[Qgis-developer] WCS and Raster improvements for QGIS

[Tim Sutton]

Hi

On Thu, Jul 12, 2012 at 5:15 PM, Marco Hugentobler
<marco.hugentobler at sourcepole.ch> wrote:
> Hi
>
> In my opinion, it is better to use the Qt classes for the network requests
> than curl. In QGIS, we have QgsNetworkAccessManager, which picks up
> automatically the network settings from the options tab (proxy settings,
> exclusion list, password, disk cache). It has nice progress reporting by
> signal/slot, the possibility to interrupt the network request and a disk
> cache. And the possibility to provide custom implementations for all that if
> necessary.
>
> Like this, WFS, WPS, WMS providers, plugin installer and open layers plugin
> (and third party python plugins) have a unified method to do network
> requests. No need to use a different network library for each one (and the
> mapping is never 1:1, there is always loss).
>
> So while it might be quicker (in terms of development time) to use the GDAL
> provider, a standalone provider is always more native and flexible (that's
> also the reason there are QGIS vector providers for postgres, wfs, gpx,
> spatialite, grass while everything can be read with the OGR provider).
>

Thanks Marco for filling in the background to the debate we had when
developing the proposal with WorldBank/GFDRR on whether to implement
the WCS provider natively or use GDAL. All of the reasons Marco
mentions make extremely good sense.

Regards

Tim



> Regards,
> Marco
>
> Am 12.07.2012 15:51, schrieb Even Rouault:
>>>
>>> Yes - Radim already made a first pass implementation using GDAL WCS
>>> though he said there were some problems with it - I think the most
>>> critical being that it doesn't support proxy access (I am speaking
>>> under correction here as I haven't looked into it in that much detail
>>> myself).
>>
>> This should be rather easy to add. It is just a matter of setting the
>> right
>> option to CPLHTTPFetch() (and thus the curl library), namely :
>>
>> <li>PROXY=val, to make requests go through a proxy server, where val is of
>> the
>>      form proxy.server.com:port_number
>> <li>PROXYUSERPWD=val, where val is of the form username:password
>>
>> Note: They can also already be used by setting the GDAL_HTTP_PROXY and
>> GDAL_HTTP_PROXYUSERPWD configuration options/environmenet variable, which
>> will
>> act on all GDAL/OGR drivers that go through the CPLHTTPFetch() function.
>>
>> I see Radim is already a GDAL committer, so there shouldn't be too much
>> overhead
>> if he wants to hack in the WCS driver.
>>
>>> I will let Radim comment on any other issues. I think from
>>> the project perspective we don't mind too much which approach is used
>>> if the result is efficient and integrates nicely into QGIS.
>>>
>>> Regards
>>>
>>> Tim
>>>
>>>
>>>
>>> --
>>> 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.
>>>
>>> Visit http://linfiniti.com to find out about:
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>>> Irc: timlinux on #qgis at freenode.net
>>> ==============================================
>>>
>>
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>
>
>
> --
> Dr. Marco Hugentobler
> Sourcepole -  Linux & Open Source Solutions
> Weberstrasse 5, CH-8004 Zürich, Switzerland
> marco.hugentobler at sourcepole.ch http://www.sourcepole.ch
> Technical Advisor QGIS Project Steering Committee
>
>
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-- 
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.

Visit http://linfiniti.com to find out about:
 * QGIS programming and support services
 * Mapserver and PostGIS based hosting plans
 * FOSS Consulting Services
Skype: timlinux
Irc: timlinux on #qgis at freenode.net
==============================================