Yann at WP&amp;Co

<p>A widget that permits blogmasters to share and exchange links to their posts based on common taxonomy, across their blogs (ie. posts having the same tags or categories). Each link is automatically associated to a thumbnail image.</p>
<h4>Share your posts!</h4>
<p>This WordPress plugin installs a <strong>new sidebar widget</strong> that can display <strong>links to relevant posts on other WordPress blogs</strong> with <strong>automatic thumbnail images</strong>.<br />
The links are chosen based on common language and taxonomy (ie posts in the same language having the same tag(s) or category).<br />
The plugin uses <strong>cache</strong> to avoid multiple database and RSS query.<br />
It has its own widget control pannel.<br />
The look & feel of the post2peer widget is very close to its cousin, the <a href="https://wordpress.org/extend/plugins/yd-recent-posts-widget/" rel="ugc">YD Recent Posts Widget</a>.</p>
<p>Please visit the <a href="http://www.yann.com/wp-plugins/post2peer-wordpress-plugin" title="Yann Dubois' Post2Peer Widget for WordPress" rel="nofollow ugc">YD Post2Peer Widget plugin support site</a><br />
 and the <a href="http://post2peer.com/about" title="Post2Peer posts and sites directory" rel="nofollow ugc">Post2Peer.com open posts directory</a> to get more info on the Post2Peer project and what’s it’s all about.</p>
<h4>Why share you posts?</h4>
<p>By using this plugin, you will automagically allow all your posts to be registered in the Post2Peer database (this uses you regular WordPress rss feed, plus a special crawler to generate thumbnails for every post).<br />
Once your posts are in the database, they will be elligible to be displayed as links on other person’s blogs (those using the plugin).<br />
Because the link selection algorithm is based on you posts’ taxonomy (tags and categories), links to your posts get to be displayed in a relevant context.<br />
This should draw new visitors to your site and improve your SEO.<br />
The inclusion in the directory is an added bonus, immediately generating deep backlinks to your site’s posts.</p>
<h4>Why display links to other’s blog posts?</h4>
<p>By enabling the Post2Peer plugin, you are able to present you site’s visitor with up-to-date, real-time info relevant to the subject the visitor is currently browsing.<br />
The links you display will very probably complement the info in your own post, so it is a way to position your site as a comprehensive reference on the given subject.<br />
The Post2Peer widget is like an enhanced RSS widget that will display relevant content agregated from a wide database of other WordPress blogs that publish similarly focused features.<br />
The fact that the content is always presented in a visual way (with a small thumbnail image next to each link) adds to the visual attractiveness of your page.</p>
<h4>It’s fun!</h4>
<p>Based on a peer-to-peer concept, the whole process will increase in quality and eventually grow to a wide community of bloggers supporting each other by automatically exchanging relevant links to posts across blogs.<br />
Even in the early stage of its deployment, this plugin is fun because it may link blog posts together in a way that you would never have expected.</p>
<h4>Active support</h4>
<p>Drop me a line on my <a href="http://www.yann.com/wp-plugins/post2peer-wordpress-plugin" title="Yann Dubois' Post2Peer Widget for WordPress" rel="nofollow ugc">YD Post2Peer Widget plugin support site</a> to report bugs, ask for specific feature or improvement, or just tell me how you’re using the plugin.<br />
It’s still in an early development stage, with new features coming out on a regular basis.</p>
<h3>Widget control pannel</h3>
<p>The widget has its own control pannel for setting-up its look and feel. You can administer it from the widgets admin page.</p>
<h3>Revisions</h3>
<p>0.1.0 Initial beta release</p>
<h3>Did you like it?</h3>
<p>Drop me a line on http://www.yann.com/wp-plugins/post2peer-wordpress-plugin</p>


Post2Peer Widget

Allows to exchange and share post links + thumbnails across Wordpress blogs, based on matching tags and categories.

