SVGo: A Go library for SVG generation

The library generates SVG as defined by the Scalable Vector Graphics 1.1 Specification (http://www.w3.org/TR/SVG11/). Output goes to the specified io.Writer.

Supported SVG elements and functions

Shapes, lines, text

circle, ellipse, polygon, polyline, rect (including roundrects), line, text

Paths

general, arc, cubic and quadratic bezier paths,

Image and Gradients

image, linearGradient, radialGradient,

Transforms

translate, rotate, scale, skewX, skewY

Animation

animate, animateMotion, animateTranslate, animateRotate, animateScale, animateSkewX, animateSkewY

Filter Effects

filter, feBlend, feColorMatrix, feColorMatrix, feComponentTransfer, feComposite, feConvolveMatrix, feDiffuseLighting, feDisplacementMap, feDistantLight, feFlood, feGaussianBlur, feImage, feMerge, feMorphology, feOffset, fePointLight, feSpecularLighting, feSpotLight,feTile, feTurbulence

Metadata elements

desc, defs, g (style, transform, id), marker, mask, pattern, title, (a)ddress, link, script, use

Building and Usage

See svgdef.[svg|png|pdf] for a graphical view of the function calls

Usage: (assuming GOPATH is set)

go get github.com/ajstarks/svgo
go install github.com/ajstarks/svgo/...

You can use godoc to browse the documentation from the command line:

$ go doc github.com/ajstarks/svgo

a minimal program, to generate SVG to standard output.

package main

import (
	"github.com/ajstarks/svgo"
	"os"
)

func main() {
	width := 500
	height := 500
	canvas := svg.New(os.Stdout)
	canvas.Start(width, height)
	canvas.Circle(width/2, height/2, 100)
	canvas.Text(width/2, height/2, "Hello, SVG", "text-anchor:middle;font-size:30px;fill:white")
	canvas.End()
}

Drawing in a web server: (http://localhost:2003/circle)

package main

import (
	"log"
	"github.com/ajstarks/svgo"
	"net/http"
)

func main() {
	http.Handle("/circle", http.HandlerFunc(circle))
	err := http.ListenAndServe(":2003", nil)
	if err != nil {
		log.Fatal("ListenAndServe:", err)
	}
}

func circle(w http.ResponseWriter, req *http.Request) {
  w.Header().Set("Content-Type", "image/svg+xml")
  s := svg.New(w)
  s.Start(500, 500)
  s.Circle(250, 250, 125, "fill:none;stroke:black")
  s.End()
}

You may view the SVG output with a browser that supports SVG (tested on Chrome, Opera, Firefox and Safari), or any other SVG user-agent such as Batik Squiggle.

Graphics Sketching with SVGo and svgplay

Combined with the svgplay command, SVGo can be used to "sketch" with code in a browser.

To use svgplay and SVGo, first go to a directory with your code, and run:

$ svgplay
2014/06/25 22:05:28 ☠ ☠ ☠ Warning: this server allows a client connecting to 127.0.0.1:1999 to execute code on this computer ☠ ☠ ☠

Next open your browser to the svgplay server you just started. svgplay only listens on localhost, and uses port 1999 (guess which year SVG was first introduced) by default

http://localhost:1999/

Enter your code in the textarea, and when you are ready to run press Shift--Enter. The code will be compiled, with the results on the right. To update, change the code and repeat. Note that compilation errors are shown in red under the code. In order for svgplay/SVGo to work, make sure that the io.Writer specified with the New function is os.Stdout.

If you want to sketch with an existing file, enter its URL:

http://localhost:1999/foo.go

SVGplay

SVGo Papers and presentations

SVGo paper from SVGOpen 2011 http://www.svgopen.org/2011/papers/34-SVGo_a_Go_Library_for_SVG_generation
Programming Pictures with SVGo https://speakerdeck.com/u/ajstarks/p/programming-pictures-with-svgo
SVGo Workshop https://speakerdeck.com/u/ajstarks/p/svgo-workshop

Tutorial Video

A video describing how to use the package can be seen on YouTube at http://www.youtube.com/watch?v=ze6O2Dj5gQ4

Package contents

svg.go: Library
newsvg: Coding template command
svgdef: Creates a SVG representation of the API
animate: Animation demo
am: Animate motion demo
amt: Animate transformation demo
android: The Android logo
bubtrail: Bubble trails
bulletgraph: Bullet Graphs (via Stephen Few)
colortab: Display SVG named colors with RGB values
compx: Component diagrams
flower: Random "flowers"
fontcompare: Compare two fonts
f50: Get 50 photos from Flickr based on a query
fe: Filter effects
funnel: Funnel from transparent circles
gradient: Linear and radial gradients
html5logo: HTML5 logo with draggable elements
imfade: Show image fading
lewitt: Version of Sol Lewitt's Wall Drawing 91
ltr: Layer Tennis Remixes
marker: Test markers
paths: Demonstrate SVG paths
pattern: Test patterns
planets: Show the scale of the Solar system
pmap: Proportion maps
randcomp: Compare random number generators
richter: Gerhard Richter's 256 colors
rl: Random lines (port of a Processing demo)
skewabc: Skew ABC
span: Text span
stockproduct: Visualize product and stock prices
svgopher: SVGo Mascot
svgplay: SVGo sketching server
svgplot: Plot data
svgrid: Compose SVG files in a grid
tsg: Twitter Search Grid
tumblrgrid: Tumblr picture grid
turbulence: Turbulence filter effect
vismem: Visualize data from files
webfonts: "Hello, World" with Google Web Fonts
websvg: Generate SVG as a web server

