Use PHP functions to achieve web page image preview effects-PHP Tutorial-php.cn

Use PHP functions to achieve web page image preview effects

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Release： 2023-06-16 06:18:01

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With the popularity of the Internet, more and more people have begun to publish articles, pictures and other content online. For website administrators and web designers, how to make the website more beautiful and easier to browse has become an issue that cannot be ignored. Among them, the picture preview effect is an important link. This article will introduce how to use PHP functions to achieve web page image preview effects.

1. What is the image preview effect?

The picture preview effect means that when the mouse moves over the picture, the picture can be enlarged or display certain information. This effect is relatively common on websites and brings a better experience to users.

2. Implementation method

To achieve the image preview effect, you need to use some front-end technologies, such as HTML, CSS and JavaScript. But this article mainly introduces how to use PHP functions to achieve image preview effects.

Using the GD library

The GD library is a PHP image processing function library that can process images through PHP programs. We can use this library to crop and enlarge images to achieve preview effects.

First you need to install the GD library on the server, and confirm whether it is installed or not through the phpinfo() function. If it is not installed, you can install it through the following command:

sudo apt-get install php7.0-gd

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Then, use the following code in the PHP file to read and display the image:

<?php
  header("Content-type: image/jpeg"); //定义要显示的文件类型
  $url = "image.jpg"; //定义图片路径
  $im = imagecreatefromjpeg($url); //读取图片文件
  imagejpeg($im); //显示图片
  imagedestroy($im); //销毁图片变量
?>

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Next, you need to crop and enlarge the image operate. Cropping can be achieved through the imagecopyresampled() function, and magnification can be achieved through multiple calculations. The following is a code example:

<?php
  $url = "image.jpg";
  $percent = 1.5; //放大倍数
  list($width, $height) = getimagesize($url); //获取图片尺寸
  $new_width = $width * $percent; //计算新的宽度
  $new_height = $height * $percent; //计算新的高度
  $image_p = imagecreatetruecolor($new_width, $new_height); //创建新图
  $image = imagecreatefromjpeg($url);  //读取原图
  imagecopyresampled($image_p, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height); //剪裁并放大
  header('Content-Type: image/jpeg');
  imagejpeg($image_p); //输出图片
  imagedestroy($image_p); //销毁变量
?>

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Using jQuery plug-in

In addition to using the GD library, we can also use some front-end libraries or plug-ins to achieve image preview effects. Among them, the more commonly used one is the jQuery plug-in.

Among the jQuery plug-ins, the most commonly used is the lightbox plug-in, which can achieve the effect of image zooming and amplification. Just reference the relevant JavaScript and CSS files in the HTML file, and add the class "lightbox" to the image link. The following is a code example:

<!DOCTYPE html>
<html>
<head>
  <title>图片预览</title>
  <script src="jquery.min.js"></script>
  <script src="lightbox.js"></script>
  <link href="lightbox.css" rel="stylesheet">
</head>
<body>
  <a href="image.jpg" class="lightbox"><img src="image.jpg" alt="示例图片"></a>
</body>
</html>

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It should be noted that using the lightbox plug-in requires referencing related JavaScript and CSS files, and for some special image formats, additional processing may be required to achieve the preview effect.

3. Summary

It is a common requirement to use PHP functions to preview web page images, which can make the website more beautiful and easier to browse. Different implementation methods have their own advantages and disadvantages, and you need to choose the appropriate method according to the specific situation. It should be noted that when using GD libraries or framework plug-ins, you must pay attention to security issues to prevent unnecessary vulnerabilities.

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