如何扩展OCR处理文件类型并添加Tesseract文本提取进度条

Hey there! Let's tackle your two OCR requirements one by one—adding PDF support and showing a progress bar during text extraction. Here's how to modify your existing WinForms code to make it work:

1. Add PDF File Support #

Tesseract can only process image files natively, so we need to convert each page of a PDF into an image first. The PdfiumViewer library is a reliable, free option for this task in .NET.

Quick Setup: #

• Install the NuGet package first: Install-Package PdfiumViewer (or search for it in the NuGet Package Manager)
• Update your code to detect PDF files and render each page as a Pix object (the format Tesseract uses)

2. Add a Progress Bar for Tesseract Extraction #

OCR is CPU-intensive, so we'll use a BackgroundWorker to run extraction in the background (avoiding UI freezes) and report progress to update the bar.

Full Modified Code #

private void btOCR_Click(object sender, EventArgs e)
{
    if (openFileDialog.ShowDialog() == DialogResult.OK)
    {
        var filePath = openFileDialog.FileName;
        var pixList = new List<Pix>();

        // Handle PDF vs image files
        if (Path.GetExtension(filePath).Equals(".pdf", StringComparison.OrdinalIgnoreCase))
        {
            // Render each PDF page to a Pix (300 DPI for good OCR accuracy)
            using (var pdfDocument = PdfiumViewer.PdfDocument.Load(filePath))
            {
                for (int pageIndex = 0; pageIndex < pdfDocument.PageCount; pageIndex++)
                {
                    using (var bitmap = pdfDocument.Render(pageIndex, 300, 300, PdfiumViewer.PdfRenderFlags.Annotations))
                    {
                        pixList.Add(Pix.FromBitmap(bitmap));
                    }
                }
            }
        }
        else
        {
            // Load image files directly
            pixList.Add(Pix.LoadFromFile(filePath));
        }

        // Set up BackgroundWorker for progress tracking
        var bgWorker = new BackgroundWorker();
        bgWorker.WorkerReportsProgress = true;

        bgWorker.DoWork += (s, args) =>
        {
            var totalPages = pixList.Count;
            var extractedText = new StringBuilder();

            // Initialize Tesseract engine (adjust tessdata path and language as needed)
            using (var ocrEngine = new TesseractEngine(@"tessdata", "eng", EngineMode.Default))
            {
                for (int i = 0; i < totalPages; i++)
                {
                    using (var page = ocrEngine.Process(pixList[i]))
                    {
                        extractedText.AppendLine($"--- Page {i+1} ---");
                        extractedText.AppendLine(page.GetText());
                    }
                    // Calculate and report progress percentage
                    int progress = (i + 1) * 100 / totalPages;
                    bgWorker.ReportProgress(progress);
                }
            }

            args.Result = extractedText.ToString();
        };

        // Update progress bar in UI thread
        bgWorker.ProgressChanged += (s, args) =>
        {
            progressBar1.Value = args.ProgressPercentage;
        };

        // Handle completion or errors
        bgWorker.RunWorkerCompleted += (s, args) =>
        {
            if (args.Error != null)
            {
                MessageBox.Show($"OCR failed: {args.Error.Message}", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            else
            {
                // Display extracted text (replace with your actual text control)
                textBoxOCRResult.Text = args.Result.ToString();
            }
            // Reset progress bar
            progressBar1.Value = 0;
        };

        // Start the background task
        bgWorker.RunWorkerAsync();
    }
}

Key Tips: #

• Ensure you have the Tesseract NuGet package installed: Install-Package Tesseract
• The tessdata folder (with language packs) should be in your app's output directory, or use an absolute path in the TesseractEngine constructor
• Add a ProgressBar control named progressBar1 to your form, set its Minimum to 0 and Maximum to 100
• Adjust the language code (e.g., "chi_sim" for simplified Chinese) and DPI value as needed for your use case

内容的提问来源于stack exchange，提问作者user9522816