// The project, which uses this code, must have references to the following assemblies:
// - Vintasoft.Imaging
// - Vintasoft.Imaging.Ocr
// - Vintasoft.Imaging.Ocr.Tesseract

/// <summary>
/// Recognizes text in images,
/// removes words with low confidence from recognized text and
/// returns recognized text.
/// </summary>
/// <param name="filename">The name of the file containing image to OCR.</param>
public string RecognizeTextAndFilterRecognitionResult(string filename)
{
    // minimum confidence
    const float MIN_CONFIDENCE = 75.0f;

    // create image collection
    using (Vintasoft.Imaging.ImageCollection images = new Vintasoft.Imaging.ImageCollection())
    {
        // add images from file to image collection
        images.Add(filename);

        // create tesseract OCR engine
        using (Vintasoft.Imaging.Ocr.Tesseract.TesseractOcr tesseractOcr = 
            new Vintasoft.Imaging.Ocr.Tesseract.TesseractOcr())
        {
            // create tesseract OCR settings
            Vintasoft.Imaging.Ocr.OcrEngineSettings settings = 
                new Vintasoft.Imaging.Ocr.OcrEngineSettings(Vintasoft.Imaging.Ocr.OcrLanguage.English);
            tesseractOcr.Init(settings);

            // create result builder
            System.Text.StringBuilder result = new System.Text.StringBuilder();

            // for each image in image collection
            foreach (Vintasoft.Imaging.VintasoftImage image in images)
            {
                // recognize the image
                Vintasoft.Imaging.Ocr.Results.OcrPage page = tesseractOcr.Recognize(image);

                // get all words in recognized text
                Vintasoft.Imaging.Ocr.Results.OcrObject[] ocrObjects = page.GetObjects(
                    Vintasoft.Imaging.Ocr.OcrObjectType.Word);
                // create list of words to remove
                System.Collections.Generic.List<Vintasoft.Imaging.Ocr.Results.OcrObject> removeObjects = 
                    new System.Collections.Generic.List<Vintasoft.Imaging.Ocr.Results.OcrObject>();
                // for each word
                foreach (Vintasoft.Imaging.Ocr.Results.OcrObject word in ocrObjects)
                {
                    // if word confidence is less than minimum confidence
                    if (word.Confidence < MIN_CONFIDENCE)
                        // add word to a list of words to remove
                        removeObjects.Add(word);
                }

                // validate recognition results (remove words with low confidence)

                Vintasoft.Imaging.Ocr.Results.OcrResultsEditor editor = 
                    new Vintasoft.Imaging.Ocr.Results.OcrResultsEditor(page);
                editor.RemoveObjects(removeObjects.ToArray());
                editor.ValidateResults();

                // get recognized text
                string text = page.GetText();
                // add recognized text to result
                result.Append(text);
                result.AppendLine();
            }

            // dispose images and clear image collection
            images.ClearAndDisposeItems();

            // return result
            return result.ToString();
        }
    }
}
                

// The project, which uses this code, must have references to the following assemblies:
// - Vintasoft.Imaging
// - Vintasoft.Imaging.Ocr
// - Vintasoft.Imaging.Ocr.Tesseract
// - Vintasoft.Imaging.Pdf

string imageFilePath = @"D:\TestImage.pdf";
// create the OCR engine
using (Vintasoft.Imaging.Ocr.Tesseract.TesseractOcr tesseractOcr = new Vintasoft.Imaging.Ocr.Tesseract.TesseractOcr())
{
    // create an array for additional OCR engines
    Vintasoft.Imaging.Ocr.Tesseract.TesseractOcr[] additionalEngines = new Vintasoft.Imaging.Ocr.Tesseract.TesseractOcr[2];
    try
    {
        // create an array for additional OCR engines
        for (int i = 0; i < additionalEngines.Length; i++)
            // create the additional OCR engine
            additionalEngines[i] = new Vintasoft.Imaging.Ocr.Tesseract.TesseractOcr();

