A PDF renderer for the goldmark markdown parser.



goldmark-pdf is a renderer for goldmark that allows rendering to PDF.

goldmark-pdf screenshot


See https://pkg.go.dev/github.com/stephenafamo/goldmark-pdf


Care has been taken to match the semantics of goldmark and its extensions.

The PDF renderer can be initiated with pdf.New() and the returned value satisfies goldmark's renderer.Renderer interface, so it can be passed to goldmark.New() using the goldmark.WithRenderer() option.

markdown := goldmark.New(

Options can also be passed to pdf.New(), the options interface to be satisfied is:

// An Option interface is a functional option type for the Renderer.
type Option interface {

Here is the Config struct that is to be modified:

type Config struct {
	Context context.Context


	// A source for images
	ImageFS fs.FS

	// All other options have sensible defaults
	Styles Styles

	// A cache for the fonts
	FontsCache fonts.Cache

	// For debugging
	TraceWriter io.Writer

	NodeRenderers util.PrioritizedSlice

Some helper functions for adding options are already provided. See option.go

An example with some more options:

            pdf.WithHeadingFont(pdf.GetTextFont("IBM Plex Serif", pdf.FontLora)),
            pdf.WithBodyFont(pdf.GetTextFont("Open Sans", pdf.FontRoboto)),
            pdf.WithCodeFont(pdf.GetCodeFont("Inconsolata", pdf.FontRobotoMono)),


The fonts that can be used in the PDF are based on the Font struct

// Represents a font.
type Font struct {
	CanUseForText bool
	CanUseForCode bool

	Category string
	Family   string

	FileRegular    string
	FileItalic     string
	FileBold       string
	FileBoldItalic string

	Type fontType

To be used for text, a font should have regular, italic, bold and bold-italic styles. Each of these has to be loaded separately.

To ease this process, variables have been generated for all the Google fonts that have these styles. For example:

var FontRoboto = Font{
	CanUseForCode:  false,
	CanUseForText:  true,
	Category:       "sans-serif",
	Family:         "Roboto",
	FileBold:       "700",
	FileBoldItalic: "700italic",
	FileItalic:     "italic",
	FileRegular:    "regular",
	Type:           fontTypeGoogle,

For codeblocks, if any other style is missing, the regular font is used in place.

var FontMajorMonoDisplay = Font{
	CanUseForCode:  true,
	CanUseForText:  false,
	Category:       "monospace",
	Family:         "Major Mono Display",
	FileBold:       "regular",
	FileBoldItalic: "regular",
	FileItalic:     "regular",
	FileRegular:    "regular",
	Type:           fontTypeGoogle,

When loading the fonts, they are downloaded on the fly using the fonts.

If you'd like to use a font outside of these, you should pass your own font struct which have been loaded into the PDF object you set in the Config. Be sure to set the FontType to FontTypeCustom so that we do not attempt to download it.


Here's a list of things that I'd love help with:

  • More documentation
  • Testing
  • Finish the (currently buggy) implementation based on gopdf




Stephen Afam-Osemene

  • Lack of image mime detection

    Lack of image mime detection

    The image renderer:

    func (r *nodeRederFuncs) renderImage(w *Writer, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
    	// while this has entering and leaving states, it doesn't appear
    	// to be useful except for other markup languages to close the tag
    	n := node.(*ast.Image)
    	if entering {
    		w.LogDebug("Image (entering)", fmt.Sprintf("Destination[%v] Title[%v]", string(n.Destination), string(n.Title)))
    		// following changes suggested by @sirnewton01, issue #6
    		// does file exist?
    		imgPath := string(n.Destination) <--------------------------------------------------
    		imgFile, err := w.ImageFS.Open(imgPath)
    		if err == nil {
    			defer imgFile.Close()
    			width, _ := w.Pdf.GetPageSize()
    			mleft, _, mright, _ := w.Pdf.GetMargins()
    			maxw := width - (mleft * 2) - (mright * 2)
    			format := strings.ToUpper(strings.Trim(filepath.Ext(imgPath), ".")) <-------
    			w.Pdf.RegisterImage(imgPath, format, imgFile)
    			w.Pdf.UseImage(imgPath, (mleft * 2), w.Pdf.GetY(), maxw, 0)
    		} else {
    			log.Printf("IMAGE ERROR: %v", err)
    			w.LogDebug("Image (file error)", err.Error())
    	} else {
    		w.LogDebug("Image (leaving)", "")
    	return ast.WalkContinue, nil

    relies on path to determine the mime type of the file. But if I use http file directory to embed/render images linked via http and not stored locally, this fails miserably unless the url contains the mime type suffix, which is rarely the case.

    Hence, there should be a built-in http file directory the mime should be determined manually by github.com/gabriel-vasile/mimetype or similar library.

