Question: resize image on upload

[stefanoberetta]

Hi!

Beautiful package, thank you!
I was trying to resize the image using the documentation in this post

(at the end, "Pre Processing")
https://24days.in/umbraco-cms/2014/all-your-images-are-belong-to-umbraco/
using the

 MediaService.Saving += (sender, args) =>{ 
   /*edit the image and save using ImageFactory.Save()*/
}

but it gives me an error

An exception of type 'System.ArgumentException' occurred in mscorlib.dll but was not handled in user code
Additional information: URI formats are not supported.

when the code saves the image.

Could you give me a suggestion to perform a resize (I want the images to be uploaded with a max resolution of 1500px) before the image is saved to the S3 Bucket?

Thank you very much
S