The Cairo driver generates PNG, BMP, PPM, PS, PDF or SVG images from GRASS display commands, using the Cairo graphics library. The image format is selected from the extension of the output file.
It is started as 'pseudo' monitor (output to an image file) and when stopped, all output from previously used display commands are written to the output file.
Example using the driver directly (bash-syntax):
export GRASS_CAIROFILE=spearfish.png export GRASS_WIDTH=800 export GRASS_HEIGHT=800 d.mon start=cairo d.rast map=elevation.10m d.vect map=streams width=1 color=blue fcolor=aqua type=area,line d.vect map=roads width=2 d.mon stop=cairo
Example using d.out.file:
d.mon x0 d.rast map=elevation.10m d.vect map=streams width=1 color=blue fcolor=aqua type=area,line d.vect map=roads width=2 d.out.file -c sf_cairo format=png size=800,800
A more complicated example using d.out.file:
r.shaded.relief map=elevation.dem r.watershed elev=elevation.dem basin=watershed.basin thresh=10000 d.mon x1 d.shadedmap rel=elevation.dem.shade drape=watershed.basin bright=30 d.vect streams color=aqua fcolor=aqua type=area,line d.vect roads where="label ~ 'light-duty road'" color=grey d.vect roads where="label ~ 'unimproved'" color=orange d.vect roads where="label ~ 'secondary highway'" color=100:100:100 width=2 d.vect roads where="label ~ 'primary highway'" color=50:50:50 width=2 d.vect railroads col=red width=2 d.vect roads where="label = 'interstate'" color=black width=3 d.vect archsites icon=basic/star size=25 fcolor=yellow d.font Andale_Mono echo "Spearfish, SD" | d.text color=black at=28,53 -b d.out.file -c sf_cairo2 format=png
The driver is still in development. Currently the way to enable Cairo driver support is to build grass with
make USE_CAIRO=1
Antialiasing is enabled by default for bitmap formats. There is currently no way of disabling this.
Cairo supports true vector format output whenever possible. However, if the selected format doesn't support a necessary feature, Cairo may fall back on rendering a bitmap representation of the image wrapped in the selected vector format.
Cairo driver output via d.out.file is supported via the -c flag.