How to use PHP to process and operate images?-PHP Tutorial-php.cn

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:

   选择图片：

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The code for uploading files can be processed in theupload.phpfile. The sample code is as follows:

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In the above code, ## The #move_uploaded_file()function moves the uploaded image to theuploads/directory and saves it on the server.

2. Picture cropping

Picture cropping is to crop the picture and keep only the required part. This is very common in practical applications, mainly including avatar cropping, advertising image cropping, etc. PHP provides the

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");

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In the above code,

imagecreatefromjpeg()andimagecrop()Read and crop a picture respectively. Once the cropping is complete, save it on the server.

3. Picture scaling

Picture scaling refers to reducing or enlarging the picture proportionally. This is very useful when processing user-uploaded images to prevent them from being too large and causing long loading times. PHP provides the

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");

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In the above code,

imagecreatefromjpeg()andimagescale()Read and scale a picture respectively. Once the scaling is complete, save it on the server.

4. Picture watermark

Picture watermark refers to adding text or other pictures to the picture. This is very useful in copyright protection, advertising, etc. PHP provides

imagecopy()andimagecopymerge()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");

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In the above code,

imagecreatefrompng()reads the watermark image, andimagecopy()merges it at the specified location. Finally, the merged image is saved on the server.

5. Image Compression

Image compression refers to reducing the size of image files to reduce loading time and save storage space. Very useful in practical applications. PHP provides the

qualityparameter in theimagejpeg()function for image compression. The sample code is as follows:

$filename = "uploads/test.jpg"; $image = imagecreatefromjpeg($filename); imagejpeg($image, "uploads/compress.jpg", 50);

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In the above code,

imagecreatefromjpeg()Read in a picture.imagejpeg()Save it on the server. Thequalityparameter is 50, which means the image quality has been reduced by 50%.

In short, it is very useful to use PHP to process and operate images. Through the above common methods, developers can easily crop, zoom, watermark and compress images. This has important implications for website performance, user experience, and content presentation.

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