Possessive form of "which" [duplicate]

The possessive form of who is whose. What is the equivalent possessive form of which?

which has the same purpose as who as a placeholder in a secondary sentence, with the difference that who is for people and living beings while which is for inanimate objects (please correct me if wrong).

Example:

An image is read and sent to the function, which's output is displayed.

Here I have used an obscure word invention: which's in place of the word I am looking for. What is the correct word to plug in, if any? Compare with a similar who-sentence:

An gift is wrapped and sent to the Peter, whose reaction is recorded.

The equivalent word in my mother tongue Danish is hvis:

Et billede læses og sendes til funktionen, hvis output vises på skærmen.

As an alternative to Scotland141's perfectly valid answer, you can use of which, although in this case the word order is slightly different:

An image is read and sent to the function, the output of which is displayed.

You could also maintain something closer to the original word order (sounding more formal):

An image is read and sent to the function, of which the output is displayed.

"Whose" still works.

An image is read and sent to the function, whose output is displayed.