Can't upload file via curl

Trying to build image autoupload php tool with curl. With other uploads like text, had no problems. But when it comes to image uploading part - I am stuck. Looked through other similar problems here at SO, but couldn't find anything that would help.

With Firefox developer tool I have found that headers sent are:

Host: www.xxxxxx.com
User-Agent: Mozilla/5.0 
Accept: */*
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate, br
Referer: https://www.xxxxxx.com
Content-Type: multipart/form-data; boundary=---------------------------54682012365
Content-Length: 13645
Origin: https://www.xxxxxx.com
DNT: 1
Connection: keep-alive
Cookie: PHPSESSID=xxxxx;
TE: Trailers

And body request:

-----------------------------54682012365
Content-Disposition: form-data; name="file"; filename="test.jpg"
Content-Type: image/jpeg

--->THERE GOES SOMETHING I BELIEVE TO BE IMAGETOTEXT(random symbols with few readable parts)<---
-----------------------------54682012365
Content-Disposition: form-data; name="ImId"

0
-----------------------------54682012365--

Tried to reproduce request with CURL

Sending headers as they are above. Body request:

$img = file_get_contents('test.jpg');
$body_message = 
'---------------------------54682012365
Content-Disposition: form-data; name="file"; filename="test.jpg"
Content-Type: image/jpeg

'.$img.'
---------------------------54682012365
Content-Disposition: form-data; name="ImId"

0
---------------------------54682012365--';

Curl options:

CURLOPT_RETURNTRANSFER => true, 
CURLOPT_HEADER => 1, 
CURLINFO_HEADER_OUT => true, 
CURLOPT_POST => 1, 
CURLOPT_POSTFIELDS => $body_message

But always get custom JSON error 'No images selected';

Tried various modifications with $body_message, tried a little bit with Curlfile, but still no success. Any thoughts?