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Quickstart: Generate a thumbnail using the Computer Vision REST API and Python

In this quickstart, you'll generate a thumbnail from an image using the Computer Vision REST API. With the Get Thumbnail method, you can specify the desired height and width, and Computer Vision uses smart cropping to intelligently identify the area of interest and generate cropping coordinates based on that region.

Prerequisites

  • An Azure subscription - Create one for free
  • Once you have your Azure subscription, create a Computer Vision resource in the Azure portal to get your key and endpoint. After it deploys, click Go to resource.
    • You will need the key and endpoint from the resource you create to connect your application to the Computer Vision service. You'll paste your key and endpoint into the code below later in the quickstart.
    • You can use the free pricing tier (F0) to try the service, and upgrade later to a paid tier for production.
  • Create environment variables for the key and endpoint URL, named COMPUTER_VISION_SUBSCRIPTION_KEY and COMPUTER_VISION_ENDPOINT, respectively.

Create and run the sample

To create and run the sample, copy the following code into the code editor.

import os
import sys
import requests
# If you are using a Jupyter Notebook, uncomment the following lines.
# %matplotlib inline
# import matplotlib.pyplot as plt
from PIL import Image
from io import BytesIO

# Add your Computer Vision subscription key and endpoint to your environment variables.
subscription_key = os.environ['COMPUTER_VISION_SUBSCRIPTION_KEY']
endpoint = os.environ['COMPUTER_VISION_ENDPOINT']

thumbnail_url = endpoint + "vision/v3.1/generateThumbnail"

# Set image_url to the URL of an image that you want to analyze.
image_url = "https://upload.wikimedia.org/wikipedia/commons/9/94/Bloodhound_Puppy.jpg"

# Construct URL
headers = {'Ocp-Apim-Subscription-Key': subscription_key}
params = {'width': '50', 'height': '50', 'smartCropping': 'true'}
data = {'url': image_url}
# Call API
response = requests.post(thumbnail_url, headers=headers, params=params, json=data)
response.raise_for_status()

# Open the image from bytes
thumbnail = Image.open(BytesIO(response.content))

# Verify the thumbnail size.
print("Thumbnail is {0}-by-{1}".format(*thumbnail.size))

# Save thumbnail to file
thumbnail.save('thumbnail.png')

# Display image
thumbnail.show()

# Optional. Display the thumbnail from Jupyter.
# plt.imshow(thumbnail)
# plt.axis("off")

Next, do the following:

  1. (Optional) Replace the value of image_url with the URL of your own image.
  2. Save the code as a file with an .py extension. For example, get-thumbnail.py.
  3. Open a command prompt window.
  4. At the prompt, use the python command to run the sample. For example, python get-thumbnail.py.

Examine the response

A successful response is returned as binary data which represents the image data for the thumbnail. The sample should display this image. If the request fails, the response is displayed in the command prompt window and should contain an error code.

Run in Jupyter (optional)

You can optionally run this quickstart in a step-by step fashion using a Jupyter Notebook on MyBinder. To launch Binder, select the following button:

Binder

Next steps

Next, explore a Python application that uses Computer Vision to perform optical character recognition (OCR); create smart-cropped thumbnails; and detect, categorize, tag, and describe visual features in images.