Azure form recognizer error: "Failed to download image from input URL."

Question

I'm following these instructions to use the layout form recognizer service from Azure Which have the following code:

########### Python Form Recognizer Async Layout #############

import json
import time
from requests import get, post

# Endpoint URL
endpoint = r"<Endpoint>"
apim_key = "<Subscription Key>"
post_url = endpoint + "/formrecognizer/v2.0-preview/Layout/analyze"
source = r"<path to your form>"

headers = {
    # Request headers
    'Content-Type': 'application/json',
    'Ocp-Apim-Subscription-Key': apim_key,
}
with open(source, "rb") as f:
    data_bytes = f.read()

try:
    resp = post(url = post_url, data = data_bytes, headers = headers)
    if resp.status_code != 202:
        print("POST analyze failed:\n%s" % resp.text)
        quit()
    print("POST analyze succeeded:\n%s" % resp.headers)
    get_url = resp.headers["operation-location"]
except Exception as e:
    print("POST analyze failed:\n%s" % str(e))
    quit()

I tried the code I got the following error:

POST analyze failed:
{"error":{"code":"FailedToDownloadImage","message":"Failed to download image from input URL."}}
POST analyze succeeded:
{'Transfer-Encoding': 'chunked', 'Content-Type': 'application/json; charset=utf-8', 'x-envoy-upstream-service-time': '4', 'apim-request-id': '515e93ee-4db8-4174-92b1-63e5c415c056', 'Strict-Transport-Security': 'max-age=31536000; includeSubDomains; preload', 'x-content-type-options': 'nosniff', 'Date': 'Sat, 06 Jun 2020 20:47:28 GMT'}
POST analyze failed:
'operation-location'

The code I'm using is:

import json
import time
from requests import get, post

I'm reading the pdf file before making the request and verifying it loaded into the variable

source = r"data/Invoice_7.pdf" 
with open(source, "rb") as f:
    data_bytes = f.read()

print (data_bytes[0:10])

Then the request details:

endpoint = r"https://xxxx.cognitiveservices.azure.com/"

apim_key = "xxxx"
post_url = endpoint + "/formrecognizer/v2.0-preview/Layout/analyze"

headers = {
    # Request headers
    'Content-Type': 'application/json',
    'Ocp-Apim-Subscription-Key': apim_key,
}

And finally making the request:

try:
    resp = post(url = post_url, data = data_bytes, headers = headers)
    print (1)
    if resp.status_code != 202:
        print("POST analyze failed:\n%s" % resp.text)
        #quit()
    print (2)
    print("POST analyze succeeded:\n%s" % resp.headers)
    print (3)
    get_url = resp.headers["operation-location"]
    print (4)
except Exception as e:
    print("POST analyze failed:\n%s" % str(e))
    #quit()

I'm printing a number at each step because I find very weird that I get both fail and successful requests responses. This is the result:

1
POST analyze failed:
{"error":{"code":"FailedToDownloadImage","message":"Failed to download image from input URL."}}
2
POST analyze succeeded:
{'Transfer-Encoding': 'chunked', 'Content-Type': 'application/json; charset=utf-8', 'x-envoy-upstream-service-time': '1', 'apim-request-id': '93a2a162-d14f-496f-ba8a-077bcfd5d3c7', 'Strict-Transport-Security': 'max-age=31536000; includeSubDomains; preload', 'x-content-type-options': 'nosniff', 'Date': 'Sat, 06 Jun 2020 21:00:20 GMT'}
3
POST analyze failed:
'operation-location'

So the code fails at this line:

get_url = resp.headers["operation-location"]

the text in the response variable is:

'{"error":{"code":"FailedToDownloadImage","message":"Failed to download image from input URL."}}'

Answer 1

As defined in the REST API documentation, you need to specify the Content-Type. When you set your Content-Type to application/json, you need to provide a public accessible source via JSON. In your case, you need to set the Content-Type to application/pdf. When you want to make this dynamic, you could make use of the PyPi package filetype.

By the way, did you know that there is a (beta) Python SDK for Form Recognizer, which you can use for your use-case.