问提取PDF的部分

EN

    static void Main(string[] args)
    {
        ConvertPDFToBmp("FilePathOfPDF");

        CropAtRect("FilePathOfConvertedImage");

        ConvertToPDF("FilePathOfCroppedImage");
    }

    public static void ConvertPDFToBmp(string filePath)
    {
        PdfDocument document = new PdfDocument();

        document.LoadFromFile(filePath);
        Image emf = document.SaveAsImage(0, Spire.Pdf.Graphics.PdfImageType.Bitmap, 400, 400);

        emf.Save("FilePath", ImageFormat.Jpeg);
    }

    public static void CropAtRect(string filePath)
    {
        Bitmap b = (Bitmap)Bitmap.FromFile(filePath);
        Rectangle r = new Rectangle(new /*Where the rectangle starts*/Point(/*Width*/, /*Height*/), (new /*How big is the rectangle*/Size(/*Width*/, /*Height*/)));
        Bitmap nb = new Bitmap(r.Width, r.Height);
        nb.SetResolution(400, 400); //Scale to keep quality
        Graphics g = Graphics.FromImage(nb);
        g.DrawImage(b, -r.X, -r.Y);

        nb.Save("FilePath", ImageFormat.Jpeg);
    }

    public static void ConvertToPDF(string filePath)
    {
        Bitmap b = (Bitmap)Bitmap.FromFile(filePath);

        PdfDocument doc = new PdfDocument();

        PdfImage pdfImage = PdfImage.FromImage(b);

        PdfUnitConvertor uinit = new PdfUnitConvertor();
        PdfPageBase page = doc.Pages.Add(new /*Size of PDF Page*/SizeF(585, 365), new PdfMargins(0f));

        page.Canvas.DrawImage(pdfImage, new /*Where the image starts*/PointF(0, 0));

        doc.SaveToFile("FilePath");
    }