动图效果：
代码：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style type="text/css">
* {
margin: 0;
padding: 0;
}
.container,
img,
.bigger {
width: 200px;
height: 200px;
}
.container {
display: inline-block;
position: relative;
background: url(images/1.png) center;
background-size: contain;
}
img {
position: absolute;
top: 0;
left: 0;
}
.box {
width: 100px;
height: 100px;
background-color: #ffff7f;
opacity: 0.7;
position: absolute;
}
.bigger {
position: relative;
display: inline-block;
overflow: hidden;
}
.biggerImg {
position: absolute;
transform: scale(2);
transform-origin: top left;
}
</style>
</head>
<body>
<div class="container">
<div class="box" style="top: 0px;left: 0px;"></div>
</div>
<div class="bigger">
<img class="biggerImg" src="./images/1.png" style="display: none;" />
</div>
</body>
<script type="text/javascript">
var container = document.querySelector(".container");
var box = document.querySelector(".box");
var bigger = document.querySelector(".biggerImg");
var width = box.parentNode.offsetWidth;
var height = box.parentNode.offsetHeight;
container.addEventListener("mousedown", function() {
bigger.style.display = "block";
container.addEventListener("mousemove", mouseMove);
container.addEventListener("mouseup", function() {
bigger.style.display = "none";
container.removeEventListener("mousemove", mouseMove);
})
});
function mouseMove(e) {
if (e.clientY - 50 < 0) {
box.style.top = 0;
bigger.style.top = 0;
} else if (e.clientY - 50 > 100) {
box.style.top = 100;
bigger.style.top = 100;
} else {
box.style.top = e.clientY - 50 + "px";
bigger.style.top = -2 * (e.clientY - 50) + "px";
}
if (e.clientX - 50 < 0) {
box.style.left = 0;
bigger.style.left = 0;
} else if (e.clientX - 50 > 100) {
box.style.left = 100;
bigger.style.left = 100;
} else {
box.style.left = e.clientX - 50 + "px";
bigger.style.left = -2 * (e.clientX - 50) + "px";
}
}
</script>
</html>