PDFsharp & MigraDoc Forum

static void ExportImage(PdfDictionary image, ImageFileInfo ifi)
{
            string filter="";
            try
            {
                    //the following line runs in an exception, because image.Elements.GetName("/Filter") contains an object array with two values ("/FlateDecode" and "/DCTDecode" and not one single value
                    filter = image.Elements.GetName("/Filter");
            }catch (Exception ex)
            {
                     PdfSharp.Pdf.PdfItem objFilter = (PdfSharp.Pdf.PdfItem)image.Elements["/Filter"];             
                     filter = objFilter.ToString();
            }
            if (filter.Contains("/DCTDecode"))
            {
                ifi.ImageFileName += ".jpg";
                ExportJpegImage(image, ifi.ImageFileName);
            }
             else if (filter.Contains("/FlateDecode"))
            {
                ifi.ImageFileName += ".png";
                ExportAsPngImage(image, ifi.ImageFileName);
            }
}

static void ExportAsPngImage(PdfDictionary image, string outputFileName)
{
            MemoryStream mms = new MemoryStream(image.Stream.Value);
            try
            {
                //The following line runs into an Exception: "Parameter is not valid"
                Bitmap bmp = new Bitmap(mms);
                bmp.Save(outputFileName, ImageFormat.Png);
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }
}

static byte[] FlateDecode(byte[] inp, bool strict)
{
            MemoryStream stream = new MemoryStream(inp);
            InflaterInputStream zip = new InflaterInputStream(stream);
            MemoryStream outp = new MemoryStream();
            byte[] b = new byte[strict ? 4092 : 1];
            try
            {
                int n;
                while ((n = zip.Read(b, 0, b.Length)) > 0)
                {
                    outp.Write(b, 0, n);
                }
                zip.Close();
                outp.Close();
                return outp.ToArray();
            }
            catch (Exception ex)
            {
                if (strict)
                    return null;
                return outp.ToArray();
            }
}

static void ExportJpegImage(PdfDictionary image, string outputFileName)
{
          // Fortunately JPEG has native support in PDF and exporting an image is just writing the stream to a file.
          byte[] stream = image.Stream.Value;
          FileStream fs = new FileStream(outputFileName, FileMode.Create, FileAccess.Write);
          BinaryWriter bw = new BinaryWriter(fs);
          bw.Write(stream);
          bw.Close();
}