I want to center align an image in a README.adoc file in GitHub.
I know that for Markdown files, adding HTML like the following works:
<p align="center">
<img width="460" height="300" src="http://www.fillmurray.com/460/300">
</p>
However, I want to write the file in AsciiDoc, not Markdown.
Suppose there is a map.png image in the same dir as the README.
image::map.png[A map, 350, align=center]
This displays the correct image, but aligned to the left.
GitHub is using Asciidoctor but strips away CSS classes and inline CSS styles. As a workaround you can use a passthrough (which is not ideal):
++++
<p align="center">
<img width="460" height="300" src="http://www.fillmurray.com/460/300">
</p>
++++
You can also comment/vote for this issue: https://github.com/github/markup/issues/984
I recommend using a conditional block to use this passthrough only when the README is rendered on GitHub:
ifdef::env-github[]
++++
<p align="center">
<img width="460" height="300" src="http://www.fillmurray.com/460/300">
</p>
++++
endif::[]
ifndef::env-github[]
image::map.png[A map, 350, align=center]
endif::[]
align="center"is ignored (doesn't exist) in the HTML code rendered by GitHub. This is probably a GitHub bug. Nothing todo with center. In your image attributes above. I wonder if you missed a numerical info for width and height. Should it be[A map, 350, 350, align="center"]asciidoctorCLI. Omitting the height attribute sizes the image to the desired width and preserves the aspect ratio in GitHub