Replace invalid image url with 404 image - .htaccess

Question

I don't know if this is possible or not, I have an image host that I've made myself. I need some last tweaks with it.
Whenever an image has been deleted or is an invalid image url, it should replace with an 404 image, so for example if someone adds this:
http://imagehosturl.com/i/34njk5n.jpg
But it's an invalid link, so I need it to show:
http://imagehosturl.com/img/notfound.jpg
Which is like this:
alt text http://tinypic.com/images/404.gif
I do know that .htaccess can do this with it's ErrorDocument 404, but I have one already when a user access to an invalid page, so it would show the 404 page.
So whenever a user hotlinks an image and it's invalid or is deleted, I need it to be replaced with the 404 image.
How can I make this?

Answer 1

Here's one potential answer:
RewriteEngine on
RewriteCond %{DOCUMENT_ROOT}%{REQUEST_URI} !-f
RewriteRule \.(gif|jpe?g|png|bmp) /path/to/logo.gif [NC,L]
Another is to use a custom scripted page:
Use the errorDocument directive
(documented at [httpd.apache.org ]) to
point a '404' error to a script (perl,
PHP, whatever). If the requested file
has an image extension (or has an
image/* mimetype; PHP supplies the
mime_content_type [us2.php.net]
function for this; I'm sure there are
many ways to do this in perl; the
MIME::Types [search.cpan.org] module
is one way), then set the
"Content-Type" header to the mimetype
of your logo image and return the
content of the logoimage to the
browser.
http://www.webmasterworld.com/forum92/3458.htm

Answer 2

<FilesMatch ".(jpg|png|gif)$">
ErrorDocument 404 "/path/to/image.jpg"
</FilesMatch>

Answer 3

With Apache, you can have multiple .htaccess files. So, if all of your images are stored in the same directory, create an .htaccess file inside of that directory and add
ErrorDocument 404 /img/notfound.jpg
This will create a custom 404 redirect that is applied only to your image directory, plus its subdirectories.

Answer 4

You can use ErrorDocument with FilesMatch directive
<filesMatch "\.(jpg|png|gif)$">
ErrorDocument 404 /image.jpg
</filesMatch>
This will show /image.jpg if a 404 image uri with jpg png or gif extension is requested.
you can also add your custom image or html markup to the errordocument :
<filesMatch "\.(jpg|png|gif)$">
ErrorDocument 404 '<img src="image.jpg">'
</filesMatch>

Answer 5

According and in addition to AdamH's answer, you should output 404 header. Here's what I'm using,
.htaccess
RewriteEngine on
RewriteCond %{DOCUMENT_ROOT}%{REQUEST_URI} !-f
RewriteRule \.(gif|jpe?g|png|bmp) /upload/image404.php [NC,L]
image404.php
<?php
$file = 'image404.jpg';
$type = 'image/jpeg';
header("HTTP/1.0 404 Not Found");
header('Content-Type:'.$type);
header('Content-Length: ' . filesize($file));
readfile($file);
?>