memorystream to system.drawing.image with transparency

I have a pdf with an embedded image and using itextsharp I 开发者_开发问答have read the image into a memorystream (after checking for subtype image).

byte[] bytes = TextSharp.text.pdf.PdfReader.GetStreamBytesRaw((iTextSharp.text.pdf.PRStream)pdfStream);

after that I use

 using (System.IO.MemoryStream memStream = new System.IO.MemoryStream(bytes))
                                    {
                                        memStream.Position = 0;
                                        System.Drawing.Image img = System.Drawing.Image.FromStream(memStream, true, true);
}

Further I save the image into a png using

img.Save(@"mypath to the file.png", ImageFormat.Png);

The problem is most of the images are coming alright..however some of them are more like negatives..please see the image here.

http://pdfaid.com/prasad.bmp (similar result with png and gif)

Can someone please guide me how to solve this?

NOTE: instead of png I tried jpg and gif but didnot make a difference.

Thank you in advance, Prasad.

Read through the posts here and hopefully they'll walk you through some answers. One person said that you might be seeing a mask of some sort and another said you might be see an image with some inverted color channels. If you can post a specific PDF we might be able to help you more.