mdtopdf

README

mdtopdf

Introduction: Markdown to PDF

This package depends on two other packages:

• The BlackFriday v2 parser to read the markdown source
• The gofpdf packace to generate the PDF

Both of the above are documented at Go Docs [http://godocs.org].

The tests included here are from the BlackFriday package. See the "testdata" folder. The tests create PDF files and thus while the tests may complete without errors, visual inspection of the created PDF is the only way to determine if the tests really pass!

The tests create log files that trace the BlackFriday parser callbacks. This is a valuable debug tool showing each callback and data provided in each while the AST is presented.

2019-09-23: It appears that the BlackFriday project is no longer active. There is a fork gomarkdown/markdown that I may be able to move to in the future if needed.

Supported Markdown

The supported elements of markdown are:

• Emphasized and strong text
• Headings 1-6
• Ordered and unordered lists
• Nested lists
• Images
• Tables (but see limitations below)
• Links
• Code blocks and backticked text

How to use of non-Latin fonts/languages is documented in a section below.

Limitations and Known Issues

1. It is common for Markdown to include HTML. HTML is treated as a "code block". There is no attempt to convert raw HTML to PDF.

2. Github-flavored Markdown permits strikethough using tildes. This is not supported at present by gofpdf as a font style.

3. The markdown link title, which would show when converted to HTML as hover-over text, is not supported. The generated PDF will show the actual URL that will be used if clicked, but this is a function of the PDF viewer.

4. Currently all levels of unordered lists use a dash for the bullet. This is a planned fix; see here.

5. Definition lists are not supported (not sure that markdown supports them -- I need to research this)

6. The following text features may be tweaked: font, size, spacing, style, fill color, and text color. These are exported and available via the Styler struct. Note that fill color only works if the text is ouput using CellFormat(). This is the case for: tables, codeblocks, and backticked text.

7. Tables are supported, but no attempt is made to ensure fit. You can, however, change the font size and spacing to make it smaller. See example.

Installation

To install the package, run the usual go get:

go get github.com/rickb777/mdtopdf

Quick start

In the cmd folder is an example using the package. It demonstrates a number of features. The test PDF was created with this command:

go run convert.go -i test.md -o test.pdf

Using non-LATIN Glyphs/Fonts

In order to use a non-Latin language there are a number things that must be done. The PDF generator must be configured with:

• the font
• a codepage map
• the content must be translated to Unicode

The above are all requirements of the PDF generator (see dependencies above). I don't know of a straightforward way to determine what the PDF generator needs. I was able to play with a little code to discover what is needed. In addition, the PDF generator testing code has some hints. My code to play with the PDF generator is at rickb777/samples/gofpdf.

In addition, this package's Styler must be used to set the font to match that is configured with the PDF generator.

A complete working example may be found for Russian in the cmd folder nameed russian.go.

Documentation

Overview

Package mdtopdf implements a PDF document generator for markdown documents.

Introduction

This package depends on two other packages:

* The BlackFriday v2 parser to read the markdown source

* The gofpdf packace to generate the PDF

The tests included here are from the BlackFriday package. See the "testdata" folder. The tests create PDF files and thus while the tests may complete without errors, visual inspection of the created PDF is the only way to determine if the tests *really* pass!

The tests create log files that trace the BlackFriday parser callbacks. This is a valuable debug tool showing each callback and data provided in each while the AST is presented.

Installation

To install the package:

go get github.com/rickb777/mdtopdf

Quick start

In the cmd folder is an example using the package. It demonstrates a number of features. The test PDF was created with this command:

go run convert.go -i test.md -o test.pdf

See README for limitations and known issues

Package mdtopdf converts markdown to PDF.

