[gdal-dev] Something wrong with writing a big raster into PDF

[Even Rouault]

Le vendredi 07 mars 2014 14:20:13, Rahkonen Jukka (Tike) a écrit :
> Hi Even,
> 
> Yes, that way I can perhaps create an all-white PDF map a bit faster but
> with no other improvement, unfortunately.

I've tried "gdal_translate UM5L.png UM5L.pdf -of pdf" on my Linux workstation 
and the the following viewers :
- Adobe Reader 9.4.2 Linux: blank image
- Okular, KDE-based PDF viewer, based on poppler library: can display a fit-to-
page overview in a few seconds, but not the full resolution image since it 
tries to allocate a 15360x15360 buffer
- Evince, GNOME-based PDF viewer, based on poppler library, uses cairo for 
display: blank image with error message "cairo context error: out of memory"
- xpdf, viewer whose code has been forked to build the poppler library: can 
display the PDF at full resolution, and in reasonable time.
- qgis (based on GDAL PDF driver, and poppler backend) : the initial overview 
computation is really really slow. Roughly half an hour. Because there's 
currently no optimization in the GDAL PDF reader to get a lower resolution 
image. Could potentially be dramatically improved by asking a rendering at 
lower DPI for overview levels, instead of querying at best DPI and then 
downsampling. But once that 32x32 overview is computed, if you go to 100% 
scale and pan, the refresh time is around 1 second after each pan.
- command line "rendering" (based on GDAL PDF driver, and poppler backend) : 
gdal_translate UM5L_tiled.pdf out.tif -co TILED=YES : 1 minute 20 sec (less if 
you specify a higher value than the default for GDAL_CACHEMAX)

I've also tried generating a JPEG2000 compressed PDF and Adore Reader is not 
happier.

Conclusion: most PDF viewers assume that a PDF page can fit in memory and don't 
use a tiling strategy to display it.

Even

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