Cairo DISPLAY DRIVER

       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:

           •   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 platform 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 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.

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       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual