[QGIS-Developer] Setting a custom CRS for the map canvas

[Matthias Kuhn]

Hi Tim,

Does it help if you directly call `mapCanvas.setDestinationCrs()` instead
of setting the crs on `mapSettings()`?

The returned mapSettings object is not meant to be modified.

Matthias


On Tue, Nov 17, 2020 at 12:58 AM Tim Sutton <tim at kartoza.com> wrote:

> Hi Folks
>
> I am trying to update a 2.x snippet I have which iteratively sets the CRS
> with sequentially higher LO values:
>
> https://gist.github.com/timlinux/1057c2c6b5ebda6ed2b5aa8c5aa21372
>
> # Uses a trick from Alexander Neto: "I created a orthographic projection
> with lisbon longitude, but with a south hemisphere latitude
> # That way kinda looks 3d"
> # This will make the QGIS use a world projection and then move the center
> # of the CRS sequentially to create a spinning globe effect
> import time
> from subprocess import call
> longitude_increments = 5
> image_counter = 1
> for i in range(-180, 180, longitude_increments):
>   definition = (
>   '+proj=ortho +lat_0=-20 +lon_0=%i +x_0=0 +y_0=0 +R=6371000 +units=m
> +no_defs +type=crs' % i)
>   crs = QgsCoordinateReferenceSystem()
>   crs.createFromProj(definition)
>   iface.mapCanvas().mapSettings().setDestinationCrs(crs)
>   #iface.mapCanvas().setMapUnits(0)
>   iface.mapCanvas().refresh()
>   iface.mapCanvas().saveAsImage(
>     '/tmp/globe-%03d.png' % image_counter)
>   image_counter += 1
>   print (definition)
>   time.sleep(1)
> # Now generate the GIF. If this fails try run the call from the command
> line
> # and check the path to convert (provided by ImageMagick) is correct...
> call('/usr/bin/convert -delay 35 -loop 0 /tmp/globe-*.png /tmp/globe.gif')
>
> The  example python above using Orthographc North will hopefully make a
> more pleasing looking spinny globe. However, in QGIS 3.x the code runs
> but if I inspect the mapcanvas CRS after setting the new CRS, it still
> shows the old CRS. Can anyone see what I am missing here?
>
> Thanks!
>
> Regards
>
> Tim
>
> --
>
> ------------------------------------------------------------------------------------------
>
> Tim Sutton
> Visit http://kartoza.com to find out about open source:
>  * Desktop GIS programming services
>  * Geospatial web development
> * GIS Training
> * Consulting Services
> Tim is a member of the QGIS Project Steering Committee
>
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