Removing images using PdfSharp | Division by Zero

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Removing images using PdfSharp

Removing images using PdfSharp

Written by Division by Zero

Wednesday, 02 February 2011 11:56

Last week someone asked me if it is possible to remove images from a Pdf to save storage. Of course it is! The next question is how.

It took me a while to figure it out. Using PdfSharp, an (not working! At least not on the Pdf I got) example on exporting images with PdfSharp and a few hour of trial and error I got a working version. I must admit it is the brute force method, since it doesn't only overwrite images, also other object like forms. Here's how it works:

// Open the PDF
PdfDocument doc = PdfReader.Open("inputfile.pdf", PdfDocumentOpenMode.Modify);

// Loop through every page
foreach (PdfPage page in doc.Pages)
{
	// Get all the resources for every page
	PdfDictionary resource = page.Elements.GetDictionary("/Resources");
	if (resource != null)
	{
	       // Get all the external objects
	       PdfDictionary objects = resource.Elements.GetDictionary("/XObject");
	       if (objects != null)
	       {
	               // Loop through every item in the external objects
	               ICollection
 items = objects.Elements.Values;
	               foreach (PdfItem item in items)
	               {
	                       // Get the reference
	                       PdfReference reference = item as PdfReference;
	                       if (reference != null)
	                       {
	                               // Get the underlying values as Pdf Object
	                               PdfDictionary xObject = reference.Value as PdfDictionary;
	                               // Overwrite the data of the object with 1 byte
	                               xObject.Stream.Value = new byte[0];
	                       }
	               }
	       }
	}
}

// Save the Pdf as another file
doc.Save("outputfile.pdf");

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