AFAIK, BDC/EMC (since PDF 1.2) are defined my the "Marked Content" chapter in the spec and are used primarily for identifying certain marks on a page. They are the basis for Tagged PDF. But they don't have an influence on the rendering. I've worked on that in FOP recently so I know a few things here.
"Optional Content" has been introduced with PDF 1.5. It is used mainly for group content together, ex. layers in Illustrator. I haven't looked at OCG closely, yet, but they allow to show and hide certain marks (content groups). Anyway, if your test files render badly, I don't think it has to do with these features. If I understand this stuff correctly, the above is mainly about switching on and off the rendering of certain marks. If you like I can take a look at your test files that don't work properly and try to have a look myself. Maybe I can give you a hint where to look. On 01.05.2009 00:55:15 Daniel Wilson wrote: > Some of my stencil-masked documents are still rendering badly. > > The only operators they use that are not implemented are the BDC and EMC > operators -- the marked-content sequence begin and end operators (section > 10.5). These are briefly discussed relative to XObjects as "Optional > Content" in section 4.10.3. > > I'm sure these things have some significance, but are they significant to > rendering a flat image -- PNG, JPG, etc. ? Or should I be looking elsewhere > for the outstanding problems? > > Thanks once again for your thoughts! > > Daniel Wilson Jeremias Maerki
