Short description:

Images contained in two PDFs generated by the same user are missing in Moodle's PDF annotation.

Testing:

1. The student uploads his documents in a repository with a "PDF Annotation" feedback type.
2. The teacher accesses the online PDF annotation: the images are missing from the preview. When he download the PDF file the images appear properly in his PDF file viewer.

Further information :

1. No other PDF has the same problem in the same repository.
2. The problem can be reproduced on our test server (using the two original files).
3. Both PDFs were generated from a Mac and the photos are .jpg taken with an iPhone.
4. I can reproduce the problem with the student PDF files, but I cannot create a PDF file with the same type of problem by myself and I have no relevant information of how these images or PDF files are differents from others.
5. If you save the PDF file via "Print as PDF" functionality and re-upload it, the problem no longer occurs
6. I think Ghostscript is not involved because
   1. It is up to date
   2. I executed the GS conversion command line directly on the two PDF files from our server. The generated PNG files do contain the images.
7. I was able to retrieve the "combined.pdf" file from the /temp/assignfeedback_editpdf/pageimages/ directory. It does not contain the images. I think the problem occurs before GS command line.

Since I can't produce problematic PDF files by myself and the student's PDF files contains sensitive information, I cannot upload it here. I am here to help or to test code if you give me specific instructions.