DPI calculator

dpicalc.cc

#include <cstdio>
#include <cmath>
#include <vector>

int main()
{
    const auto sizes = {12.1, 13.3, 14.0};
    const auto res_x = {1440.0, 1680.0, 1920.0, 2048.0, 2560.0, 2880.0, 3840.0};
    const double aspect = 10.0/16.0;
    const double x_multiple = 1.0/(1.0 + aspect*aspect);

    std::printf("inches\tresolution\tppi\n");
    for (double size : sizes) {
        double x_size = std::sqrt(size*size*x_multiple);
        for (double res : res_x) {
            double ppi = res / x_size;
            std::printf("%0.1f\t%0.0fx%0.0f\t%0.1f\n",
                        size, res, res*aspect, ppi);
        }
    }

    return 0;
}