FastStone Photo Resizer - Convert and Rename images in batch mode Support JPEG, BMP, GIF, PNG, TIFF and JPEG2000
Image Resizer for Windows - Lets you resize images by right-clicking.
PhotoBulk - PhotoBulk is a bulk image editor for Mac that was created for the best experience of batch editing. With this image editing software for macOS you can add watermarks, optimize and resize pictures, convert images or rename photos in bulk.
Assetizr - A super fast image resizing tool
IrfanView - IrfanView ... one of the most popular viewers worldwide.
Squash 2 for Mac - The easiest way to compress and optimize images for the web