Functions and types

Many functions use x, y to specify an object's location, and w, h to specify the object's width and height. Where applicable, a final optional argument specifies the style to be applied to the object. The style strings follow the SVG standard; name:value pairs delimited by semicolons, or a series of name="value" pairs. For example: "fill:none; opacity:0.3" or fill="none" opacity="0.3" (see: http://www.w3.org/TR/SVG11/styling.html)

The SVG type:

type SVG struct {
    Writer   io.Writer
}

Most operations are methods on this type, specifying the destination io.Writer.

The Offcolor type:

type Offcolor struct {
	Offset  uint8
	Color   string
	Opacity float64
}

is used to specify the offset, color, and opacity of stop colors in linear and radial gradients

The Filterspec type:

type Filterspec struct {
	In string
	In2 string
	Result string
}

is used to specify inputs and results for filter effects

Structure, Scripting, Metadata, Transformation and Links

New(w io.Writer) *SVG

Constructor, Specify the output destination.

Start(w int, h int, attributes ...string)

begin the SVG document with the width w and height h. Optionally add additional elements (such as additional namespaces or scripting events) http://www.w3.org/TR/SVG11/struct.html#SVGElement

Startview(w, h, minx, miny, vw, vh int)

begin the SVG document with the width w, height h, with a viewBox at minx, miny, vw, vh. http://www.w3.org/TR/SVG11/struct.html#SVGElement

Startunit(w int, h int, unit string, ns ...string)

begin the SVG document, with width and height in the specified units. Optionally add additional elements (such as additional namespaces or scripting events) http://www.w3.org/TR/SVG11/struct.html#SVGElement

Startpercent(w int, h int, ns ...string)

begin the SVG document, with width and height in percent. Optionally add additional elements (such as additional namespaces or scripting events) http://www.w3.org/TR/SVG11/struct.html#SVGElement

StartviewUnit(w, h int, unit string, minx, miny, vw, vh int)

begin the SVG document with the width w, height h, in the specified unit, with a viewBox at minx, miny, vw, vh. http://www.w3.org/TR/SVG11/struct.html#SVGElement

End()

end the SVG document

Script(scriptype string, data ...string)

Script defines a script with a specified type, (for example "application/javascript"). if the first variadic argument is a link, use only the link reference. Otherwise, treat variadic arguments as the text of the script (marked up as CDATA). if no data is specified, simply close the script element. http://www.w3.org/TR/SVG/script.html

Style(scriptype string, data ...string)

Style defines a script with a specified type, (for example "text/css"). if the first variadic argument is a link, use only the link reference. Otherwise, treat variadic arguments as the text of the script (marked up as CDATA). if no data is specified, simply close the style element. https://www.w3.org/TR/SVG/styling.html#StyleElement

Group(s ...string)

begin a group, with arbitrary attributes http://www.w3.org/TR/SVG11/struct.html#GElement

Gstyle(s string)

begin a group, with the specified style. http://www.w3.org/TR/SVG11/struct.html#GElement

Gid(s string)

begin a group, with the specified id.

Gtransform(s string)

begin a group, with the specified transform, end with Gend(). http://www.w3.org/TR/SVG11/coords.html#TransformAttribute

Translate(x, y int)

begins coordinate translation to (x,y), end with Gend(). http://www.w3.org/TR/SVG11/coords.html#TransformAttribute

Scale(n float64)

scales the coordinate system by n, end with Gend(). http://www.w3.org/TR/SVG11/coords.html#TransformAttribute

ScaleXY(x, y float64)

scales the coordinate system by x, y. End with Gend(). http://www.w3.org/TR/SVG11/coords.html#TransformAttribute

SkewX(a float64)

SkewX skews the x coordinate system by angle a, end with Gend(). http://www.w3.org/TR/SVG11/coords.html#TransformAttribute

SkewY(a float64)

SkewY skews the y coordinate system by angle a, end with Gend(). http://www.w3.org/TR/SVG11/coords.html#TransformAttribute

SkewXY(ax, ay float64)

SkewXY skews x and y coordinate systems by ax, ay respectively, end with Gend(). http://www.w3.org/TR/SVG11/coords.html#TransformAttribute

Rotate(r float64)

Svgo

Install / Use

README