How to use PHP to process and operate images?
With the continuous development of the Internet, pictures have become an important medium for people to communicate and disseminate information online. For website developers, processing and manipulating images is very necessary. Among many programming languages, PHP is a very popular language. This article will introduce how to use PHP to process and operate images.
1. Image upload
In web pages, users are usually required to upload images, and the file upload mechanism provided by PHP makes image uploading very simple. The following is a sample code:
<html> <body> <form action="upload.php" method="post" enctype="multipart/form-data"> <label for="file">选择图片：</label> <input type="file" name="file" id="file"><br> <input type="submit" name="submit" value="上传"> </form> </body> </html>
The code for uploading files can be processed in the upload.php file. The sample code is as follows:
<?php
if (isset($_POST["submit"])) {
$file_name = $_FILES["file"]["name"];
$file_tmp = $_FILES["file"]["tmp_name"];
move_uploaded_file($file_tmp, "uploads/" . $file_name);
echo "上传成功。";
}
?>In the above code, ## The #move_uploaded_file() function moves the uploaded image to the uploads/ directory and saves it on the server.
imagecrop() function for image cropping. The sample code is as follows:
$filename = "uploads/test.jpg"; $image = imagecreatefromjpeg($filename); $crop_image = imagecrop($image, ['x' => 0, 'y' => 0, 'width' => 200, 'height' => 200]); imagejpeg($crop_image, "uploads/crop.jpg");
imagecreatefromjpeg() and imagecrop()Read and crop a picture respectively. Once the cropping is complete, save it on the server.
imagescale() function to perform image scaling. The sample code is as follows:
$filename = "uploads/test.jpg"; $image = imagecreatefromjpeg($filename); $scale_image = imagescale($image, 200); imagejpeg($scale_image, "uploads/scale.jpg");
imagecreatefromjpeg() and imagescale()Read and scale a picture respectively. Once the scaling is complete, save it on the server.
imagecopy() and imagecopymerge() functions for image watermark processing. The sample code is as follows:
$filename = "uploads/test.jpg";
$image = imagecreatefromjpeg($filename);
$watermark = imagecreatefrompng("watermark.png");
imagecopy($image, $watermark, 0, 0, 0, 0, imagesx($watermark), imagesy($watermark));
imagejpeg($image, "uploads/watermark.jpg");imagecreatefrompng() reads the watermark image, and imagecopy() merges it at the specified location. Finally, the merged image is saved on the server.
quality parameter in the imagejpeg() function for image compression. The sample code is as follows:
$filename = "uploads/test.jpg"; $image = imagecreatefromjpeg($filename); imagejpeg($image, "uploads/compress.jpg", 50);
imagecreatefromjpeg()Read in a picture. imagejpeg()Save it on the server. The quality parameter is 50, which means the image quality has been reduced by 50%.
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