[Qgis-user] Clipping WMS Layer for Export to Geo PDF

[Charles Dixon-Paver]

The latest releases of QGIS support "clipping settings" for map frames in
layouts [1]. This means that you can "clip" the map frame to a specific
shape within the layout, or an atlas item. You cannot clip the map to a
specific feature, however, but I expect you could get around this by
creating an atlas from a layer with only one feature. I'm not very familiar
with Avenza so I'm unsure how well this would suit your needs.

One other thing to note is that your "area of interest" polygon does not
necessarily need to be differenced with a bounding area separately, as you
may simply use the "Inverted Polygons" style to mask off your relevant area
of interest.

Regards

[1]
https://qgis.org/en/site/forusers/visualchangelog316/index.html#clip-layout-maps-to-shape


On Sat, 31 Jul 2021 at 12:02, kirk <kirk at nortekresources.com> wrote:

> Hi Stewart
> I assume you are using a rater as a background layer and therefore you
> will always end up with a rectangle as your final extent.  If you clip to
> an irregular polygon, you will still have a rectangle but the outer area
> that had been clipped out will be transparent.  This is how raters work as
> they are regular grids.  The disadvantage of clipping to an irregular
> polygon is that you will create an additional alpha channel which defines
> the transparency but adds to the file size.
>
> I would consider making a number of smaller maps with some overlap to use
> with avenza.
>
> Kirk Schmidt
>
>
>
> Sent from my Galaxy
>
>
> -------- Original message --------
> From: Stewart Holt <stewartbholt at gmail.com>
> Date: 2021-07-30 4:38 p.m. (GMT-04:00)
> To: User List QGIS <qgis-user at lists.osgeo.org>
> Subject: [Qgis-user] Clipping WMS Layer for Export to Geo PDF
>
> I am working on a GeoPDF map to use in the Avenza map app. It is an 80
> mile hiking trail which stair steps from SW to NE. I am using a WMTS layer
> as a background. I want to avoid having the PDF as large as a rectangle
> containing this trail. I created a polygon and used it to select the extent
> for the map, but it did not clip the map but instead it created a
> rectangular extent containing the polygon.
>
> Next I created a larger rectangular polygon covering the area and cut out
> a ring for the trail and included this layer in the map. The result was the
> inclusion of all of the WMTS  map layer as before with my mask layer able
> to block unwanted areas. This does not reduce file size, ofcourse.
>
> I think what that did is the correct behavior. What I need is a way to
> clip the WMTS layer on the fly. I think having the export to PDF being able
> to do this would be the best approach.
>
> Can anyone think of how to accomplish this without exporting the WMTS
> layer and then clipping it with a polygon?
>
> Thanks,
>
> Stewart
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