Several years ago I wrote a freeware program called A Ruler for Windows; it lets you measure things on your screen in pixels.  You can have multiple rulers open on your screen at once, and they can be transparent if you like. In any case, as I am now starting to design PCBs with Easyeda I am finding this tool invaluable. If you're interested, you can download a copy from the website - just google "A Ruler for Windows" and it should come up as the top result (assuming no ads). Unfortunately, as the name implies, it only works with Windows. Hope it will be of help to you.