Using OcrFormatProvider
| Minimum Version | Q1 2025 |
|---|
RadPdfProcessing supports Optical Character Recognition (OCR). OCR is the electronic or mechanical conversion of images of typed, handwritten, or printed text into machine-encoded text from a scanned document. The library uses the OcrFormatProvider class that allows you to import an image which is returned as a RadFixedPage. By default, the OcrFormatProvider takes as a parameter a TesseractOcrProvider implementation which uses the third-party library Tesseract. However, you can provide any custom implementation instead.
You can find all the dependencies and required steps for the implementation in the Prerequisites article.
TesseractOcrProvider Public API
The following table lists the available methods and properties:
| Method/Property | Description |
|---|---|
| TesseractOcrProvider(string dataPath) | Constructor that takes as a parameter the path to the parent directory that contains the "tessdata" folder. |
LanguageCodes | The language codes to use for the Tesseract OCR engine. You can find the corresponding trained data for each language and their codes here. The value is "eng" by default. |
CorrectVerticalPosition | Indicates whether the OCR processor will try to correct the vertical position of the text. (Not available in .NET Framework) |
DataPath | The path to the parent directory that contains the "tessdata" folder. |
ParseLevel | Indicates the level of parsing that the OCR processor performs - OcrParseLevel.Line or OcrParseLevel.Word. |
GetAllTextFromImage | Extracts all text from an image and returns it as a single string. |
GetTextFromImage | Extracts the text from an image and returns the words and their bounding rectangles. |
// Requirement for Images in .NET Standard - https://docs.telerik.com/devtools/document-processing/libraries/radpdfprocessing/cross-platform/images
//FixedExtensibilityManager.ImagePropertiesResolver = new ImagePropertiesResolver();
TesseractOcrProvider tesseractOcrProvider = new TesseractOcrProvider(".");
tesseractOcrProvider.LanguageCodes = new List<string>() { "eng" };
//tesseractOcrProvider.CorrectVerticalPosition = false; // Available in .NET Standard
tesseractOcrProvider.DataPath = @"..\..\..\";
tesseractOcrProvider.ParseLevel = OcrParseLevel.Line;
string imagePath = @"..\..\..\images\image.png";
string imageText = tesseractOcrProvider.GetAllTextFromImage(File.ReadAllBytes(imagePath));
Dictionary<Rectangle, string> imageTextAndTextDimentions = tesseractOcrProvider.GetTextFromImage(File.ReadAllBytes(imagePath));
OcrFormatProvider OcrProvider = new OcrFormatProvider(tesseractOcrProvider);
RadFixedDocument document = new RadFixedDocument();
RadFixedPage page = new RadFixedPage();
page = OcrProvider.Import(new FileStream(imagePath, FileMode.Open), null);
document.Pages.Add(page);
string outputPath = "output.pdf";
PdfFormatProvider pdfFormatProvider = new PdfFormatProvider();
using (Stream output = File.OpenWrite(outputPath))
{
pdfFormatProvider.Export(document, output, TimeSpan.FromSeconds(10));
}You can find a complete example of implementing an OcrFormatProvider in our SDK repository.