8.17 Images

A link immediately preceded by a ! will be treated as an image. The link text will be used as the image’s alt text:

![la lune](lalune.jpg "Voyage to the moon")

![movie reel]

[movie reel]: movie.gif

8.17.1 Extension: implicit_figures

An image with nonempty alt text, occurring by itself in a paragraph, will be rendered as a figure with a caption. The image’s alt text will be used as the caption.

![This is the caption](/url/of/image.png)

How this is rendered depends on the output format. Some output formats (e.g. RTF) do not yet support figures. In those formats, you’ll just get an image in a paragraph by itself, with no caption.

If you just want a regular inline image, just make sure it is not the only thing in the paragraph. One way to do this is to insert a nonbreaking space after the image:

![This image won't be a figure](/url/of/image.png)\

Note that in reveal.js slide shows, an image in a paragraph by itself that has the r-stretch class will fill the screen, and the caption and figure tags will be omitted.

8.17.2 Extension: link_attributes

Attributes can be set on links and images:

An inline ![image](foo.jpg){#id .class width=30 height=20px}
and a reference ![image][ref] with attributes.

[ref]: foo.jpg "optional title" {#id .class key=val key2="val 2"}

(This syntax is compatible with PHP Markdown Extra when only #id and .class are used.)

For HTML and EPUB, all known HTML5 attributes except width and height (but including srcset and sizes) are passed through as is. Unknown attributes are passed through as custom attributes, with data- prepended. The other writers ignore attributes that are not specifically supported by their output format.

The width and height attributes on images are treated specially. When used without a unit, the unit is assumed to be pixels. However, any of the following unit identifiers can be used: px, cm, mm, in, inch and %. There must not be any spaces between the number and the unit. For example:

![](file.jpg){ width=50% }

• Dimensions may be converted to a form that is compatible with the output format (for example, dimensions given in pixels will be converted to inches when converting HTML to LaTeX). Conversion between pixels and physical measurements is affected by the --dpi option (by default, 96 dpi is assumed, unless the image itself contains dpi information).
• The % unit is generally relative to some available space. For example the above example will render to the following.
  • HTML: <img href="file.jpg" style="width: 50%;" />
  • LaTeX: \includegraphics[width=0.5\textwidth,height=\textheight]{file.jpg} (If you’re using a custom template, you need to configure graphicx as in the default template.)
  • ConTeXt: \externalfigure[file.jpg][width=0.5\textwidth]
• Some output formats have a notion of a class (ConTeXt) or a unique identifier (LaTeX \caption), or both (HTML).
• When no width or height attributes are specified, the fallback is to look at the image resolution and the dpi metadata embedded in the image file.