Rails 5.2 ActiveStorage crop attachment before upload

Question

I am able to resize the avatar in the view using

<%= image_tag @user.avatar.variant(resize: "100x100")

But I am wondering if there is a way to resize it before actually uploading the avatar.

When I run the same line in my controller, I get this error:

undefined method `variant' for # <ActionDispatch::Http::UploadedFile:0x00007fcecfdac190>

Answer 1

In order to resize before uploading you can use HTML5 canvas element + Javascript to do the desired processing and then send the image to the server.

Check this question for more details.