专为 C# 打造的 PDF 类库

/// <summary>
/// Generate PDF document From Multiple Images in C# using PDF Library
/// </summary>
public void GeneratePdf()
{
    //Initialize C# PDF Library
    PdfCommon.Initialize();
    //Create a PDF document
    using (var doc = PdfDocument.CreateNew())
    {
        //Read images
        var files = System.IO.Directory.GetFiles(@"c:\Examples\Images\", "*.*", System.IO.SearchOption.AllDirectories);
        foreach (var file in files)
        {
            //Create empty PdfBitmap
            using (PdfBitmap pdfBitmap = PdfBitmap.FromFile(file))
            {
                //Create Image object
                var imageObject = PdfImageObject.Create(doc, pdfBitmap, 0, 0);
                //Calculate size of image in PDF points
                var size = CalculateSize(pdfBitmap.Width, pdfBitmap.Height);
                //Add empty page to PDF document
                var page = doc.Pages.InsertPageAt(doc.Pages.Count, size);
                //Insert image to newly created page
                page.PageObjects.Add(imageObject);
                //set image matrix
                imageObject.Matrix = new FS_MATRIX(size.Width, 0, 0, size.Height, 0, 0);
                //Generate PDF page content to content stream
                page.GenerateContent();
            }
        }
        // Save  PDF document as "saved.pdf" in no incremental mode
        doc.Save(@"c:\Examples\test.pdf", SaveFlags.NoIncremental);
    }
}
/// <summary>
/// The function takes width and height of the bitmap in pixels as well as 
/// horizontal and vertical DPI and calculates the size of the PDF page. 
/// To understand the conversion you should know the following:
///     One inch contains exactly 72 PDF points;
///     DPI of the scanned image may vary and depends on scanning resolution
/// </summary>
private FS_SIZEF CalculateSize(int width, int height, float dpiX = 300, float dpiY = 300)
{
    return new FS_SIZEF()
    {
        Width = width * 72 / dpiX,
        Height = height * 72 / dpiY
    };
}