shared_ptrをvectorに入れる時の初期化方法

sharedvector.cpp

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <vector>
#include <memory>

class Color {
public:
    int r, g, b, a;

public:
    Color() : r(0), g(0), b(0), a(255) {}
    Color(int r, int g, int b, int a = 255) : r(r), g(g), b(b), a(a) {}
};

int main(int argc, char* argv[]) {
    std::vector<std::shared_ptr<Color>> colors(256);
    //colors.resize(256, std::make_shared<Color>());
    std::generate(
            colors.begin(),
            colors.end(),
            []() -> std::shared_ptr<Color> {
                return std::make_shared<Color>();
            }
        );

    for (auto it = colors.begin(); it != colors.end(); it++) {
        std::shared_ptr<Color> c = *it;
        if (c) {
            std::printf("[%d, %d, %d, %d] %d\n", c->r, c->g, c->b, c->a, c.use_count());
        } else {
            std::printf("Invalid!\n");
        }
    }

    return 0;
}