Adding attributes to links and images has been requested for a long time on the Markdown discussion list. I was fairly opposed to this, as most of the proposals really disrupted the readability of the syntax. I consider myself a “Markdown purist”, meaning that I took John’s introduction to heart:
The overriding design goal for Markdown’s formatting syntax is to make it as readable as possible. The idea is that a Markdown-formatted document should be publishable as-is, as plain text, without looking like it’s been marked up with tags or formatting instructions. While Markdown’s syntax has been influenced by several existing text-to-HTML filters, the single biggest source of inspiration for Markdown’s syntax is the format of plain text email.
Because there was not a syntax proposal that I felt fit this goal, I was generally opposed to the idea.
Then, Choan C. Gálvez proposed a brilliantly simple syntax that stayed out of the way. By simply appending the attributes to the link reference information, which is already removed from the text itself, it doesn’t disturb the readability.
For example:
This is a formatted ![image][] and a [link][] with attributes.
[image]: http://path.to/image "Image title" width=40px height=400px
[link]: http://path.to/link.html "Some Link" class=external
style="border: solid black 1px;"
This will generate width and height attributes for the image, and a border around the link. And while it can be argued that it does look “like it’s been marked up with tags [and] formatting instructions”, even I can’t argue too strongly against it. The link and the title in quotes already look like some form of markup, and the the additional tags are hardly that intrusive, and they offer a great deal of functionality. They might even be useful in further functions (citations?).
The attributes must continue after the other link/image data, and may contain
newlines, but must start at the beginning of the line. The format is
attribute=value or attribute="multi word value". Currently, MultiMarkdown
does not attempt to interpret or make any use of any of these attributes.
Also, you can’t have a multiword attribute span a newline.
NOTE: As of version 6, MultiMarkdown will also allow attributes in inline links as well:
Colored [link](http://example.net "Title" style="color:red")