[luatex] help with script replacing image

[Pablo Rodriguez]

Dear list,

I need to produce a bunch of PDF files at work, that someone else
validates. Validation is performed on paper with a pen. After that, I
have to handle all those sheets again.

Since the amount can be huge, I wanted to offer pure PDF files that are
added an image for validation.

The image must be added after the PDF generation. Since there are
different kinds of documents, this image has to be placed at different
possitions in the document.

The basic idea that came to my mind is to add an image in the PDF
generation, which could be replaced with the validating image.

I have asked about this in the ConTeXt mailing list and Hans kindly
replied () that the following might work (not tested it himself):

    1. Append an xobject (xform) in the PDF file.

    2. Overload old image with new content.

    3. For the second step, revision number of objects
       and extra xref table would be needed.

Well, I must admit that I cannot code this myself. I guess it would be
a simple script. But this is beyond my knowledge.

Would anyone be so kind to help me in writing a luatex script for the
image replacement?

Many thanks for your help,

Pablo
-- 
http://www.ousia.tk