How to use Layui to achieve image dragging and zooming effects

How to use Layui to achieve image dragging and zooming effects

In modern web design, the interactive effect of images has become an important means to increase the vitality and user experience of web pages. Among them, image dragging and zooming effects are one of the common and popular interaction methods. This article will introduce how to use the Layui framework to achieve image dragging and zooming effects, and provide specific code examples.

1. Introduce the Layui framework and related dependencies:

First, we need to introduce the Layui framework and related dependencies into the HTML file. It can be introduced through the following code example:

<link rel="stylesheet" href="https://cdn.staticfile.org/layui/2.5.6/css/layui.css">
<script src="https://cdn.staticfile.org/layui/2.5.6/layui.js"></script>
<script src="https://cdn.staticfile.org/jquery/3.5.1/jquery.min.js"></script>

2. Create the HTML structure:

Next, we need to create the HTML structure of the image in the HTML file and add the id attribute to it. It can be created through the following code example:

<div id="image-container">
  <img src="/static/imghw/default1.png"  data-src="path/to/your/image.jpg"  class="lazy" id="image" alt="image" draggable="false">
</div>

3. Write CSS styles:

In order to achieve image dragging and zooming effects, we need to write some necessary CSS styles. This can be achieved through the following code example:

#image-container {
  position: relative;
  width: 600px;
  height: 400px;
  overflow: hidden;
}

#image {
  position: absolute;
  cursor: move;
  width: 100%;
  height: 100%;
  object-fit: contain;
}

4. Write JavaScript code:

Finally, we need to write JavaScript code to achieve the drag and zoom effect of the image. This can be achieved through the following code example:

layui.use(['layer'], function(){
  var layer = layui.layer;
  
  // 获取图片容器和图片对象
  var imageContainer = document.getElementById('image-container');
  var image = document.getElementById('image');
  
  // 定义图片大小范围
  var imageMinWidth = 100;
  var imageMaxWidth = 800;
  var imageMinHeight = 100;
  var imageMaxHeight = 800;
  
  // 定义图片缩放比例
  var scaleFactor = 0.1;
  
  // 定义图片拖拽状态
  var dragging = false;
  var dragStartX = 0;
  var dragStartY = 0;
  
  // 监听鼠标按下事件
  image.addEventListener('mousedown', function(event){
    dragging = true;
    dragStartX = event.clientX - image.offsetLeft;
    dragStartY = event.clientY - image.offsetTop;
    image.style.cursor = 'grabbing';
  });
  
  // 监听鼠标移动事件
  imageContainer.addEventListener('mousemove', function(event){
    if(dragging){
      var offsetX = event.clientX - dragStartX;
      var offsetY = event.clientY - dragStartY;
      
      image.style.left = offsetX + 'px';
      image.style.top = offsetY + 'px';
    }
  });
  
  // 监听鼠标放开事件
  image.addEventListener('mouseup', function(){
    dragging = false;
    image.style.cursor = 'grab';
  });
  
  // 监听鼠标滚轮事件
  image.addEventListener('wheel', function(event){
    event.preventDefault();
    
    var delta = Math.sign(event.deltaY);
    var width = image.width + delta * scaleFactor * image.width;
    var height = image.height + delta * scaleFactor * image.height;
    
    if(width > imageMinWidth && width < imageMaxWidth && height > imageMinHeight && height < imageMaxHeight){
      image.width = width;
      image.height = height;
    }
  });
});

At this point, we have completed the code writing to use Layui to achieve image dragging and zooming effects. Through the above code, the user can change the position of the image by dragging it and zoom in and out of the image through the scroll wheel. In addition, we also limit the minimum and maximum size range of images.

Summary:

In this article, we introduced in detail how to use Layui to implement image dragging and zooming by introducing the Layui framework and related dependencies, creating an HTML structure, writing CSS styles and JavaScript code Effect. I hope this article will be helpful to friends who want to learn and practice this interactive effect.

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