OCR: Obtain and edit the OCR results

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The text recognition result in an image is returned as an OCR page (an instance of OcrPage class).

The OCR page contains text regions (instances of OcrTextRegion class). The text region contains paragraphs (instances of OcrParagraph class). The paragraph contains text lines (instances of OcrTextLine class). The text line contains words (instances of OcrWord class). The word contains symbols (instances of OcrSymbol class).

All elements (OcrPage, OcrTextRegion, OcrParagraph, OcrTextLine, OcrWord, OcrSymbol) contain:

Location of element on image (OcrObject.Location)
Orientation of element on image (OcrObject.Orientation)
Text writing direction in element (OcrObject.WritingDirection)
Confidence ratio for recognition result (OcrObject.Confidence)
Text of element (OcrTextObject.Text).

OcrWord class also contains the font name of recognized text (OcrWord.Font).

OcrPage class allows to obtain the OCR result as formatted text (OcrPage.GetFormattedText) and non-formatted text (OcrPage.GetText).

Often it is necessary to process the OCR results, for example, remove words with low confidence or unite two and more results into one.
OcrResultsEditor class is intended for such processing of OCR results.

Here is C#/VB.NET code that shows how to remove words with low confidence from OCR results:

/// <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();
        }
    }
}

VB.NET

''' <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 Function RecognizeTextAndFilterRecognitionResult(filename As String) As String
    ' minimum confidence
    Const  MIN_CONFIDENCE As Single = 75F

    ' create image collection
    Using images As New Vintasoft.Imaging.ImageCollection()
        ' add images from file to image collection
        images.Add(filename)

        ' create tesseract OCR engine
        Using tesseractOcr As New Vintasoft.Imaging.Ocr.Tesseract.TesseractOcr()
            ' create tesseract OCR settings
            Dim settings As New Vintasoft.Imaging.Ocr.OcrEngineSettings(Vintasoft.Imaging.Ocr.OcrLanguage.English)
            tesseractOcr.Init(settings)

            ' create result builder
            Dim result As New System.Text.StringBuilder()

            ' for each image in image collection
            For Each image As Vintasoft.Imaging.VintasoftImage In images
                ' recognize the image
                Dim page As Vintasoft.Imaging.Ocr.Results.OcrPage = tesseractOcr.Recognize(image)

                ' get all words in recognized text
                Dim ocrObjects As Vintasoft.Imaging.Ocr.Results.OcrObject() = page.GetObjects(Vintasoft.Imaging.Ocr.OcrObjectType.Word)
                ' create list of words to remove
                Dim removeObjects As New System.Collections.Generic.List(Of Vintasoft.Imaging.Ocr.Results.OcrObject)()
                ' for each word
                For Each word As Vintasoft.Imaging.Ocr.Results.OcrObject In ocrObjects
                    ' if word confidence is less than minimum confidence
                    If word.Confidence < MIN_CONFIDENCE Then
                        ' add word to a list of words to remove
                        removeObjects.Add(word)
                    End If
                Next

                ' validate recognition results (remove words with low confidence)

                Dim editor As New Vintasoft.Imaging.Ocr.Results.OcrResultsEditor(page)
                editor.RemoveObjects(removeObjects.ToArray())
                editor.ValidateResults()

                ' get recognized text
                Dim text As String = page.GetText()
                ' add recognized text to result
                result.Append(text)
                result.AppendLine()
            Next

            ' dispose images and clear image collection
            images.ClearAndDisposeItems()

            ' return result
            Return result.ToString()
        End Using
    End Using
End Function

Here is C#/VB.NET code that shows how to recognize text in two images (with different resolution) of the same document and unite the OCR results:

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();
        }
    }
}

VB.NET

Dim imageFilePath As String = "D:\TestImage.pdf"
' create the OCR engine
Using tesseractOcr As New Vintasoft.Imaging.Ocr.Tesseract.TesseractOcr()
    ' create an array for additional OCR engines
    Dim additionalEngines As Vintasoft.Imaging.Ocr.Tesseract.TesseractOcr() = New Vintasoft.Imaging.Ocr.Tesseract.TesseractOcr(1) {}
    Try
        ' create an array for additional OCR engines
        For i As Integer = 0 To additionalEngines.Length - 1
            ' create the additional OCR engine
            additionalEngines(i) = New Vintasoft.Imaging.Ocr.Tesseract.TesseractOcr()
        Next

        ' create the OCR engine manager
        Dim engineManager As New Vintasoft.Imaging.Ocr.OcrEngineManager(tesseractOcr, additionalEngines)

        ' load a PDF document from file
        Using pdfDocument As New Vintasoft.Imaging.Pdf.PdfDocument(imageFilePath)
            ' create the OCR engine settings and
            ' specify that German text will be recognized
            Dim settings As New Vintasoft.Imaging.Ocr.OcrEngineSettings(Vintasoft.Imaging.Ocr.OcrLanguage.German)

            ' if PDF document is empty
            If pdfDocument.Pages.Count = 0 Then
                Return
            End If

            ' get the first PDF page
            Dim pdfPage As Vintasoft.Imaging.Pdf.Tree.PdfPage = pdfDocument.Pages(0)
            ' scales, which should be applied to the PDF page before text recognition
            Dim scales As Single() = New Single() {0.5F, 1.5F}
            ' an array that contains the scaled OCR results
            Dim scaledOcrResults As Vintasoft.Imaging.Ocr.Results.OcrPage() = New Vintasoft.Imaging.Ocr.Results.OcrPage(scales.Length - 1) {}

            ' for each scale
            For i As Integer = 0 To scales.Length - 1
                ' render the scaled PDF page
                Using renderedImage As Vintasoft.Imaging.VintasoftImage = pdfPage.Render(scales(i))
                    ' recognize text in scaled PDF page
                    scaledOcrResults(i) = engineManager.Recognize(renderedImage, settings)
                End Using
            Next

            ' if text is recognized
            If scaledOcrResults.Length > 0 Then
                Dim resultEditor As Vintasoft.Imaging.Ocr.Results.OcrResultsEditor

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

                ' for each recognition result
                For i As Integer = 0 To scaledOcrResults.Length - 1
                    If scales(i) = 1F Then
                        Continue For
                    End If

                    ' create the OCR results editor
                    resultEditor = New Vintasoft.Imaging.Ocr.Results.OcrResultsEditor(scaledOcrResults(i))

                    ' calculate the "downscale" factor
                    Dim downScale As New Vintasoft.Imaging.Scale(1F / scales(i), 1F / scales(i))
                    ' "downscale" the OCR result
                    resultEditor.ScaleOcrPage(downScale)
                Next


                ' combine the scaled OCR results into the final OCR result

                ' set the first scaled OCR result as the final OCR result
                Dim finalOcrResult As Vintasoft.Imaging.Ocr.Results.OcrPage = 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 i As Integer = 1 To scaledOcrResults.Length - 1
                    ' add the scaled OCR result to the OCR results editor
                    resultEditor.AddRegions(scaledOcrResults(i))
                Next
                ' validate the final OCR result
                resultEditor.ValidateResults()


                ' get the recognized text from the final OCR result
                Dim ocrPageContent As String = finalOcrResult.GetText()

                Dim textFilePath As String = 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)
            End If
        End Using
    Finally
        ' for each additional OCR engine
        For i As Integer = 0 To additionalEngines.Length - 1
            If additionalEngines(i) IsNot Nothing Then
                ' dispose the additional OCR engine
                additionalEngines(i).Dispose()
            End If
        Next
    End Try
End Using

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