GRASS logo

Cairo DISPLAY DRIVER

Table of contents

Cairo display driver for bitmap or vector output using the Cairo graphics library.

DESCRIPTION

The Cairo driver generates PNG, BMP, PPM, PS, PDF or SVG images by GRASS display commands, using the Cairo graphics library. The image format is selected from the extension of the output file. The Cairo driver is used for GRASS display commands by default if available, otherwise PNG driver is used.

USAGE

Environment variables

The Cairo driver can be enabled by setting GRASS_RENDER_IMMEDIATE variable, eg.
export GRASS_RENDER_IMMEDIATE=cairo
Several environment variables affect the operation of the Cairo driver:

EXAMPLES

PNG Example

Example: using the driver to generate a PNG file (bash-syntax):
export GRASS_RENDER_IMMEDIATE=cairo
export GRASS_RENDER_FILE=nc_spm.png
export GRASS_RENDER_WIDTH=800
export GRASS_RENDER_HEIGHT=800
export GRASS_RENDER_FILE_READ=TRUE

g.region raster=elevation
d.rast map=elevation
d.vect map=streams width=1 color=blue fcolor=aqua type=area,line
d.vect map=roadsmajor width=2

PDF Examples

Example: using the driver to generate a PDF vector file with a vector map (bash-syntax):
export GRASS_RENDER_IMMEDIATE=cairo
export GRASS_RENDER_FILE=nc_spm.pdf
export GRASS_RENDER_WIDTH=800
export GRASS_RENDER_HEIGHT=800

g.region vector=roadsmajor
# activate vector font
d.font Vera
d.vect map=roadsmajor layer=1 display=shape attrcolumn=ROAD_NAME lcolor=0:90:255

Example: using the driver to generate a PDF raster file with a raster map (bash-syntax):

export GRASS_RENDER_IMMEDIATE=cairo
export GRASS_RENDER_FILE=nc_spm.pdf
export GRASS_RENDER_WIDTH=800
export GRASS_RENDER_HEIGHT=800

g.region raster=elevation
d.rast map=elevation

SVG Example

Example: using the driver to generate a SVG vector file with a vector map (bash-syntax):
export GRASS_RENDER_IMMEDIATE=cairo
export GRASS_RENDER_FILE=vectormap.svg

g.region vector=roadsmajor
d.vect map=roadsmajor -c

NOTES

The driver is still in development. Enable it by specifying --with-cairo when configuring GRASS. This requires a reasonably recent version of the Cairo libraries and a working pkg-config.

Antialiasing is enabled by default for bitmap formats. There is currently no way of disabling this.

The resolution of the output images is defined by current region extents. Use g.region -p to get the number of rows and cols and use the environment variables to set the image size. If you would like a larger image, multiply both rows and cols by the same whole number to preserve the aspect ratio.

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.

SEE ALSO

PNG driver, PS driver, HTML driver, variables

d.rast, d.vect, d.mon, d.erase, d.redraw

AUTHOR

Lars Ahlzen <lars (at) ahlzen.com>
and the GRASS Development Team.

Last changed: $Date: 2015-05-18 02:16:49 -0700 (Mon, 18 May 2015) $


Main index | Topics index | Keywords index | Graphical index | Full index

© 2003-2017 GRASS Development Team, GRASS GIS 7.2.3svn Reference Manual