rgb to hex

t11e21.rgbtohex.cpp

// t11e21.rgbtohex.cpp
// juanfc 2023-11-22
// 

#include <iostream>
#include <array>
using namespace std;

typedef array<int,3> TRGB;


void test(TRGB rgb);

int main()
{
    test((TRGB){{255, 255, 255}}); // "FFFFFF"
    test((TRGB){{255, 255, 300}}); // "FFFFFF"
    test((TRGB){{0,0,0}});         // "000000"
    test((TRGB){{148, 0, 211}});   // "9400D3"
    return 0;
}


string rgb2hex(TRGB rgb);

void test(TRGB rgb)
{
    cout << rgb[0] << ", ";
    cout << rgb[1] << ", ";
    cout << rgb[2] << ": ";
    cout << rgb2hex(rgb) << endl;
}


string int2str(int n, int base=10, int width=0);

string rgb2hex(TRGB rgb)
{
    string r;
    for (int i = 0; i < 3; ++i)
        r += int2str((rgb[i] > 255)? 255:rgb[i], 16, 2);
    return r;
}


string int2str(int n, int base, int width)
{
    string r;
    if (n == 0) {
        r += '0';
    } else {
        int sign = (n < 0) ? -1 : 1;
        n *= sign;
        while (n > 0) {
            int remainder = n % base;
            n /= base;
            r += ((remainder < 10) ? '0' : 'A'-10) + remainder;
        }
        if (sign == -1) r += '-';
    }
    for (int i = r.length(); i < width; ++i)
        r += '0';

    // reversing
    int j = r.size() - 1;
    for (int i = 0; i < j; i++, j--) {
        char t = r[i];
        r[i] = r[j];
        r[j] = t;
    }
    return r;
}