无法在Django Templets中渲染模型的ImageField

Question

的 Models.py

window.onbeforeunload = function() {
    return "You have some unsaved changes";
};

Views.py

class Blog(models.Model):
    title = models.CharField(max_length=100, unique=True)
    slug = models.SlugField(max_length=100, unique=True)
    body = models.TextField()
    content_photo = models.ImageField(upload_to='passive_income/',blank=True)
    posted = models.DateTimeField(db_index=True, auto_now_add=True)
    author = models.CharField(max_length=255, blank=True)
    status = models.BooleanField(default=True)
    category = models.ForeignKey('blog.Category')

view_post.html

def view_post(request, slug):
    return render_to_response('blog/view_post.html', {
        'post': get_object_or_404(Blog, slug=slug)
    })

我的疑问是，当网址打开浏览器时，它不会显示图片。