https://www.onread.com/js/epub/hooks/default/smartimages.js?v=1465990458

1EPUBJS.Hooks.register("beforeChapterDisplay").smartimages = function(callback, renderer){
2		var images = renderer.contents.querySelectorAll('img'),
3			items = Array.prototype.slice.call(images),
4			iheight = renderer.height,//chapter.bodyEl.clientHeight,//chapter.doc.body.getBoundingClientRect().height,
5			oheight;
6
7		if(renderer.layoutSettings.layout != "reflowable") {
8			callback();
9			return; //-- Only adjust images for reflowable text
10		}
11
12		items.forEach(function(item){
13
14			var size = function() {
15				var itemRect = item.getBoundingClientRect(),
16					rectHeight = itemRect.height,
17					top = itemRect.top,
18					oHeight = item.getAttribute('data-height'),
19					height = oHeight || rectHeight,
20					newHeight,
21					fontSize = Number(getComputedStyle(item, "").fontSize.match(/(\d*(\.\d*)?)px/)[1]),
22					fontAdjust = fontSize ? fontSize / 2 : 0;
23
24				iheight = renderer.contents.clientHeight;
25				if(top < 0) top = 0;
26
27				if(height + top >= iheight) {
28
29					if(top < iheight/2) {
30						// Remove top and half font-size from height to keep container from overflowing
31						newHeight = iheight - top - fontAdjust;
32						item.style.maxHeight = newHeight + "px";
33						item.style.width= "auto";
34					}else{
35						if(height > iheight) {
36							item.style.maxHeight = iheight + "px";
37							item.style.width= "auto";
38							itemRect = item.getBoundingClientRect();
39							height = itemRect.height;
40						}
41						item.style.display = "block";
42						item.style["WebkitColumnBreakBefore"] = "always";
43						item.style["breakBefore"] = "column";
44
45					}
46
47					item.setAttribute('data-height', newHeight);
48
49				}else{
50					item.style.removeProperty('max-height');
51					item.style.removeProperty('margin-top');
52				}
53			}
54
55			var unloaded = function(){
56				// item.removeEventListener('load', size); // crashes in IE
57				renderer.off("renderer:resized", size);
58				renderer.off("renderer:chapterUnload", this);
59			};
60
61			item.addEventListener('load', size, false);
62
63			renderer.on("renderer:resized", size);
64
65			renderer.on("renderer:chapterUnload", unloaded);
66
67			size();
68
69		});
70
71		if(callback) callback();
72
73}