[Qgis-user] Python script to iterate through attributes and then refresh the canvas - doesn't show any map....

[Joris Hintjens]

hello frank, for the OSM problem, see thread: 
 "Printing with OSM layer"
form earlier today and the answers of Joost and Paulo to that. 




Op 4-nov.-2014, om 13:59 heeft Frank van Baar <frank at van-baar.com> het volgende geschreven:

> Hi Joris,
>  
> Thanks for your suggestion – didn’t realize atlas worked this way. It however does not completely do what I want to do – the layer which it changes the filter for also has specific formatting to highlight the region etc. AND the OSM layer doesn’t always display right.
>  
> Any other suggestions anyone?
> 
> Frank
>  
> Van: Joris Hintjens [mailto:jorishin at gmail.com] 
> Verzonden: 04 November 2014 11:27
> Aan: Frank van Baar
> CC: Qgis-user at lists.osgeo.org
> Onderwerp: Re: [Qgis-user] Python script to iterate through attributes and then refresh the canvas - doesn't show any map....
>  
> Why not use atlas generation in the print composer?
>  Seems to me this corresponds with your „what i’m trying to achieve”
> grts
> Joris
>  
>  
> Op 4-nov.-2014, om 09:14 heeft Frank van Baar <frank at van-baar.com> het volgende geschreven:
> 
> 
> Hi,
> 
>  
> Am completely stuck with a QGIS project in Python and tried everything but nothing seems to work. The python script does work as such BUT the canvas never shows the map and therefor the exported maps are empty….
> 
>  
> What I’m trying to achieve:
> 
> ·       Create a Python script that iterates through a series of ca. 2500 polygons based on attribute value, zoom to layer extend and save the canvas for each attribute as an image file.
> 
> ·       I then use the image files in other documents
> 
>  
> The issue is that while manually I get the canvas to reload and display the map, this doesn’t happen when running the python script. Have tried couple of ways:
> 
> 1.      Don’t load the project each time and just change the filter
> 
> 2.      Add sleep timers to give the canvas time to refresh etc.
> 
> 3.      Tried different QGIS versions (2.2, 2.4 & 2.6 on Win 64x)
> 
>  
> But all to no avail…. Hope somebody’s got a great idea how to solve it.
> 
>  
> Regards,
> 
> Frank
> 
>  
> Python code:
> 
>  
> # File location & specifications
> 
> PROJECTPATH = 'C:/Users/Frank/Documents /Targetting/Kaarten/'
> 
> PROJECTFILE = 'C:/Users/Frank/Documents /Targetting/TargettingkaartV26qgs.qgs'
> 
> EXTSNAPSHOTS = '.jpg'
> 
> EXTSNAPSHOTS2 = '.png'
> 
> SUFFIX = '65Plus_v1'
> 
> last_id = 1
> 
> while last_id < 5:
> 
>         # Clear map canvas
> 
>         QgsMapLayerRegistry.instance().removeAllMapLayers()
> 
>         qgis.utils.iface.mapCanvas().refresh()
> 
>        
>         # Open QGIS project
> 
>         QgsProject.instance().setFileName(PROJECTFILE)
> 
>         QgsProject.instance().read()
> 
>         qgis.utils.iface.mapCanvas().refresh()
> 
>         time.sleep(30) 
> 
>         canvas = qgis.utils.iface.mapCanvas()
> 
>         acl = canvas.layer(0)
> 
>         qgis.utils.iface.mapCanvas().layer(0).selectAll()
> 
>         selection = 'RijNo = ' + str(last_id)
> 
>        
>         acl.setSubsetString( selection )
> 
>         acl.triggerRepaint
> 
>         canvas.layer(1).triggerRepaint 
> 
>         time.sleep(5)  
> 
>         qgis.utils.iface.setActiveLayer(acl)
> 
>         # Zoom in and out to refresh potential issues with OpenLayer
> 
>         canvas.zoomByFactor(3)
> 
>         canvas.zoomByFactor(0.5)
> 
>         qgis.utils.iface.zoomToActiveLayer()
> 
>         qgis.utils.iface.mapCanvas().refresh()
> 
>        
>         time.sleep(10)
> 
>         # Save project
> 
>         p=QgsProject.instance()
> 
>         p.setFileName(PROJECTFILE)
> 
>         p.write()
> 
>         # Save content of map canvas as image
> 
>         p = str(last_id) + 'kaart_'
> 
>         qgis.utils.iface.mapCanvas().saveAsImage(PROJECTPATH+ p + SUFFIX + EXTSNAPSHOTS)
> 
>         last_id = last_id +1
> 
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