AGG

[Umberto Nicoletti]

Peter,
artifacts (in your case pixelation) are expected in jpg images due to
the compression algorithm:
http://en.wikipedia.org/wiki/Compression_artifact

Umberto

On 6/14/07, Peter Bruton <peter.bruton at nrcan.gc.ca> wrote:
> Hello;
>
> I have been experimenting with AGG in MapServer (CVS April 26/2007) using
> various OUTPUTFORMATs and found the results inconsistent.  To experiment
> with various OUTPUTFORMATs (DRIVERs and IMAGEMODEs), a series of mapfiles
> were created that have a single line layer where all features are drawn as
> black lines with a width of one pixel.
>
> DRIVER GD/GIF and IMAGEMODE PC256
> The lines were rendered as expected.  I performed this test as a baseline.
> http://dev.atlas.gc.ca/cgi-bin/mapserv_dev?map=/home/atlas/mapdata/english/pb_gd_gif_pc256.map&mode=map
>
> DRIVER AGG/PC256 and IMAGEMODE RGBA
> While anti-aliasing was present the pattern of the line was not consistent.
>  Sometimes a solid line and other times there were gaps in the line.
> http://dev.atlas.gc.ca/cgi-bin/mapserv_dev?map=/home/atlas/mapdata/english/pb_agg_pc_rgba.map&mode=map
>
> DRIVER AGG/PNG and IMAGEMODE RGBA
> While anti-aliasing was present, the lines were gray and not black.  In
> addition the pattern of the line was not consistent.  Sometimes a solid line
> and other times there were gaps in the line.
> http://dev.atlas.gc.ca/cgi-bin/mapserv_dev?map=/home/atlas/mapdata/english/pb_agg_png_rgba.map&mode=map
>
> DRIVER AGG/PNG24 and IMAGEMODE RGBA
> While anti-aliasing was present, the lines were gray and not black.  In
> addition the pattern of the line was not consistent.  Sometimes a solid line
> and other times there were gaps in the line.
> http://dev.atlas.gc.ca/cgi-bin/mapserv_dev?map=/home/atlas/mapdata/english/pb_agg_png24_rgba.map&mode=map
>
> DRIVER AGG/JPG and IMAGEMODE RGBA
> While this produced the best rendering of the line, the background was
> pixelated around the line.
> http://dev.atlas.gc.ca/cgi-bin/mapserv_dev?map=/home/atlas/mapdata/english/pb_agg_jpg_rgba.map&mode=map
>
> DRIVER AGG/GIF and IMAGEMODE RGBA
> While anti-aliasing was present the pattern of the line was not consistent.
>  Sometimes a solid line and other times there were gaps in the line.
> http://dev.atlas.gc.ca/cgi-bin/mapserv_dev?map=/home/atlas/mapdata/english/pb_agg_gif_rgba.map&mode=map
>
> It is not clear to me why gray and/or lines with inconsistent patterns were
> returned.   Are the DRIVER/IMAGEMODE conbinations I am using not compatible
> with one another?  Or am I missing something else.
>
> The symbol definition I am using for the lines in the mapfiles is:
>
> SYMBOL
>    TYPE ELLIPSE
>    NAME solidline
>    POINTS
>      1 1
>    END
>    FILLED true
> END
>
> Any insight to the problems I am having is appreciated.
>
> Peter Bruton
>