mapnik-org/mapnik — Issue #672: set_rectangle_alpha2() doesn't blend alpha correctly
Author: artemp
Created: 2011-10-11 08:07:32+00:00
State: closed
Labels: Symbolizers

If I render a RasterSymbolizer using opacity < 1.0, mapnik pre-multiplies the other channels by the alpha when blending it into the destination image.

This means if you have a RasterSymbolizer with a white image and 50% opacity, it will come out grey in the output.