[gdal-dev] gdal_translate adding 'dashed' lines to output

[Even Rouault]

Le jeudi 23 janvier 2014 22:49:33, John Gray a écrit :
> I've been trying to use "gdal_translate" to convert a USGS GeoPDF to a
> GeoTiff file.  It appears to be working correctly except for one issue.
> During the conversion a number of horizontal lines appear in the
> output.  They appear at a few latitudes in the file - it looks like a
> dashed line across the image with a lot of space between each dash (but
> you have to zoom in to see them).  When I view the produced GeoTiff file
> in an image viewer here is what I see (zoomed in and cropped):
> 
> http://www.graysolutions.com/temp/LenexaLines.png
> 
> I've circled the improper lines in this image.  When I view the GeoPDF
> in Acrobat these lines do not appear (so I do not believe they are part
> of the source image).
> 
> Has anybody seen this problem before or know how to keep it from happening?
> 
> ---------
> 
> Additional Details:
> 
> For the example above I rendered only the raster orthoimage layer,
> however when the full contents of the file are rendered I still see the
> 'dashes' in the output.
> 
> The source GeoPDF file I'm working with can be downloaded here (~25 MB,
> downloads as a .zip file):
> 
> http://ims.er.usgs.gov/gda_services/download?item_id=5689818
> 
> I'm using GDAL compiled for Windows from
> http://www.gisinternals.com/sdk/.  I tried using both the 'stable' and
> 'development' versions and the results were the same (running on Windows
> 8.1).  The command line used:
> 
> gdal_translate -of GTiff --config GDAL_PDF_LAYERS "Images.Orthoimage"
> --config GDAL_PDF_DPI 150 KS_Lenexa_20120905_TM_geo.pdf Lenexa.tif

I've just tried the above with a recent version of the Poppler library that is 
used by the PDF driver for the rendering and there are no such artifacts.
I've also just tried with the Poppler version used by the builds on 
gisinternals, which is a bit obsolete now, and I do see the artifacts.
So the builds on gisinternals would benefit from an upgrade of the Poppler 
library. You might want to contact Tamas Szekeres about this.

> 
> I'm using the DPI setting to scale the image down so the output isn't so
> large (without this it is a ~950 MB file).  I did render one without
> setting this (rendering at the native resolution) and the dahses were
> still there.  I've also tried this for other GeoPDF files in the same
> series and experienced similar results.
> 
> Thanks,
> 
> John
> 
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