[Qgis-developer] qgis web

Richard Duivenvoorde rdmailings at duif.net
Sun Feb 13 07:03:34 EST 2011

Mohammed Rashad wrote:
> I am trying to build an online shapefile viewer using qgis as a backend. 
> for that i need to render qgis output to a image(.png) file
> I cannot use QgsMapCanvas class because it requires QApplication I 
> cannot use any class from qgis_gui
> but qgis_core can be used.
>  QgsVectorLayer * mypLayer = new QgsVectorLayer(myLayerPath, 
> myLayerBaseName, myProviderName);
>   QgsSingleSymbolRenderer *mypRenderer = new 
> QgsSingleSymbolRenderer(mypLayer->geometryType());
>   QList<QgsMapCanvasLayer> myLayerSet;
>   mypLayer->setRenderer(mypRenderer);
>   if (mypLayer->isValid())
>   {
>     cout << "Layer is valid";
>   }
>   else
>   {
>     cout << "Layer is NOT valid";
>     return;
>   }
> the following code works for me in Wt. It prints layer is valid or 
> invalid according to the parameters to QgsVectorLayer()
> can I set mypLayer->setRenderer of the above code to an image file so 
> that rendering occurs on a image file of my choice?
> It hope now the problem is clear.Now can you help me?

Nope, sorry I'm not that deep into cpp coding.

But from what you write it seems that you actually want a WMS. So why 
not have a look at the mapserver_qgis WMS? This can generate an image 
from a given qgis-project file for you. It's also probably interesting 
to look into that code https://svn.osgeo.org/qgis/trunk/qgis/src/mapserver/

Actually I'm also wondering if it would be easy to build a mini python 
application which:
1) reads a qgs project file (see mapserver export plugin for that)
2) then paints the map on a given hidden mapcanvas of a given size and 
bbox (this is the hard part I think?)
3) writes this to an image

Maybe somebody else?


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