Double-click Image Downloader per Marnes

This addon won't be maintained further. I'm shelving this project due to lack of interest/utility and too much burden. The addon will remain available for download as long as the store allows, and the source on gitlab will also remain available to fork.
I do have a greasyfork account and may publish works there in the future. I have mild intentions to reimplement the core functionality of CSL, IBCP, and DID as public userscripts.

Available for Chrome too.

Downloading images

• (double)(right)click on images
• hover over them and click the button that appears
• drag and drop an image onto the hover button
• select page content (or point at an image) and use the context menu

Extras

• trigger a notification on successful downloads
• rename downloaded images using patterns and variables for better mass organization*
• use filters to limit functionality if it gets in the way
• visually customize the hover button
• "image downloaded" effect for visual feedback can be disabled

*uncertain support in Firefox: addon will automatically disable feature until supported

FAQ

• How does it work on thumbnail galleries?
  This addon downloads the image you directly interact with, i.e. the thumbnail. This is an unfortunately but deliberately omitted feature. Most browsers download link targets when alt-clicking on links, and most thumbnail galleries link each thumbnail to its full size source. Therefore, you do not actually need an addon to download most thumbnail galliers. For more complex galleries, addons dedicated to this purpose exist. You could also install Copy Selected Links and use a download manager.

The Options screen will automatically open after add-on updates if they force a change to any of your settings.

Please rate/review/donate! :)
A lot of time and work goes into creating my addons, and making changes or troubleshooting issues for users. This particular addon has cost hundreds of hours by now. Any donations are greatly appreciated.

Cross-browser
Please note that not all features work the same (or at all) as WebExtension support in browsers is not perfect yet.

Problem, bug, broken, question, request?
Please use the linked support site or email for all non-review communication. AMO policy protects both users and developers by demanding certain quality standards from addons as well as reviews. Severely disfunctional addons are not published. Reviews and ratings must consider the entire addon, set reasonable expectations, and be timeless: a bad rating focusing solely on a systemic bug or on a problem not suffered by other users will stay long after the issue is resolved. AMO also gives extremely limited communication abilities, so contacting me properly will get your issue resolved much better and faster.