package main

import (
  "bytes"
  "fmt"
  "log"

  "github.com/goccy/go-graphviz"
)

func main() {
  g := graphviz.New()
  graph, err := g.Graph()
  if err != nil {
    log.Fatal(err)
  }
  defer func() {
    if err := graph.Close(); err != nil {
      log.Fatal(err)
    }
    g.Close()
  }()
  n, err := graph.CreateNode("n")
  if err != nil {
    log.Fatal(err)
  }
  m, err := graph.CreateNode("m")
  if err != nil {
    log.Fatal(err)
  }
  e, err := graph.CreateEdge("e", n, m)
  if err != nil {
    log.Fatal(err)
  }
  e.SetLabel("e")
  var buf bytes.Buffer
  if err := g.Render(graph, "dot", &buf); err != nil {
    log.Fatal(err)
  }
  fmt.Println(buf.String())
}

path := "/path/to/dot.gv"
b, err := ioutil.ReadFile(path)
if err != nil {
  log.Fatal(err)
}
graph, err := graphviz.ParseBytes(b)

g := graphviz.New()
graph, err := g.Graph()
if err != nil {
  log.Fatal(err)
}

// create your graph

// 1. write encoded PNG data to buffer
var buf bytes.Buffer
if err := g.Render(graph, graphviz.PNG, &buf); err != nil {
  log.Fatal(err)
}

// 2. get as image.Image instance
image, err := g.RenderImage(graph)
if err != nil {
  log.Fatal(err)
}

// 3. write to file directly
if err := g.RenderFilename(graph, graphviz.PNG, "/path/to/graph.png"); err != nil {
  log.Fatal(err)
}