        // create the OCR engine manager
        Vintasoft.Imaging.Ocr.OcrEngineManager engineManager = 
            new Vintasoft.Imaging.Ocr.OcrEngineManager(tesseractOcr, additionalEngines);

        // load a PDF document from file
        using (Vintasoft.Imaging.Pdf.PdfDocument pdfDocument = 
            new Vintasoft.Imaging.Pdf.PdfDocument(imageFilePath))
        {
            // create the OCR engine settings and
            // specify that German text will be recognized
            Vintasoft.Imaging.Ocr.OcrEngineSettings settings = 
                new Vintasoft.Imaging.Ocr.OcrEngineSettings(Vintasoft.Imaging.Ocr.OcrLanguage.German);

            // if PDF document is empty
            if (pdfDocument.Pages.Count == 0)
                return;

            // get the first PDF page
            Vintasoft.Imaging.Pdf.Tree.PdfPage pdfPage = pdfDocument.Pages[0];
            // scales, which should be applied to the PDF page before text recognition
            float[] scales = new float[] { 0.5f, 1.5f };
            // an array that contains the scaled OCR results
            Vintasoft.Imaging.Ocr.Results.OcrPage[] scaledOcrResults = 
                new Vintasoft.Imaging.Ocr.Results.OcrPage[scales.Length];

            // for each scale
            for (int i = 0; i < scales.Length; i++)
            {
                // render the scaled PDF page
                using (Vintasoft.Imaging.VintasoftImage renderedImage = pdfPage.Render(scales[i]))
                {
                    // recognize text in scaled PDF page
                    scaledOcrResults[i] = engineManager.Recognize(renderedImage, settings);
                }
            }

            // if text is recognized
            if (scaledOcrResults.Length > 0)
            {
                Vintasoft.Imaging.Ocr.Results.OcrResultsEditor resultEditor;

                // "downscale" the OCR results, this is necessary
                // because we scaled PDF page before text recognition

                // for each recognition result
                for (int i = 0; i < scaledOcrResults.Length; i++)
                {
                    if (scales[i] == 1f)
                        continue;

                    // create the OCR results editor
                    resultEditor = new Vintasoft.Imaging.Ocr.Results.OcrResultsEditor(scaledOcrResults[i]);

                    // calculate the "downscale" factor
                    Vintasoft.Imaging.Scale downScale = new Vintasoft.Imaging.Scale(1f / scales[i], 1f / scales[i]);
                    // "downscale" the OCR result
                    resultEditor.ScaleOcrPage(downScale);
                }


                // combine the scaled OCR results into the final OCR result

                // set the first scaled OCR result as the final OCR result
                Vintasoft.Imaging.Ocr.Results.OcrPage finalOcrResult = scaledOcrResults[0];

                // create the OCR results editor for the final OCR result
                resultEditor = new Vintasoft.Imaging.Ocr.Results.OcrResultsEditor(finalOcrResult);
                // for each scaled OCR result starting from the second
                for (int i = 1; i < scaledOcrResults.Length; i++)
                {
                    // add the scaled OCR result to the OCR results editor
                    resultEditor.AddRegions(scaledOcrResults[i]);
                }
                // validate the final OCR result
                resultEditor.ValidateResults();


                // get the recognized text from the final OCR result
                string ocrPageContent = finalOcrResult.GetText();

                string textFilePath = System.IO.Path.Combine(
                    System.IO.Path.GetDirectoryName(imageFilePath),
                    System.IO.Path.GetFileNameWithoutExtension(imageFilePath) + ".txt");
                // save the recognition results
                System.IO.File.WriteAllText(textFilePath, ocrPageContent, System.Text.Encoding.UTF8);
            }
        }
    }
    finally
    {
        // for each additional OCR engine
        for (int i = 0; i < additionalEngines.Length; i++)
        {
            if (additionalEngines[i] != null)
                // dispose the additional OCR engine
                additionalEngines[i].Dispose();
        }
    }
}