    My quickly built fs is:

    type HttpFs struct{}
    func (f *HttpFs) Open(name string) (fs.File, error) {
    	res, err := http.Get(name)
    	if err != nil {
    		return nil, err
    	return &HttpFile{r: res}, nil
    type HttpFile struct {
    	r *http.Response
    func (f *HttpFile) Stat() (fs.FileInfo, error) {
    	return &HttpInfo{r: f.r}, nil
    func (f *HttpFile) Read(p []byte) (int, error) {
    	return f.r.Body.Read(p)
    func (f *HttpFile) Close() error {
    	return f.r.Body.Close()
    type HttpInfo struct {
    	r *http.Response
    func (i *HttpInfo) Name() string {
    	fn := strings.TrimPrefix(i.r.Request.URL.Path, "/")
    	if fn == "" {
    		if _, params, err := mime.ParseMediaType(i.r.Header.Get("Content-Disposition")); err == nil {
    			fn = params["filename"]
    	if filepath.Ext(fn) == "" {
    		mt, _, _ := mime.ParseMediaType(i.r.Header.Get("Content-Type"))
    		if spl := strings.Split(mt, "/"); len(spl) > 0 {
    			if fn == "" {
    				fn = spl[0]
    			fn += "." + spl[len(spl)-1]
    	return filepath.Base(fn)
    func (i *HttpInfo) Size() int64 {
    	return i.r.ContentLength
    func (i *HttpInfo) Mode() fs.FileMode {
    	return fs.ModeIrregular
    func (i *HttpInfo) ModTime() time.Time {
    	if t, err := time.Parse(time.RFC1123, i.r.Header.Get("Last-Modified")); err == nil {
    		return t
    	return time.Time{}
    func (i *HttpInfo) IsDir() bool {
    	return false
    func (i *HttpInfo) Sys() any {
    	return i.r
    opened by ivanjaros 12
  • Tables do not render correctly

    Tables do not render correctly

    If the cell contents are longer than the heading length of the column then the next column will overwrite the last part of the previous column. Column widths are determined based on the values in the header row. Column contents do not wrap (at least not without changing the row height, which I have not tested).

    This makes the table functionality not very useful except for the simplest of tables, which is a shame since otherwise the generated PDF looks very good.

    opened by tjdavis3 6
  • Add option to recode embedded images when they are too large

    Add option to recode embedded images when they are too large

    When I link big image(say 4MB), it will be embedded into the pdf file as is, making the file size that much larger.

    I think there should be an option to convert images above configured size into jpeg and embed those re-coded images instead of the originals. This can save a lot of disk space in case the assets' quality is not of utmost importance(which is usually the case, very few people embed high-resolution images into PDF documents).

    With the FS branch with the new file system, there is access to file size via Stat() and mime detection is present as well, which can be used to invoke the code, that will look something like this:

    import (
    func Resize(srcMime string, src io.Reader, dst io.Writer, documentWidth int) error {
    	var img image.Image
    	var err error
    	switch srcMime {
    	case "image/jpeg":
    		img, err = jpeg.Decode(src)
    	case "image/gif":
    		img, err = gif.Decode(src)
    	case "image/png":
    		img, err = png.Decode(src)
    	case "image/webp":
    		img, err = webp.Decode(src)
    		return errors.New("unsupported input mime type: " + srcMime)
    	if err != nil {
    		return err
           if img.Bounds().Dx() < documentWidth {
                  documentWidth = img.Bounds().Dx()
    	filter := imaging.Lanczos // best quality but slow
    	img = imaging.Resize(img, documentWidth, 0, filter)
    	return jpeg.Encode(dst, img, nil) // jpeg has the best compression with sufficient quality for this purpose
    opened by ivanjaros 0
  • Local links/navigation is not working

    Local links/navigation is not working

    Having local navigation, like:

    # <a name="top"></a>Markdown Test Page
    * [Headings](#Headings)
    * [Paragraphs](#Paragraphs)
    * [Blockquotes](#Blockquotes)
    * [Lists](#Lists)
    * [Horizontal rule](#Horizontal)
    * [Table](#Table)
    * [Code](#Code)
    * [Inline elements](#Inline)
    # <a name="Headings"></a>Headings
    # Heading one
    Sint sit cillum pariatur eiusmod nulla pariatur ipsum. Sit laborum anim qui mollit tempor pariatur nisi minim dolor. Aliquip et adipisicing sit sit fugiat commodo id sunt. Nostrud enim ad commodo incididunt cupidatat in ullamco ullamco Lorem cupidatat velit enim et Lorem. Ut laborum cillum laboris fugiat culpa sint irure do reprehenderit culpa occaecat. Exercitation esse mollit tempor magna aliqua in occaecat aliquip veniam reprehenderit nisi dolor in laboris dolore velit.
    ## Heading two


    will render links but they won't work.

    opened by ivanjaros 11
  • Image ALT is ignored

    Image ALT is ignored

    When image is not loaded, it's alt text is ignored:

    ![The San Juan Mountains are beautiful!](san-juan-mountains.jpggg "San Juan Mountains Alt Text")


    opened by ivanjaros 0
  • Image caption is not centered

    Image caption is not centered

    Image with caption will have it rendered aligned to the left of the document instead of centered, with the image.

    For example: ![The San Juan Mountains are beautiful!](/assets/images/san-juan-mountains.jpg "San Juan Mountains")

    will end up like: obrázok

    opened by ivanjaros 0
  • Small images are stretched for the entire width of the document

    Small images are stretched for the entire width of the document

    I have a testing document which contains a small image of 176px*176px dimensions. The problem is that this image will be scaled to the entire width of the document, which does not look good and is most likely not desired because it would not be rendered as such in HTML document, unless specifically configured with CSS.

    The code responsible for this behavior is: https://github.com/stephenafamo/goldmark-pdf/blob/master/renderer_funcs.go#L581

    I think that if the image is smaller than the width of the document, it should be kept as is and if the image is wider, only then it should be scaled down to fit the document.

    opened by ivanjaros 0
Stephen Afam-Osemene
Part Programmer, Part Engineer, Part Entrepreneur. I have many interests that converge on improving lives with technology
Stephen Afam-Osemene
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