High density screen (retina) support

I think that it would be helpful to support high density images perhaps in the wagtail images tag so an image can appear crisp on HDPI devices such as phones and newer computers.

For example: {% image profile_image fill-200x200-c90-hdpi %}

[davecranwell]

I created a responsive image tag for another project, the code for which is here (I’ve quickly copied this from another codebase and stripped out the stuff which is private, therefore this gist is untested, be warned): https://gist.github.com/davecranwell/baf42b089d71b94fd229. It’s basically a clone of wagtail’s own {% image %} tag but with responsive features.

It’s intended for use with picturefill (http://scottjehl.github.io/picturefill/) so supports 2x images through the srcset attribute. It doesn’t currently support picture.

One significant problem with this tag is that it immediately generates all the various image sizes you define in your srcset, the instant the tag is run during template compilation. I believe this is problematic for sites hosting their images off-server e.g S3, where images renditions need to be rendered offline.

You may find this tag is suitable for your needs though.

[gasman]

Covered by #285 and #3573