Image recognition settings

Aspose.OCR for Java allows for very flexible customization of recognition accuracy, performance, and other settings by calling the methods of the RecognitionSettings object.

These settings are applicable when extracting text from single-page raster images in JPEG, PNG, TIFF, BMP, and GIF formats.

Method	Parameter	Default state	Description
`setAllowedCharacters`	Case-sensitive string of characters or one of the predefined character sets: `CharactersAllowedType.ALL` - try to recognize all characters. `CharactersAllowedType.LATIN_ALPHABET` - only recognize case-insensitive Latin / English text (`A` to `Z` and `a` to `z`), without accented characters. `CharactersAllowedType.DIGITS` - recognize only binary, octal, decimal, or hexadecimal numbers (`0`-`9` and `A` to `F`).	All characters from the selected recognition language.	The whitelist of characters Aspose.OCR engine will look for.
`setAutoContrast`	`true` - enable `false` - disable	Disabled	Automatically increase the contrast of images before proceeding to recognition.
`setAutoDenoising`	`true` - enable `false` - disable	Disabled	Automatically remove noise from images before proceeding to recognition.
`setAutoSkew`	`true` - enable `false` - disable	Enabled	Automatically correct image tilt (deskew) before proceeding to recognition.
`setDetectAreas`	`true` - enable `false` - disable	Enabled	Automatically select the optimal areas detection algorithm that suits the most common use cases.
`setDetectAreasMode`	`DetectAreasMode`	Automatic	Manually override the default document areas detection method.
`setIgnoredCharacters`	Case-sensitive string of characters	All characters are recognized	A blacklist of characters that are ignored during recognition.
`setLanguage`	Recognition language	Extended Latin characters, including diacritics	Specify a language for recognition.
`setLinesFiltration`	`true` - enable `false` - disable	Enabled	Set to `true` to recognize text in tables. Set to `false` to improve performance by ignoring table structures and treating tables as plain text.
`setPreprocessingFilters`	Image preprocessing filter	None	Apply image processing filters that enhance an image before it is sent to the OCR engine.
`setRecognitionAreas`	`ArrayList<Rectangle>`	Entire image	List of areas of the image from which to extract text.
`setRecognizeSingleLine`	`true` - enable `false` - disable	Disabled	Recognize a single-line image. Disables automatic document region detection. Improves the recognition performance of simple images.
`setSkew`	Skew angle, `double`	0	Manually rotate the image by the specified degree.
`setThreadsCount`	Number of threads, `int`	Automatic	The number of CPU threads used for recognition.
`setThresholdValue`	Binarization threshold, `int`	Automatic	Override the automatic binarization settings.
`setUpscaleSmallFont`	`true` - enable `false` - disable	Disabled	Improve small font recognition and detection of dense lines.

Applicable to

Example

The following code example shows how to fine-tune recognition:

// Create instance of OCR API
AsposeOCR api = new AsposeOCR();
// Specify recognition settings
RecognitionSettings recognitionSettings = new RecognitionSettings();
recognitionSettings.setAllowedCharacters(CharactersAllowedType.LATIN_ALPHABET);
recognitionSettings.setAutoDenoising(true);
recognitionSettings.setDetectAreasMode(DetectAreasMode.DOCUMENT);
recognitionSettings.setSkew(90);
// Extract text from image
RecognitionResult result = api.RecognizePage("source.png", recognitionSettings);
System.out.println("Recognition result:\n" + result.recognitionText + "\n\n");

Multi-page document recognition settings