You could have downloaded InspectPNG 1.1 for Mac from our application library for free. This free software for Mac OS X was originally developed by opcoders.com. The application lies within Design & Photo Tools, more precisely General.
From the developer:
InspectPNG is an app that helps you examine the low-level internals of PNG image files.
You may want to check out more software for Mac, such as PhotoBX+, which might be related to InspectPNG.