characters, and writingArea, defining the size of the writing area, which aid in recognition accuracy.

  • Developers should utilize the initWithPreContext:writingArea: initializer to create an instance of this class, providing relevant contextual data.

  • preContext should ideally contain as many preceding characters as possible, up to around 20, to enhance recognition accuracy within the language model.

  • The writingArea property helps disambiguate character recognition, especially in cases like lowercase versus uppercase letters.

MLKDigitalInkRecognitionContext


@interface MLKDigitalInkRecognitionContext : NSObject

Information about the context in which an ink has been drawn.

Pass this object to a DigitalInkRecognizer alongside an ink to improve the recognition quality.

  • Characters immediately before the position where the recognized text should be inserted.

    This information is used by the recognizer’s language model to improve recognition.

    Example: a text field contains “hello”, with the cursor right after “o”. The user handwrites something that looks like “world”. If the pre-context is set to “hello”, the recognizer will be able to output “ world”, with a leading space.

    If the text field contains “hello” with the cursor between “e” and the first “l”, then the pre-context must be set to “he”.

    A good rule of thumb for pre-context length is: as many characters as possible, including spaces, until around 20. The optimal number depends on the exact recognition model that is used. Getting the best speed/accuracy tradeoff may require a bit of tuning.

    Declaration

    Objective-C

    @property (nonatomic, readonly, nullable) NSString *preContext;

  • Size of the writing area.

    This is used by some recognition models to disambiguate some cases. Example: lowercase vs. uppercase (“o” vs. “O”).

    See also WritingArea.

    Declaration

    Objective-C

    @property (nonatomic, readonly, nullable) MLKWritingArea *writingArea;

  • Unavailable. Use init(preContext:writingArea:) instead.

    Declaration

    Objective-C

    - (nonnull instancetype)init;

  • Creates a DigitalInkRecognitionContext object.

    Declaration

    Objective-C

    - (nonnull instancetype)initWithPreContext:(nullable NSString *)preContext
                               writingArea:
                                   (nullable MLKWritingArea *)writingArea;

    Parameters

    preContext

    Characters immediately before the position where the recognized text should be inserted. See the description of the property with the same name for more details.
    writingArea

    Properties of the region of the canvas where the ink has been drawn. See the description of the property with the same name for more details.