This makes sense as System.Drawing (aka GDI+) was mainly used for WinForms and has never been supported for web servers. I suspect Mono ported it to support the

This makes sense as System.Drawing (aka GDI+) was mainly used for WinForms and has never been supported for web servers. I suspect Mono ported it to support their Windows Forms port. It may just work on Windows but it won't keep working when used server-side in a web app. MS specifically recommend against using it in ASP.NET. I learned the hard way what happens if you ignore the warnings when I was supporting a site that did this. Edit: I wrote about image optimization and resizing in chapter four of my book on ASP.NET Core - https://unop.uk/book/ https://unop.uk/book/