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[](http://travis-ci.org/diagrams/diagrams-cairo)
_diagrams-cairo_ is a rendering backend for [diagrams], a powerful,
flexible, declarative domain-specific language for creating vector graphics,
using the [Haskell programming language][haskell].
[diagrams]: http://projects.haskell.org/diagrams/
[haskell]: http://www.haskell.org/haskellwiki/Haskell
_diagrams-cairo_ is implemented using the [cairo] rendering engine and
is a fully-featured, officially supported backend for diagrams.
[cairo]: http://www.cairographics.org/
# Installation
```
cabal update && cabal install gtk2hs-buildtools diagrams-cairo
```
# Basic usage
A simple example that uses _diagrams-cairo_ to draw a blue circle:
```haskell
{-# 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.
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