encoder.cpp

#include <SFML/Graphics.hpp>
#include <string>
#include <fstream>
#include <sstream>
#include <iostream>
#include <array>

static const std::string base64_chars =
"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"0123456789+/";

std::string base64_encode(const std::string& data)
{
	std::string ret;
	std::array<unsigned char, 3> char_array;

	for (auto begin = data.begin(), end = data.end(), it = begin; it != end; ++it)
	{
		auto index = it - begin;

		// Read a group of three bytes (avoid buffer overrun by replacing with 0)
		char_array[index % char_array.size()] = *it;

		if (index % char_array.size() != char_array.size() - 1) continue;

		// Transform into four base 64 characters
		ret += base64_chars[(char_array[0] & 0xfc) >> 2];
		ret += base64_chars[((char_array[0] & 0x03) << 4) + ((char_array[1] & 0xf0) >> 4)];
		ret += base64_chars[((char_array[1] & 0x0f) << 2) + ((char_array[2] & 0xc0) >> 6)];
		ret += base64_chars[((char_array[2] & 0x3f) << 0)];
	}

	return ret;
}

std::string stringFromFile(const std::string& file)
{
	std::ifstream fin;
	fin.open(file, std::ios::binary);
	std::ostringstream out;
	out << fin.rdbuf();
	fin.close();
	return out.str();
}

int main()
{
	std::string encoded = base64_encode(stringFromFile("sfml-logo-small.png"));
	std::ofstream file;
	file.open("sfml-logo-small.pin");
	file << encoded;
}