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.

Installation

cabal update && cabal install gtk2hs-buildtools diagrams-cairo

Basic usage

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.

Advanced usage

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.