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.
circle, ellipse, polygon, polyline, rect (including roundrects), line, text
general, arc, cubic and quadratic bezier paths,
image, linearGradient, radialGradient,
translate, rotate, scale, skewX, skewY
animate, animateMotion, animateTranslate, animateRotate, animateScale, animateSkewX, animateSkewY
filter, feBlend, feColorMatrix, feColorMatrix, feComponentTransfer, feComposite, feConvolveMatrix, feDiffuseLighting, feDisplacementMap, feDistantLight, feFlood, feGaussianBlur, feImage, feMerge, feMorphology, feOffset, fePointLight, feSpecularLighting, feSpotLight,feTile, feTurbulence
desc, defs, g (style, transform, id), marker, mask, pattern, title, (a)ddress, link, script, use
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.
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
-
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
A video describing how to use the package can be seen on YouTube at http://www.youtube.com/watch?v=ze6O2Dj5gQ4
- 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
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
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)
rotates the coordinate system by r degrees, end with Gend(). http://www.w3.org/TR/SVG11/coords.html#TransformAttribute
TranslateRotate(x, y int, r float64)
translates the coordinate system to (x,y), then rotates to r degrees, end with Gend().
RotateTranslate(x, y int, r float64)
rotates the coordinate system r degrees, then translates to (x,y), end with Gend().
Gend()
end the group (must be paired with Gstyle, Gtransform, Gid).
ClipPath(s ...string)
Begin a ClipPath http://www.w3.org/TR/SVG/masking.html#ClippingPaths
ClipEnd()
End a ClipPath http://www.w3.org/TR/SVG/masking.html#ClippingPaths
Def()
begin a definition block. http://www.w3.org/TR/SVG11/struct.html#DefsElement
DefEnd()
end a definition block.
Marker(id string, x, y, w, h int, s ...string)
define a marker http://www.w3.org/TR/SVG11/painting.html#MarkerElement
MarkerEnd()
end a marker
Mask(id string, x int, y int, w int, h int, s ...string)
creates a mask with a specified id, dimension, and optional style. http://www.w3.org/TR/SVG/masking.html
MaskEnd()
ends the Mask element.
Pattern(id string, x, y, width, height int, putype string, s ...string)
define a Pattern with the specified dimensions, the putype can be either "user" or "obj", which sets the patternUnits attribute to be either userSpaceOnUse or objectBoundingBox. http://www.w3.org/TR/SVG11/pservers.html#Patterns
Desc(s string)
specify the text of the description. http://www.w3.org/TR/SVG11/struct.html#DescElement
Title(s string)
specify the text of the title. http://www.w3.org/TR/SVG11/struct.html#TitleElement
Link(href string, title string)
begin a link named "href", with the specified title. http://www.w3.org/TR/SVG11/linking.html#Links
LinkEnd()
end the link.
Use(x int, y int, link string, s ...string)
place the object referenced at link at the location x, y. http://www.w3.org/TR/SVG11/struct.html#UseElement
Circle(x int, y int, r int, s ...string)
draw a circle, centered at x,y with radius r. http://www.w3.org/TR/SVG11/shapes.html#CircleElement
Ellipse(x int, y int, w int, h int, s ...string)
draw an ellipse, centered at x,y with radii w, and h. http://www.w3.org/TR/SVG11/shapes.html#EllipseElement
Polygon(x []int, y []int, s ...string)
draw a series of line segments using an array of x, y coordinates. http://www.w3.org/TR/SVG11/shapes.html#PolygonElement
Rect(x int, y int, w int, h int, s ...string)
draw a rectangle with upper left-hand corner at x,y, with width w, and height h. http://www.w3.org/TR/SVG11/shapes.html#RectElement
CenterRect(x int, y int, w int, h int, s ...string)
draw a rectangle with its center at x,y, with width w, and height h.
Roundrect(x int, y int, w int, h int, rx int, ry int, s ...string)
draw a rounded rectangle with upper the left-hand corner at x,y, with width w, and height h. The radii for the rounded portion is specified by rx (width), and ry (height).
Square(x int, y int, s int, style ...string)
draw a square with upper left corner at x,y with sides of length s.
