[gdal-dev] extract vector/raster data from GeoPDF

[Joaquim Luis]

Brent Fraser wrote:
> I see the example calculation of the transformation matrix, and a 
> statement "I created a GeoPDF by running the Postscript file through 
> Ghostscript to create a Postscript file that looks like this"
> 
> But I don't see where the georeferencing is written into PDF to make it 
> a GeoPDF.  Is it a Ghostscript command line?

Brent,

One only has to convert it to pdf using ghostscript.
I did it with GMT's ps2raster, like that

ps2raster quad.ps -Tf -A

Joaquim Luis

> 
> Brent
> 
> Klokan Petr Přidal wrote:
>> Hi,
>>
>> There is a great blog post (and the linked "worked example" post with 
>> details):
>> http://geopdf.blogspot.com/2009/02/geopdf-map-for-worked-example.html
>>
>> It shows you how to create geopdf via GhostScript - so there is
>> already a practical open-source example how to encode the georeference
>> into the PDF/PS according the OGC standard - for use in Acrobat
>> Reader. To add support for such tag in MapServer, which generates pdf
>> dynamicaly via pdflib, should not be totally problematic.
>>
>> Decoding is not as hard either, there are nice libraries like poppler
>> (http://poppler.freedesktop.org/), which allows you to parse vectors
>> (and convert them to SVG for example) or rasterize the PDF files (into
>> TIFF,...) via Cairo.
>> The work is in assigning correct geographic coordinates to the
>> coordinate system internally used in PDF files and especially write
>> the bridge to the outside world (with GDAL/OGR).
>> I am afraid that authors of the GeoPDF standard would not like this,
>> as it seems that the idea of GeoPDF is "see it in the Acrobat, print
>> it, but that's all". At least I think so, because they discontinued
>> their Geopdf2geotiff product and all the conversion tools are just one
>> way - into GeoPDF. Please correct me...
>>
>> Anyway, in this moment you can quite easily use utility like
>> "pdfimages" to extract full quality image tiles from any GeoPDF (like
>> those from USGS) and merge it based on their location in PDF into one
>> GDAL file via VRT (gdalbuildvrt) with a bit of hacking. This is what I
>> did for my favorite USGS DRG of Grand Canyon ;-).
>> Look at: http://klokan.mzk.cz/~klokan/geopdf/ - soon I will update the
>> MapTiler.org overlay examples...
>>
>> Unfortunately all PDF parsing libraries I know are GPL, and that means
>> we can't use them for the gdal driver - because of the license issues.
>> But to create a GPL utility for converting GeoPDF to anything what
>> GDAL/OGR supports should be OK. Poppler can be the best base of such
>> GDAL-based utility for reading/rasterizing of the GeoPDF files.
>>
>> Now just find a sponsor and time to make it ;-).
>>
>> Best,
>>
>> Klokan Petr Pridal
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