Some example code for re-sizing images in PHP.

ExamplePicture.class.php

<?php
/**
 * This file contains the class ExamplePicture.
 * @package ExampleMiddleWare
**/

/**
 * Include files
**/
require_once("bmp.php");

/**
 * This class resizes images. 
 * onle one static function to set the users Avatar.
 * It is likely to remain that way.
 * @package ExampleMiddleWare
**/
class ExamplePicture {

	/**
	 * Copies a bmp to a png, while scaling it.
	 * @param string $srcFile The name of the source file.
	 * @param string $destFile The name of the destination file
	 * @param int $width The width of the destination image.
	 * @param int $height The height of the destination image.
	**/
	public static function ScaleBmp2Png($srcFile, $destFile, $width, $height) {
		$srcInfo = getimagesize($srcFile);
		$im = imagecreatefrombmp($srcFile);
		$im_dest = imagecreatetruecolor ($width, $height);
		imagealphablending($im_dest, false);

		imagecopyresampled
			($im_dest, $im, 0, 0, 0, 0, 
			$width, $height, $srcInfo[0], $srcInfo[1]);

		imagesavealpha($im_dest, false);
		imagepng($im_dest, $destFile);
	}


	/**
	 * Copies a gif, while scaling it.
	 * @param string $srcFile The name of the source file.
	 * @param string $destFile The name of the destination file
	 * @param int $width The width of the destination image.
	 * @param int $height The height of the destination image.
	**/
	public static function ScaleGif($srcFile, $destFile, $width, $height) {

		$srcInfo = getimagesize ($srcFile);
		$im = imagecreatefromgif($srcFile);
		$im_dest = imagecreatetruecolor ($width, $height);
		imagealphablending($im_dest, false);

		imagecopyresampled
			($im_dest, $im, 0, 0, 0, 0, 
			$width, $height, $srcInfo[0], $srcInfo[1]);

		imagesavealpha($im_dest, true);
		imagegif($im_dest, $destFile);
	}


	/**
	 * Copies a jpeg, while scaling it.
	 * @param string $srcFile The name of the source file.
	 * @param string $destFile The name of the destination file
	 * @param int $width The width of the destination image.
	 * @param int $height The height of the destination image.
	**/
	public static function ScaleJpeg($srcFile, $destFile, $width, $height) {

		$srcInfo = getimagesize ($srcFile);
		$im = imagecreatefromjpeg($srcFile);
		$im_dest = imagecreatetruecolor ($width, $height);
		imagealphablending($im_dest, false);

		imagecopyresampled
			($im_dest, $im, 0, 0, 0, 0, 
			$width, $height, $srcInfo[0], $srcInfo[1]);

		imagesavealpha($im_dest, true);
		imagejpeg($im_dest, $destFile);
	}


	/**
	 * Copies a png, while scaling it.
	 * @param string $srcFile The name of the source file.
	 * @param string $destFile The name of the destination file
	 * @param int $width The width of the destination image.
	 * @param int $height The height of the destination image.
	**/
	public static function ScalePng($srcFile, $destFile, $width, $height) {
		$srcInfo = getimagesize ($srcFile);
		$im = imagecreatefrompng($srcFile);
		$im_dest = imagecreatetruecolor ($width, $height);
		imagealphablending($im_dest, false);

		imagecopyresampled
			($im_dest, $im, 0, 0, 0, 0, 
			$width, $height, $srcInfo[0], $srcInfo[1]);

		imagesavealpha($im_dest, true);
		imagepng($im_dest, $destFile);
	}
}

?>