Install-Package UglyToad.PdfPig

using UglyToad.PdfPig;
using UglyToad.PdfPig.Content;
using System.Drawing.Imaging;
using System.IO;

class PdfImageExtractor
{
    public static void ExtractImagesFromPdf(string pdfPath, string outputFolder)
    {
        if (!Directory.Exists(outputFolder))
            Directory.CreateDirectory(outputFolder);

        using (var document = PdfDocument.Open(pdfPath))
        {
            int imageIndex = 0;
            foreach (var page in document.GetPages())
            {
                foreach (var image in page.GetImages())
                {
                    // 獲取原始字節(jié)和格式
                    var bytes = image.Data;
                    var format = GetImageFormat(image);

                    if (format != null)
                    {
                        string fileName = Path.Combine(outputFolder, $"image_{imageIndex++}.{format}");
                        File.WriteAllBytes(fileName, bytes);
                        Console.WriteLine($"Saved: {fileName}");
                    }
                }
            }
        }
    }

    private static string? GetImageFormat(XObjectImage image)
    {
        return image.Type switch
        {
            "Jpeg" => "jpg",
            "Png" => "png",
            "Jpx" => "jp2", // JPEG2000
            "CCITTFax" => "tiff", // 常見于掃描文檔
            _ => null // 未知格式暫不處理
        };
    }
}

PdfImageExtractor.ExtractImagesFromPdf("report.pdf", @"./extracted_images");

Install-Package itext7

using iText.Kernel.Pdf;
using iText.Kernel.Pdf.Canvas.Parser;
using iText.Kernel.Pdf.Canvas.Parser.Data;
using iText.Kernel.Pdf.Canvas.Parser.Listener;
using System.IO;

public class ImageExtractor : IRenderListener
{
    private readonly string _outputDir;
    private int _imageCount = 0;

    public ImageExtractor(string outputDir)
    {
        _outputDir = outputDir;
        Directory.CreateDirectory(outputDir);
    }

    public void BeginTextBlock() { }
    public void EndTextBlock() { }
    public void RenderText(TextRenderInfo renderInfo) { }

    public void RenderImage(ImageRenderInfo renderInfo)
    {
        try
        {
            var image = renderInfo.GetImage();
            if (image != null)
            {
                byte[] bytes = image.GetImageAsBytes();
                string extension = GetExtension(renderInfo);
                string path = Path.Combine(_outputDir, $"itext_img_{_imageCount++}.{extension}");
                File.WriteAllBytes(path, bytes);
                Console.WriteLine($"Extracted: {path}");
            }
        }
        catch (System.Exception ex)
        {
            Console.WriteLine($"Failed to extract image: {ex.Message}");
        }
    }

    private string GetExtension(ImageRenderInfo info)
    {
        var filter = info.GetImage().GetPdfObject().GetAsStream().GetAsName(iText.Kernel.Pdf.PdfName.Filter);
        if (filter == null) return "png";
        if (filter.Equals(iText.Kernel.Pdf.PdfName.DCTDecode)) return "jpg";
        if (filter.Equals(iText.Kernel.Pdf.PdfName.FlateDecode)) return "png";
        if (filter.Equals(iText.Kernel.Pdf.PdfName.JPXDecode)) return "jp2";
        if (filter.Equals(iText.Kernel.Pdf.PdfName.CCITTFaxDecode)) return "tiff";
        return "bin";
    }
}

// 使用方法
public static void ExtractWithItext(string pdfPath, string outputDir)
{
    using var reader = new PdfReader(pdfPath);
    using var pdfDoc = new PdfDocument(reader);

    var extractor = new ImageExtractor(outputDir);
    for (int i = 1; i <= pdfDoc.GetNumberOfPages(); i++)
    {
        PdfCanvasProcessor processor = new PdfCanvasProcessor(extractor);
        processor.ProcessPageContent(pdfDoc.GetPage(i));
    }
}

var bitmap = PdfiumViewer.PdfDocument.Load("scan.pdf").Render(0, 300, 300, true);
bitmap.Save("page.png", ImageFormat.Png);