Go Graphics (gg) - 纯Go实现的2D图形渲染库

gg 是一个用纯Go语言实现的2D图形渲染库。

安装

go get -u github.com/fogleman/gg

或者使用gopkg.in获取特定主版本：

go get -u gopkg.in/fogleman/gg.v1

文档

• godoc: https://godoc.org/github.com/fogleman/gg
• pkg.go.dev: https://pkg.go.dev/github.com/fogleman/gg?tab=doc

Hello, Circle!

看有多简单！

package main

import "github.com/fogleman/gg"

func main() {
    dc := gg.NewContext(1000, 1000)  // 创建1000x1000的画布
    dc.DrawCircle(500, 500, 400)     // 在(500,500)位置画半径为400的圆
    dc.SetRGB(0, 0, 0)               // 设置颜色为黑色
    dc.Fill()                        // 填充
    dc.SavePNG("out.png")            // 保存为PNG
}

示例

包含了许多示例，主要用于测试代码，但也适合学习。

创建上下文

有几种创建上下文的方法：

NewContext(width, height int) *Context
NewContextForImage(im image.Image) *Context
NewContextForRGBA(im *image.RGBA) *Context

绘图函数

DrawPoint(x, y, r float64)
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)
DrawRegularPolygon(n int, x, y, r, rotation float64)
DrawImage(im image.Image, x, y int)
DrawImageAnchored(im image.Image, x, y int, ax, ay float64)
SetPixel(x, y int)

MoveTo(x, y float64)
LineTo(x, y float64)
QuadraticTo(x1, y1, x2, y2 float64)
CubicTo(x1, y1, x2, y2, x3, y3 float64)
ClosePath()
ClearPath()
NewSubPath()

Clear()
Stroke()
Fill()
StrokePreserve()
FillPreserve()

文本函数

DrawString(s string, x, y float64)
DrawStringAnchored(s string, x, y, ax, ay float64)
DrawStringWrapped(s string, x, y, ax, ay, width, lineSpacing float64, align Align)
MeasureString(s string) (w, h float64)
MeasureMultilineString(s string, lineSpacing float64) (w, h float64)
WordWrap(s string, w float64) []string
SetFontFace(fontFace font.Face)
LoadFontFace(path string, points float64) error

颜色函数

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)

描边和填充选项

SetLineWidth(lineWidth float64)
SetLineCap(lineCap LineCap)
SetLineJoin(lineJoin LineJoin)
SetDash(dashes ...float64)
SetDashOffset(offset float64)
SetFillRule(fillRule FillRule)

渐变和图案

SetFillStyle(pattern Pattern)
SetStrokeStyle(pattern Pattern)
NewSolidPattern(color color.Color)
NewLinearGradient(x0, y0, x1, y1 float64)
NewRadialGradient(x0, y0, r0, x1, y1, r1 float64)
NewConicGradient(cx, cy, deg float64)
NewSurfacePattern(im image.Image, op RepeatOp)

变换函数

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()

堆栈函数

Push()
Pop()

裁剪函数

Clip()
ClipPreserve()
ResetClip()
AsMask() *image.Alpha
SetMask(mask *image.Alpha)
InvertMask()

辅助函数

Radians(degrees float64) float64
Degrees(radians float64) float64
LoadImage(path string) (image.Image, error)
LoadPNG(path string) (image.Image, error)
SavePNG(path string, im image.Image) error

另一个示例

package main

import "github.com/fogleman/gg"

func main() {
    const S = 1024
    dc := gg.NewContext(S, S)
    dc.SetRGBA(0, 0, 0, 0.1)  // 设置半透明黑色
    for i := 0; i < 360; i += 15 {
        dc.Push()  // 保存当前状态
        // 绕中心点旋转
        dc.RotateAbout(gg.Radians(float64(i)), S/2, S/2)
        // 绘制椭圆
        dc.DrawEllipse(S/2, S/2, S*7/16, S/8)
        dc.Fill()  // 填充
        dc.Pop()   // 恢复之前的状态
    }
    dc.SavePNG("out.png")
}