white noise image generator

#include <random>
#include <SFML/Graphics.hpp>
#include "globals.h"

using namespace typ;

const u32 VIDW = 800, VIDH = 600;

std::random_device rd;
std::mt19937 gen;
std::uniform_int_distribution<> distrib(0, 255);

sf::Image *img_generate(u32 w, u32 h, u32 selection=0, u32 variation=0)
{
    u32 setalpha=0;
    u8 pixels[(w*h*4)];
    switch(selection)
    {
    case 0: //randomized data, colorized white noise
        for (int i=0;i<w*h*4;i++)
        {
            if(setalpha == 3)
            {
                pixels[i] = 0xff;
                setalpha = 0;
            }
            else
            {
                pixels[i] = distrib(gen);
                setalpha++;
            }
        }
        return new sf::Image(sf::Vector2u(w,h),pixels);
        break;
    case 1: //variation 0 for red, 1 for green, 2 for blue

        for (int i=0;i<w*h*4;i++)
        {
            if(setalpha == 3)
            {
                pixels[i] = 0xff;
                setalpha = 0;
            }
            else
            {
                if(setalpha == variation) pixels[i] = 255;
                else pixels[i] = 0;
                setalpha++;
            }
        }
        return new sf::Image(sf::Vector2u(w,h),pixels);
        break;
    }
    return 0;
}



int main()
{
    std::mt19937 gen(rd());

    sf::RenderWindow window(sf::VideoMode({VIDW, VIDH}), "SFML C++ demo!");
    sf::CircleShape shape(100.f);
    shape.setFillColor(sf::Color::Green);

    sf::Font font("anonymous_pro.ttf");
    sf::Text text(font);
    text.setString("truetype font render");
    text.setCharacterSize(48);
    text.setFillColor(sf::Color::Black);
    text.setPosition(sf::Vector2f(64,64));

    sf::Image img = *img_generate(800,600,0);
    //img.saveToFile("rainbow-snow.png");

    sf::Texture tex(img);
    sf::Sprite spr(tex);
    const auto onClose = [&window](const sf::Event::Closed&)
    {
        window.close();
    };

    const auto onKeyPressed = [&window](const sf::Event::KeyPressed& keyPressed)
    {
        if (keyPressed.scancode == sf::Keyboard::Scancode::Escape)
            window.close();
    };

    while (window.isOpen())
    {
        window.handleEvents(onClose, onKeyPressed);
        while (const std::optional event = window.pollEvent())
        {
            if (event->is<sf::Event::Closed>())
                window.close();
        }

        window.clear(sf::Color::Black);
        window.draw(spr);
        window.draw(text);
        window.display();
    }
}