Path(p string, s ...style)
draw the arbitrary path as specified in p, according to the style specified in s. http://www.w3.org/TR/SVG11/paths.html
Arc(sx int, sy int, ax int, ay int, r int, large bool, sweep bool, ex int, ey int, s ...string)
draw an elliptical arc beginning coordinate at sx,sy, ending coordinate at ex, ey width and height of the arc are specified by ax, ay, the x axis rotation is r
if sweep is true, then the arc will be drawn in a "positive-angle" direction (clockwise), if false, the arc is drawn counterclockwise.
if large is true, the arc sweep angle is greater than or equal to 180 degrees, otherwise the arc sweep is less than 180 degrees. http://www.w3.org/TR/SVG11/paths.html#PathDataEllipticalArcCommands
Bezier(sx int, sy int, cx int, cy int, px int, py int, ex int, ey int, s ...string)
draw a cubic bezier curve, beginning at sx,sy, ending at ex,ey with control points at cx,cy and px,py. http://www.w3.org/TR/SVG11/paths.html#PathDataCubicBezierCommands
Qbezier(sx int, sy int, cx int, cy int, ex int, ey int, tx int, ty int, s ...string)
draw a quadratic bezier curve, beginning at sx, sy, ending at tx,ty with control points are at cx,cy, ex,ey. http://www.w3.org/TR/SVG11/paths.html#PathDataQuadraticBezierCommands
Qbez(sx int, sy int, cx int, cy int, ex int, ey int, s...string)
draws a quadratic bezier curver, with optional style beginning at sx,sy, ending at ex, sy with the control point at cx, cy. http://www.w3.org/TR/SVG11/paths.html#PathDataQuadraticBezierCommands
Line(x1 int, y1 int, x2 int, y2 int, s ...string)
draw a line segment between x1,y1 and x2,y2. http://www.w3.org/TR/SVG11/shapes.html#LineElement
Polyline(x []int, y []int, s ...string)
draw a polygon using coordinates specified in x,y arrays. http://www.w3.org/TR/SVG11/shapes.html#PolylineElement
Image(x int, y int, w int, h int, link string, s ...string)
place at x,y (upper left hand corner), the image with width w, and height h, referenced at link. http://www.w3.org/TR/SVG11/struct.html#ImageElement
Text(x int, y int, t string, s ...string)
Place the specified text, t at x,y according to the optional style specified in s. http://www.w3.org/TR/SVG11/text.html#TextElement
Textspan(x int, y int, t string, s ...string)
Place specified text, t at x,y according to the optional style specified in s. https://www.w3.org/TR/SVG11/text.html#TSpanElement Use this method with Span(...). End with TextEnd()
Span(t string, s ...string)
Create a text span t, using optional style s
TextEnd()
End a text span
Textlines(x, y int, s []string, size, spacing int, fill, align string)
Places lines of text in s, starting at x,y, at the specified size, fill, and alignment, and spacing.
Textpath(t string, pathid string, s ...string)
places optionally styled text along a previously defined path.
http://www.w3.org/TR/SVG11/text.html#TextPathElement
RGB(r int, g int, b int) string
creates a style string for the fill color designated by the (r)ed, g(reen), (b)lue components. http://www.w3.org/TR/css3-color/
RGBA(r int, g int, b int, a float64) string
as above, but includes the color's opacity as a value between 0.0 (fully transparent) and 1.0 (opaque).
LinearGradient(id string, x1, y1, x2, y2 uint8, sc []Offcolor)
constructs a linear color gradient identified by id,
along the vector defined by (x1,y1), and (x2,y2).
The stop color sequence defined in sc. Coordinates are expressed as percentages.
