Install the GD library<\/li><\/ol>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: <\/p>
sudo apt-get install php7.2-gd<\/pre> In Windows systems, find the following statement in the php configuration file php.ini: <\/p>
;extension=php_gd2.dll<\/pre> Change it to: <\/p>
extension=php_gd2.dll<\/pre>Save and restart php. <\/p>
- Crop pictures<\/li><\/ol>
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: <\/p>
\/\/載入原圖\n$src = imagecreatefromjpeg('test.jpg');\n\n\/\/裁剪原圖\n$dst = imagecreatetruecolor(100, 100);\nimagecopyresampled($dst, $src, 0, 0, 50, 50, 100, 100, 100, 100);\n\n\/\/保存裁剪后的圖片\nimagejpeg($dst, 'test_crop.jpg');\n\n\/\/釋放原圖和裁剪后的圖片\nimagedestroy($src);\nimagedestroy($dst);<\/pre> 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. <\/p>\n
3. Summary<\/p>\n
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. <\/p>"}
Home
Backend Development
PHP Tutorial
PHP implements image upload and cropping functions
PHP implements image upload and cropping functions
Jun 23, 2023 am 09:31 AM
php
upload picture
Cropping function
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>圖片上傳</title>
</head>
<body>
<form action="upload.php" method="post" enctype="multipart/form-data">
<input type="file" name="file">
<input type="submit" value="上傳">
</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
// 指定文件上傳的目錄
$target_dir = "uploads/";
$target_file = $target_dir . basename($_FILES["file"]["name"]);
// 獲取文件類型
$imageFileType = strtolower(pathinfo($target_file,PATHINFO_EXTENSION));
// 檢查文件是否是圖片
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.";
$uploadOk = 0;
}
}
// 如果文件已經(jīng)存在，提示并退出
if (file_exists($target_file)) {
echo "Sorry, file already exists.";
$uploadOk = 0;
}
// 檢查文件大小
if ($_FILES["file"]["size"] > 500000) {
echo "Sorry, your file is too large.";
$uploadOk = 0;
}
// 允許上傳的圖片類型
if($imageFileType != "jpg" && $imageFileType != "jpeg" && $imageFileType != "png" && $imageFileType != "gif" ) {
echo "Sorry, only JPG, JPEG, PNG & GIF files are allowed.";
$uploadOk = 0;
}
// 如果沒(méi)有錯(cuò)誤，進(jìn)行文件上傳
if ($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:
//載入原圖
$src = imagecreatefromjpeg('test.jpg');
//裁剪原圖
$dst = imagecreatetruecolor(100, 100);
imagecopyresampled($dst, $src, 0, 0, 50, 50, 100, 100, 100, 100);
//保存裁剪后的圖片
imagejpeg($dst, 'test_crop.jpg');
//釋放原圖和裁剪后的圖片
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.
The above is the detailed content of PHP implements image upload and cropping functions. For more information, please follow other related articles on the PHP Chinese website!
Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
How to get the current session ID in PHP?
Jul 13, 2025 am 03:02 AM
The method to get the current session ID in PHP is to use the session_id() function, but you must call session_start() to successfully obtain it. 1. Call session_start() to start the session; 2. Use session_id() to read the session ID and output a string similar to abc123def456ghi789; 3. If the return is empty, check whether session_start() is missing, whether the user accesses for the first time, or whether the session is destroyed; 4. The session ID can be used for logging, security verification and cross-request communication, but security needs to be paid attention to. Make sure that the session is correctly enabled and the ID can be obtained successfully.
PHP get substring from a string
Jul 13, 2025 am 02:59 AM
To extract substrings from PHP strings, you can use the substr() function, which is syntax substr(string$string,int$start,?int$length=null), and if the length is not specified, it will be intercepted to the end; when processing multi-byte characters such as Chinese, you should use the mb_substr() function to avoid garbled code; if you need to intercept the string according to a specific separator, you can use exploit() or combine strpos() and substr() to implement it, such as extracting file name extensions or domain names.
How do you perform unit testing for php code?
Jul 13, 2025 am 02:54 AM
UnittestinginPHPinvolvesverifyingindividualcodeunitslikefunctionsormethodstocatchbugsearlyandensurereliablerefactoring.1)SetupPHPUnitviaComposer,createatestdirectory,andconfigureautoloadandphpunit.xml.2)Writetestcasesfollowingthearrange-act-assertpat
How to split a string into an array in PHP
Jul 13, 2025 am 02:59 AM
In PHP, the most common method is to split the string into an array using the exploit() function. This function divides the string into multiple parts through the specified delimiter and returns an array. The syntax is exploit(separator, string, limit), where separator is the separator, string is the original string, and limit is an optional parameter to control the maximum number of segments. For example $str="apple,banana,orange";$arr=explode(",",$str); The result is ["apple","bana
JavaScript Data Types: Primitive vs Reference
Jul 13, 2025 am 02:43 AM
JavaScript data types are divided into primitive types and reference types. Primitive types include string, number, boolean, null, undefined, and symbol. The values are immutable and copies are copied when assigning values, so they do not affect each other; reference types such as objects, arrays and functions store memory addresses, and variables pointing to the same object will affect each other. Typeof and instanceof can be used to determine types, but pay attention to the historical issues of typeofnull. Understanding these two types of differences can help write more stable and reliable code.
Using std::chrono in C
Jul 15, 2025 am 01:30 AM
std::chrono is used in C to process time, including obtaining the current time, measuring execution time, operation time point and duration, and formatting analysis time. 1. Use std::chrono::system_clock::now() to obtain the current time, which can be converted into a readable string, but the system clock may not be monotonous; 2. Use std::chrono::steady_clock to measure the execution time to ensure monotony, and convert it into milliseconds, seconds and other units through duration_cast; 3. Time point (time_point) and duration (duration) can be interoperable, but attention should be paid to unit compatibility and clock epoch (epoch)
How to pass a session variable to another page in PHP?
Jul 13, 2025 am 02:39 AM
In PHP, to pass a session variable to another page, the key is to start the session correctly and use the same $_SESSION key name. 1. Before using session variables for each page, it must be called session_start() and placed in the front of the script; 2. Set session variables such as $_SESSION['username']='JohnDoe' on the first page; 3. After calling session_start() on another page, access the variables through the same key name; 4. Make sure that session_start() is called on each page, avoid outputting content in advance, and check that the session storage path on the server is writable; 5. Use ses
How does PHP handle Environment Variables?
Jul 14, 2025 am 03:01 AM
ToaccessenvironmentvariablesinPHP,usegetenv()orthe$_ENVsuperglobal.1.getenv('VAR_NAME')retrievesaspecificvariable.2.$_ENV['VAR_NAME']accessesvariablesifvariables_orderinphp.iniincludes"E".SetvariablesviaCLIwithVAR=valuephpscript.php,inApach
See all articles
