From RealWorld Graphics:
Picture Resizer (64-Bit) is a tool for batch resizing of JPG pictures and photos. Picture Resizer (64-Bit) will resize JPG images and save them next to the originals. Names of the new pictures will be based on the original names, with a suffix indicating their size. For example, the resized version of MyPhoto.jpg will be called MyPhoto-400.jpg, where the number 400 indicates the size of the picture. The tool is using high-quality resizing method, where color of each pixel is a weighted average of all covered pixels from the original image. Linear interpolation is used when zooming in and the algorithm is optimized to work with gamma-corrected pictures.