gg - Go Graphics - 2D rendering in Go with a simple API.
jopen
9年前
Go Graphics
gg is a library for rendering 2D graphics in pure Go.
Installation
go get github.com/fogleman/gg
Hello, Circle!
Look how easy!
package main import "github.com/fogleman/gg" func main() { dc := gg.NewContext(1000, 1000) dc.DrawCircle(500, 500, 400) dc.SetRGB(0, 0, 0) dc.Fill() dc.SavePNG("out.png") }Creating Contexts
There are a few ways of creating a context.
NewContext(width, height int) *Context NewContextForImage(im image.Image) *Context NewContextForRGBA(im *image.RGBA) *ContextDrawing Functions
Ever used a graphics library that didn't have functions for drawing rectangles or circles? What a pain!
DrawLine(x1, y1, x2, y2 float64) DrawRectangle(x, y, w, h float64) DrawRoundedRectangle(x, y, w, h, r float64) DrawCircle(x, y, r float64) DrawArc(x, y, r, angle1, angle2 float64) DrawEllipse(x, y, rx, ry float64) DrawEllipticalArc(x, y, rx, ry, angle1, angle2 float64) DrawImage(im image.Image, x, y int) DrawImageAnchored(im image.Image, x, y int, ax, ay float64) MoveTo(x, y float64) LineTo(x, y float64) QuadraticTo(x1, y1, x2, y2 float64) CubicTo(x1, y1, x2, y2, x3, y3 float64) ClosePath() ClearPath() Clear() Stroke() Fill() StrokePreserve() FillPreserve()Text Functions
DrawString(s string, x, y float64) DrawStringAnchored(s string, x, y, ax, ay float64) MeasureString(s string) (w, h float64) SetFontFace(fontFace font.Face) LoadFontFace(path string, points float64)Color Functions
Colors can be set in several different ways for your convenience.
SetRGB(r, g, b float64) SetRGBA(r, g, b, a float64) SetRGB255(r, g, b int) SetRGBA255(r, g, b, a int) SetColor(c color.Color) SetHexColor(x string)Stroke & Fill Options
SetLineWidth(lineWidth float64) SetLineCap(lineCap LineCap) SetLineJoin(lineJoin LineJoin) SetFillRule(fillRule FillRule)Transformation Functions
Identity() Translate(x, y float64) Scale(x, y float64) Rotate(angle float64) Shear(x, y float64) ScaleAbout(sx, sy, x, y float64) RotateAbout(angle, x, y float64) ShearAbout(sx, sy, x, y float64) TransformPoint(x, y float64) (tx, ty float64) InvertY() Push() Pop()Helper Functions
Sometimes you just don't want to write these yourself.
Radians(degrees float64) float64 Degrees(radians float64) float64 LoadPNG(path string) (image.Image, error) SavePNG(path string, im image.Image) errorWhat's Missing?
If you need any of the features below, I recommend using cairo instead. Or even better, implement it and submit a pull request!
- Clipping Regions
- Gradients / Patterns
- Dashed Lines*
* might be implemented soon
How Do it Do?
gg is mostly a wrapper around github.com/golang/freetype/raster. The goal is to provide some more functionality and a nicer API that will suffice for most use cases.
Another Example
See the output of this example below.
package main import "github.com/fogleman/gg" func main() { const S = 1024 dc := gg.NewContext(S, S) dc.SetRGBA(0, 0, 0, 0.1) for i := 0; i < 360; i += 15 { dc.Push() dc.RotateAbout(gg.Radians(float64(i)), S/2, S/2) dc.DrawEllipse(S/2, S/2, S*7/16, S/8) dc.Fill() dc.Pop() } dc.SavePNG("out.png") }