load.cpp

GLuint load_texture(std::istream& in) {
    std::string str;
    in >> str;
    if (str != "P3") throw std::runtime_error("Input file must be plain PPM.\n");

    int width, height;
    in >> width >> height;
    if (width == 0 || height == 0) throw std::runtime_error("Input file empty or invalid.\n");

    int pixel_depth;
    in >> pixel_depth;
    if (pixel_depth != 255) throw std::runtime_error("Input file must be plain PPM.\n");
    std::cout << width << " " << height << "\n";

    std::vector<GLubyte> data;
    data.reserve(width * height * 3);
    for (int i = 0; i < (width * height * 3); ++i) {
        int pixel = 0;
        in >> pixel;
        data.push_back(pixel);
    }

    GLuint tex;
    glGenTextures(1, &tex);
    glBindTexture(GL_TEXTURE_2D, tex);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, &data[0]);

    return tex;
}