javascript - 如何在不增加尺寸的情况下放大图像？

Question

我想在图像上获得缩放效果但不增加其在屏幕上的大小，我能够使用“transform:scale()”使图像获得某种缩放效果，但我不希望它占用的空间增加了，这就是我增加比例 () 时发生的情况。

我怎样才能得到这个？目前我实现的效果是在我的测试站点，以后会是博客/作品集:http://marcosroot.pythonanywhere.com/blog/

将鼠标悬停在图像中会产生这种效果。

PS:代码如下所示:

&__media {
    transition: transform .25s ease-in-out;

    &:hover {
        transform: scale(1.025);
    }
}

Answer 1

这种方法没有依赖性，适用于所有现代浏览器。 JavaScript 通过 setProperty 更新 CSS 变量，当您移动鼠标时，缩放图像的 background-position 会动态更新.

const zoomify = (width, height) => {
  const el = document.querySelector('.zoomify');
  el.style.width = `${width}px`;
  el.style.height = `${height}px`;
  el.addEventListener('mousemove', handleMouseMove, false);
}

function handleMouseMove(e) {
  const dimensions = this.getBoundingClientRect();
  const [x, y] = [
    e.clientX - dimensions.left,
    e.clientY - dimensions.top
  ];
  const [percentX, percentY] = [
    Math.round(100 / (dimensions.width / x)),
    Math.round(100 / (dimensions.height / y))
  ];
  this.style.setProperty('--mouse-x', percentX);
  this.style.setProperty('--mouse-y', percentY);
}

zoomify(320, 212);

* {
  box-sizing: border-box;
}

html,
body {
  padding: 10px;
}

.starting-image {
  width: 100%;
  height: 100%;
}

.zoomify {
  display: inline-block;
  position: relative;
  overflow: hidden;
}

.zoomify::after {
  content: '';
  position: absolute;
  z-index: 1;
  width: 100%;
  height: 100%;
  opacity: 0;
  background-image: url("https://images.unsplash.com/photo-1528763216729-fb67cba479db?ixlib=rb-0.3.5&ixid=eyJhcHBfaWQiOjEyMDd9&s=728e3916b52b079634aa7c7f82af612d&auto=format&fit=crop&w=6774&q=80%206774w,%20https://images.unsplash.com/photo-1528763216729-fb67cba479db?ixlib=rb-0.3.5&ixid=eyJhcHBfaWQiOjEyMDd9&s=728e3916b52b079634aa7c7f82af612d&auto=format&fit=crop&w=6774&q=80%206774w");
  background-size: cover;
  background-position: center center;
  background-repeat: no-repeat;
  will-change: background-position;
}

.zoomify:hover .starting-image {
  opacity: 0;
  position: absolute;
}

.zoomify:hover::after {
  opacity: 1;
  background-size: 250%;
  cursor: zoom-in;
  background-position: calc(var(--mouse-x) * 1%) calc(var(--mouse-y) * 1%);
}

<div class="zoomify">
  <img class="starting-image" src="https://images.unsplash.com/photo-1528763216729-fb67cba479db?ixlib=rb-0.3.5&ixid=eyJhcHBfaWQiOjEyMDd9&s=728e3916b52b079634aa7c7f82af612d&auto=format&fit=crop&w=6774&q=80%206774w,%20https://images.unsplash.com/photo-1528763216729-fb67cba479db?ixlib=rb-0.3.5&ixid=eyJhcHBfaWQiOjEyMDd9&s=728e3916b52b079634aa7c7f82af612d&auto=format&fit=crop&w=6774&q=80%206774w" alt="diner">
</div>