[gdal-dev] Neatline for USGS PDF maps

[Even Rouault]

Le mercredi 17 avril 2013 17:34:13, Eli Adam a écrit :
> I found this in drafts and it appears I failed to send it.  Sorry for
> delay.  Sent partly for the list archives at this point.
> 
> On Sat, Jan 19, 2013 at 8:14 AM, Even Rouault
> 
> <even.rouault at mines-paris.org> wrote:
> >> Looking more closely at those files, I see that there are various
> >> registration blocks. The algorithm up to now was to select the
> >> registration block whose neatline covered the most area in terms of
> >> pixels. In the case of
> >> OR_Newport_North_20110824_TM_geo.pdf, those blocks are :
> >> "UTM Grid and Projection"
> >> "Orthoimage"
> >> "Map Layers"
> >> "Adjoining Quadrangles Diagram"
> >> 
> >> The number and names of blocks may change, but in all USGS topo PDFs
> >> samples I've tried, the "Map Layers" is always present and seems to the
> >> one that lead to the best results, so I've just pushed a change to
> >> select it when it is found.
> 
> --config GDAL_PDF_NEATLINE is very helpful.  Did you find the
> registration name blocks with one of the supporting PDF libraries?  Is
> it possible to find these multiple registration name blocks from gdal?
>  (I tried: gdalinfo --debug on without success.)
> 

I can see them in the "PDF: Description = " lines

$ gdalinfo --debug on ~/gdal/data/geopdf/OR_Newport_North_20110824_TM_geo.pdf
PDF: DPI guessed from contents stream = 600.0509320574655
PDF: OGC Encoding Best Practice style detected
PDF: LGIDict Version : 2.3
PDF: Description = UTM Grid and Projection
PDF: This is the largest neatline for now
PDF: LGIDict Version : 2.3
PDF: Description = Orthoimage
PDF: Not the largest neatline. Skipping it
PDF: LGIDict Version : 2.3
PDF: Description = Map Layers
PDF: The "Map Layers" registration will be selected
PDF: LGIDict Version : 2.3
PDF: Description = Adjoining Quadrangles Diagram
PDF: Not the largest neatline. Skipping it
PDF: Description = Map Layers
[...]