Creating an Image with PHP’s GD

Added on Monday, December 15th, 2008. Written by DEVpapers.

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.

Solution

PHP’s GD library is a great tool to manipulate graphics on the fly. Use the ImageCreate() function and then use the ImagePng(), ImageJpeg(), or ImageGif function, depending on your system:

<?php
header( “Content-type: image/gif” );
$im = ImageCreate( 153, 20 ); // width, height

$red = ImageColorAllocate( $im, 255, 0, 0 );
$white = ImageColorAllocate( $im, 255, 255, 255 );

ImageString($im,3,3,3,”Programmabilities.com”,$white);
ImageGif( $im );
// Or ImageGif($im, $filename) if you want to save
// it to a file. –Provide an optional second argument.

ImageDestroy( $im ); // Free memory
?>

Discussion

If you run the preceding script, you should see something like the image on this page: http://programmabilities.com/php/image-create.php. Let’s go over this line by line:

Line 2: Print the header telling the Web browser thet this is a GIF image.

Line 3: Create a GD image stream that can be manipulated by any of the other GD functions. The format of this image is not determined until we tell GD that it is a GIF and print it out on line 9.

Line 5: Create the background color for the image and set it to red using the ImageColorAllocate() function.

Line 6: Create the foreground color for the image and set it to white by using the ImageColorAllocate() function.

Line 8: Draw a string to image $im using a built-in font at x-pixel location of 3 and a y-pixel location of 3. The contents of the string is “Programmabilities.com” and the color of the string is white, denoted by the variable $white.

Line 9: Convert the image to a GIF and output to the browser.

Line last: Destroy the memory allocated for the GIF. This is done when the script executes anyway.