Introduction

PHP is not limited to creating just HTML output. It can also be used to create and manipulate image files in a variety of different image formats, including gif, png, jpg, wbmp, and xpm. Even more convenient, PHP can output image streams directly to a browser. You will need to compile PHP with the GD library of image functions for this to work. GD and PHP may also require other libraries, depending on which image formats you want to work with.

You can use the image functions in PHP to get the size of JPEG, GIF, PNG, SWF, TIFF and JPEG2000 images.

Requirements

If you have the GD library (available at http://www.boutell.com/gd/) you will also be able to create and manipulate images.

The format of images you are able to manipulate depend on the version of GD you install, and any other libraries GD might need to access those image formats. Versions of GD older than gd-1.6 support GIF format images, and do not support PNG, where versions greater than gd-1.6 support PNG, not GIF.

You may wish to enhance GD to handle more image formats.

You may wish to enhance GD to deal with different fonts. The following font libraries are supported:

If you have PHP compiled with --enable-exif you are able to work with information stored in headers of JPEG and TIFF images. This way you can read meta data generated by digital cameras as mentioned above. These functions does not require the GD library.

Installation

To enable GD-support configure PHP --with-gd[=DIR], where DIR is the GD base install directory. To use the recommended bundled version of the GD library configure --with-gd. In Windows you'll include php_gd2.dll as an extension in php.ini. There is also php_gd.dll for GD1 but it's not preferred.

Enhance the capabilities of GD to handle more image formats by specifying the --with-XXXX configure switch to your PHP configure line.

Enhance the capabilities of GD to deal with different fonts by specifying the --with-XXXX configure switch to your PHP configure line.

Runtime Configuration

The behaviour of these functions is affected by settings in php.ini.

Exif supports automatically conversion for Unicode and JIS character encodings of user comments when module mbstring is available. This is done by first decoding the comment using the specified characterset. The result is then encoded with another characterset which should match your HTTP output.

Here is a short explanation of the configuration directives.

Resource Types

This extension has no resource types defined.

Predefined Constants

The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.

Examples

Example 1. PNG creation with PHP <?php header("Content-type: image/png"); $string = $_GET['text']; $im = imagecreatefrompng("images/button1.png"); $orange = imagecolorallocate($im, 220, 210, 60); $px = (imagesx($im) - 7.5 * strlen($string)) / 2; imagestring($im, 3, $px, 9, $string, $orange); imagepng($im); imagedestroy($im); ?>

This example would be called from a page with a tag like: <img src="button.php?text">. The above button.php script then takes this "text" string and overlays it on top of a base image which in this case is "images/button1.png" and outputs the resulting image. This is a very convenient way to avoid having to draw new button images every time you want to change the text of a button. With this method they are dynamically generated.