starting with GD2

ajdegans

Hey there,,,

If i want on the fly image resizing for a photogallery...

What functions should i look up and how can i implement this best?

I looked at phpnet and theres a whole lot of stuff about GD2 but (again) i cannot seem to find an answer...

Any ideas welcome! Thanks in advance! 😃

section31

Doing it with GD would be difficult and limited...
Check if you're server has image magick installed.

http://www.imagemagick.org/

just a few threads down i found this

http://www.phpbuilder.com/board/showthread.php?s=&threadid=10287864

ajdegans

Hi there, thanks for your reply...

ImageMagick looks promising 🙂 but honestly i have no idea if its installed on the server... It my private server with a standard config... apache1.3.31/php4.3.9/mysql4.21 or i thought.... running on win2k pro sp4, but i dont know what comes standard with either PHP or Apache, i found GD in the php.ini so i figured that would be best since its native then?

Anyway... How does this work? I cannot really find anything like functions as of now... also the download link for the windows compiled .dll does not work on http://pecl.php.net/package/imagick 🙁

got some pointers?

Weedpacket

Originally posted by section31
Doing it with GD would be difficult and limited...

Bollocks; it's trivial. There's a function for it: [man]imagecopyresized[/man] Two, in fact. The other one is [man]imagecopyresampled[/man] and would probably give better quality.

ajdegans

i will look into that 😉

imagemagick seems weird !

Thanks weedpacket 🙂

<?php
// The file
$filename = 'test.jpg';

// Set a maximum height and width
$width = 200;
$height = 200;

// Content type
header('Content-type: image/jpeg');

// Get new dimensions
list($width_orig, $height_orig) = getimagesize($filename);

if ($width && ($width_orig < $height_orig)) {
   $width = ($height / $height_orig) * $width_orig;
} else {
   $height = ($width / $width_orig) * $height_orig;
}

// Resample
$image_p = imagecreatetruecolor($width, $height);
$image = imagecreatefromjpeg($filename);
imagecopyresampled($image_p, $image, 0, 0, 0, 0, $width, $height, $width_orig, $height_orig);

// Output
imagejpeg($image_p, null, 100);
?>

Php example...

I Could use this snippet and alter it a little for my needs. But this makes a 2nd image i suppose?

Any way to make it work with temporary files? like when someone loads the page it creates the images... and when the visitor leaves the images are deleted or lost again...

Or isnt that functional / practical

section31

That code creates a jpeg on the fly...it doesn't put it on your server...

but if you do want to delete a file...use the unlink function...

http://us2.php.net/manual/en/function.unlink.php

Weedpacket

A bit tidier would be to have the image's src= attribute link to a PHP script (the above sample, with $filename determined by examining the URL's querystring) that generates the thumbnail. It doesn't save the file on the server, it sends it straight out to the client.

To save the image on the server, use imagejpeg's second argument and leave out the header. It'll be up to you to decide when it would be safe to delete it (probably can't do it immediately, because if you did they'd probably be deleted before the request to see them comes back from the client. You'd have to look through your collection of temporary thumbnail images every now and then to see which ones are too old to be worth keeping. There'll probably be dozens of duplicate thumbnails - one for each view of the page - suggesting that you might as well just generate the thumbnails once and reuse them. But that's not "on the fly" any more).

section31

I just benchmarked both gd and imagemagick on my server ...and GD is extremely slow.

Using a high megapixel 3MB image.

Using Image Magick v5
average .45 seconds

Using GD
Using imagecopyresized - average 2 seconds
Using imagecopyresampled - average 11 seconds.

Amazing isn't it.

Server stats: http://server23.totalchoicehosting.com/serverDetails/

Weedpacket

What's network latency like for users under typical conditions?

More time still could be saved by not doing the resizing on the fly, but instead caching the thumbnails; then the time it takes to copy a 3MB file to the server becomes relevant, and the time to resize becomes a constant that amortises toward zero over time.

section31

The network latency is negligible, since i have it write directly the server.


<?php
function mtime (){
  $mtime = explode(" ",microtime());  $mtime = $mtime[1] + $mtime[0];
  return $mtime;
}

$tstart = mtime();
// The file
$filename = 'hugepic.jpg';

// Set a maximum height and width
$width = 200;
$height = 200;

// Content type
//header('Content-type: image/jpeg');

// Get new dimensions
list($width_orig, $height_orig) = getimagesize($filename);

if ($width && ($width_orig < $height_orig))
   $width = ($height / $height_orig) * $width_orig;
else
   $height = ($width / $width_orig) * $height_orig;

// exec (" convert -quality 40 -size '{$width}x{$height}' '$filename' -resize '{$width}x{$height}' +profile \"*\" 'tn_{$filename}' ");


// Resample
$image_p = imagecreatetruecolor($width, $height);
$image = imagecreatefromjpeg($filename);
imagecopyresized($image_p, $image, 0, 0, 0, 0, $width, $height, $width_orig, $height_orig);

// Output
imagejpeg($image_p, 'newpic.jpg', 60);

$tend = mtime();
$totaltime = round(($tend - $tstart),3);

echo "<br /><h1> Page Load Time: $totaltime seconds. </h1>";
?>

Weedpacket

Originally posted by section31
The network latency is negligible, since i have it write directly the server.

Ah, so when I'm over here at the end of a 56kbps connection, I get the result as quickly as I would if I were sitting where you are at your server?

ajdegans

lol thats stupid section31... Offcoarse a 56k6 is slower as a 2mb adsl...

Maybe the server is fast enough, but the connection aint.... So if the scripts generates images so fast the connection cannot cope up its a useless thing for me since im on a 2mb adsl line with my server 🙂

ajdegans

Originally posted by ajdegans
// Content type
header('Content-type: image/jpeg');

Is the header really nessecary?

When ever i use a line like that i get errors about headers being send out already... obviously!

How do i fix that?

section31

Originally posted by ajdegans
Is the header really nessecary?

When ever i use a line like that i get errors about headers being send out already... obviously!

How do i fix that?

no...the reason i commented it out was because I have the resized image saved to the server..

if you want it to just output to the browser...leave the second argument to null... then uncomment the header function...

The reason you get those errors is because you have already sent data out of the script. You must call header before you send anything out to the browser.

All of this info I just told you can be found in php's manual.. make this your personal friend if you plan on writing scripts yourself.

Originally posted by php.net
Remember that header() must be called before any actual output is sent, either by normal HTML tags, blank lines in a file, or from PHP.

Originally posted by php.net
The filename argument is optional, and if left off, the raw image stream will be output directly. To skip the filename argument in order to provide a quality argument just use an empty string (''). By sending an image/jpeg content-type using header(), you can create a PHP script that outputs JPEG images directly.

section31

Originally posted by ajdegans
lol thats stupid section31... Offcoarse a 56k6 is slower as a 2mb adsl...

Maybe the server is fast enough, but the connection aint.... So if the scripts generates images so fast the connection cannot cope up its a useless thing for me since im on a 2mb adsl line with my server 🙂

You calling me stupid? Look at my script the time is taken before anything is sent to the browser... Who's the dummy now.

ajdegans

ignores that

Dude, regardless of test scores, IT IS OFFTOPIC.

And for calling you stupid. I dont think you are... probably youre a better coder then i am, but your post just didnt make sense to us 🙂
:evilgrin: