A free program for Android, by Z Mobile Apps.
Photo Resizer is the most efficient and powerful tool for resizing your images. The app is created to provide you with the tools for the right pixels and proportions for social network posting.
Photo Resizer is a fast and easy-to-use image optimizer tool that gives your digital images the perfect size and configuration to suit a wide range of applications. The app supports JPEG and PNG formats. You can choose between batch mode and single mode. Batch mode is designed to help you resize multiple images at once.
Additionally, this tool is designed to be useful for a variety of situations, such as when you send an e-mail with attached pictures.