CODEWITHSUNDEEP
c++aspect-ratio
Tom Tetlaw
Tom Tetlaw

Reputation: 113

Compare aspect ratios given width and height

Given a list of screen sizes, how do I detect which ones are in 4:3 16:9 aspect ratio? I can use width / height to get it but for 16:9 sizes I sometimes get 1.778 and sometimes I get 1.777778 due to rounding errors.

Upvotes: 1

Views: 3521

Answers (4)

Luis
Luis

Reputation: 12048

You can force the rounding to be always the same, and then you can compare the values:

float ratio = (int)((width / height) * 100);

You will get always 177 for 16:9 and 133 for 4:3

good luck

Upvotes: 3

Marios V
Marios V

Reputation: 1174

you must use an epsilon value for the comparison. You can have a look at: http://www.cygnus-software.com/papers/comparingfloats/comparingfloats.htm

Upvotes: 0

george.zakaryan
george.zakaryan

Reputation: 980

compare with some epsilon proximity.

should be something like:

double epsilon = 0.01;
if(math.abs(screen1.height/screen1.width - screen2.height/screen2.width) < epsilon)
{
//equal ratios
}

Upvotes: 0

Kerrek SB
Kerrek SB

Reputation: 477070

Check if 4 * height == 3 * width or 16 * height == 9 * width.

Remember the definition of a rational number: It is an equivalence class of pairs of integers (m, n) sub­ject to the equivalence (m, n) ≡ (m', n') if and only if n' m = n m'.

Upvotes: 11

Related Questions