Dynamically Resize Images "on the fly"

Arty_Ziff

I use something like this to resize dynamically images. Is there a way to wrap this in a function and class that when called returns the image object?

<? 
$src_img = imagecreatefromjpeg('./path/to/image.jpg'); 
$srcsize = getimagesize('./path/to/image.jpg'); 
$dest_x = 200; 
$dest_y = (200 / $srcsize[0]) * $srcsize[1]; 
$dst_img = imagecreatetruecolor($dest_x, $dest_y); 
imagecopyresampled($dst_img, $src_img, 0, 0, 0, 0, $dest_x, $dest_y, $srcsize[0], $srcsize[1]); 
header("content-type: image/jpeg"); 
imagejpeg($dst_img); 
imagedestroy($src_img); 
imagedestroy($dst_img); 
?>

For exacmple, right now I could use it to dynamically resize images by having it inline in the HTML:

<img src="./image_script.php?img=image_name.jpg">

But if it could be wrapped in a class / function, it could be done without exposing the script to possible exploitation maybe...

I'd like to avoid resizing the image and dumping it in a temp directory. That could get huge.

Weedpacket

function resize_image($filename)
{
$path = basename($filename); // trim off leading /../foo/stuff
$path = './path/to/'.$path; // and put ours on.
$src_img = imagecreatefromjpeg($path);
$srcsize = getimagesize($path);
$dest_x = 200;
$dest_y = (200 / $srcsize[0]) * $srcsize[1];
$dst_img = imagecreatetruecolor($dest_x, $dest_y);
imagecopyresampled($dst_img, $src_img, 0, 0, 0, 0, $dest_x, $dest_y, $srcsize[0], $srcsize[1]);
header("content-type: image/jpeg");
imagejpeg($dst_img);
imagedestroy($src_img);
imagedestroy($dst_img);
}

Still doesn't check that the file actually exists, of course.

Arty Ziff wrote:
I'd like to avoid resizing the image and dumping it in a temp directory. That could get huge.

If you mean generating the thumbnails once and storing them in a directory, and serving those: that is better than regenerating them every time you want to serve them. Less processing power, less memory consumption, less time. More disk space, sure, but not that much more. (For one project, at one point I had 65,000 JPEGs (624x352 pixels stored with a high quality setting); all told they occupied just over 1.2GB. I could put that on my phone and still have enough space left over for a web site, its database, and the software to serve it all. It's trivial for a modern PC or server box.)

Arty_Ziff

I'm looking for an alternative to using something like:

<img src="./image_resize.php?img=image.jpg">

Because I'm not sure it's the most efficient way to do it, and I think it may be a security risk.

Overall, I'm looking for a way to have thumbnails without actually having the overhead of saving them for each image.

The problem with using a function is that it produces a header, so you can't embed it in the page without buffering, I think, because there will be an error for sending more than one header...

JPnyc

have you considered client-side scripting? You can do this with JavaScript.

Arty_Ziff

JPnyc;10879380 wrote:
have you considered client-side scripting? You can do this with JavaScript.

The object is to reduce the load time. A thumbnail is a smaller file than the original. This can be done with JS?

Weedpacket

Arty Ziff wrote:
without actually having the overhead of saving them for each image.

I pointed out that the overhead of not saving them for each image is much higher, for many reasons (one of which is that resizing the images on the fly increases load time).

Adding cache control headers to the response is also a big win. Under Apache, adding an .htaccess file to the thumbnail directory in question with

Header set Cache-Control public
ExpiresByType image/jpeg "access plus 1 month"

Would mean that (a) clients will cache JPEGs served out of that directory, (b) proxies between your sever and the client will cache JPEGs served out of that directory, and (c) while they still have it cached, it will be a month before either bothers your server for it again.