The Mozilla Developer Network (MDN) is the best place to look this stuff up.
HTMLImageElement (which inherits from Element)
Image doesn't actually do much - you'll probably want to manipulate it via the canvas methods:
HTMLCanvasElement and CanvasRenderingContext2D
Construct 2 uses the canvas method to generate new images for auto-mirror/auto-flip. Beware of browser security limitations though: no image manipulation methods work on the file:// protocol for security reasons, so anything you do will only work in HTTP mode.