API endpoint - /api/2/img/[IMAGE-URL]/resize?size=[NEW-SIZE]
Resize - resizes image with preserving aspect ratio and optimizes it using lossy compression. If you need the exact size then use fit operation.
size (required) - new size (in pixels) of the image in the format WIDTH and xHEIGHT.
dppx (optional) - Number of dots per pixel defines the ratio between device and CSS pixels. The query parameter is a hint that enables extra optimisations for high density screens. The format is a float number in the same format as window.devicePixelRatio.
You can specify only one dimension and the second will be calculated according to the image's aspect ratio.
size=200 - resize to 200 px wide preserving aspect ratio
size=x80 - resize to 80 px high preserving aspect ratio
dppx=2 - sending a hint to the API that screen has DPI=2
You can see URL of the examples by "right-click -> Copy Image address"