artemp/mapnik — Issue #512: Need to enforce AA/default gamma function post #428/r1557
Author: artemp
Created: 2011-10-11 16:23:08+00:00
State: open
Labels: Agg_Renderer

When gamma is set on the ras_ptr, subsequent calls to reset() do not affect/reset gamma (as I assumed), and a non-default value will propagate to other features rendered on the raster surface after the gamma is modified to a value other than the default of 1.

Thanks to Oliver for reporting:

http://oliverobrien.co.uk/2010/02/prettier-maps-with-mapnik-0-7-0/

The effect is simply that symbolizers that do not allow gamma to be controlled may loose AA'ing when rendered after a polygon that was intended to have less AA by reducing gamma.

We need to enforce the default of gamma == 1 by setting agg::gamma_linear() for all symbolizers.