Monday, October 26, 2020

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## #1 2020-10-17 01:44:24 pm

Joy
Member
From:: South Tirol
Registered: 2008-07-04
Posts: 649
Website

### Calculate ratio of screen boundaries

I'd need to calculate the screen ratio of my screen

Basically I could write a handler calculating the greatest common factor, but since I'm not into math my routine would be longer, slower and I'd take some time to complete it.

Maybe somebody wrote a similar script already.

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## #2 2020-10-17 02:05:59 pm

robertfern
Member
Registered: 2011-11-29
Posts: 76

### Re: Calculate ratio of screen boundaries

Here it is

#### Applescript:

screenRatio(3840, 2160)

on screenRatio(h as integer, w as integer)
local c
set c to GCD(h, w)
display alert "Screen Ratio is " & (h div c) & " by " & (w div c)
return {h div c, w div c}
end screenRatio

on GCD(x as integer, y as integer)
local r
repeat while y ≠ 0
set r to x mod y
set x to y
set y to r
end repeat
return x as integer
end GCD

Last edited by robertfern (2020-10-17 02:08:55 pm)

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## #3 2020-10-18 09:17:10 am

peavine
Member
From:: Prescott, Arizona
Registered: 2018-09-04
Posts: 644

### Re: Calculate ratio of screen boundaries

My math skills are pretty basic but I was interested by robertfern's solution, which works great. Out of curiosity I did a search on gcd and found the Wikipedia article on greatest common divisor. If I understand correctly, robertfern's script uses Euclid's algorithm.

Just as a project to work on, I decided to try and write a solution using brute-force AppleScript. It's only marginally slower than robertfern's script, although my script requires 4011 calculations and comparisons to achieve what robertfern's script accomplishes with only 4 calculations.

#### Applescript:

set screenRatio to getRatio(3840, 2160)

on getRatio(x, y)
set xDivisors to getDivisors(x)
set yDivisors to getDivisors(y)
repeat with aGCD in xDivisors
if aGCD is in yDivisors then exit repeat
end repeat
return {x div aGCD, y div aGCD}
end getRatio

on getDivisors(theNumber)
set theDivisors to {}
repeat with i from theNumber to 1 by -1
if theNumber mod i = 0 then set end of theDivisors to i
end repeat
return theDivisors
end getDivisors

BTW, the calculations employed in robertferns script with Euclid's algorithm are:

3840 div 2160 = 1 with a remainder of 1680
2160 div 1680 = 1 with a remainder of 480
1680 div 480 = 3 with a remainder of 240
480 div 240 = 2 with a remainder of 0

Thus the GCD is 240 and the screen ratio is:

3840 div 240 = 16
2160 div 240 = 9

Also, just as a point of information which has no impact on the script's accuracy, the variables h and w in robertfern's script appear to be reversed (assuming a normally-sized computer screen).

Last edited by peavine (2020-10-21 09:21:38 am)

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