To provide context i have a Slack bot that allows users to create ads, i am able to use a dialog to fetch the listing title, description and price. What am looking for is a way to allow users to also add images. 

The [file.upload](https://api.slack.com/methods/files.upload) seems to allow the bot to upload files but what i want is lo be able to allow users to select the files locally and upload them, the bot will then be able to capture this and respond accordingly. 

This is what i have so far

```
@app.route('/new', methods=['POST'])
def new_listing():

    # Get payload
    api_url = 'https://slack.com/api/dialog.open'

    trigger_id = request.form.get('trigger_id')

    dialog = {
        "callback_id": "marketplace",
        "title": "Create a new listing",
        "submit_label": "Create",
        "notify_on_cancel": True,
        "state": "Item",
        "elements": [
            {
                "type": "text",
                "label": "Listing Title",
                "name": "listing_title"
            },
            {
                "type": "text",
                "label": "Listing description",
                "name": "listing_description"
            },
            {
                "type": "text",
                "label": "Listing Price",
                "name": "listing_price"
            }
        ]
    }

    api_data = {
        "token": oauth_token,
        "trigger_id": trigger_id,
        "dialog": json.dumps(dialog)
    }

    res = requests.post(api_url, data=api_data)
    print(res.content)

    return make_response()

@app.route('/message_actions', methods=['POST'])
def message_actions():
    user_id = request.form['user']['id']

    submission = request.form['submission']
    title = submission['listing_title']
    description = submission['listing_description']
    price = submission['listing_price']

    # Add the listing to the database

    return make_response()

```