Phil Endecott wrote:
I need to extract the geolocation metadata from a GeoPDF file.
If you're not familiar with this format, it's something that was
developed by a company called TerraGo Technologies and was adopted as a
"best practice" by the Open Geospatial Consortium. There is a document
describing it via http://www.opengeospatial.org/standards/bp (look for
"GeoPDF"; click-through but free-looking license required). Basically
it provides a method to associate positions in the document with
latitude-longitude positions on the ground.
The method used is to define "map frames" that are added to the parent
PDF page object. As I understand it, there is a new key 'LGIDict' in
the page object, which is an array of dictionaries one per map frame,
each of which contains a set of entries like containing matrices,
bounding boxes etc. that define the geolocation for that frame.
Well I have cobbled together something that gets the page objects and I
can see the 'LGIDict' that I was looking for. I had to hack Page.h to
make the pageObj public; is there some better way that I should have
been doing that?
I was confused for a while because the example GeoPDF that I linked to before:
Here's an example of a GeoPDF file:
ftp://ftp2.cits.rncan.gc.ca/pub/cantopo/50k_pdf/092/g/cantopo_092g06_pdf.zip
seems to not have the LGIDict, nor anything else additional in the page
object. Of course I assumed by code was wrong for a long time before
suspecting the file. A test with another file got the LGIDict immediately.
To help with debugging, I was wondering if there is any easy way to
decode the PDF to a point where I can see its unencoded text (or
however one describes this first level of encoding). Specifically the
GeoPDF document describes stuff at this level:
105 0 obj
<<
/Type /Page
/LGIDict 104 0 R
......
endobj
104 0 obj
<<
/Type /LGIDict
/Version (2.1)
/CTM
.......
What do I have to do to see that?
Regards,
Phil.
_______________________________________________
poppler mailing list
[email protected]
http://lists.freedesktop.org/mailman/listinfo/poppler
