How do you cite website images in a PowerPoint presentation?

Does anyone know how to cite images taken from the web and placed in a PowerPoint presentation?

Or, if you aren’t sure about PowerPoint citations, what is the proper way to cite an image taken from the web? APA and MLA are both acceptable. It is for a university class.

Thanks in advance!
The presentation is very image heavy. Citations cannot be made on the same slide. I’m also not asking where to put the citations, I would like to find the proper citation format.