cairodriver(1grass) GRASS GIS User's Manual cairodriver(1grass)
Cairo DISPLAY DRIVER
Cairo display driver for bitmap or vector output using the Cairo graph-
ics 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, oth-
erwise PNG driver is used.
USAGE
Environment variables
The Cairo driver can be enabled by setting GRASS_RENDER_IMMEDIATE vari-
able, eg.
export GRASS_RENDER_IMMEDIATE=cairo
Several environment variables affect the operation of the Cairo driver:
• GRASS_RENDER_WIDTH=xxx
the width of the image map (default is 640).
• GRASS_RENDER_HEIGHT=yyy
the height of the image map (default is 480).
• GRASS_RENDER_BACKGROUNDCOLOR=RRGGBB
specifies the background color to use in RGB notation (hex or
R:G:B values). Named colors are also supported. Default is
FFFFFF (white).
• GRASS_RENDER_TRANSPARENT=[TRUE|FALSE]
sets transparent background on (TRUE) or off (FALSE, default).
• GRASS_RENDER_ANTIALIAS
can be default, none, gray, or subpixel, corresponding to
cairo_antialias_t
• GRASS_RENDER_FILE=filename
the name and format of the resulting image file, default is
map.png.
The image format is determined from the file extension.
Supported bitmap formats:
• .png - Portable Network Graphics (PNG)
• .bmp - Windows Bitmap (BMP, 32-bpp) (these are not readable
by some older viewers)
• .ppm - Portable Pixmap (PPM + PGM for alpha channel)
Supported vector formats:
• .pdf - Portable Document Format (PDF)
• .ps - PostScript (PS)
• .svg - Scalable Vector Graphics (SVG)
(Note: Some formats may not be available, depending on your plat-
form and the Cairo library that GRASS was built with.)
• GRASS_RENDER_FILE_READ
if TRUE, the Cairo driver will initialize the image from the
contents of GRASS_RENDER_FILE.
(Note: This is only supported for bitmap formats)
• GRASS_RENDER_FILE_MAPPED
if TRUE, the Cairo driver will map GRASS_RENDER_FILE as its
framebuffer, rather than using memory.
(Note: This only works with BMP files.)
• GRASS_RENDER_CAIRO_SCREEN
defines Cairo screen
• GRASS_RENDER_CAIRO_VISUAL
defines Cairo visual
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 cur-
rently no way of disabling this.
The resolution of the output images is defined by current region ex-
tents. 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.
Main index | Topics index | Keywords index | Graphical index | Full in-
dex
© 2003-2022 GRASS Development Team, GRASS GIS 7.8.7 Reference Manual
GRASS 7.8.7 cairodriver(1grass)
Generated by dwww version 1.14 on Sun Dec 29 18:44:18 CET 2024.