How to handle an image(uploaded) to compress in various sizes

[AC Question]

I have doubts to compress an image when user uploaded ,
after it has to save in where?
Where can we save the original one?
How we can use the compressed image?

 

[ManiacJoe]

We need a lot more details.

Who is uploading the image?
What app are they using to upload the image?
What server are they uploading the image to?