image popup: zoom, pan, scroll, pin, scale
目前为
// 1. to use hover over the image(container) to view a popup of the target image
// 2. to zoom in/out use wheel up/down. to reset press the scroll button
// 3. click left mouse to lock popup this will make it move along with the mouse, click again to release (indicated by green border)
// 4. while being locked"Y" the wheel up/down will act as scroll up/down
// 5. double click will lock it on screen preventing it from being hidden
// 6. hover below the image and click blue bar this will make a 3rd mode for wheel bottom, which will scroll next/previous image under an album
// 7. while locked at screen (indicated by red outline) a single click with the blurred background will unblur it, only one popup per time, so the locked popup will prevent other popup to spawn
// 8. double clicking on blurred background will de-spawn popup
// 9. click on top right corner to scale image
// 10. to turn on/off hover at the bottom of the page
