>>>> There is also the dired-do-isearch command that searches in marked files.
>>>>
>>>> OTOH, when such "making text visible to search" would be implemented
>>>> for isearch, then it will be used automatically by query-replace that
>>>> relies on the same search functions.
>>>
>>> That's true...
>>>
>>> So we basically need some new functionality for switching to text mode
>>> in image buffers when we're doing searches?
>>
>> Maybe isearch-open-necessary-overlays should detect if there is an image
>> over point, then switch the buffer to text mode.
>
> Here is one possible fix, but I'm still unsure if using image functions
> in isearch is a good style.  Perhaps a better fix would be to add this
> code to a buffer-local isearch-mode-hook in image-mode.el that runs
> when isearch starts.

Here is a more correct implementation: