Join GitHub today
GitHub is home to over 28 million developers working together to host and review code, manage projects, and build software together.Sign up
Make inflated blurring image behavior optional #2165
#1478 added code to create an internal image that is inflated in order to help blur outside the visual tile and therefore create a more seamless look to blurred shapes across tiles.
This new approach works perfectly when the data being blurred extends outside tile extents. In Mapnik this requires that the query to fetch data is buffered. But this requirement is problematic in at least three cases:
So, overall #1478 improves the possibility of seamless blurring under the right conditions, but under the wrong conditions it actually makes artifacts more severe. For example previously artifacts were subtle:
But now, if the data is not buffered (in this case it is clipped per tile without buffers) the artifacts are more visible:
Therefore after reviewing these compromises I think the behavior added in #1478 should be a runtime option, and default off. So, you will need to opt-in to get this advanced support for seamless blurring and at that time you'll need to be more careful about buffering your data.