Function: flip_image

--Usage--
> flip_image(input: image, horizontal: true)

Flip an image horizontally or vertically.

--Parameters--
! Parameter	Type			Description
| @input@	[[type:image]]		Image to flip.
| @horizontal@	[[type:boolean]]		Flip horizontally or vertically?

--Examples--
> flip_image("image_logo.png")  ==  [[Image]]
>>> flip_image(<img src="image_logo.png" alt='"image_logo.png"' style="border:1px solid black;vertical-align:middle;margin:1px;" />) == <img src="image_logo_vflip.png" alt='"image_logo_vflip.png"' style="border:1px solid black;vertical-align:middle;margin:1px;" />

--See also--
| [[fun:rotate]]		Rotate an image