How do I return an image in fastAPI?

Question

Using the python module fastAPI, I can\'t figure out how to return an image. In flask I would do something like this:

@app.route(\"/vector_image\", methods=[         


        

Answer 1

Thanks to @biophetik's answer, with an important reminder that caused me confusion: If you're using BytesIO especially with PIL/skimage, make sure to also do img.seek(0) before returning!

@app.get("/generate")
def generate(data: str):
  img = generate_image(data)
  print('img=%s' % (img.shape,))
  buf = BytesIO()
  imsave(buf, img, format='JPEG', quality=100)
  buf.seek(0) # important here!
  return StreamingResponse(buf, media_type="image/jpeg",
    headers={'Content-Disposition': 'inline; filename="%s.jpg"' %(data,)})

Answer 2

All the other answer(s) is on point, but now it's so easy to return an image

from fastapi.responses import FileResponse

@app.get("/")
async def main():
    return FileResponse("your_image.jpeg")

Answer 3

The answer from @SebastiánRamírez pointed me in the right direction, but for those looking to solve the problem, I needed a few lines of code to make it work. I needed to import FileResponse from starlette (not fastAPI?), add CORS support, and return from a temporary file. Perhaps there is a better way, but I couldn't get streaming to work:

from starlette.responses import FileResponse
from starlette.middleware.cors import CORSMiddleware
import tempfile

app = FastAPI()
app.add_middleware(
    CORSMiddleware, allow_origins=["*"], allow_methods=["*"], allow_headers=["*"]
)

@app.post("/vector_image")
def image_endpoint(*, vector):
    # Returns a raw PNG from the document vector (define here)
    img = my_function(vector)

    with tempfile.NamedTemporaryFile(mode="w+b", suffix=".png", delete=False) as FOUT:
        FOUT.write(img)
        return FileResponse(FOUT.name, media_type="image/png")

Answer 4

You can do something very similar in FastAPI

from fastapi import FastAPI, Response

app = FastAPI()

@app.post("/vector_image/")
async def image_endpoint():
    # img = ... # Create the image here
    return Response(content=img, media_type="image/png")

Answer 5

I had a similar issue but with a cv2 image. This may be useful for others. Uses the StreamingResponse.

import io
from starlette.responses import StreamingResponse

app = FastAPI()

@app.post("/vector_image")
def image_endpoint(*, vector):
    # Returns a cv2 image array from the document vector
    cv2img = my_function(vector)
    res, im_png = cv2.imencode(".png", cv2img)
    return StreamingResponse(io.BytesIO(im_png.tobytes()), media_type="image/png")

Answer 6

It's not properly documented yet, but you can use anything from Starlette.

So, you can use a FileResponse if it's a file in disk with a path: https://www.starlette.io/responses/#fileresponse

If it's a file-like object created in your path operation, in the next stable release of Starlette (used internally by FastAPI) you will also be able to return it in a StreamingResponse.