Gallery loading slowly [duplicate] - php

Question

This question already exists:
Closed 10 years ago.
Possible Duplicate:
Thumbnails in php generated gallery loading slow
Code link can be found on the bottom of the page.
The site is running from 1and1.co.uk linux based system, good enough to load the gallery much faster than it currently does.
The php generated thumbnails are loading a bit slow, can you tell me why?
http://site-perf.com/cgi-bin/show.cgi?id=vz5le19Fp5E
code:
http://satinaweb.com/tmp/functions.txt
Here is crop.php:
$sourceimage = $_GET['a'];
function crop($sourceimage) {
// Draw & resize
header('Content-Type: $imsz[\'mime\']');
list($width, $height) = getimagesize($sourceimage);
if($width > $height){
$new_width = 100;
$new_height = 75;
} else {
$new_width = 75;
$new_height = 100;
}
$image = imagecreatefromjpeg($sourceimage);
$image_p = imagecreatetruecolor($new_width, $new_height);
imagecopyresampled($image_p, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
imagejpeg($image_p);
imagedestroy($image_p);
imagedestroy($image);
}
crop($sourceimage);
If you have questions, please ask!

Answer 1

What you should have noticed from your site-perf graph most is that,
I'm not going to look through all your code, but you have a file called crop.php. This is going to be slow because it (presumably) crops the images on every page load, which takes a relatively long time (made apparent from the site-perf data); for each request, the browser spends most of it's time waiting for the server to respond.
You should consider using a cache folder to store cropped images and serve them up as-is to reduce loading time.
In crop.php, you could do something like this (pseudo code):
IF original image newer than cropped OR cropped doesn't exist
Load original image
Crop original image
Save cropped image to cache folder
ELSE
Serve already-cropped image from cache
ENDIF
Every time you call crop(), you read the image, modify it and spit it out to the client. This is incredibly wasteful, because you need to re-process the image for every request. You're even destroying the image afterwards (not that this makes much difference). Instead, use is_file() with a cache directory, and save the image to disk as well as sending it to the client.
Now, your script might look like this:
$sourceimage = $_GET['a'];
$cache_dir = dirname(__FILE__) . "/cache"; // Cache directory
$cache_file = $cache_dir . '/' . $source_image; // Path to cached image
function crop($sourceimage) {
header('Content-Type: $imsz[\'mime\']');
// If cached version of cropped image doesn't exist, create it
if(!is_file($cache_file)) {
list($width, $height) = getimagesize($sourceimage);
if($width > $height) {
$new_width = 100;
$new_height = 75;
} else {
$new_width = 75;
$new_height = 100;
}
$image = imagecreatefromjpeg($sourceimage);
$image_p = imagecreatetruecolor($new_width, $new_height);
imagecopyresampled($image_p, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
imagejpeg($image_p, $cache_file); // Save image file to disk
} else { // If cached file exists, output to browser without processing
echo file_get_contents($cache_file);
}
}
crop($sourceimage);
This is untested, but should work. Please don't just copy and paste the above code; read through it and make sure you understand how and why it does what it does.

Answer 2

Your page is loading slowly due to HTTP requests being queued.
Although each image is small, the requests are spending a large proportion of their time queued, waiting for other requests to finish before they start, in the worst cases, they are waiting for one and a half seconds before they even start downloading.
The second delay is then caused by the time it takes to create the images.
The actual download was nearly instant after waiting for these other processes.
Queued 1600ms
Waiting 986ms
Download 0ms
Rather than generate the correct sized images every time, why not store the result to be used on subsequent visits - this means the page will be slow once and then much faster all other times.
If the time your script took to crop the images was shorted, the queueing would be shorter too. Here is an example...
Check in a folder for the cropped image
If it exists, serve it (no computation required)
If it doesn't exist, generate it
Save the result in the folder to cache it