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Enlarge to Fill Stand-Alone Image Viewer

Make stand-alone images fill the viewport regardless of whether they are too wide or too tall

  1. // ==UserScript==
  2. // @name        Enlarge to Fill Stand-Alone Image Viewer
  3. // @author      Jefferson "jscher2000" Scher
  4. // @namespace   JeffersonScher
  5. // @version     0.5
  6. // @copyright   Copyright 2020 Jefferson Scher
  7. // @license     BSD-3-Clause
  8. // @description Make stand-alone images fill the viewport regardless of whether they are too wide or too tall
  9. // @match       https://*/*
  10. // @grant       none
  11. // ==/UserScript==
  12.  
  13. var tgt;
  14. function resizeImg(e){
  15.   // don't resize when full size
  16.   if (tgt.className.indexOf('overflowing') > -1) return;
  17.   var whratio = tgt.width / tgt.height;
  18.   var vpratio = window.innerWidth / window.innerHeight;
  19.   if (whratio < vpratio){ // width needs more help
  20.     tgt.width = parseInt(document.body.clientWidth);
  21.     tgt.height = Math.round(tgt.width * (1 / whratio));
  22.     // repeat to account for scroll bar
  23.     tgt.width = parseInt(document.body.clientWidth);
  24.     tgt.height = Math.round(tgt.width * (1 / whratio));
  25.   } else {
  26.     tgt.height = window.innerHeight;
  27.     tgt.width = Math.round(tgt.height * whratio);
  28.     // repeat to account for scroll bar
  29.     tgt.height = window.innerHeight;
  30.     tgt.width = Math.round(tgt.height * whratio);
  31.   }
  32. }
  33. var resizeTimeout;
  34. function resizeThrottler(){
  35.   if(!resizeTimeout){
  36.     resizeTimeout = window.setTimeout(function(){resizeTimeout = null; resizeImg();}, 200);
  37.   }
  38. }
  39. if (document.querySelector('head').innerHTML.indexOf('TopLevelImageDocument.css') > -1) {
  40.   tgt = document.querySelector('body img'); // first image in body
  41.   tgt.addEventListener('click', resizeImg, false);
  42.   window.addEventListener('resize', resizeThrottler, false); 
  43.   window.setTimeout(resizeImg, 50);
  44. }