Attach an image file to a BigCommerce Product - multipartform-data

Question

The BigCommerce API documentation suggests that image files can be uploaded through the API, without having to upload it elsewhere first:
POST /catalog/products/{product_id}/images
Creates an image on a product. Publically accessible URLs and files (form post) are valid parameters
Emphasis mine. My attempts, variations on the below, mostly come back with 422 image_url must be present if uploading by url.
curl -X POST \
https://api.bigcommerce.com/stores/redacted/v3/catalog/products/123/images \
-H 'accept: application/json' \
-H 'cache-control: no-cache' \
-H 'content-type: multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW' \
-H 'x-auth-client: redacted' \
-H 'x-auth-token: redacted' \
-F productImage=#img_123.jpg \
-F image_url=image_123.jpg
What does a correctly formed request look like, that POSTs an image file to a product?
Related:
Bigcommerce Python API, how do I create a product with an image?

Answer 1

A correctly formed request looks like this:
curl -X POST \
https://api.bigcommerce.com/stores/js......7j/v3/catalog/products/32011/images \
-H 'accept: application/json' \
-H 'cache-control: no-cache' \
-H 'content-type: multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW' \
-H 'x-auth-client: ts2.........................r0r' \
-H 'x-auth-token: ihq.........................5b2' \
-F 'image_file=#Downloads/img_2405.jpg'
However, certain images can cause the misleading error; such as this one.
It's not clear what property of the file causes the error, but compressing or otherwise re-saving the image resolves the problem.