Licenced Software
Adobe Photoshop
Photoshop is widely regarded as the industry standard for image editing. The software has a wide array of functionality, but may be difficult for newcomers. You may use an older version of Photoshop through the Program Kiosk.
For newer versions of Photoshop through Adobe Creative Cloud you need a license. This subscription fee must be paid by your yourself or by your unit. Please talk to your superior or local IT on how to get a license if needed.
Free Software
Gimp
Gimp is a free image editing tool for Windows, Mac, and Linux and is the industry standard for free image editing. The software can open and save files with the same file format as Photoshop.
You may download Gimp from Software Center or through http://www.gimp.org/.
Pixlr
If you do not wish to download an image editor you may use pixlr.com through your web browser.
Windows
Paint
Paint is built into Windows and is a very simple image editor. It is effective if you need to make quick and easy edits to a photo, but lacks a lot of features you may want in an image editor.
Mac
Photos
Photos is included in all MacOS devices and allows you to make simple edits to photos if needed.
Preview
In MacOS you also have Preview which may allow you to compress and reformat images if needed.