Robert Prey
Banned
- Joined
- Sep 8, 2011
- Messages
- 6,705
Obviously not. He probably just Googled "PDF AND layers" and just copypasted the one paragraph that seemed to say what he wanted to say, without really understanding any of it.
The printable objects in the Obama PDF are transparency groups. These associate content with a clipping mask. Here's what the Adobe PDF language reference has to say about them.
"Note: The concept of a transparency group is independent of existing notions of “group” or “layer” in applications such as Adobe Illustrator. Those groupings reflect logical relationships among objects that are meaningful when editing those objects, but they are not part of the imaging model."
(Adobe Systems. PDF Reference: Adobe portable document format version 1.4. 3d ed., Addison-Wesley: 2001, p. 411, emphasis added)
It is expressly against Adobe's design intent to conflate transparency objects in PDF files with logical layers in their creative products. Yet this is exactly what Mara Zebest did.
Layered content in PDF documents is implemented by Acrobat Professional using a PieceInfo entry in an object of type /Page. "Applications can use this dictionary as a place to store any private data they wish in connection with that page or form. Such private data can convey information meaningful to the application that produces it (such as information on object grouping for a graphics editor or the layer information used by Adobe Photoshop), but is typically ignored by general-purpose PDF viewer applications" (Ibid., p. 581, emphasis added).
Adobe here tells us what to look for in PDFs that retain any sort of information about logical layers from their original editors and creators. Zebest's expectation is uninformed.
How many PagePiece entries are there in the Obama PDF's single /Page object? Robert, can you answer that? Hm, I can.
"a single page of the PDF file can contain different layers with different content."
What is it about this straight forward statement that you do not understand, Jay?
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