Mizuho Ogino

<p>By uploading a PDF attachment, this plugin convert the cover page to jpeg and attach it as a post thumbnail file. It also allows displaying a thumbnail icon and inserting PDF link with a cover image into the editor.</p>
<h4>Available only for WordPress 4.0+, also only on the server which  ImageMagick and GhostScript are installed.</h4>
<p>This plugin hooks to the media editor and generates the first page image of PDF by using ImageMagick with GhostScript. It requires no setup, just activate the plugin via the admin install page. Allow to set a PDF as an image.</p>
<h4>How it works</h4>
<p>This Plugin replaces and extends the following features.</p>
<ul>
<li>Generate cover image of PDF by using ImageMagick. Generated Image has different size variations and is attached to PDF.</li>
<li>Register Generated Image as Featured Image (post-thumbnail) of PDF.</li>
<li>Display Generated Image as icon instead of Mime-type Icon in Admin Page.</li>
<li>Hide Generated Image file itself in Media Library. (v1.2 or later)</li>
<li>Replace link text with JPG when inserting PDF to Text Editor.</li>
<li>Delete Generated Image when deleting PDF from Media Library.</li>
<li>Allow to manage and output Generated Image and PDF on manually in template file. (see Other Notes.)</li>
<li>Allow to set PDF as Featured Image and to use functions in the same way as image file. (v1.2 or later, see Other Notes.)</li>
<li>Allow to control maximum size of Generated Image and other default settings in Plugin Page. (v1.3.4 or later)</li>
</ul>
<h4>Generated Items</h4>
<p>A generated image file is registered as post children of a PDF file and it has different size variations. Files build a tree like below.</p>
<ul>
<li>my-file.pdf (Your PDF)
<ul>
<li>my-file-pdf.jpg (Generated Cover Image of Your PDF)
<ul>
<li>my-file-pdf-1024×768.jpg (Large Size)</li>
<li>my-file-pdf-300×225.jpg (Medium Size)</li>
<li>my-file-pdf-150×150.jpg (Thumbnail size)</li>
<li>…(And Your Custom File Sizes)</li>
</ul>
</li>
</ul>
</li>
</ul>
<h4>Insert HTML into the editor</h4>
<p>Select a PDF file in the Media Uploader and insert it into the the editor. An output HTML is automatically rewritten like below.</p>
<pre><code><a class="link-to-pdf" title="dummy-pdf" href="http://exmaple.com/wp-content/uploads/2015/01/dummy-pdf.pdf" target="_blank"><img width="227" height="320" class="size-medium wp-image-9999 thumb-of-pdf" src="http://exmaple.com/wp-content/uploads/2015/01/dummy-pdf-pdf-227x320.jpg" alt="thumbnail-of-dummy-pdf" /></a>
</code></pre>
<p>*If you are using a document viewer plugin (like GDE) and want insert html which is made by it, select “Default (Title)” of “media” selector.</p>
<h4>Get thumbnail in template file</h4>
<p>A generated image ID is stored in [‘_thumbnail_id’] custom field of a PDF attachment post. An image ID is exportable by using get_post_thumbnail_id($your_pdf_id) or get_post_meta($your_pdf_id, ‘_thumbnail_id’, true) functions in a template file.</p>
<pre><code>$pdf_id = 'your PDF file ID';
if ( $thumbnail_id = get_post_thumbnail_id( $pdf_id ) ) {
echo '<a class="pdf-link image-link" href="'.wp_get_attachment_url( $pdf_id ).'" title="'.esc_attr( get_the_title( $pdf_id ) ).'" target="_blank">'.wp_get_attachment_image ( $thumbnail_id, 'medium' ).'</a>';
}
</code></pre>
<p>Or more simply, you can call images and link to PDF files by wp_get_attachment_image($your_pdf_id, $size) and wp_get_attachment_link($your_pdf_id, $size) functions. (v1.2 or later) *If the plugin is deactivated, this function just will return empty.</p>
<pre><code>$pdf_id = 'your PDF file ID';
echo wp_get_attachment_image ( $pdf_id, 'medium' );
echo wp_get_attachment_link ( $pdf_id, 'medium' );
</code></pre>
<p>If you call all PDFs that are attached to the post. You can get them by get_posts function.</p>
<p>Examples.<br />
Dynamically get PDFs that are attached to the post.</p>
<pre><code><?php
$pdfs = get_posts( 'posts_per_page=-1&post_type=attachment&post_mime_type=application/pdf&post_parent='.$post->ID );
if( $pdfs ): foreach( $pdfs as $pdf ):
  $thumbnail_id = get_post_thumbnail_id( $pdf->ID );
  if( $thumbnail_id ):
    echo '<li>';
    echo '<a href="'wp_get_attachment_url( $pdf->ID )'" class="link-to-pdf">';
    echo wp_get_attachment_image ( $thumbnail_id, 'medium' );
    echo '</a>';
    echo '</li>';
  endif;
endforeach; endif;
?>
</code></pre>
<h4>Set PDF thumbnail as Featured Image</h4>
<p>The plugin support you to set PDF as Featured Image. (v1.2 or later)<br />
Strictly explaining, when you set a PDF as Featured Image, the plugin automatically set the thumbnail which is registered with this PDF.<br />
You can call thumbnail by using get_the_post_thumbnail function.</p>
