Úprava obrázku pomocí PHP GD knihovny

<?php
/*
 * Editing of images using PHP GD Library
 * Author: Jiri Thiemel <Thiemel.Jiri@gmail.com>
 */

function create_image($file, $new_width, $new_height)
{
	# If GD Library is not installed
	if (!function_exists("gd_info"))
		send_file($file);
	
	# Get new sizes
	if (!is_numeric($new_width))
		unset($new_width);
	
	if (!is_numeric($new_height))
		unset($new_height);
	
	list($width, $height)=getimagesize($file);
	
	if (isset($new_width) && !isset($new_height))
	{
		$newwidth=$new_width;
		$newheight=$new_width/$width*$height;
	}
	else if (isset($new_height) && !isset($new_width))
	{
		$newheight=$new_height;
		$newwidth=$new_height/$height*$width;
	}
	else if (isset($new_width) && isset($new_height))
	{
		$newwidth=$new_width;
		$newheight=$new_height;
	}
	else
	{
		$newwidth=$width;
		$newheight=$height;
	}

	# Load image
	switch(exif_imagetype($file))
	{
	  case 1:	$source=imagecreatefromgif($file); $content_type="image/gif"; break;
	  case 2:	$source=imagecreatefromjpeg($file); $content_type="image/jpeg"; break;
	  case 3:	$source=imagecreatefrompng($file); $content_type="image/png"; break;
	}
	
	# New image
	if(function_exists("imagecreatetruecolor") && $content_type!="image/png" && $content_type!="image/gif")
		$thumb=imagecreatetruecolor($newwidth, $newheight);
	else
		$thumb=imagecreate($newwidth, $newheight);

	# Resize image
	imagecopyresized($thumb, $source, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);

	# Output
	header("Content-type: ".$content_type);
	header("Last-Modified: ".date('r',filemtime($file)));

	if ($newwidth==$width && $newheight==$newheight)
		readfile($file);
	else
	{
		switch(exif_imagetype($file))
		{
			case IMAGETYPE_JPEG:	imagejpeg($thumb, null, 95);	break;
			case IMAGETYPE_GIF:		imagegif($thumb, null, 95);		break;
			case IMAGETYPE_PNG:
				if (function_exists('imagesavealpha'))
				{
					imagealphablending($thumb, false);
					imagesavealpha($thumb, true);
				}
				imagepng($thumb, null, 95);
				break;
		}
	}

	die();
}