http://www.w3.org/TR/SVG11/pservers.html#LinearGradients
RadialGradient(id string, cx, cy, r, fx, fy uint8, sc []Offcolor)
constructs a radial color gradient identified by id, centered at (cx,cy), with a radius of r. (fx, fy) define the location of the focal point of the light source. The stop color sequence defined in sc. Coordinates are expressed as percentages. http://www.w3.org/TR/SVG11/pservers.html#RadialGradients
Animate(link, attr string, from, to int, duration float64, repeat int, s ...string)
Animate animates the item referenced by the link, using the specified attribute The animation starts at coordinate from, terminates at to, and repeats as specified. Addtional attributes may be added as needed. https://www.w3.org/TR/SVG11/animate.html#AnimateElement
AnimateMotion(link, path string, duration float64, repeat int, s ...string)
AnimateMotion animates the referenced object link along the specified path
https://www.w3.org/TR/SVG11/animate.html#AnimateMotionElement
AnimateTranslate(link string, fx, fy, tx, ty int, duration float64, repeat int, s ...string)
AnimateTranslate animates the translation transformation (link refers to the object to animate, fx, fy are from coordinates, tx, ty are the to coordinates) https://www.w3.org/TR/SVG11/animate.html#AnimateTransformElement
AnimateRotate(link string, fs, fc, fe, ts, tc, te int, duration float64, repeat int, s ...string)
AnimateRotate animates the rotation transformation (link refers to the object to animate, f[s,c,e] are the from start, center, and end angles, t[s,c,e] are the start, center, and end angles) https://www.w3.org/TR/SVG11/animate.html#AnimateTransformElement
AnimateScale(link string, from, to, duration float64, repeat int, s ...string)
AnimateScale animates the scale transformation (link refers to the object to animate, from and to specify the scaling factor) https://www.w3.org/TR/SVG11/animate.html#AnimateTransformElement
AnimateSkewX(link string, from, to, duration float64, repeat int, s ...string)
AnimateSkewX animates the skewX transformation ((link refers to the object to animate, from and to specify the skew angle) https://www.w3.org/TR/SVG11/animate.html#AnimateTransformElement
AnimateSkewY(link string, from, to, duration float64, repeat int, s ...string)
AnimateSkewY animates the skewY transformation (link refers to the object to animate, and from and to specify the skew angle) https://www.w3.org/TR/SVG11/animate.html#AnimateTransformElement
Filter(id string, s ...string)
Filter begins a filter set Standard reference: http://www.w3.org/TR/SVG11/filters.html#FilterElement
Fend()
Fend ends a filter set Standard reference: http://www.w3.org/TR/SVG11/filters.html#FilterElement
FeBlend(fs Filterspec, mode string, s ...string)
FeBlend specifies a Blend filter primitive Standard reference: http://www.w3.org/TR/SVG11/filters.html#feBlendElement
FeColorMatrix(fs Filterspec, values [20]float64, s ...string)
FeColorMatrix specifies a color matrix filter primitive, with matrix values Standard reference: http://www.w3.org/TR/SVG11/filters.html#feColorMatrixElement
FeColorMatrixHue(fs Filterspec, value float64, s ...string)
FeColorMatrix specifies a color matrix filter primitive, with hue values Standard reference: http://www.w3.org/TR/SVG11/filters.html#feColorMatrixElement
FeColorMatrixSaturate(fs Filterspec, value float64, s ...string)
FeColorMatrix specifies a color matrix filter primitive, with saturation values Standard reference: http://www.w3.org/TR/SVG11/filters.html#feColorMatrixElement
FeColorMatrixLuminence(fs Filterspec, s ...string)
FeColorMatrix specifies a color matrix filter primitive, with luminence values Standard reference: http://www.w3.org/TR/SVG11/filters.html#feColorMatrixElement
FeComponentTransfer()
FeComponentTransfer begins a feComponent filter Element> Standard reference: http://www.w3.org/TR/SVG11/filters.html#feComponentTransferElement
FeCompEnd()
FeCompEnd ends a feComponent filter Element>
FeComposite(fs Filterspec, operator string, k1, k2, k3, k4 int, s ...string)
FeComposite specifies a feComposite filter primitive Standard reference: http://www.w3.org/TR/SVG11/filters.html#feCompositeElement
FeConvolveMatrix(fs Filterspec, matrix [9]int, s ...string)
FeConvolveMatrix specifies a feConvolveMatrix filter primitive Standard reference: http://www.w3.org/TR/SVG11/filters.html#feConvolveMatrixElement
