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PHP implements image upload and cropping functions

WBOYOriginal: 2023-06-23 09:31:351746browse

PHP, as a commonly used back-end programming language, is widely used in the field of website development. Among them, image uploading and cropping are one of the commonly used functions in website development. The following will introduce how to use PHP to implement image upload and cropping functions.

1. Image upload function

First introduce the implementation of the image upload function. The following code implements a simple image upload function:

<html>
    <head>
        <meta charset="UTF-8">
        <title>图片上传</title>
    </head>
    <body>
        <form action="upload.php" method="post" enctype="multipart/form-data">
            <input type="file" name="file">
            <input type="submit" value="上传">
        </form>
    </body>
</html>

There is a form on this page, and the action attribute of the form points to a processing script named upload.php. The form's enctype attribute must be set to "multipart/form-data" before binary files can be uploaded. A simple form is provided here and can be modified as needed.

The following is the processing script for upload.php:

<?php
// 指定文件上传的目录
$target_dir = "uploads/";
$target_file = $target_dir . basename($_FILES["file"]["name"]);

// 获取文件类型
$imageFileType = strtolower(pathinfo($target_file,PATHINFO_EXTENSION));

// 检查文件是否是图片
if(isset($_POST["submit"])) {
    $check = getimagesize($_FILES["file"]["tmp_name"]);
    if($check !== false) {
        echo "File is an image - " . $check["mime"] . ".";
        $uploadOk = 1;
    } else {
        echo "File is not an image.";
        $uploadOk = 0;
    }
}

// 如果文件已经存在，提示并退出
if (file_exists($target_file)) {
    echo "Sorry, file already exists.";
    $uploadOk = 0;
}

// 检查文件大小
if ($_FILES["file"]["size"] > 500000) {
    echo "Sorry, your file is too large.";
    $uploadOk = 0;
}

// 允许上传的图片类型
if($imageFileType != "jpg" && $imageFileType != "jpeg" && $imageFileType != "png" && $imageFileType != "gif" ) {
    echo "Sorry, only JPG, JPEG, PNG & GIF files are allowed.";
    $uploadOk = 0;
}

// 如果没有错误，进行文件上传
if ($uploadOk == 0) {
    echo "Sorry, your file was not uploaded.";
} else {
    if (move_uploaded_file($_FILES["file"]["tmp_name"], $target_file)) {
        echo "The file ". basename( $_FILES["file"]["name"]). " has been uploaded.";
    } else {
        echo "Sorry, there was an error uploading your file.";
    }
}
?>

This script first obtains the uploaded file processing target path and file type, and then checks the file type and file size. If the file type and size meet the standards, the file will be uploaded, otherwise an error message will be prompted.

2. Image cropping function

The image cropping function refers to cropping the image after uploading it, so that the image size, proportion, etc. meet the requirements. The following describes how to use PHP to implement the image cropping function. In this article, we use the PHP library-GD library to process images.

Install the GD library

Before using the GD library, you need to ensure that the library has been installed, otherwise it needs to be installed. In Linux systems, you can install the GD library through the following command:

sudo apt-get install php7.2-gd

In Windows systems, find the following statement in the php configuration file php.ini:

;extension=php_gd2.dll

Change it to:

extension=php_gd2.dll

Save and restart php.

Crop pictures

Before using the GD library, you need to load the picture into the program. You can use functions such as Imagecreatefromjpeg(), Imagecreatefrompng(), Imagecreatefromgif() to load images in different formats. The following is a simple cropping program:

//载入原图
$src = imagecreatefromjpeg('test.jpg');

//裁剪原图
$dst = imagecreatetruecolor(100, 100);
imagecopyresampled($dst, $src, 0, 0, 50, 50, 100, 100, 100, 100);

//保存裁剪后的图片
imagejpeg($dst, 'test_crop.jpg');

//释放原图和裁剪后的图片
imagedestroy($src);
imagedestroy($dst);

This program uses the image processing function imagecreatetruecolor() to generate a blank image, and then uses the imagecopyresampled() function to crop and copy the original image to the blank image. Finally, use the imagejpeg() function to save the cropped image.

3. Summary

In PHP, you can easily upload and crop images using the upload form and GD library. This function is very commonly used in website development. Mastering the basic skills of uploading and cropping images will be of immeasurable help to students who are new to website development.

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