How to calculate the aspect ration from a floating point number

I am given a floating number such as 1.77720212936401 and I want to be able to calculate roughly what the aspect ratio is as a width:height string with width and height being small natural numbers.

JD

///

I have come up with this, currently testing to see if it covers all areas:

    static public string Ratio(float f)
    {
        bool carryon = true;
        int index = 0;
        double roundedUpValue = 0;
        while (carryon)
        {
 开发者_JAVA技巧           index++;
            float upper = index*f;

            roundedUpValue = Math.Ceiling(upper);

            if (roundedUpValue - upper <= (double) 0.1)
            {
                carryon = false;
            }
        }

        return roundedUpValue + ":" + index;
    }

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Try multiplying it by small integers in a loop and check if the result is close to an integer.

double ar = 1.7777773452;
for (int n = 1; n < 20; ++n) {
    int m = (int)(ar * n + 0.5); // Mathematical rounding
    if (fabs(ar - (double)m/n) < 0.01) { /* The ratio is m:n */ }
}

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Check out wikipedia, use pre-defined values and estimate the nearest ratio.

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Perhaps it is 1.777:1 but it is very difficult to be definitive when you tell us so little.

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In most cases the actual input is not a floating point number, but you have width, height and you get the floating point number by dividing them.

In such a case, the problem can be reduced to finding the greatest common divisor:

private static int greatestCommonDivisor(int a, int b) {
    return (b == 0) ? a : greatestCommonDivisor(b, a % b);
}

private static String aspectRatio(int width, int height) {
    int gcd = greatestCommonDivisor(width, height);

    if (width > height) {
        return String.Format("{0} / {1}", width / gcd, height / gcd);
    } else {
        return String.Format("{0} / {1}", height / gcd, width / gcd);
    }
}