Minimap / Navigator panel for quick pan navigation on zoomed images

Windows OS version

Windows 11 25H2

ImageGlass version

10.0.3.720-rc-win-x64

ImageGlass release

Classic

1️⃣ Describe the feature

Add a minimap / navigator panel (distinct from the magnification window in #537) that shows a thumbnail of the entire image with a visible rectangle indicating the currently viewed viewport area.

When the image is zoomed in (e.g., 200%, 400%), the minimap makes it easy to see where you are within the overall image.

Users can click and drag the viewport rectangle on the minimap to instantly pan the main view to that location.

The minimap should be:

1. Dockable / floating (e.g., bottom-right corner overlay or side panel).
2. Toggleable via a shortcut or toolbar button.
3. Auto-hidden or semi-transparent when not interacting, to avoid obstructing the image.

This is fundamentally a navigation aid, not a magnifier. Different from https://github.com/d2phap/ImageGlass/issues/537

2️⃣ How to use feature

1. Open a large-resolution image in ImageGlass.
2. Zoom in (e.g., 300% or higher) so only a portion of the image is visible.
3. Open the minimap via toolbar button or shortcut (e.g., N). Even better, enable auto-open in settings so it pops up automatically as soon as you zoom in.
4. A small thumbnail of the full image appears, with a highlighted rectangle showing your current viewport.
5. Click and drag the rectangle on the minimap to jump to a different region of the image instantly.
6. The minimap updates in real-time as you pan or zoom in the main view.
7. Press the shortcut again or click the close button to hide the minimap.

3️⃣ Additional context

A good reference implementation is QuickView — a fast, Direct2D-powered image viewer for Windows. It includes a minimap/navigation panel that lets you drag the viewport to quickly jump around large zoomed images.

I hope it's okay to reference another project here — no disrespect to ImageGlass intended; I only want to provide a concrete example of the feature I'm describing. QuickView works well, but since it is Windows-only, I would love to see a similar cross-platform minimap feature in ImageGlass.

The issue names no implementation files or tests. Start by comparing ImageGlass's existing zoom and pan behavior with the QuickView reference and the distinction from #537; done means a cross-platform minimap can show the viewport, support dragging to pan, update during navigation, and be toggled or auto-hidden.