Lektor Markdown Extension for Image and Link attributes

This plugin hacks up Lektor’s Markdown renderer to add syntax which allows arbitrary HTML attributes to be set on image and link tags.

Motivation

Markdown, as implemented in Lektor, provides nice shorthand syntax for marking up images. It does not provide any syntax for controlling image styling, e.g., sizing and alignment. This plugin molests Markdowns syntax for image (and link) titles to allow setting arbitrary HTML attributes on image and link tags.

On using raw HTML

It is true that one can simply include raw HTML <img> tags within Markdown text. However, since this bypasses Markdown processing altogether, it also bypasses Lektor’s resolution of image/link URLs. This can be undesirable.

Setting attributes on link and image tags in Markdown text

These hacks allow one to set attributes on image and link tags, by overloading Markdown’s syntax for setting title attributes.

If the title of a Markdown image or link looks like a set of (non-empty) HTML attributes, they are interpreted as such, and stuck onto the produced <a> or <img> tag.

![My cat, Fluffy](fluffy.jpg "class=img-responsive")

will produce

<img src="fluffy.jpg" class=img-responsive>

If you do want to set a title as well, you may surround the extra attributes with angle brackets and append them at the end of the title. Both of these are equivalent:

![My cat, Fluffy](fluffy.jpg "Fluffy at rest <class=img-responsive>")

![My cat, Fluffy](fluffy.jpg "title='Fluffy at rest' class=img-responsive")

If you’d like to set a title, when the title text looks like a set of HTML attributes, simply append an empty set of angle brackets to the title:

![My cat, Fluffy](fluffy.jpg "Fluffy=resting <>")

This works with reference-style links and images as well:

Here’s a photo of [my cat][]:  ![fluffy][]

[fluffy]: fluffy.jpg   (style='width: 80px;')
[my cat]: <http://fluffy.example.org>   'Fluffy’s website <class="external link">'

Testing

We now use hatch for packaging and development.

To run all tests, including under a full matrix of python and lektor versions, as well as combined coverage tests:

hatch run full

The dev environment specifies additional dependencies useful for development. E.g. I start emacs via:

hatch run dev:emacs lektor_markdown_image_attrs.py &

Acknowledgments

Ideas were gleaned from this blog post by Baron Schwartz.

Author

Jeff Dairiki dairiki@dairiki.org