How To Use Python Flask To Display Images From Postgres

Python Flask is the perfect tool to quickly and easily create web apps and display data from Postgres. It is a lightweight web framework that is fast, reliable, and easy to use. With Flask, you can build web applications that interact with Postgres and display images in the browser.

To use Python Flask and Postgres to display images, you will need to first create a database in Postgres and store the images in it. Then, you will need to create a Flask application that connects to the Postgres database and retrieves the images. Finally, you will need to create a route in the Flask application that displays the images.

Table of Contents

1. How to create a database in Postgres?

To create a database in Postgres, you will need to open the Postgres command line interface and type in the command “CREATE DATABASE <database_name>;“.
This will create a new database with the specified name. You can then use the command “\c <database_name>” to connect to the newly created database.

2. How to store images in Postgres?

To store images in Postgres, you will need to create a table in the database that stores the image data.

The table should have columns for the image name, type, size, and data. Below is the create table commands.
```
"CREATE TABLE <table_name> (name VARCHAR(255), type VARCHAR(255), size INTEGER, data BYTEA);".
```

You can then use the Postgres command line interface to insert the image data into the table like below.

INSERT INTO <table_name> (name, type, size, data) VALUES ('<image_name>', '<image_type>', <image_size>, '<image_data>');".

3. How to create a Flask application.

Creating a Flask application is actually quite simple.
First, start by importing the Flask module.

Then create a Flask instance using the Flask() method.
Add a route for the home page using the @app.route(‘/’) decorator.
After that, define a function for the home page using the def keyword.

Finally, add a main block that runs the Flask application using the app.run() method.

Below is the example source code.

from flask import Flask

app = Flask(__name__)

@app.route('/')
def hello_world():
   return 'Hello World'

if __name__ == '__main__':
   app.run()

4. How to connect to the Postgres database and retrieve images in Flask.

In order to connect to a Postgres database and retrieve images in Flask, you will need to first install the relevant packages.

You can use `pip install psycopg2` to install the Postgres database adapter for Python.
Once the packages have been installed, you need to set up the database connection. This can be done by creating a database connection with the method `connect()`.
Next, you need to create a cursor object to execute the database queries. This is done using the `cursor()` method. The cursor object will be used to execute queries and fetch the result sets.
To retrieve an image from the database, you can use the `execute()` method and pass it an SQL query that retrieves an image.
The image can then be fetched using the `fetchone()` method and stored in a variable.

5. How to connect to Postgres in Flask using psycopg2.

Connecting to PostgreSQL in Flask using Psycopg2 is relatively straightforward.
To get started, you’ll need to install the Python packages for Flask, PostgreSQL, and Psycopg2. You can do this using the pip package manager with the following commands:
```
pip install flask
pip install psycopg2
pip install psycopg2-binary
```
Once the packages are installed, you can create your Flask application. At the top of the file, you’ll need to import the packages you just installed:
```
import flask
import psycopg2
```

Next, you’ll need to create your PostgreSQL connection by providing the connection details. You’ll need to specify the connection string, username, and password:
```
conn = psycopg2.connect(host="hostname",database="dbname", user="username", password="password")
```
Finally, you can create an instance of the cursor to execute queries against the database:
```
cur = conn.cursor()
```

You can use the cursor from the Psycopg2 package to execute queries against the database.

6. How to retrieve an image from Postgres using psycopg2.

Retrieving images from a Postgres database using psycopg2 is a relatively straightforward procedure.
You need to install the psycopg2 library and connect to the database, then you can execute your Postgres SQL query to retrieve the image data.

Once you have the image data, you can use the Python Imaging Library (PIL) to get the image into a usable format. Below is the example source code.

# Import necessary libraries
import psycopg2
from PIL import Image

# Connect to the Postgres database
conn = psycopg2.connect(host="host", user="user", password="password", dbname="database")

# Execute the SQL query to retrieve the image data
cur = conn.cursor()
cur.execute('SELECT image_data FROM images WHERE image_id = ?', [image_id])
image_data = cur.fetchone()[0]

# Use PIL to get the image into a usable format
image = Image.open(image_data)

7. How to display images from Postgres in flask HTML.

To render an image from Postgres in Flask HTML, you need to first create a database connection.
Then, create an endpoint to serve the image and set the response headers.

Use the send_file method to render the image from Postgres. The code should look something like this:

@app.route('/image_from_postgres')
def render_image():
    # create a database connection
    db = psycopg2.connect(
        database=dbname,
        user=user,
        password=password,
        host=host,
        port=port
    )
    # create a cursor
    cur = db.cursor()
    # execute the SQL query
    cur.execute("SELECT img FROM table_name WHERE id=1")
    # retrieve the image
    img = cur.fetchone()[0]
    # set the response headers
    response = make_response(img)
    response.headers.set('Content-Type', 'image/png')
    response.headers.set('Content-Disposition', 'attachment', filename='image_name.png')
    # return the response
    return response