How to Render NumPy Array as Image in FastAPI: Troubleshooting White Square Issue?

How to Display NumPy Array as Image in FastAPI

Problem:

Despite having a NumPy array representing an image, it appears as a white square when attempting to render it.

Solution:

Option 1: Return Image as Bytes

Using a custom Response class, follow these steps:

1. Load the image from disk or convert an in-memory NumPy array to an image using PIL or OpenCV.
2. Save the image into a BytesIO buffer using the save() or imencode() method, respectively.
3. Set the Content-Disposition header to specify inline viewing or downloading.
4. Return the image bytes in a Response with the media_type set to the appropriate image format (e.g., 'image/png').

Option 2: Return Image as JSON-encoded NumPy Array

This option is not ideal for displaying images in the browser but allows you to encode the NumPy array as JSON and decode it back into an image on the client side.

1. Convert the NumPy array to a list using the tolist() method.
2. Encode the list as JSON and return it in a Response.
3. On the client side, decode the JSON string back into a NumPy array and use PIL or OpenCV to create an image from it.

Note:

• For both options, setting the Content-Disposition header is crucial for displaying the image in the browser.
• StreamingResponse is not necessary if the NumPy array is loaded into memory and can be efficiently returned in a single response.

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