Thanks! Just one example:
New version Sketch included these artboard’s presets:
I started with iPhone 6 375x667px.
Supposably I want use embedded image for profile picture 50x50px. I prepared image 150x150 px, 72dpi and imported into Sketch. Then:
I scaled image to 50x50px for artboard 1x is for the non-retina display and my export panel will look like this:
3 images as a result: 50x50 (@ 1x.png), 100x100 (@ 2x.png), 150x150 (@ 2x.png)