The images are uploaded by way of the back end enterprise application. When they are loaded they are automatically optimized for file size. Then many default sizes are created automatically, specific sizes that are used by various sites. The most powerful aspect of the service is that any size imag can be called and created on demand. Other various options can be requested as well.
See the images here in the slider that shows both landscape and portrait images in the VillaDirect Guest app and the search results and property pages at various websites. The app uses the on-demand service while most of the websites use the default sizes that were created automatically when the images were originally uploaded.