4

I have a set of GeoPDFs that I converted to GeoTiffs. However, the end results are horrible. They are very pixelated. The command I passed was

gdal_translate -of GTiff inFile outFile -co COMPRESS=NONE -co JPEG_QUALITY= 100.

Is there a setting that I am missing because some of the outputs are unreadable. By comparison the outputs I get from Global Mapper 15 are super sharp. Sadly there is a whole other world of problems with GLmapper though.

I was interested in the resample settings but figured that the default method of nearest neighbor would be the sharpest.

  • Can you share a sample file? With your command no resampling should happen because you do not change the resolution and JPEG_QUALITY does not have any effect because you do not use compression. I guess that you have PDF file with vector layers and it may be that GDAL is not very good with with rasterizing them but that must be tested with real data before making a judgement. – user30184 Jan 13 '15 at 16:07
  • I am pretty new to Stack Exchange and don't know how to share files yet. Here is the original source - nps.gov/hfc/cfm/carto-atoz-geopdf.cfm. I figured JPEG_QUALITY wouldn't do anything but I put it in the command to cover my bases. The pdfs have multiple vector layers which is what is causing issues in GLmapper. – Tom Jan 13 '15 at 16:27
  • Taking the first one of the list, ogrinfo is not able to open it with the pdf driver. So I assume the layers are all raster and not any vector format GDAL can understand. – AndreJ Jan 13 '15 at 16:39
  • Interesting, I didn't think it possible to convert from GEOpdf to a different non-raster format. I will look at ogr2ogr and see if that can help. But I am unfamiliar with QGIS and need to get this wrapped up fast. My preferred answer is to get a cleaner output from my original script. – Tom Jan 13 '15 at 16:43
5

You can improve the result with this command line:

gdal_translate -of GTiff PARAmap1.pdf out1File.tif --config GDAL_PDF_DPI 300

According to http://www.gdal.org/frmt_pdf.html, the default is 150dpi.

For higher quality than 300dpi, you have to be very patient ;-)

I was able to extract vector data from USGS topo PDFs with ogr2ogr in Convert GeoPDF with GDAL, but ogrinfo refuses to read your pdf files. So no chance on that side. The manpage for vector support is http://gdal.org/1.11/ogr/drv_pdf.html

  • This is the best I could do with my version of GDAL too. The result for the pdf map I tested nps.gov/hfc/carto/PDF/ACADmap2.pdf looks quite good. The original file seems to contain vector graphics and therefore the lines and texts are sharp at any scale. However, for tiff, jpeg, png etc. vectors must be rasterized in any case. In addition, GDAL can't find vector data from the PDF so rasterizing is the only possibility. Not finding vector layers means probably that I lack podofo or poppler support gdal.org/frmt_pdf.html. – user30184 Jan 13 '15 at 18:02
  • Have you tested the USGS Topo PDFs I mentioned in the other topic? They work for me as vector data with the same GDAL. They are made with ESRO ArcSOC, while the ones here are from Adobe Illustrator CS5. ESRI seems to produce GDAL-friendly output. – AndreJ Jan 13 '15 at 18:37

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.