The example below taken from the Lake Forest College Research Guide shows the citation technique for an image in the APA format.

Figure 1. B. pertussis by
J. L. Carson, 2003. Used
with permission. ¹
¹ From “Three genomes and whooping cough,” by E. R. Winstead, 2003, Genome News Network . Copyright 2000 - 2004 by the J. Craig Venter Institute. Reproduced with permission of the photographer. Available at http://www.genomenewsnetwork.org/articles/09_03/ whooping_cough.php
Shown directly below is a citation for the image if you include it in your References, but APA style does not require you to do so.
Give the address of the page on which the image appeared rather than the address of the image to assist retrieval of the image at a later date.