Question

I’m trying to dynamically rename a jpeg image file as it’s displayed to the user.

I have a file image_generate.php with the following code:

$file = $_GET['file'];
$imagepath = "path/to/image.jpg";
$image = imagecreatefromjpeg($imagepath);
header('Content-Type: image/jpeg');

$filename = "[site.com]_some_image_name_here";
header('Content-Disposition: attachment; filename="' . $filename . '.jpg"');

imagejpeg($image, NULL, 100);
imagedestroy($image); // Free up memory

And it’s called by an html image tag like so:

<img src="image_generate.php?file=imagenamehere" />

So far, the output has the following results:

• When I right-click on the image, and click “View Image,” a download dialogue pops up and asks if I’d like to save the file “[site.com]_some_image_name_here.jpg” (I want this to happen)
• If I right-click on the image, and click “Save Image As,” or “Save Image,” the filename that’s to be saved shows up as the original filename (whatever the variable $file was able to fetch).

How can I fix the second part? I’d like to modify the filename of the image even when the user clicks “Save Image As” or “Save Image.”

I DID try to change the code to this:

...

$rename = $filename . ".jpg";
imagejpeg($image, $rename, 100);
imagedestroy($image); // Free up memory

But the image fails to show up on the page with the html tag (shows up as a broken image).
I’m not very familiar with html headers and Content-Dispositions. I’m guessing there’s an error in there somewhere..?
Any ideas?

Thank you for reading!

Edit: .htaccess below

<IfModule mod_rewrite.c>

RewriteEngine On

# Sends image download request to image_generate.php for parsing
RewriteRule ^path/from/img/tag/downloads/(.*).jpg$ path/to/image_generate.php?file=$1 [NC,L]
RewriteRule ^path/to/image_generate.php$ /home/path/to/image_generate.php [NC,L]

</IfModule>

Answer 1

Different browsers will have different behaviors.

For example, Internet Explorer doesn’t try to fetch any header information before displaying the save file dialog when doing a Right Click > Save Image As (It automatically assumes you want to save the result of the request, regardless of what the result is). Neither does Firefox. Therefore, for IE & Firefox, it will be impossible to specify the filename by specifying it in the headers.

A more elegant and UA-compatible way of doing this would be by using Apache’s mod_rewrite to do URL rewriting. URL rewriting allows you to reroute a request made to a URL towards another.

To set this up, you need to create a .htaccess file in the directory where image_generate.php is located containing the following:

RewriteEngine On
RewriteRule ^generated/([a-z0-9-]+)\.jpg$  generated_image.php?file=$1  [L]

Then, simply modify your HTML to point to your rewritten URL.

<img src="generated/imagenamehere.jpg" />

This also have the advantage of making your image generation completely seamless to the user (URL wise, it looks simply like a static image).

More information about mod_rewrite can be found here:

• mod_rewrite – Apache HTTP Server
• mod_rewrite Cheat Sheet (V2) – Added Bytes by Dave Child