void Image::invertcolors(){
    int width = this->width();
    int height = this->height();
    for (int y = 0; y < height; y++){
        for (int x = 0; x < width; x++){
            (*this)(x,y)->red = 255-(*this)(x,y)->red;
            (*this)(x,y)->green = 255-(*this)(x,y)->green;
            (*this)(x,y)->blue = 255-(*this)(x,y)->blue;
        }
    }
}