<pre><code>echo get_the_post_thumbnail ( $post->ID, 'medium' );
</code></pre>
<p>May you want pdf file from the post thumbnail.</p>
<pre><code>$thumb_id = get_post_thumbnail_id ( $post->ID );
$pdf_id = get_post( $thumb_id )->post_parent;
if ( $pdf_id && get_post_mime_type ( $pdf_id ) === 'application/pdf' ){
  $pdf = get_post($pdf_id);
  echo '<a class="link-to-pdf" href="'.wp_get_attachment_url($pdf_id).'" title="'.esc_html($pdf->post_title).'" target="_blank">'.get_the_post_thumbnail().'</a>'."\n";
}
</code></pre>
<h4>Display attachment data with in caption</h4>
<p>The plugin allows you to insert [caption] short-code into the post content area as when insert an image. If you want to display attachment title, description, file type, file size and so on, use img_caption_shortcode filter in your functions.php.<br />
Here’s an example code…<br />
    function add_attachment_data_in_caption( $empty, $attr, $content ) {<br />
        $attr = shortcode_atts( array( ‘id’=>”, ‘align’=>’alignnone’, ‘width’=>”, ‘caption’=>” ), $attr );<br />
        if ( 1 > (int) $attr[‘width’] || empty( $attr[‘caption’] ) ) return ”;<br />
        if ( $attr[‘id’] ) {<br />
            $attr[‘id’] = ‘id=”‘ . esc_attr( $attr[‘id’] ) . ‘” ‘;<br />
            $attachment_id = explode(‘_’, $attr[‘id’]);<br />
            $attachment_id = $attachment_id[1];// get attachment id<br />
            if( get_post_mime_type ( $attachment_id ) === ‘application/pdf’ ){<br />
                $attachment = get_post( $attachment_id );<br />
                $bytes = filesize( get_attached_file( $attachment->ID ) );<br />
                if ($bytes >= 1073741824) $bytes = number_format($bytes / 1073741824, 2). ‘ GB’;<br />
                elseif ($bytes >= 1048576) $bytes = number_format($bytes / 1048576, 2). ‘ MB’;<br />
                elseif ($bytes >= 1024) $bytes = number_format($bytes / 1024, 2). ‘ KB’;<br />
                elseif ($bytes > 1) $bytes = $bytes. ‘ bytes’;<br />
                elseif ($bytes == 1) $bytes = $bytes. ‘ byte’;<br />
                else $bytes = ‘0 bytes’;<br />
                $attr[‘caption’] =<br />
                  ‘title : ‘ .$attachment->post_title. ‘<br />‘ . // title<br />
                  ‘caption : ‘ .$attr[‘caption’]. ‘<br />‘ .// caption<br />
                  ‘size : ‘ .$bytes. ‘<br />‘ . // file size<br />
                  ‘filetype : ‘ .get_post_mime_type ( $attachment_id ). ‘<br />‘ . // file type<br />
                  ‘description : ‘ .$attachment->post_content. ‘<br />‘; // description<br />
            }<br />
        }</p>
<pre><code>    return 
      '<div ' .$attr['id']. 'class="wp-caption ' .esc_attr( $attr['align'] ). '" style="max-width: ' .( 10 + (int) $attr['width'] ). 'px;">' .
      do_shortcode( $content ). '<p class="wp-caption-text">' .$attr['caption']. '</p>' .
      '</div>';
}
add_filter('img_caption_shortcode', 'add_attachment_data_in_caption', 10, 3);
</code></pre>
<h4>Generate thumbnails of all PDFs in the media library</h4>
<p>You can generate thumbnails of any already-uploaded PDFs.<br />
Activate the plugin and Click “Generate Thumbnails Now” link in “settings”. (v1.3.3 or later)</p>
<h4>Change attachment link attributes</h4>
<pre><code>function pigen_filter_attachment_link ( $html, $attach_id, $attach_url, $attach_output ){
  $attach_title = get_the_title( $attach_id );
  $html = '<a class="link-to-pdf" href="'.$attach_url.'" rel="attachment wp-att-' .esc_attr($attach_id). '" title="'.esc_attr( $attach_title ).'" target="_blank">' .$attach_output. '</a>';
  return $html;
};
add_filter( 'pigen_filter_attachment_link', 'pigen_filter_attachment_link', 10, 4 );
</code></pre>
<h4>Change thumbnail attributes</h4>
<pre><code>function pigen_filter_attachment_output ( $attach_output, $thumbnail_id, $thumbnail, $size, $align ){
  $attach_output =  '<img src="'. $thumbnail[0] .'" alt="'.get_post_meta( $thumbnail_id, '_wp_attachment_image_alt', true ).'" width="'. $thumbnail[1] .'" height="'. $thumbnail[2] .'" class="'.( $align ? 'align' .$align. ' ' : '' ). 'size-' .esc_attr( $size ). ' wp-image-'.$thumbnail_id.'" />';
  return $attach_output;
};
add_filter( 'pigen_filter_attachment_output', 'pigen_filter_attachment_output', 10, 5 );
</code></pre>
<h4>Modify imageMagick’s Settings</h4>
<p>Filters allow you to add your own modify imageMagick’s behaviour by hooking.</p>
<p>Sample usage for imageMagick user.</p>
<pre><code>function pigen_filter_convert_file_basename( $file_basename ){
  $file_basename = str_replace( '.jpg', '.png', $file_basename );
  return $file_basename;
};
add_filter( 'pigen_filter_convert_file_basename', 'pigen_filter_convert_file_basename' );

