You no longer will find Aperture in App store. The new photo application is not as advanced as Aperture, but you can do most of the things that you would need to do. I was trying to resize some pictures that I took on my iPhone 6s Plus, but I could not find. I could see the option to crop, but not to resize. I wanted to make the image smaller in size, reduce some quality so that it could load fast on web pages.
What you need to do is after doing all the editing work, select file export and you will get the above menu. You can set the size, quality, etc
Check out this Video if you are interested in creating a service to resize an image
“Most smartphones these days take high-resolution photos. It’s a great thing, of course! But it comes with a price: huge file size. For example, a photo taken with an iPhone is around 4MB. It’s even bigger when you upload photos from a DSLR camera!”