Render dot to png generated empty file

[fengttt]

I am trying to render a dot file to png. Here is my simple function.

func RenderDot(dot string, fn string) error {
	ctx := context.Background()
	g, err := graphviz.New(ctx)
	if err != nil {
		return err
	}
	defer g.Close()
	graph, err := graphviz.ParseBytes([]byte(dot))
	if err != nil {
		return err
	}

	err = g.RenderFilename(ctx, graph, graphviz.PNG, fn)
	return err
}

When trying to render "digraph G {Hello->World}", there is no error, but the generated png file is 0 byte. Any hint that what I did wrong?

[roopeshsn]

+1

[roopeshsn]

I also tried RenderImage method before RenderFilename, but generated file size is 0 bytes as you said.

[huasonl]

+1

[little-nil]

+1

But you can use the following encoding scheme as an alternative.

    ctx := context.Background()
g, err := graphviz.New(ctx)
if err != nil {
	return nil, err
}
dag, err := g.Graph()
if err != nil {
	return nil, err
}
defer func() {
	if err := dag.Close(); err != nil {
		log.Fatal(err)
	}
	g.Close()
}()
    // create nodes and edges
    ...
    buf := new(bytes.Buffer)
err = g.Render(ctx, dag, "png", buf)
    if err != nil {
	return nil, err
}
    err = os.WriteFile("xxxxxx.png", buf.Bytes(), 0o644)
    if err != nil {
	return nil, err
}