ehtb3.ext.user.js

// ==UserScript==
// @name           E-Hentai - Test Banners 3.0
// @include        https://e-hentai.org/*
// @include        https://forums.e-hentai.org/*
// ==/UserScript==

document.addEventListener('dblclick', function(e) {

  if (!e.target)
    return;
  
  if (e.target.nodeName === 'IMG' && e.target.clientWidth === 770 && e.target.clientHeight === 136) {

    if (e.target.parentNode.id == 'botm') {

      var input = document.createElement('input');
      input.setAttribute('type', 'file');

      input.addEventListener('change', function(e) {
        if (!e.target.files.length || !/^image/.test(e.target.files[0].type)) return;
        var reader = new FileReader();
        reader.onload = function(data) {
          document.querySelector('#botm > img').style.cssText =
            'padding-left: 770px; box-sizing: border-box; background: url(' + data.target.result + ')';
        };
        reader.readAsDataURL(e.target.files[0]);
      }, false);

      document.body.appendChild(input);
      input.style.cssText = 'display: block; width: 0; height: 0; overflow: hidden; opacity: 0';
      input.click();


    } else {

      var canvas = document.createElement('canvas'), context = canvas.getContext('2d');
      canvas.setAttribute('width', 971);
      canvas.setAttribute('height', 284);
      canvas.className = 'bannerCanvas';

      var background = new Image();
      background.onload = function() { context.drawImage(this, 0, 0); };
      background.src = 'http://i.imgur.com/sHO93Lf.png';

      var banner = new Image();
      banner.onload = function() { context.drawImage(this, 97, 13); };
      banner.src = e.target.src;

      e.target.parentNode.insertBefore(canvas, e.target);
      e.target.style.display = 'none';

    }

  } else if (e.target.nodeName == 'CANVAS' && /bannerCanvas/.test(e.target.className)) {

    e.target.nextElementSibling.style.display = null;
    e.target.parentNode.removeChild(e.target);

  }

}, false);