Flask to return image stored in database

My images are stored in a MongoDB, and I'd like to return them to the client, here is how the code is like:

@app.route("/images/<int:pid>.jpg")
def getImage(pid):
    # get image binary from MongoDB, which is bson.Binary type
    return image_binary

However, it seems that I can't return binary directly in Flask? My idea so far:

1. Return the base64 of the image binary. The problem is that IE<8 doesn't support this.
2. Create a temporary file then return it with send_file.

Are there better solutions?