Allow option for rendering 'thinner' lines with AGG output

[springmeyer]

Mapnik allows for users to specify fractional width for line symbolizers. These are interpreted by the agg renderer in such a way that the line looks thinner, whereby the color and intensity is lessened.

My opinion is that this 'thinner' output is a desirable feature, and users would benefit from either being able to supply fractional line widths or use an AGG renderer FORMATOPTION for different results.

This message captures the mapnik comparison issue and includes links to the images compared and the mapserver mapfile used.

​http://www.nabble.com/Re%3A-Fractional-line-widths--p19041876.html

[springmeyer]

Screen shot of image comparison, mapnik left, mapserver right

[springmeyer]

Same pitch I made to Qgis, for reference:

​https://trac.osgeo.org/qgis/ticket/969

[springmeyer]

Just realized that r7923 Ticket #2766 must begin to address this issue.

Can anyone comment on what more needs to be done with the agg renderer to use doubles to approximate thinner lines?

[sdlime]

Those tickets do address the issue. You can set fractional line widths and the AGG code uses those values. GD still rounds values to the nearest int but it works great for AGG. Download the dev code and try it!

Steve

[springmeyer]

Great stuff! I finally had a chance to rebuild with the latest SVN Head(r7971) and yes, the thinner line width look great.

Awesome improvement!

[springmeyer]

Mapserver example graphic with 0.1 line width using AGG renderer

[springmeyer]

Mapnik example graphic width 0.1 line width using AGG renderer

[springmeyer]

Here are two comparison graphics now that look nearly identical between mapserver and mapnik.

MapServer

Mapnik

Close Comparion (MapServer on top)

[springmeyer]

New comparison using fractional widths in mapserver