diagrams-cairo is a rendering backend for diagrams, a powerful, flexible, declarative domain-specific language for creating vector graphics, using the Haskell programming language.
diagrams-cairo is implemented using the cairo rendering engine and is a fully-featured, officially supported backend for diagrams.
cabal update && cabal install gtk2hs-buildtools diagrams-cairo
A simple example that uses diagrams-cairo to draw a blue circle:
{-# LANGUAGE NoMonomorphismRestriction #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE TypeFamilies #-}
import Diagrams.Prelude
import Diagrams.Backend.Cairo.CmdLine
d :: Diagram B
d = circle 1 # fc blue
main = mainWith (pad 1.1 d)Save this to file named Circle.hs and compile it:
ghc --make Circle.hs
This will generate an executable which, when run, outputs a blue
circle to some file. Run the executable with the --help option to
find out more about how to call it.
$ ./Circle --help
./Circle
Usage: ./Circle [-w|--width WIDTH] [-h|--height HEIGHT] [-o|--output OUTPUT]
[--loop] [-s|--src ARG] [-i|--interval INTERVAL]
Command-line diagram generation.
Available options:
-?,--help Show this help text
-w,--width WIDTH Desired WIDTH of the output image
-h,--height HEIGHT Desired HEIGHT of the output image
-o,--output OUTPUT OUTPUT file
-l,--loop Run in a self-recompiling loop
-s,--src ARG Source file to watch
-i,--interval INTERVAL When running in a loop, check for changes every INTERVAL seconds.
ommand-line diagram generation.
The output type will be automatically determined from the file extension. Currently PNG, PDF, PS, and SVG are supported.
$ ./Circle -o circle.png -w 400
The command above generates a PNG file with a width of 400px.
Instead of just creating a standalone executable, the cairo backend can also be called from within a larger program. For more information, see the Diagram.Backend.Cairo module.