How to open a C++ image using SFML?

Question

I am still at the beginning and need to open a C++ image using SFML, at the moment I am using a code that uses the address of the image, but all this via code and what I need is that this address where the image is informed by the user.

Example:

c:\desktop\teste.png

the code I intend to modify and this:

    sf::Image imagem;
if (!imagem.loadFromFile("imagem.png")) {
    cout<<"Erro ao abrir a imagem!"<<endl;
}

Answer 1

I don’t know the SFML in depth, but because it is a library for access to multimedia resources I believe it has no resources to facilitate the request of the file name to the user (or at least it must be very difficult to build it using the class Window).

An alternative is to use a graphical library such as Qt. You could build your own graphical interface for this, but it is quite common (and facilitates the use of users accustomed to the operating system) to utilize the standard file selection window.

With Qt you can do it this way:

#include <QFileDialog>
QString arquivo = QFileDialog::getOpenFileName(this, "Abrir imagem", ".", "Arquivos PNG (*.png);; Todos os arquivos (*.*)"));
if(arquivo.length())
{
    sf::Image imagem;
    if (!imagem.loadFromFile(arquivo.toStdString())) {
        cout<<"Erro ao abrir a imagem!"<<endl;
    }
}

This code will open a file selection window like the one below (example reproduced of that OS thread in English - I didn’t get to execute the code here), where the user can select the existing file or even type the path. By clicking the OK button (the image is in another language, but it doesn’t matter), the window is closed and the method QFileDialog::getOpenFileName returns a string with the path and name of the selected file. Just use it in the `Image::loadFromFile' method of the SFML library, as illustrated above.

Answer 2

The SFML alone offers no way to ask the user to select an image. But, you can use an Image Selection Dialog from a Toolkit such as Qt, wxWidgets or using the API of your program’s own target system.

For Windows (using WIN32 API) you can open a window to select an image using the following function:

#include <Windows.h> // Para a janela de selecionar o arquivo
#include <string>
#include <cstring>

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

sf::Texture LoadTexture(void)
{
    OPENFILENAME ofn;

    ZeroMemory(&ofn, sizeof(ofn));

    ofn.lStructSize = sizeof(ofn);
    ofn.hwndOwner = 0;
    ofn.lpstrDefExt = 0;
    ofn.lpstrFile = new TCHAR[512];
    ofn.lpstrFile[0] = '\0';
    ofn.nMaxFile = 512;
    ofn.lpstrFilter = NULL;
    ofn.nFilterIndex = 0;
    ofn.lpstrInitialDir = NULL;
    ofn.lpstrTitle = L"Selecione uma Imagem";
    ofn.Flags = 0;

    GetOpenFileName(&ofn);

    // Converte para std::string.
    std::wstring wstr = ofn.lpstrFile;
    std::string str(wstr.begin(), wstr.end());

    // Armazenará a imagem.
    sf::Texture texture;

    // Verifica se o arquivo é válido e se foi possível carregar.
    if (!texture.loadFromFile(str))
    {
        MessageBox(NULL, L"Imagem inválida!", L"Erro", MB_OK);
    }

    return texture;
}

Then link to a sf::Sprite:

sf::Texture textura = LoadTexture(); // chama a função anterior.

// Vincula a texture ao sprite.
sf::Sprite sprite;
sprite.setTexture(textura);

And finally, just draw:

window.draw(sprite);