Add automatic simplification to mask clipping paths when exporting layouts #57703
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Add QgsAbstractGeometry::simplifyByDistance, which is a direct port of GEOS Douglas Peucker algorithm. This is a trivial algorithm to implement, and we benefit from avoiding the conversion to/from GEOS geometries.
And API mechanism to propagate these from layout exports down to the render context Gives us a place to specify fine-tuned control over masking settings for map renders
This results in much smaller output file sizes, and files which load much quicker in PDF viewers/editors Refs qgis#50734 Refs qgis#54788
multigeometries to separate geometries in the vector This gives us more scope to optimise which geometries we want to use when rendering objects within a particular part of the map
Move the geometry repair to when we add it to the render context, instead of every time we retrieve it
By simplifying line strings PRIOR to buffering, we get a significant performance bump, as we're not asking GEOS to buffer excessively detailed linestrings and then immediately discarding most of the vertices.
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@troopa81 can I get a review of this? |
Yes, I'll review it |
| std::unique_ptr< QgsAbstractGeometry > buffered; | ||
| if ( mSimplifyTolerance > 0 ) | ||
| { | ||
| // For performance, we apply a lower level of simplification to the line BEFORE doing the buffer. |
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I'm afraid that it doesn't improve this issue
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Can you retest please? There's no way the gridded/pixelated mask output could be exported by this branch.
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Way better
painterpath way
geometry way
Can we make it a little less agressive by default to have a prettier renderering
Yes, there's a couple of reasons why it needs to be different:
The native simplification method is extremely fast. We want to simplify prior to the union or the GEOS union is very slow. But the output of the union can add additional vertices (when masks overlap and GEOS fully nodes them), which we can also strip away (with the cheap simplify call) and ensure smallest possible output file size. |
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Thanks for the review @troopa81 ! It's much appreciated! |
When the (currently non-default) geometry backend is used for selective masking (see #57623), we now apply a conservative amount of simplification to the clipping paths when exporting layouts to pdf /svg.
This results in much smaller file sizes, and PDFs /SVGs which are much faster to load in viewers/editors.
Refs #50734
Refs #54788
(I think we could safely make the simplification factor more aggressive, but I've opted for an initially conservative amount while we discuss the rest of these changes)