Merge pull request #52 from stanim/doc

improve README.md

README.md

@@ -1,12 +1,14 @@
 draw2d
 ======
 
-Package draw2d is a pure [go](http://golang.org) 2D vector graphics library with support for multiple output devices such as [images](http://golang.org/pkg/image) (draw2d), pdf documents (draw2dpdf) and opengl (draw2dopengl), which can also be used on the google app engine.
-This library is inspired by [postscript](http://www.tailrecursive.org/postscript) and [HTML5 canvas](http://www.w3.org/TR/2dcontext/).
+Package draw2d is a pure [go](http://golang.org) 2D vector graphics library with support for multiple output devices such as [images](http://golang.org/pkg/image) (draw2d), pdf documents (draw2dpdf) and opengl (draw2dopengl), which can also be used on the google app engine. It can be used as a pure go [Cairo](http://www.cairographics.org/) alternative.
 
 See the [documentation](http://godoc.org/github.com/llgcode/draw2d) for more details.
 
-The package depends on [freetype-go](http://code.google.com/p/freetype-go) package for its rasterization algorithm.
+Features
+--------
+
+Operations in draw2d include stroking and filling polygons, arcs, Bézier curves, drawing images and text rendering with truetype fonts. All drawing operations can be transformed by affine transformations (scale, rotation, translation).
 
 Installation
 ------------
@@ -17,14 +19,75 @@ Install [golang](http://golang.org/doc/install). To install or update the packag
 go get -u github.com/llgcode/draw2d
 ```
 
-and start coding using one of the [Samples](https://github.com/llgcode/draw2d.samples).
+Quick Start
+-----------
+
+The following Go code generates a simple drawing and saves it to an image file with package draw2d:
+
+```go
+// Initialize the graphic context on an RGBA image
+dest := image.NewRGBA(image.Rect(0, 0, 297, 210.0))
+gc := draw2d.NewGraphicContext(dest)
+
+// Set some properties
+gc.SetFillColor(color.RGBA{0x44, 0xff, 0x44, 0xff})
+gc.SetStrokeColor(color.RGBA{0x44, 0x44, 0x44, 0xff})
+gc.SetLineWidth(5)
+
+// Draw a closed shape
+gc.MoveTo(10, 10) // should always be called first for a new path
+gc.LineTo(100, 50)
+gc.QuadCurveTo(100, 10, 10, 10)
+gc.Close()
+gc.FillStroke()
+
+// Save to file
+draw2d.SaveToPngFile(fn, dest)
+```
+
+The same Go code can also generate a pdf document with package draw2dpdf:
+
+```go
+// Initialize the graphic context on an RGBA image
+dest := draw2dpdf.NewPdf("L", "mm", "A4")
+gc := draw2d.NewGraphicContext(dest)
+
+// Set some properties
+gc.SetFillColor(color.RGBA{0x44, 0xff, 0x44, 0xff})
+gc.SetStrokeColor(color.RGBA{0x44, 0x44, 0x44, 0xff})
+gc.SetLineWidth(5)
+
+// Draw a closed shape
+gc.MoveTo(10, 10) // should always be called first for a new path
+gc.LineTo(100, 50)
+gc.QuadCurveTo(100, 10, 10, 10)
+gc.Close()
+gc.FillStroke()
+
+// Save to file
+draw2dpdf.SaveToPdfFile(fn, dest)
+```
+
+There are more examples here: https://github.com/llgcode/draw2d.samples
+
+Drawing on opengl is provided by the draw2dgl package.
+
+Acknowledgments
+---------------
+
+[Laurent Le Goff](https://github.com/llgcode) wrote this library, inspired by [Postscript](http://www.tailrecursive.org/postscript) and [HTML5 canvas](http://www.w3.org/TR/2dcontext/). He implemented the image and opengl backend with the [freetype-go](https://code.google.com/p/freetype-go/) package. Also he created a pure go [Postscript interpreter](https://github.com/llgcode/ps), which can read postscript images and draw to a draw2d graphic context. [Stani Michiels](https://github.com/stanim) implemented the pdf backend with the [gofpdf](https://github.com/jung-kurt/gofpdf) package.
 
 
-Softwares and Packages using draw2d
------------------------------------
 
- - [golang postscript interpreter](https://github.com/llgcode/ps)
- - [gonum plot](https://github.com/gonum/plot)
+Packages using draw2d
+---------------------
+
+ - [ps](https://github.com/llgcode/ps): Postscript interpreter written in Go
+ - [gonum/plot](https://github.com/gonum/plot): drawing plots in Go
+ - [go.uik](https://github.com/skelterjohn/go.uik): a concurrent UI kit written in pure go.
+ - [smartcrop](https://github.com/muesli/smartcrop): content aware image cropping
+ - [karta](https://github.com/peterhellberg/karta): drawing Voronoi diagrams
+ - [chart](https://github.com/vdobler/chart): basic charts in Go
 
 References
 ---------

draw2d.go

@@ -4,7 +4,7 @@
 // Package draw2d is a pure go 2D vector graphics library with support
 // for multiple output devices such as images (draw2d), pdf documents
 // (draw2dpdf) and opengl (draw2dopengl), which can also be used on the
-// google app engine.
+// google app engine. It can be used as a pure go Cairo alternative.
 //
 // Features
 //
@@ -51,18 +51,25 @@
 //
 // Acknowledgments
 //
-// Laurent Le Goff wrote this library, inspired by postscript and
-// HTML5 canvas. He implemented the image and opengl backend. Also
-// he created a pure go Postscripter interpreter which can draw to a
-// draw2d graphic context (https://github.com/llgcode/ps). Stani
-// Michiels implemented the pdf backend.
+// Laurent Le Goff wrote this library, inspired by Postscript and
+// HTML5 canvas. He implemented the image and opengl backend with the
+// freetype-go package. Also he created a pure go Postscript
+// interpreter, which can read postscript images and draw to a draw2d
+// graphic context (https://github.com/llgcode/ps). Stani Michiels
+// implemented the pdf backend with the gofpdf package.
 //
 // The package depends on freetype-go package for its rasterization
 // algorithm.
 //
 // Packages using draw2d
 //
-// - https://github.com/llgcode/ps
+// - https://github.com/llgcode/ps: Postscript interpreter written in Go
 //
-// - https://github.com/gonum/plot
+// - https://github.com/gonum/plot: drawing plots in Go
+//
+// - https://github.com/muesli/smartcrop: content aware image cropping
+//
+// - https://github.com/peterhellberg/karta: drawing Voronoi diagrams
+//
+// - https://github.com/vdobler/chart: basic charts in Go
 package draw2d