Mouseover Popup Image Viewer

A fork of MPIV (Mouseover Popup Image Viewer).
Developed on https://github.com/tophf/mpiv

Requires a modern browser

Chrome or Chromium-based 55+
FF 52+ for the main features
FF 63+ for the config dialog as it's built with ShadowDOM

Usage

Activate	hover the target
Deactivate	move cursor off target, or click, or zoom out fully
Ignore target	hold `Shift` -> hover the target -> release the key
Freeze popup	hold `Shift` -> leave the target -> release the key
Force-activate (videos or small pics)	hold `Ctrl` -> hover the target -> release the key

Start zooming	configurable (automatic or via right-click) or tap `Shift` while popup is visible
Zoom	mouse wheel

Rotate	`L` `r` for "left" or "right"
Flip/mirror	`h` `v` for "horizontal" or "vertical"
Previous/next (in album)	mouse wheel, `j` `k` or `←` `→` keys

Antialiasing	`a`
Caption in info	`c`
Download	`d`
Fullscreen	`f`
Info	`i`
Mute	`m`
Night mode	`n`
Open in tab	`t`

Configure	userscript manager toolbar icon -> User Script Commands -> `MPIV: configure`

Major changes to the original MPIV:

Most rules were updated/enhanced, some added, some dead hostings removed.
ShadowDOM support added for sites built with Web Components e.g. Polymer.
Ancient browsers aren't supported anymore because the code is using the modern JS syntax.

Config

Click MPIV: Configure in your userscript manager popup menu. Screenshot is shown below.

Minor/technical changes to the original MPIV:

Advanced "e" syntax for sites that show a small overlay when hovering thumbnails (usually transparent or semi-transparent) thus effectively hiding the thumbnails from MPIV. Now you can specify "e": {".parent": ".image"} where .parent selector should match the closest parent element that contains both the overlay and the actual image, which MPIV will find using the .image selector applied relatively to that parent element. To refer to that parent, use :scope like this: {".parent": .":scope > img:first-child"}. To specify multiple parent-image relations: "e": {".parent1": ".image1", ".parent2": ".image2"}.
New rule property "u" (a single string or an array of strings) that performs a very fast plain-string check. Only when it succeeds, the slow regexp "r" is checked. Special symbols may be specified in "u" property to increase the reliability of matching: ||, |, ^ - same syntax as in AdBlock filters, see the source code of the script for usage examples.
- ||foo.bar/path, here || means "domain or subdomain" so the pattern matches domains like foo.bar or subdomain.foo.bar and doesn't match unrelated domains partially like for example foofoo.bar
- |foo matches things that start with foo (the entire URL is checked so that means http at least, usually)
- ^ is a URL part separator (like / or ? or :) but not a letter/number, neither any of %._-. Additionally, when used at the end like foo^ it also matches when the source ends with foo
New rule property "anonymous": true to make the requests for this rule anonymously (i.e. without sending cookies).
The internal status updates are not exposed by default on the <html> node because doing so slows down complex sites due to recalculation of the entire page layout. Instead only the hovered node (as reported by the matching rule) receives status updates on its mpiv-status attribute (it's not the class nor data- attribute to avoid confusing sites with unknown stuff being present in these standard places). If you were using the global status feature to customize CSS of those statuses, you'll need to enable it manually in the MPIV's config dialog.

See the MPIV Wiki for more info on writing rules in general and this comment for gallery rules in particular.