>Are you just balking at the possibility of passing in an Image that is already in memory, but isn't yet converted to an ImageCorrFunc? I guess that just seemed like a logical intermediate option without a specific application in mind.

Yes.  I would rather see the user free to specify *any* image, not to be interpreted as input for an `ImageCorrFunc` (which is already covered) but to be used for the padding as is.  Sent directly to `pad_image`, in other words.  This seems potentially more valuable as it's general and doesn't duplicate what can already be done by either passing a string or passing an `ImageCorrFunc`.