如何使用 FastAPI 将 numpy 数组作为图像返回？

Question

I load an image with img = imageio.imread('hello.jpg') . I want to return this numpy array as an image. I know I can do return FileResponse('hello.jpg') , however, in the future, I will have the pictures as numpy arrays.

How can I return the numpy array img from FastAPI server in a way that it is equivalent to return FileResponse('hello.jpg') ?

Answer 1

You shouldn't be using StreamingResponse , as suggested by some other answer. If the numpy array is fully loaded into memory from the beginning, StreamingResponse does not make sense at all. Please have a look at this answer . You should instead useResponse , by passing the image bytes (after writing to BytesIO buffered stream, as described in the documentation ) defining the media_type , as well as setting the Content-Disposition header, as described here , so that the image is viewed in the browser. Example below:

import io
import imageio
from imageio import v3 as iio
from fastapi import Response

@app.get("/image", response_class=Response)
def get_image():
    im = imageio.imread("test.jpeg") # 'im' could be an in-memory image (numpy array) instead
    with io.BytesIO() as buf:
        iio.imwrite(buf, im, plugin="pillow", format="JPEG")
        im_bytes = buf.getvalue()
        
    headers = {'Content-Disposition': 'inline; filename="test.jpeg"'}
    return Response(im_bytes, headers=headers, media_type='image/jpeg')

Answer 2

You can use StreamingResponse ( https://fastapi.tiangolo.com/advanced/custom-response/#using-streamingresponse-with-file-like-objects ) to do it eg, but before you will need to convert your numpy array to the io.BytesIO or io.StringIO