clickpick.cpp

#include <SFML/Graphics.hpp>
#include <cstdio>

static void loadXorTextureInto(sf::Image& img)
{
    img.create(256u, 256u);
    for(unsigned x = 0u; x < img.getSize().x; ++x)
        for(unsigned y = 0u; y < img.getSize().y; ++y)
            img.setPixel(x, y, sf::Color(x ^ y, x ^ y, x ^ y));
}

static bool goodimgcoords(sf::Vector2i coords, const sf::Image& img)
{
    if(coords.x < 0 || coords.y < 0)
        return false;

    return coords.x < img.getSize().x && coords.y < img.getSize().y;
}

static sf::Color handleClick(sf::Vector2f coords, const sf::Sprite& spr, const sf::Image& img)
{
    if(!spr.getGlobalBounds().contains(coords))
        return sf::Color::Black;

    const auto itrans = spr.getTransform().getInverse();
    const auto inspritecoords = sf::Vector2i(itrans.transformPoint(coords));
    if(!goodimgcoords(inspritecoords, img))
        return sf::Color::Black;

    return img.getPixel(inspritecoords.x, inspritecoords.y);
}

int main(int argc, char ** argv)
{
    sf::RenderWindow app(sf::VideoMode(800u, 600u), "Clicking");
    sf::Image img;
    loadXorTextureInto(img);
    sf::Texture tex;
    tex.loadFromImage(img);
    sf::Sprite spr(tex);
    spr.setOrigin(sf::Vector2f(311.f, 74.f));
    spr.setPosition(sf::Vector2f(400.f, 400.f));
    spr.setScale(2.f, 1.5f);
    spr.setRotation(54.f);
    sf::Color background = sf::Color(0x7f0000ff);
    while(app.isOpen())
    {
        sf::Event eve;
        while(app.pollEvent(eve))
        {
            if(eve.type == sf::Event::Closed)
                app.close();

            if(eve.type == sf::Event::MouseMoved)
                background = handleClick(app.mapPixelToCoords(sf::Vector2i(eve.mouseMove.x, eve.mouseMove.y)), spr, img);
        }//while app poll event eve

        app.clear(background);
        app.draw(spr);
        app.display();
    }//while app is open
}