[Qgis-user] Always render as raster losing opacity control and simplify vector layers

[Michael Dufty]

I’ve had an interesting couple of days dealing with PDF sizes.  We have a very large vector layer of flood model output, being put into an A3 map covering a large area.
Initially this produced a 5MB ish PDF, but at some stage the PDF size jumped to 30MB.  It looks like the new “simplify geometries to reduce output size” option was not working.
We were able to get around this by forcing the layer to render as a raster in the layer properties.
A couple of days later we decided the layer should have 100% opacity instead of 80%.
The opacity displayed correctly in the main map and layout, but in the PDF exports it stayed stubbornly at 80%.
Turning off the force to render as raster allowed the opacity to display correctly again.  The file size stayed low too, so simplify geometries seems to work again.

At this stage we have solved the practical problem, but I’m still curious about the underlying issue.

Switching back to render as raster broke it again.
Re-adding the shapefile did not work.
Forcing another layer to render as raster resulted in both correct behaviour on the new layer, and fixing the problem on the old layer.
Turning off the forcing on the second layer, results in the first layer playing up again.

Initial issues were using 3.10.1 now on 3.12.

Anyone have a clue what might be going on?
Seems like there might be a cached version of the rasterization somewhere, but it recurs even if I change the colour.
I notice raster layers have opacity set in a different place to vector layers, so perhaps the opacity level for the generated raster layer has somehow been saved somewhere.

Michael Dufty

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