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