[mapserver-users] GD rendering: polygons vs lines

[Gregor at HostGIS]

Hey guys. I have an interesting rendering issue here.

We are using the GD renderer for this project, since it's faster than 
AGG to the degree that we want to offer it as a speedy option. But the 
polygon outlines look bad in some cases, especially circles.

The center one in black, we render the polygon as a line layer instead. 
We were surprised to see that the curvature is MUCH smoother and those 
wedge-cut artifacts are gone.

https://www.cartograph.com/~gregor/1.gif

Any ideas as to why this is and how we can improve the edges to look 
like the line version? Is this something in GD or in how MapServer uses 
GD? Is there perhaps some defines we can change in the source?

An obvious approach is to make 2 layers: a polygon with no outlinecolor 
for the fill, and a line for the border. But this would be two layers 
instead of one, with the resulting slower rendering anyway.

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