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Because the Image Editor depends on several dialog arguments, it's not as straight forward as opening the url in a new window.
You need to open the dialog using EPiServer script methods.These links should guide you in the right direction:
http://world.episerver.com/en/Articles/Items/Modal-Dialogs-in-the-EPiServer-UI-for-non-IE-Browsers/
https://www.coderesort.com/p/epicode/browser/Intergen.EP.MultiPageProperty/5.x/Intergen/Dialogs/MultipageSelector.aspx