I found a very handy way to resize an image without installing additional tool on macOS.

Add Hotkey to trigger Adjust Size... feature in App Preview

The default image preview app has an awesome resize feature. What I do is just trigger it by using a global shortcut.

Got to System Preferences → Keyboard → App Shortcuts, then add Preview with this new global hotkey to app Preview, see screenshot

Double click to open an Image in Preview

Use hotkey ⌘ + ⇧ + c, to trigger the adjust size feature in Preview, then select the size and save it. Job is Done !!!