I am using mupdf to render PDFs in my c++ application but I also need to edit PDFs (inserting a picture for example) but I cannot for the life of my figure out how - it's not documented very well. Ghostscript says that there is an API in mupdf to modify PDFs here http://www.ghostscript.com/MuPDF.html.
Ultimately I am hoping to be able to edit PDFs using MuPDF rather than using another library.
Any help would be appreciated, thanks!
The modification API in MuPDF is for editing the structure of a PDF (such as reordering pages, adding or removing annotations, etc) at a fairly low level. The graphics in PDF are based on a "content stream" object containing the commands for drawing a page using a subset of PostScript. There are no functions for editing these graphics content streams in MuPDF.
However, if all you want to do is add an image on top of the page, you can do so by creating an annotation object for the page. You'll need to create the PDF dictionary objects for the annotation, an image object, an appearance stream to draw the image object, and hook them up to the page. You'll need a good understanding of the PDF format to do this though.
You'll want to use the latest git checkout of MuPDF since we've recently (post 1.0 release) added some convenient functions for editing objects and updating streams with new content.