gistfile1.php

function embed_images($content){
    $embed_images = preg_replace_callback('/https?:\/\/([A-z0-9]+[_\-]?[A-z0-9]+\.)*[A-z0-9]+\-?[A-z0-9]+\.[A-z]{2,}(\/.*)*\/?/i', "addimg",$content);
    return $embed_images;
}

function addimg($url){
    global $post;
    $title = $post ->post_title;
    $imgurl = preg_replace('/((^http[s]{0,1}:)\/\/(.+).(gif|jpg|bmp|png))/i', '<img src="$1" alt="'.$title.'" /><pre>$1</pre>',$url[0]);
    if($imgurl !== $url[0]){
        // return the replace output if it's an image
        return $imgurl;
    }else{
        // return the orinal matched url if it's not an image
        return $url[0];
    }
    
}
add_filter('the_content', 'embed_images');