Our friend Hermitian is responding to my findings that the Xerox created documents contain JPEGs with embedded comments in them. I found such comments in the WH PDF as well as the WH Tax Form PDF used to scan in the President’s tax returns… Of course, this is quite strong data in support of my hypothesis. So what does Hermitian do?
Yup ! It figures that Xerox would plant a useless comment in all their JPEGS.
It is irrelevant why Xerox would put comments in their JPEGs, one can speculate but the fact is that they do. They have no impact on how the file is rendered, they are just a tag added by the JPEG creation software used by Xerox.
I wonder why Preview would leave it in there ?
This is best understood when realizing that Preview is not a JPEG editor or bitmap editor. You can manipulate PDF objects but Preview does not touch the embedded image Xobjects. This makes a lot of sense because it has no reason to resave them. In fact, resaving a JPEG as JPEG may lead to additional quality reductions, even when saved at full quality. But one can do the experiment and print a JPEG to PDF and then extract the JPEG and look at the metadata. It remains exactly the same.