Jason Pruim wrote:
>
> On Jan 16, 2007, at 4:10 PM, Jochem Maas wrote:
>
>> generating/resampling image data is a relatively heavy job for a script
>> to perform. there maybe optimizations available in the script itself but
>> generally caching the results the generation/resampling action is the
>> way to
>> increase performance ... you need a mechanism to check/store/retrieve
>> cached
>> images [and a way to automatically regenerate a cached image when the
>> source
>> image has changes].
>>
>> another thing to consider on top of caching is to store the cached
>> data on a
>> 'ram' drive ... on linux I often use a sub directory on /dev/shm
>> (which is
>> a part of the filesystem which actually exists only in shared memory -
>> more than
>> likely that you dont have access to this on a shared hosting environment.
>
> Luckily I'm not in a shared hosting environment. :) I sit about 3 feet
> away from the server that is running my script. I will look into caching
> the info though to see if I can figure out what I would have to
> change/add/delete to accomplish this.
I wouldn't bother with worrying about stored cached image output on
/dev/shm until you have got caching working - although disk access is relatively
slow it's not half as slow as regenerating a thumbnail on every request.
here is a class that might help you when it comes to caching images,
assuming you can work out how it works ;-)
(I'm sure this class is not perfect but it works for me :-)
<?php
class ImageCache
{
var $validTypes = array('png','gif','jpeg');
var $cacheFileName;
var $cacheFileType;
var $cacheDir;
var $im;
/* you must give a valid 'cache' dir */
function ImageCache($cDir)
{
$this->cacheDir = $cDir;
}
/* generate a cache file name for the image your are generating
* if your generated output image is dependent on the values of one or more
request
* variables then you should add the names to the $args array e.g.
*
* your script take width/height parameter: /image.php?width=200&height=160
*
* $args should be the following array: array('width', 'height');
*/
function genCacheFileName($args = array(), $type = '', $prefix = '')
{
/* name/val pair delimiter in the string that results in the hash for
the cache id */
$qHashMark = '%~^*';
$qry = array();
$args = (array)$args; natsort($args);
foreach ($args as $arg) {
if (($val = $this->getR( $arg, false )) !== false) {
$qry[] = "{$arg}=".str_replace($qHashMark,'',$val);
}
}
$sep = '-:-';
$hash = md5($_SERVER['HTTP_HOST'] .$sep. $_SERVER['SCRIPT_NAME'] .$sep.
join($qHashMark,$qry));
if (!in_array($type, $this->validTypes)) {
if ($type == 'jpg') {
$type = 'jpeg';
} else {
$type = 'png';
}
}
$this->cacheFileType = $type;
if (!$prefix) {
$prefix = 'cacheimg';
}
return ($this->cacheFileName = "{$prefix}_{$hash}.{$type}");
}
/* get the fullpath to the location where the cache file is saved/stored */
function getCacheFilePath()
{
return $this->cacheDir . '/' . $this->cacheFileName;
}
/* Return true if the cache file is younger than the source file(s),
* false otherwise.
*
* if this func returns true you can output the relevant cache file,
* if false is returned it's your responsibility to generate the output file
* and save it to the location given by $this->getCacheFilePath()
*
* the (array of) files passed to this function should be complete paths,
* not just filesnames.
*/
function checkCache( $files = array() )
{
$cacheState = true;
$cf = $this->getCacheFilePath();
$mTime = is_readable($cf) ? filemtime($cf): 0;
$lastModified = gmdate("D, d M Y H:i:s ", $mTime)."GMT";
$files = (array) $files;
if (!count($files) || !$mTime) {
$cacheState = false;
} else {
foreach($files as $file) {
if ($mTime < filemtime( $file )) {
$cacheState = false;
break;
}
}
}
if ($cacheState) {
$headers = getallheaders();
if (isset($headers['If-Modified-Since']) &&
($headers['If-Modified-Since'] == $lastModified)) {
/* The UA has the exact same image we have. */
header("HTTP/1.1 304 Not Modified");
exit;
} else {
unset($headers);
header("Last-Modified: ".$lastModified);
return true;
}
} else {
// not cached - or cache invalidated
// must cache the (new) data.
return false;
}
}
function showImage($type = '', $quality = 100)
{
header( "Content-type: image/{$this->cacheFileType}" );
readfile( $this->getCacheFilePath() );
exit;
}
function getR($v = '', $r = null, $t = null)
{
if (!empty($v)) { if (isset($_REQUEST[$v]))
{$r=!is_null($t)?$t:$_REQUEST[$v];} }
return $r;
}
}
?>
>
> Would upgrading to PHP 5* be of any help?
not specifically in this case, but I would recommended using php5
if your starting out and developing new stuff.
php4 is not being actively developed (security & bug fixes still occur).
it's not wrong to use php4, and many people have no choice, but I recommend
trying to stay on top of whats current and given that your not (AFAICT) running
any legacy code there is nothing really stopping you.
> I've thought about upgrading
> but not knowing much about how to run the server from the command
> line(Part of what I'm learning) I didn't want to screw anything up.
>
>
test servers are there to be screwed up, kind of. when your learning and trying
things
out thing break occasionally. ommelettes, breaking eggs, all that jazz.
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