Generating thumbnail in simple php

When we are doing a website with gallery options,their araise situation where we want to generate thumbnails of images. This is neccessry because it helps in loading images fast and also wecvan specify the size of the image we want to see. just include this code in your project. copy the below code and paste in a file named thumb.php.
<?php

$site_config['document_root'] = $_SERVER['DOCUMENT_ROOT'].'/dadmin/';
$thumb_size = 128; //all thumbnails are this maximum width or height if not specified via get
$site_config['absolute_uri']=str_replace('///','//',str_replace('thumb.php?'.$_SERVER['QUERY_STRING'],'',$_SERVER['REQUEST_URI']));
$site_config['path_thumbnail']=$site_config['absolute_uri'].'/cache/'; //where to cache thumbnails on the server, relative to the DOCUMENT_ROOT
$image_error=$site_config['document_root'].$site_config['absolute_uri'].'/images/icons/image_error.png'; // used if no image could be found, or a gif image is specified

$thumb_size_x = 0;
$thumb_size_y = 0;

# Define quality of image
if (@$_GET["quality"]<>0) {
$quality = $_GET["quality"];
} else {
$quality = 80;
}

# Define size of image (maximum width or height)- if specified via get.
if (@$_GET["size"]<>0) {
$thumb_size=intval($_GET["size"]);
}
if (intval(@$_GET["sizex"])>0)
{
$thumb_size_x=intval($_GET["sizex"]);
if (intval(@$_GET["sizey"])>0)
{
$thumb_size_y=intval($_GET["sizey"]);
} else {
$thumb_size_y=$thumb_size_x;
}
}

if (file_exists($_GET['file']))
{
$filename=$_GET['file'];
} else {
$filename=str_replace('//','/',$site_config['document_root'].$site_config['absolute_uri'].'/'.$_GET["file"]);
}

# If calling an external image, remove document_root
if (substr_count($filename, "http://")>0)

{
$filename=str_replace($site_config['document_root'].$site_config['absolute_uri'].'/','',$filename);
}

$filename=str_replace("\'","'",$filename);
$filename=rtrim($filename);
$filename=str_replace("//","/",$filename);
$fileextension=substr($filename, strrpos ($filename, ".") + 1);

$cache_file=str_replace('//','/',$site_config['document_root'].$site_config['path_thumbnail'].md5($filename.@$thumb_size.@$thumb_size_x.@$thumb_size_y.@$quality).'.'.$fileextension);

# remove cache thumbnail?
if (@$_GET['nocache']==1)
{
if (file_exists($cache_file))
{
#remove the cached thumbnail
unlink($cache_file);
}
}

if ((file_exists($cache_file)) && (@filemtime($cache_file)>@filemtime($filename)))
{
header('Content-type: image/'.$fileextension);
header("Expires: Mon, 26 Jul 2030 05:00:00 GMT");
header('Content-Disposition: inline; filename='.str_replace('/','',md5($filename.$thumb_size.$thumb_size_x.$thumb_size_y.$quality).'.'.$fileextension));
echo (join('', file( $cache_file )));
exit; # no need to create thumbnail - it already exists in the cache
}

# determine php and gd versions
$ver=intval(str_replace(".","",phpversion()));
if ($ver>=430)
{
$gd_version=@gd_info();
}

# define the right function for the right image types
if (!$image_type_arr = @getimagesize($filename))
{
header('Content-type: image/png');
if(@$_GET['noerror'])
{
exit;
} else {
echo (join('', file( $site_config['document_root'].$image_error )));
exit;
}
}
$image_type=$image_type_arr[2];

switch ($image_type)
{
case 2: # JPG
if (!$image = @imagecreatefromjpeg ($filename))
{
# not a valid jpeg file
$image = imagecreatefrompng ($image_error);
$file_type="png";
if (file_exists($cache_file))
{
# remove the cached thumbnail
unlink($cache_file);
}
}
break;

case 3: # PNG
if (!$image = @imagecreatefrompng ($filename))
{
# not a valid png file
$image = imagecreatefrompng ($image_error);
$file_type="png";
if (file_exists($cache_file))
{
# remove the cached thumbnail
unlink($cache_file);
}
}
break;

case 1: # GIF
if (!$image = @imagecreatefromgif ($filename))
{
# not a valid gif file
$image = imagecreatefrompng ($image_error);
$file_type="png";
if (file_exists($cache_file))
{
# remove the cached thumbnail
unlink($cache_file);
}
}
break;
default:
$image = imagecreatefrompng($image_error);
break;

