Xcode - View Screen size

Question

I am in the process of learning iOS development with XCode. I created a project to implement some of the things I've been learning and to begin learning how to manage image sizes and placement on different sized screens ie iPhone 8, iPhone 8+, iPad, etc. I am currently using XCode 10 Beta and I noticed that the View size on the main storyboard is half the actual screen size of any device I select to to View As:. For instance if I select View As: iPhone 8 the screen size is 375x667 instead of being 750x1334 like the actual device. I discovered this because I created a square image of 100x100px and thought I would be able to line up 7 across the screen. To my surprise the images took up twice as much screen as I had calculated.

Can anyone let me know why the screen Views in XCode are half that of actual screen size?

Do I just always assume to make my graphics half the size I would actually want them?

Edit: Here's a screenshot of what I am referring to in XCode

When I click on the empty view in the the XCode storyboard pane this is this resolution it displays for the view. Also, when I export my graphics from Illustrator the are exported with the @1x, @2x, and @3x variants. However, when I place an image in the view that is 100x100px it takes up about 1/3 of the screen instead of 1/7 of the screen as I would expect on a iPhone 8 which has a resolution of 750x1334.

Edit #2: So after playing around more with XCode I do see that the resolution for the views are in Points not pixels however, in this screenshot for a iPhone 8+ View:

I would assume with a screen resolution of 1080x1920 @3x the Point resolution would be 360x640 for an iPhone 8+ not 414x736.

Answer 1

It has to do with the difference between points and pixels. On the original iPhone when it was release it was 1 point per pixel but as resolution got better it became 2x pixels per point (4 pixels). Now the resolution is 3x pixels per point on some of the newer devices (9 pixels).

https://www.google.com/amp/s/blog.fluidui.com/designing-for-mobile-101-pixels-points-and-resolutions/amp/