By default, ImageZoom generates thumbnails on the fly, when each image is viewed by the user. Image resizing is very fast and generally doesn't cause any delays, when original images are fairly small.
However, it is not always convenient to generate web-ready images and you simply need to show your original photos in a gallery. In this case, original photographs can be large and it might take some time to generate the thumbnails for each viewer. In this case, set EnableCacheDirectory = true
When caching is enabled, ImageZoom will create a directory directly underneath your images directory, where it will put all the thumbnails. It will do this when image is viewed for the first time, then it will simply check if a thumbnail is available and use it to show the image.
For example, let's say that you've set
ImageUrl = "~/images/vacation"
When caching is enabled, ImageZoom will create a directory under
Note: ASPNET user will need write permissions, so your application could create the directory and populate it with thumbnails.