REBOL [
	title: "Calculate Image Aspect Ratio"
	date: 13-Mar-2008
	author: ["James Irwin" "The Untitled One"]
	email: rebolyte--gmail--com
	license: ['MIT http://www.opensource.org/licenses/mit-license.php]
]

calc-ratio: calculate-image-aspect-ratio: func [
	"Calculate a new aspect ratio from given dimensions."
	image-size [pair!] "Size of original image."
	desired [integer!] "New desired width."
	/height "Instead of width, specify new desired height."
][
	orig-width: first image-size
	orig-height: second image-size
	either height [
		; Use height variable
		x: orig-width * desired
		desired-opposite: round/half-ceiling x / orig-height
		res: to pair! rejoin [desired-opposite "x" desired]
	][
		; Use width variable
		x: orig-height * desired
		desired-opposite: round/half-ceiling x / orig-width
		res: to pair! rejoin [desired "x" desired-opposite]
	]
]

print {Enter something like "calc-ratio 1024x786 800".}
print {Enter "help calc-ratio" to see more on how to use this function.}
halt