Index

• Variables
• type Color
  • func ColorOf(css string) Color
  • func Grey(level int) Color
• type PdfRenderer
  • func NewPdfRenderer(orientation, paperSize, fontDir string) *PdfRenderer
  • func (r *PdfRenderer) Output(w io.Writer) error
  • func (r *PdfRenderer) Process(markdown []byte) *PdfRenderer
  • func (r *PdfRenderer) RenderFooter(w io.Writer, ast *bf.Node)
  • func (r *PdfRenderer) RenderHeader(w io.Writer, ast *bf.Node)
  • func (r *PdfRenderer) RenderNode(w io.Writer, node *bf.Node, entering bool) bf.WalkStatus
  • func (r *PdfRenderer) ToFile(pdfFile string) error
• type Styler

Variables

var (
	Black = Color{0, 0, 0}
	White = Color{255, 255, 255}
)

Types

type Color

type Color struct {
	Red, Green, Blue int
}

Color is expressed in RGB components (0 - 255). For a nice picker, see https://www.w3schools.com/colors/colors_picker.asp

func ColorOf

func ColorOf(css string) Color

ColorOf implements basic CSS-like colours such as "#0366d6".

func Grey

func Grey(level int) Color

Grey returns a grey of some level between 0 and 255.

type PdfRenderer

type PdfRenderer struct {
	// Pdf can be used to access the underlying created gofpdf object
	// prior to processing the markdown source
	Pdf *gofpdf.Fpdf

	// trace/log file - used if not blank
	TracerFile string

	// normal text
	Normal Styler

	// link text
	Link Styler

	// backticked text
	Backtick Styler

	// blockquote text
	Blockquote  Styler
	IndentValue float64

	// Headings
	H1 Styler
	H2 Styler
	H3 Styler
	H4 Styler
	H5 Styler
	H6 Styler

	// Table styling
	THeader Styler
	TBody   Styler
	// contains filtered or unexported fields
}

PdfRenderer is the struct to manage conversion of a markdown object to PDF format.

func NewPdfRenderer

func NewPdfRenderer(orientation, paperSize, fontDir string) *PdfRenderer

NewPdfRenderer creates and configures an PdfRenderer object, which satisfies the BlackFriday Renderer interface.

Any the parameters may be blank, with the defaults being "portrait", "A4", "."

It is not safe to use instances in more than one goroutine.

func (*PdfRenderer) Output

func (r *PdfRenderer) Output(w io.Writer) error

Output renders PDF content to a writer.

func (*PdfRenderer) Process

func (r *PdfRenderer) Process(markdown []byte) *PdfRenderer

Process sets the markdown source and must be called prior to ToFile or Output.

func (*PdfRenderer) RenderFooter

func (r *PdfRenderer) RenderFooter(w io.Writer, ast *bf.Node)

RenderFooter is not supported.

func (*PdfRenderer) RenderHeader

func (r *PdfRenderer) RenderHeader(w io.Writer, ast *bf.Node)

RenderHeader is not supported.

func (*PdfRenderer) RenderNode

func (r *PdfRenderer) RenderNode(w io.Writer, node *bf.Node, entering bool) bf.WalkStatus

RenderNode is a default renderer of a single node of a syntax tree. For block nodes it will be called twice: first time with entering=true, second time with entering=false, so that it could know when it's working on an open tag and when on close. It writes the result to w.

The return value is a way to tell the calling walker to adjust its walk pattern: e.g. it can terminate the traversal by returning Terminate. Or it can ask the walker to skip a subtree of this node by returning SkipChildren. The typical behavior is to return GoToNext, which asks for the usual traversal to the next node. (above taken verbatim from the blackfriday v2 package)

func (*PdfRenderer) ToFile

func (r *PdfRenderer) ToFile(pdfFile string) error

ToFile renders to a PDF file.

type Styler

type Styler struct {
	Font      string
	Style     string
	Size      float64
	Spacing   float64
	TextColor Color
	FillColor Color
}

Styler is the struct to capture the styling features for text Size and Spacing are specified in points. The sum of Size and Spacing is used as line height value in the gofpdf API