Function

GLuint MatVGLTexture::loadTextureFromImage(std::string file)
{
    // The enumeration for GL errors.
    GLenum error = GL_NO_ERROR;

    // Check the very last part of the file name for the extension.
    std::size_t extension = file.find_last_of(".");
    std::string extensionStr = file.substr(extension + 1);

    // Now if the file is a BMP.
    if (extensionStr == "BMP" || extensionStr == "bmp")
        this->m_surface = SDL_LoadBMP(file.c_str()); // Use this function.
    else
        this->m_surface = IMG_Load(file.c_str()); // Else, use SDL_Image.

    this->m_assertion.assert(false, this->m_surface != nullptr, IMG_GetError());

    // Create an OpenGL texture.
    glGenTextures(1, &this->m_textureID);
    error = glGetError();
    this->m_assertion.assert(false, error == GL_NO_ERROR,
                             gluErrorString(error));

    // Now bind the texture.
    glBindTexture(GL_TEXTURE_2D, this->m_textureID);
    error = glGetError();
    this->m_assertion.assert(false, error == GL_NO_ERROR,
                             gluErrorString(error));

    // Give the image to OpenGL so that it can be used.
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB,
                 this->m_surface->w, this->m_surface->h,
                 0, GL_RGB, GL_UNSIGNED_BYTE,
                 this->m_surface->pixels);
    error = glGetError();
    this->m_assertion.assert(false, error == GL_NO_ERROR,
                             gluErrorString(error));

    // Now we can free the SDL2 surface.
    SDL_FreeSurface(this->m_surface);
    this->m_surface = nullptr;

    // Good filtering.
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    error = glGetError();
    this->m_assertion.assert(false, error == GL_NO_ERROR,
                             gluErrorString(error));

    // Get the texture ID.
    return this->m_textureID;
}