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

[Brent Fraser]

Joaquim,

   Doing the format conversion from .ps to pdf is one thing (and there are 
several ways to do it), but embedding the georeferencing in the PDF to make it a 
GeoPDF is the interesting bit.  I haven't found any open source project capable 
of do that.  Or even capable of writing the PDF elements (e.g. Frames) necessary 
for writing the GeoPDF information.  But I remain hopeful...

Brent

Joaquim Luis wrote:
> 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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> 
>