Until new image formats gain widespread adoption, resizing is still required, and you may need to do this dynamically for different devices. Perhaps, you also have user-submitted image content, although you need to be very careful with this from a security point of view. Some image libraries are not safe, and a specially-crafted image can exploit your system. In fact, many image-processing libraries have issues when they are used in a web context.
If you are not extremely diligent and careful, then you can easily end up with memory leaks, which can take down your web server. It is always a good idea to separate and sandbox a process that deals with large media files.
Coming from a .NET standpoint, it can be tempting to use ...