FeDiffuseLighting(fs Filterspec, scale, constant float64, s ...string)
FeDiffuseLighting specifies a diffuse lighting filter primitive, a container for light source Element>s, end with DiffuseEnd()
FeDiffEnd()
FeDiffuseEnd ends a diffuse lighting filter primitive container Standard reference: http://www.w3.org/TR/SVG11/filters.html#feDiffuseLightingElement
FeDisplacementMap(fs Filterspec, scale float64, xchannel, ychannel string, s ...string)
FeDisplacementMap specifies a feDisplacementMap filter primitive Standard reference: http://www.w3.org/TR/SVG11/filters.html#feDisplacementMapElement
FeDistantLight(fs Filterspec, azimuth, elevation float64, s ...string)
FeDistantLight specifies a feDistantLight filter primitive Standard reference: http://www.w3.org/TR/SVG11/filters.html#feDistantLightElement
FeFlood(fs Filterspec, color string, opacity float64, s ...string)
FeFlood specifies a flood filter primitive Standard reference: http://www.w3.org/TR/SVG11/filters.html#feFloodElement
FeFuncLinear(channel string, slope, intercept float64)
FeFuncLinear is the linear form of feFunc Standard reference: http://www.w3.org/TR/SVG11/filters.html#feComponentTransferElement
FeFuncGamma(channel, amplitude, exponent, offset float64)
FeFuncGamma is the gamma curve form of feFunc Standard reference: http://www.w3.org/TR/SVG11/filters.html#feComponentTransferElement
FeFuncTable(channel string, tv []float64)
FeFuncGamma is the form of feFunc using a table of values Standard reference: http://www.w3.org/TR/SVG11/filters.html#feComponentTransferElement
FeFuncDiscrete(channel string, tv []float64)
FeFuncGamma is the form of feFunc using discrete values Standard reference: http://www.w3.org/TR/SVG11/filters.html#feComponentTransferElement
FeGaussianBlur(fs Filterspec, stdx, stdy float64, s ...string)
FeGaussianBlur specifies a Gaussian Blur filter primitive Standard reference: http://www.w3.org/TR/SVG11/filters.html#feGaussianBlurElement
FeImage(href string, result string, s ...string)
FeImage specifies a feImage filter primitive Standard reference: http://www.w3.org/TR/SVG11/filters.html#feImageElement
FeMerge(nodes []string, s ...string)
FeMerge specifies a feMerge filter primitive, containing feMerge Element>s Standard reference: http://www.w3.org/TR/SVG11/filters.html#feMergeElement
FeMorphology(fs Filterspec, operator string, xradius, yradius float64, s ...string)
FeMorphologyLight specifies a feMorphologyLight filter primitive Standard reference: http://www.w3.org/TR/SVG11/filters.html#feMorphologyElement
FeOffset(fs Filterspec, dx, dy int, s ...string)
FeOffset specifies the feOffset filter primitive Standard reference: http://www.w3.org/TR/SVG11/filters.html#feOffsetElement
FePointLight(x, y, z float64, s ...string)
FePointLight specifies a fePpointLight filter primitive Standard reference: http://www.w3.org/TR/SVG11/filters.html#fePointLightElement
FeSpecularLighting(fs Filterspec, scale, constant float64, exponent int, color string, s ...string)
FeSpecularLighting specifies a specular lighting filter primitive, a container for light source elements, end with SpecularEnd()
FeSpecEnd()
FeSpecularEnd ends a specular lighting filter primitive container Standard reference: http://www.w3.org/TR/SVG11/filters.html#feSpecularLightingElement
FeSpotLight(fs Filterspec, x, y, z, px, py, pz float64, s ...string)
FeSpotLight specifies a feSpotLight filter primitive Standard reference: http://www.w3.org/TR/SVG11/filters.html#feSpotLightElement
FeTile(fs Filterspec, in string, s ...string)
FeTile specifies the tile utility filter primitive Standard reference: http://www.w3.org/TR/SVG11/filters.html#feTileElement
FeTurbulence(fs Filterspec, ftype string, bfx, bfy float64, octaves int, seed int64, stitch bool, s ...string)
FeTurbulence specifies a turbulence filter primitive Standard reference: http://www.w3.org/TR/SVG11/filters.html#feTurbulenceElement
Blur(p float64)
Blur function by standard deviation
Brightness(p float64)
Brightness function (0-100)
Grayscale()
Apply a grayscale filter to the image
HueRotate(a float64)
Rotate Hues (0-360 degrees)
Invert()
Invert the image's colors
Saturate(p float64)
Percent saturation, 0 is grayscale
Sepia()
Apply sepia tone
Grid(x int, y int, w int, h int, n int, s ...string)
draws a grid of straight lines starting at x,y, with a width w, and height h, and a size of n.
Thanks to Jonathan Wright for the io.Writer update.
