Defining the whitelist of characters

Limiting a subset of characters instead of using the full list for a selected language can greatly improve recognition accuracy, increase speed, and reduce resource consumption.

You can define a list of characters Aspose.OCR engine will look for by specifying them as a case-sensitive string in alphabet property of recognition settings. Characters that do not match the provided list are ignored.

// Prepare images
var source = Module.WasmAsposeOCRInput();
source.url = filename;
var content = new Module.WasmAsposeOCRInputs();
content.push_back(source);
// Limiting characters to be identified
var settings = Module.WasmAsposeOCRRecognitionSettings();
settings.alphabet = "AÁBCDEÉFG12345";
// Recognize image
var result = Module.AsposeOCRRecognize(content, settings);

Alternatively, you can specify the predefined collection of characters in allowed_characters property of recognition settings. It will make your code more readable when working with massive whitelists.

Preset	Numeric value	Allowed characters
Module.CharactersAllowedType.ALL	0	Recognize all characters.
Module.CharactersAllowedType.LATIN_ALPHABET	1	Only recognize case-insensitive Latin / English text (A to Z and a to z), without accented characters, punctuation, numbers, end the like.
Module.CharactersAllowedType.DIGITS	2	Recognize only binary, octal, decimal, or hexadecimal numbers (0-9 and A to F).

// Prepare images
var source = Module.WasmAsposeOCRInput();
source.url = filename;
var content = new Module.WasmAsposeOCRInputs();
content.push_back(source);
// Instruct OCR engine to recognize numbers only
var settings = Module.WasmAsposeOCRRecognitionSettings();
settings.allowed_characters = Module.CharactersAllowedType.DIGITS;
// Recognize image
var result = Module.AsposeOCRRecognize(content, settings);