Q:
1) Magic bullet - is there an existing function that identifies if one
element is 100% obscured by any combination of elements layered above
it? (IE: Element exists on a page but is not visible.)
2) Realistic alternative - where can I find the relative z-index value
of each embedded element?
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A:
is there an existing function that identifies if one element is
100% obscured by any combination of elements layered above it?
If you only care whether Element's bounding boxes are overlapping you
can easily determine the extent of overlaps between two bounding boxes
using pdftron.PDF.Element.GetBBox() and
pdftron.PDF.Rect.IntersectRect().
Since Elements may be transparent or may have holes (e.g. text glyphs,
etc), it would be hard to implement a function that does not rely on
bounding box information.
Where can I find the relative z-index value of each embedded element?
You only need to keep a counter when traversing the element display
list (http://www.pdftron.com/net/samplecode.html#ElementReader). The
value of the counter is the z-index of the Element.