JSFiddle - React, Tailwind, and code Playground

HTML

<iframe id="photopea" src="https://www.photopea.com" width="630" height="500" />

JavaScript

var wnd = document.getElementById("photopea").contentWindow;
window.addEventListener("message", ppReady);

function ppReady(e) {
	window.removeEventListener("message", ppReady);
	var request = new XMLHttpRequest();
	request.open("GET", "https://d32-a.sdn.szn.cz/d_32/c_img_F_R/JIevtr.jpeg", true);
	request.responseType = "arraybuffer";
	request.onload = loaded;
	request.send();
}

function loaded(e) {
	var ab = e.target.response;  // ArrayBuffer
	wnd.postMessage(ab, "*");
}