Free PNG Optimizer

Free PNG Optimizer aims to free up space on hard drives, digital cameras and other such devices by reducing the size occupied by image files. It offers support for PNG, JPG, JPEG, BMP, GIF, TIF, TIFF, EMF and WMF format.
The setup operation does not take a long time to finish, after which you are greeted by a regular window with an intuitive structure, representing Free PNG Optimizer's interface.
Images can be added to the task list using either the file browser or drag-and-drop support. You can also export the file list to import it at a later time.
As you have probably figured out, batch processing is possible, meaning that you can work with multiple items at once to reduce overall task time.
All you have to do is adjust the optimization level, set the output location (same as source files or custom) and, optionally enable Free PNG Optimizer to overwrite existing files instead of creating new ones.
The program carries out optimization tasks pretty quickly and does not hog system resources, since it uses low CPU and RAM. No errors were shown in our tests, and the app did not hang or crash. Unfortunately, Free PNG Optimizer has not been updated for a while. Other than that, it can be handled by all types of users, even beginners.