Image processing functions in PHP

PHP, as a popular scripting language, provides many useful functions in image processing. This article will introduce some commonly used PHP image processing functions.

1. gd library

The GD library is an open source graphics library that can dynamically generate images, including saving images in multiple formats. The GD library supports multiple formats including JPG, PNG, GIF, etc. By using the GD library, you can create complex images, add various texts, and various effects such as shadows, tilt, and more in PHP.

Creating an image is very simple, you just need to specify the image width and height using the imagecreatetruecolor() function.

<?php
$width = 400; //设置图像宽度
$height = 300; //设置图像高度
$image = imagecreatetruecolor($width, $height); //创建图像
?>

Executing the above code will create a new image. Next, we can add text to this image, draw lines, add various effects, and more. The following are some commonly used image processing functions.

2. Image cutting

Image cropping is a common operation. You can cut an image to a specified length and width through the imagecrop() function. The following is a sample code for this function:

<?php
$srcImage = imagecreatefromjpeg('source.jpg'); //加载源图像
$cropped = imagecrop($srcImage, ['x' => 0, 'y' => 0, 'width' => 200, 'height' => 200]); //剪切图像
?>

3. Image resizing

Scaling an image is a common processing method, and you can use the imagescale() function to scale the image. Here is the sample code for this function:

<?php
$image = imagecreatefromjpeg('source.jpg'); //加载图像
$scale = 0.5; //缩放比例
$width = imagesx($image) * $scale; //计算新的宽度
$height = imagesy($image) * $scale; //计算新的高度
$newImage = imagescale($image, $width, $height); //缩放图像
?>

In the above example, we have reduced the source image by 50%.

4. Image rotation

Rotating images is a more complex processing method that can be achieved using the imagerotate() function. Here is the sample code for this function:

<?php
$image = imagecreatefromjpeg('source.jpg'); //加载图像
$angle = 45; //旋转角度
$newImage = imagerotate($image, $angle, 0); //旋转图像
?>

In this example, we rotate the image 45 degrees.

5. Add watermark

Adding watermark is a common operation and can be achieved using the imagestring() function. Here is the sample code for this function:

<?php
$image = imagecreatefromjpeg('source.jpg'); //加载图像
$textColor = imagecolorallocate($image, 255, 255, 255); //设置文本颜色
$fontSize = 16; //设置字体大小
$text = 'www.example.com'; //设定水印文本
imagestring($image, $fontSize, 10, 10, $text, $textColor); //添加水印
?>

In the above example, we are adding a text watermark to the image.

Summary

PHP provides numerous image processing functions, including cutting, scaling, rotating, adding watermarks, etc. The gd library is one of the most commonly used libraries, but there are other libraries available, such as ImageMagick. By using these functions, you can easily implement various image processing operations in PHP.

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