[mapserver-users] AGG renderer: Is there a way to disable the antialias feature with pattern brushes?

[Tamas Szekeres]

2009/10/19 Thomas Bonfort <thomas.bonfort at camptocamp.com>

> > Is there a way to disable antialias support with the agg renderer when
> > drawing vector symbol based pattern fills?
>
> Not that I know of.
>
> > I've just wanted to construct some of the pre-defined mapinfo fill
> patterns
> > (see image attached) but it seems the results are quite different by
> using
> > the agg and gd renderers (the latter is the desired result). Another
> issue
> > with this kind of antialiased drawing is that we may encounter glitches
> at
> > the tile borders (for example when drawing hatches this way.)
>
> yes, the antialiasing will almost always cause unwanted results if you
> want your symbols to fit together at tile borders.
> why not use the dedicated hatch symbol in this case ?
>
>
I'm not to satisfied with the hatch symbol in this case, since the pattern
definition should be 'self-contained', whereas for the hatch symbol we rely
on the style settings (ie angle, width) as well. This approach cannot be
used with the styleitem "auto" feature (MapInfo tab data source) since the
angle and the width of the style are not controlled by the OGR driver. So as
to use the hatch symbol, I would prefer setting the angle and width within
the symbol definition itself.



>
> that symbol seems invalid to me, it creates 4 lines with no length,
> and thus aren't rendered. GD assumed in this case that you wanted to
> render a single pixel, AGG will not make this assumption and skip the
> shape
>
>
That's good to know about this difference. How could I define a single pixel
within a vector symbol with the AGG renderer then?

With regards to the pattern definition, I would also live along with
specifying those patterns as pixmap symbols (with transparent background) as
well. Do you know about an option to override the pixel color with the color
of the style definition to avoid that the pattern can be rendered only a
single color?

Best regards,

Tamas
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