Basic knowledge of php gd library

echo phpinfo();
?>

Save it, then open phpinfo.php through the browser, search for 'gd', and see if there is any of the following:

If it is stated that the system already supports the GD library, if not, you need to recompile PHP to support the GD library. 3. Image formats supported by GD The GD library does not support all image formats by default. From the information in the picture above, you can see which image formats the system's GD library supports. JPG Support indicates that the JPG format is supported, and those not listed are not supported. 4. Classification of GD functions I think GD functions can be divided into 6 categories: 1. Obtain information 2. Create images 3. Draw a picture 4. Copy 5. Output 6. Destroy

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