function pigen_filter_convert_imageMagick( $imageMagick, $before_name, $after_name, $max_width, $max_height ){
  $imageMagick = "convert -density 150 -quality 80 -background black -flatten {$max_width}x{$max_height} {$before_name} {$after_name}";
  return $imageMagick;
};
add_filter( 'pigen_filter_convert_imageMagick', 'pigen_filter_convert_imageMagick', 10, 5 );
</code></pre>
<p>Sample usage for imagick extension user.</p>
<pre><code>function pigen_filter_convert_file_basename( $file_basename ){
  $file_basename = str_replace( '.jpg', '.png', $file_basename );
  return $file_basename;
};
add_filter( 'pigen_filter_convert_file_basename', 'pigen_filter_convert_file_basename' );

function pigen_filter_convert_imagick( $imagick ){
  $imagick->setImageBackgroundColor( 'black' );
  $imagick->setCompressionQuality( 80 );
  $imagick->setImageFormat( 'png' );
return $imagick;
};
add_filter( 'pigen_filter_convert_imagick', 'pigen_filter_convert_imagick' );
</code></pre>
<h4>Automatically save image/PDF as featured image</h4>
<p>Automatically set PDF thumbnail as featured image.</p>
<pre><code>function save_pdf_thumb_as_featuredimage ( $post_id ) { 
    if ( wp_is_post_revision( $post_id ) ) return; 
    if ( get_post_type( $post_id ) !== 'post' ) return; // set your post type
    if ( get_post_meta( $post_id, '_thumbnail_id', true ) ) return; // post already has featured image
    $attaches = get_posts ( 'post_parent='.$post_id.'&numberposts=-1&post_type=attachment&post_mime_type=application/pdf&orderby=menu_order&order=ASC' );
    if ( $attaches ): foreach( $attaches as $attach ):
        if ( $thumb_id = get_post_meta( $attach->ID, '_thumbnail_id', true ) ){ // if pdf has thumbnail
            update_post_meta( $post_id, '_thumbnail_id', $thumb_id );
            break;
        }
    endforeach; endif;
}
add_action( 'save_post', 'save_pdf_thumb_as_featuredimage' );
</code></pre>
<p>Automatically set first image/PDF as featured image.</p>
<pre><code>function save_thumbnail_as_featuredimage ( $post_id ) { 
    if ( wp_is_post_revision( $post_id ) ) return;
    if ( get_post_type( $post_id ) !== 'post' ) return; // set your post type
    if ( get_post_meta( $post_id, '_thumbnail_id', true ) ) return; // post already has featured image
    $args = array(
        'post_parent' => $post_id,
        'post_type' => 'attachment',
        'numberposts' => -1,
        'post_status' => null,
        'orderby' => 'menu_order date',
        'order' => 'ASC ASC'
    );
    $attaches = get_posts($args);
    if ( $attaches ): foreach( $attaches as $attach ):
        if ( $attach->post_mime_type == 'application/pdf' ){
            if ( $thumb_id = get_post_meta( $attach->ID, '_thumbnail_id', true ) ){ // if pdf has thumbnail
                update_post_meta( $post_id, '_thumbnail_id', $thumb_id );
                break;
            }
        } elseif ( preg_match("/^image\//", $attach->post_mime_type ) ) {
            update_post_meta( $post_id, '_thumbnail_id', $attach->ID );
            break;
        }
    endforeach; endif;
}
add_action( 'save_post', 'save_thumbnail_as_featuredimage' );
</code></pre>


PDF Image Generator

Also ties in really nicely with the media uploader, the image is set as the 'icon' field of the attachment, as one would want. PS The feature for generating images for existing pdfs is at the bottom of the settings - scroll down to see (unlike me the first time)!

Super stuff. Works perfectly.

Very impressed with how quick and easy it was to get up and running with the generated pdf views.

Great Little Plugin

Generate automatically cover image of PDF by using ImageMagick. Allow user to insert PDF link with thumbnail into editor and set as Featured Image.

Post2Peer Widget vs PDF Image Generator