[Qgis-user] Serial map from template composer. Working with QGIS 2.2, problems with QGIS 2.4

Wed Oct 1 03:43:10 PDT 2014

Hi Andrea,

Are you aware that QGIS already supports serial printing out of the box 
without scripting? I would first test if that works fine for you before 
bothering with scripts. QGIS 2.2 had serial printing in core, 2.4 has it 
improved and 2.6 has a lot more improvements. I am pretty sure that many 
(most?) cases can now be handled out of the box.

Andreas

On 01.10.2014 10:54, Andrea Amparore wrote:
> Dear QGIS users community,
>
> I'm a new member and I am stuck on a problem since few days, maybe 
> someone can help me with this.
>
> I have developed a stand-alone python script for making serial maps 
> using PyQGIS library.
>
> The maps should follow a specific format that is indicated by a 
> template .qpt file.
>
> This template file is opened and edited with lxml library in order to 
> add information about the map (title, date, source, etc).
>
> The modified .qpt is then loaded into a new composition, the layers 
> are added and the map exported.
>
> Everything was working perfectly since I’ve been using QGIS 2.2. Few 
> days ago I have updated QGIS to the latest version 2.4 and now the 
> output is sadly empty: map elements are displayed (frame, legend, 
> title..), but no layer appears on the map.
>
> The script is correct, because it still run correctly on another 
> machine having QGIS 2.2. Is there anything that I have to modify for 
> running it with QGIS 2.4?
>
> This is a very basic version of the script.
>
> import os
> from qgis.core import *
> from qgis.gui import *
> from PyQt4.QtCore import *
> from PyQt4.QtGui import *
> from PyQt4.QtXml import *
> import lxml.etree as etree
>
> print "setting prefix"
> QgsApplication.setPrefixPath("/usr", True)
> print "initiating qgis"
> QgsApplication.initQgis()
> print 'creating new app'
> app = QgsApplication([], True)
> #removing old layers
> QgsMapLayerRegistry.instance().removeAllMapLayers()
>
> script_folder = os.path.dirname(__file__)
> project_folder = os.path.dirname(script_folder)
> output_folder = os.path.join(project_folder, 'map_outputs')
> xml_folder = os.path.join(project_folder, 'project_outputs')
> shapefile_folder = os.path.join(project_folder, 'shapefile_folder')
>
> template_composer = os.path.join(project_folder, 
> 'basic_composer_template_QGIS24.qpt')
> polyg_shapefile = os.path.join(shapefile_folder, 'polygon.shp') # crs 
> EPSG:4326 - WGS 84
> point_shapefile = os.path.join(shapefile_folder, 'point.shp') # crs 
> EPSG:32615 - WGS 84 / UTM zone 15N
>
> mapname = "Test Map"
> srid = 4326
> provider_name = 'ogr'
> layerset = []
>
> #add layer 1
> vlayer_name= 'polygon layer'
> vdata_source = polyg_shapefile
> print "Loading EQ buffers"
> layer = QgsVectorLayer(vdata_source, vlayer_name, provider_name)
> print "Buffers loaded"
> QgsMapLayerRegistry.instance().addMapLayer(layer)
> layerset.append(layer.id <http://layer.id>())
>
> #add layer 2
> point_layer_name= 'point layer'
> point_data_source = point_shapefile
> point_layer = QgsVectorLayer(point_data_source, point_layer_name, 
> provider_name)
> QgsMapLayerRegistry.instance().addMapLayer(point_layer)
> layerset.append(point_layer.id <http://point_layer.id>())
>
> # Set up the map renderer that will be assigned to the composition
> map_renderer = QgsMapRenderer()
> #preparing the map the extent - 3 times wider than the polygon layer's 
> extent
> rect = layer.extent()
> rect.scale(3)
> # Set the labelling engine for the canvas
> labelling_engine = QgsPalLabeling()
> map_renderer.setLabelingEngine(labelling_engine)
> # Enable on the fly CRS transformations
> map_renderer.setProjectionsEnabled(True)
> # Now set up the composition
> composition = QgsComposition(map_renderer)
> #set WGS84 as destination crs
> map_projection = QgsCoordinateReferenceSystem(srid, 
> QgsCoordinateReferenceSystem.PostgisCrsId)
> map_projection_descr = map_projection.description()
> map_renderer.setDestinationCrs(map_projection)
>
> #open the composer template and edit it
> with open(template_composer, 'r') as f:
>     tree  = etree.parse(f)
>     #setting extent
>     for elem in tree.iter(tag = 'Extent'):
>         elem.attrib['xmax'] = str(rect.xMaximum())
>         elem.attrib['xmin'] = str(rect.xMinimum())
>         elem.attrib['ymax'] = str(rect.yMaximum())
>         elem.attrib['ymin'] = str(rect.yMinimum())
>     #editing the title
>     for elem in tree.iter(tag = 'ComposerLabel'):
>             for child in elem:
>                 if child.tag == 'ComposerItem':
>                     if child.attrib['id'] == "__maintitle__":
>                         elem.attrib['labelText'] = mapname
>     #save the edited composer as a new file
>     new_composer = os.path.join(xml_folder, mapname + "_composer.qpt")
>     tree.write(new_composer)
>
> #open the newly created composer
> new_composerfile = file(new_composer, 'rt')
> new_composer_content = new_composerfile.read()
> new_composerfile.close()
> document = QDomDocument()
> document.setContent(new_composer_content)
> result = composition.loadFromTemplate(document)
>
> # Get the main map canvas on the composition and set the layers
> composerMap = composition.getComposerMapById(0)
> composerMap.renderModeUpdateCachedImage()
> map_renderer.setLayerSet(layerset)
>
> #legend
> legend = QgsComposerLegend(composition)
> legend.model().setLayerSet(map_renderer.layerSet())
> legend.model().setLayerSet
> composition.addItem(legend)
> legend.setItemPosition (25,122)
> legend.setFrameEnabled(True)
> legend.setScale(.7)
>
> #save image
> print 'saving image'
> image = composition.printPageAsRaster(0)
> image.save(os.path.join(output_folder,mapname) + ".png")
>
> In this link you can find the 2 shapefiles and the composer template 
> that you need for running the script, and the example of failed 
> export: http://we.tl/8y3SrCxlGM
>
> Thanks in advance.
>
> Regards,
>
> Andrea
>
>
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