If you want to extract analog or digital line art from an image with a background, you can do so by using the [Convert brightness to opacity] function.
How to download
Select the image you want to convert on the [Layer] palette and then select [Edit] menu -> [Convert brightness to opacity]
If you are using PRO/EX, you can also extract it by changing the [Expression color] setting in [Layer Property].
You can change or undo the [Layer Property] settings once completed.
For details on how to extract using [Layer Property], please refer to this article.