如何使用Swift选择图像的一部分，裁剪并保存？

I am trying to create an iOS app using Swift to capture images and let the user save a selected portion of the image. In many cam based apps, I noticed that a rectangular frame is offered to let the users choose the desired portion. This involves either sliding the edges of the rectangle or moving the corners to fit the required area.I am trying to create an iOS app using Swift to