}

# define size of original image
$image_width = imagesx($image);
$image_height = imagesy($image);

# define size of the thumbnail
if (@$thumb_size_x>0)
{
# define images x AND y
$thumb_width = $thumb_size_x;
$factor = $image_width/$thumb_size_x;
$thumb_height = intval($image_height / $factor);
if ($thumb_height>$thumb_size_y)
{
$thumb_height = $thumb_size_y;
$factor = $image_height/$thumb_size_y;
$thumb_width = intval($image_width / $factor);
}
} else {
# define images x OR y
$thumb_width = $thumb_size;
$factor = $image_width/$thumb_size;
$thumb_height = intval($image_height / $factor);
if ($thumb_height>$thumb_size)
{
$thumb_height = $thumb_size;
$factor = $image_height/$thumb_size;
$thumb_width = intval($image_width / $factor);
}
}

# create the thumbnail
if ($image_width < 4000) //no point in resampling images larger than 4000 pixels wide - too much server processing overhead - a resize is more economical
{
if (substr_count(strtolower($gd_version['GD Version']), "2.")>0)
{
//GD 2.0
$thumbnail = ImageCreateTrueColor($thumb_width, $thumb_height);
imagecopyresampled($thumbnail, $image, 0, 0, 0, 0, $thumb_width, $thumb_height, $image_width, $image_height);
} else {
//GD 1.0
$thumbnail = imagecreate($thumb_width, $thumb_height);
imagecopyresized($thumbnail, $image, 0, 0, 0, 0, $thumb_width, $thumb_height, $image_width, $image_height);
}
} else {
if (substr_count(strtolower($gd_version['GD Version']), "2.")>0)
{
# GD 2.0
$thumbnail = ImageCreateTrueColor($thumb_width, $thumb_height);
imagecopyresized($thumbnail, $image, 0, 0, 0, 0, $thumb_width, $thumb_height, $image_width, $image_height);
} else {
# GD 1.0
$thumbnail = imagecreate($thumb_width, $thumb_height);
imagecopyresized($thumbnail, $image, 0, 0, 0, 0, $thumb_width, $thumb_height, $image_width, $image_height);
}
}

# insert string
if (@$_GET['tag']<>"")
{
$font=1;
$string= $_GET['tag'];
$white = imagecolorallocate ($thumbnail, 255, 255, 255);
$black = imagecolorallocate ($thumbnail, 0, 0, 0);
imagestring ($thumbnail, $font, 3, $thumb_height-9, $string, $black);
imagestring ($thumbnail, $font, 2, $thumb_height-10, $string, $white);
}

switch ($image_type)
{
case 2: # JPG
header('Content-type: image/jpeg');
header('Content-Disposition: inline; filename='.str_replace('/','',md5($filename.$thumb_size.$thumb_size_x.$thumb_size_y.$quality).'.jpeg'));
@imagejpeg($thumbnail,$cache_file, $quality);
imagejpeg($thumbnail,'',$quality);

break;
case 3: # PNG
header('Content-type: image/png');
header('Content-Disposition: inline; filename='.str_replace('/','',md5($filename.$thumb_size.$thumb_size_x.$thumb_size_y.$quality).'.png'));
@imagepng($thumbnail,$cache_file);
imagepng($thumbnail);
break;

case 1: # GIF
if (function_exists('imagegif'))
{
header('Content-type: image/gif');
header('Content-Disposition: inline; filename='.str_replace('/','',md5($filename.$thumb_size.$thumb_size_x.$thumb_size_y.$quality).'.gif'));
@imagegif($thumbnail,$cache_file);
imagegif($thumbnail);
} else {
header('Content-type: image/jpeg');
header('Content-Disposition: inline; filename='.str_replace('/','',md5($filename.$thumb_size.$thumb_size_x.$thumb_size_y.$quality).'.jpg'));
@imagejpeg($thumbnail,$cache_file);
imagejpeg($thumbnail);
}
break;
}

//clear memory
imagedestroy ($image);
imagedestroy ($thumbnail);

?>

and now in the place where you want to view thumbnail image...put this code
<a href="../uploads/<?php echo $records[$i]['img_loc'];?>" target="_blank">
<img src="thumb.php?file=../uploads/<?php echo $records[$i]['img_loc'];?>&size=50px" alt="<?php echo $records[$i]["img_loc"];?>" class="thumb"></a>

specify image and size here...