How Do You Render a NumPy Image Array in FastAPI?

Rendering NumPy Array in FastAPI

While the article "How to return a numpy array as an image using FastAPI?" provides useful information, it does not directly address the issue of displaying the image. To remedy this, let's delve deeper into the underlying techniques:

Option 1: Return Image as Bytes

This method entails converting the image data into bytes using libraries like PIL or OpenCV. The resulting bytes can then be served as a custom response with appropriate content type and headers.

Using PIL:

<code class="python">from PIL import Image
import io

@app.get('/image', response_class=Response)
def get_image():
    im = Image.open('test.png')
    with io.BytesIO() as buf:
        im.save(buf, format='PNG')
        im_bytes = buf.getvalue()
    headers = {'Content-Disposition': 'inline; filename=&quot;test.png&quot;'}
    return Response(im_bytes, headers=headers, media_type='image/png')</code>

Using OpenCV:

<code class="python">import cv2

@app.get('/image', response_class=Response)
def get_image():
    arr = cv2.imread('test.png', cv2.IMREAD_UNCHANGED)
    success, im = cv2.imencode('.png', arr)
    headers = {'Content-Disposition': 'inline; filename=&quot;test.png&quot;'}
    return Response(im.tobytes(), headers=headers, media_type='image/png')</code>

Option 2: Return Image as JSON-Encoded NumPy Array

While this approach is not recommended for displaying images, it can be used to convert the image to a JSON-encoded numpy array, which can be later converted back to an image on the client side.

Using PIL:

<code class="python">from PIL import Image
import numpy as np

@app.get('/image')
def get_image():
    im = Image.open('test.png')
    arr = np.asarray(im)
    return json.dumps(arr.tolist())</code>

Using OpenCV:

<code class="python">import cv2

@app.get('/image')
def get_image():
    arr = cv2.imread('test.png', cv2.IMREAD_UNCHANGED)
    return json.dumps(arr.tolist())</code>

To display the image using this method, you would need to convert the received bytes or JSON-encoded data back to an image format on the client side.

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