artemp/mapnik — Issue #840: faster text placement and rendering
Author: artemp
Created: 2011-10-11 16:38:33+00:00
State: open
Labels: Core_Library

Text rendering is showing up as overwhelmingly expensive (> 50 % of rendering time) in some tests with osm data using oprofile/shark (~ 32 % rendering, ~17 % placement of total rendering time)

We need to look at any possible optimizations.

It appears that halos are particularly expensive (when removed text rendering takes only 4.5% of total time and then placement is larger).

Also, in particularly (for the foss4g tests) is is clear we need faster ways for sparse labeling.

Ideas for fast sparse labeling are:

* minimum feature length/size to place that can be checked even before collision detector
* `margin` property for text (distance from nearest label bbox to label's buffer) to drop labels early on before more expensive dimension checks
* bug check: does `min_distance` really work across features?