Extract images from scans

I have scanned PDF documents. These are shown in the PDF as an image and are only a few KB in size. The following code creates images that are significantly larger than the PDF itself. I also thought that the quality would be worse. Is there a way to export the scanned document (image) one to one as a graphic and this with the same file size?

Resolution resolution = new Resolution(300);
JpegDevice jpegDevice = new JpegDevice(resolution, 100);
jpegDevice.Process(pdfDocument.Pages[1], imageStream);

The page has in resource an XImageCollection Collection. The graphic of the document appears to be stored there in fragments. But in which positions are they put together again? Is this a better way?

Thanks
Stephan

@sk21

Would you kindly share your sample PDF document with us. We will test the scenario in our environment and share our feedback with you accordingly.