How to use JavaScript to achieve the scrolling and zooming effect of images?

How to use JavaScript to achieve the scrolling and zooming effect of images?

In modern web design, pictures are often an integral part. In order to enhance the user experience, we often need to perform some special effects processing on pictures. This article will introduce how to use JavaScript to achieve the scrolling and zooming effect of images, and provide specific code examples.

First, we need to add an image element to the HTML file, for example:

<img  src="/static/imghwm/default1.png"  data-src="image.jpg"  class="lazy"  id="myImage" / alt="How to use JavaScript to achieve the scrolling and zooming effect of images?" >

Then, define a function in the JavaScript file to achieve the scrolling zoom effect, the code is as follows:

function zoomImageOnScroll() {
  var image = document.getElementById('myImage');
  var originalWidth = image.width;
  var originalHeight = image.height;

  window.addEventListener('scroll', function() {
    var scrollTop = window.pageYOffset || document.documentElement.scrollTop;
    var newWidth = originalWidth - scrollTop;
    var newHeight = originalHeight - scrollTop;

    // 设置新的图片宽度和高度
    image.style.width = newWidth + 'px';
    image.style.height = newHeight + 'px';
  });
}

// 调用函数实现滚动缩放效果
zoomImageOnScroll();

Next, when the web page is scrolled, the width and height of the image will be scaled accordingly according to the position of the scroll bar. During scrolling, the image's width and height gradually decrease until it reaches its initial size.

It should be noted that the scroll event of the window object is used here to monitor the scrolling action. During the scrolling process, we change the size of the image by calculating the position of the scroll bar (i.e. scrollTop).

In addition, some improvements can be made to the function according to needs. For example, you can set a minimum width and minimum height based on the position of the scroll bar to prevent the image from scaling too small. The code is as follows:

function zoomImageOnScroll() {
  var image = document.getElementById('myImage');
  var originalWidth = image.width;
  var originalHeight = image.height;

  var minWidth = 200; // 设置最小宽度
  var minHeight = 200; // 设置最小高度

  window.addEventListener('scroll', function() {
    var scrollTop = window.pageYOffset || document.documentElement.scrollTop;
    var newWidth = originalWidth - scrollTop;
    var newHeight = originalHeight - scrollTop;

    // 判断是否超过最小宽度和最小高度
    if (newWidth < minWidth) {
      newWidth = minWidth;
    }
    if (newHeight < minHeight) {
      newHeight = minHeight;
    }

    // 设置新的图片宽度和高度
    image.style.width = newWidth + 'px';
    image.style.height = newHeight + 'px';
  });
}

// 调用函数实现滚动缩放效果
zoomImageOnScroll();

By setting the minimum width and minimum height, you can ensure that the image will not be scaled too small, thus affecting the user experience.

To sum up, by listening to scroll events in JavaScript and changing the size of the image according to the position of the scroll bar, we can achieve the scrolling and zooming effect of the image. The above is just a simple example, you can make further modifications and optimizations according to actual needs.

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