Python 在烧瓶中过帐图像未保存到数据库

我正在尝试在我的flask项目中创建一个新页面，我可以使用它在主页上发布一篇带有标题和图像的新闻文章。我已经成功地发布了标题和内容，但图像没有保存

路线：

@app.route("/news", methods=['GET', 'POST'])
@login_required
def home_news():    
    form = AddNewsForm()      
    if form.validate_on_submit():        
        picture_file = form.picture.data
        news = News(image_file=picture_file, title=form.title.data, content=form.content.data, author=current_user)
        db.session.add(news)
        db.session.commit()
        flash('News has been added!', 'success')
        return redirect(url_for('home')) 
   
    return render_template('home_news.html', form=form)

表格：

型号：

class News(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    image_file = db.Column(db.String(20), nullable=False, default='default.jpg')
    title = db.Column(db.String(100), nullable=False)
    date_posted = db.Column(db.DateTime, nullable=False, default=datetime.utcnow )   
    content = db.Column(db.Text, nullable=False)       
    user_id = db.Column(db.Integer, db.ForeignKey('user.id'), nullable=False)

    def __repr__(self):
        return f"Post('{ self.image_file}', { self.title}', '{ self.content}', '{ self.date_posted}')"

模板：

{% block content %}
   <div class="new-list">
    <h1>Latest news</h1>
  {% for new in news.items %}
    <article class="media content-section">
     
      <div class="media-body">
        <div class="article-metadata">
          {{ new.author.username }}         
        </div>
        <h2>{{ new.title }}</h2>
        <img class="rounded-circle account-img" src="{{ new.image_file }}">
        <p class="article-content">{{ new.content }}</p>
      </div>
    </article>
  {% endfor %}  
</div>
  {% endblock content %}

{%block content%}
最新消息
{news.items%中的新项目为%s}
{{new.author.username}
{{new.title}}
{{new.content}
{%endfor%}
{%endblock内容%}

如果我不添加一张默认图片，我想让它发布一张默认图片，这样只有帐户用户“admin”可以发布到它，但是我一直坚持只获取它来保存图片，其余的我都不知道

{% block content %}
   <div class="new-list">
    <h1>Latest news</h1>
  {% for new in news.items %}
    <article class="media content-section">
     
      <div class="media-body">
        <div class="article-metadata">
          {{ new.author.username }}         
        </div>
        <h2>{{ new.title }}</h2>
        <img class="rounded-circle account-img" src="{{ new.image_file }}">
        <p class="article-content">{{ new.content }}</p>
      </div>
    </article>
  {% endfor %}  
</div>
  {% endblock content %}