[Qgis-user] Raster data formats

Agustin Lobo alobolistas at gmail.com
Sat May 16 06:38:17 EDT 2009


The problem is, as I understand it, that Juan is not using Windows but 
Linux. And while
ECW&Mrsid support is simply added by
the user to the current binary distribution of qgis
for windows (i.e., see 
http://sites.google.com/site/eospansite/qsig-for-windows )
getting the same support for qgis installed from binaries for linux is
simply impossible.
You must go through the much more cumbersome
process of
(1) Compiling gdal with support for ecw and Mrsid
(2) Compiling qgis with that particular gdal

Certainly, not a 5 minutes task (in particular for users who just don't even
know what compiling means...)

So, effectively, regarding qgis, linux users are in disadvantage. Or, in 
other
words, for a regular user of qgis, using windows is better. An astonishing
contradiction for gnu software.

The roots of the problem are in gdal, it's true. But the branches are in 
qgis
and, after having exchanged messages in the gdal list
http://n2.nabble.com/Tickets-2385-and-2683-(ECW-and-MrSID-plugins)-tt2767156.html#none
I'm convinced that the problem will not be solved unless the communities 
behind
programs using gdal get involved.

Agus

Tim Sutton wrote:
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> Hi
>
> Alex Mandel wrote:
>   
>> Juan Pedro Pérez Alcántara wrote:
>>     
>>> Hello,
>>>
>>> perhaps this is a silly one, but I'm quite frustrated with conversions
>>> from popular raster formats in the Windows/ArcGIS world to the
>>> Linux/QGIS one. For example, ECW and MrSID are most popular. I think
>>> JPEG2000 should be a good candidate for a raster format in QGIS. As far
>>> as I know, it is fast (piramidized by nature, so to say),
>>> georreferenced, and they work flawlessly and smoothly (my experience, at
>>> least) in QGIS. Perhaps all of you, much experienced than me for sure,
>>> think that JPEG2000 is not the way and that GeoTIFF or whatever should
>>> do the job. If it is so, I'll stick obviously to that option instead.
>>>
>>> I have been messing around with quite a bunch of libraries to deal with
>>> the conversion. First, there is GDAL, with which I'm able to transform
>>> ECW to almost any GeoTIFF or JPEG that works with QGIS very well, and
>>> with JPEG compression, not so far in size from the ECW source. But then
>>> I tried to use ImageMagick and/or Jasper to convert to JPEG2000, and
>>> here is where I get stuck. I stripped off in gdal_translate the GeoTIFF
>>> tags with BASELINE, but to no avail in ImageMagick, it says always (with
>>> TIFF, JPEG, etc.) that it cannot write the image. Same with JASPER: I
>>> tried to convert from a gdal_translated jpeg, but without result. What
>>> is that I'm missing? Do you have a proven workflow to do this job? 
>>>
>>> And with MrSID... not experimented by now, but I tremble only thinking
>>> in that :)
>>>
>>> Perhaps I'm too obsessed with size (file sizes, I mean!!! :) ), and I'm
>>> messing around too much with that subject, when GeoTIFF is providing
>>> good results with a slight size increase. Given the size of hard drives
>>> today (and that I'm not in the massive storage business in the GIS
>>> scene), I think is a fair trade-off for an easy and straightforward
>>> conversion workflow. I'd like very much to hear your opinions about
>>> this.
>>>
>>> Thanks in advance, this is my first post. QGIS is great and thanks to it
>>> and we have almost left behind the so-called industrial standard in GIS.
>>> Congratulations for the great job.
>>>
>>> Greetings from Spain,
>>>
>>> Juan Pedro Pérez Alcántara
>>>
>>>       
>> I think I'm a little confused, if you have GDAL compiled with ECW and
>> MrSID format these should open in QGIS. Note the most recent version of
>> the windows QGIS standalone is shipping with MrSID support.
>>
>> FYI, the MrSID license is more open, and LizardTech is a sponsor of OSGEO.
>>
>> Alex
>>     
>
> Also note that if you want ECW support in windows builds of QGIS 1.0.2
> or 1.1.0, you can simply download the ECW dlls from Erdas (by getting
> the SDK) and place the dlls into the Quantum GIS/bin directory. We could
> not include them in the installer by default for licensing reasons, but
> by adding those dlls its pretty easy to get it working.
>
> Also note that in my testing the JASPER jp2 raster loading via GDAL is
> quite slow (frustratingly slow really) on the only real performant way
> to use a wavelet compressed raster at this stage is to use the Kakadu,
> Mr Sid or ECW drivers (all of which are proprietary software).
>
> Lastly it is probably more appropriate to use gdal_translate to convert
> between raster formats than imagemagick, since gdal's conversions are
> 'spatially aware' and will retain all georeferencing etc. data in the image.
>
> Regards
>
>
> - --
>
> Tim Sutton - QGIS Project Steering Committee Member (Release  Manager)
> ==============================================
> Please do not email me off-list with technical
> support questions. Using the lists will gain
> more exposure for your issues and the knowledge
> surrounding your issue will be shared with all.
>
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