Yuriy Stepanov

<p>The pluginplug-in, with two additional SQL queries, joins the original data sample $wp_query->posts all meta fields, all files and images, for each image the direct url to small, medium, and large image is formed. There’s no need to use functions the_post_thumbnail  and get_post_meta.</p>
<h4>How it works</h4>
<p>So let’s say we go to the home page of our blog, WordPress gives us a list of the latest 10 records. Let me remind you these are already in the global object in the array $wp_query-> posts. Let’s begin from creating a list of ID (number of records to which they are stored in the database).</p>
<h4>Form the first SQL query:</h4>
<ul>
<li>$query = “SELECT $wpdb->posts.* FROM $wpdb->posts WHERE  $wpdb->posts.post_parent IN(’21’,’29’,’30’,’35’,’38’,’42’,’46’,’48’,’49’,’55’) AND $wpdb->posts.post_parent<br />
AND $wpdb->posts.post_type = ‘attachment'”;</li>
</ul>
<p>A normal translation is «find all the child entries for entries with the numbers (’21 ‘, ’29?, ’30 ‘, ’35?, ’38 ‘, ’42?, ’46 ‘, ’48?, ’49 ‘, ’55 ‘)». And the type of records required to be «attachment». That is, in short, we find all the files (attachment) which we downloaded for our 10 entries.</p>
<p>Again we form a list of ID: the first 10 ID entries and add the ID of files (attachments). Attachments as ordinary records are stored in one table – wp_posts.</p>
<h4>Now we use the function update_meta_cache:</h4>
<ul>
<li>$all_meta = update_meta_cache(‘post’, $ar_all_id);</li>
</ul>
<p>$ar_all_id – here are the original recordings and attachments</p>
<p>So everything just gets in the cache and subsequent calls get_post_meta will derive value from the cache. The rest is a matter of technique – the data must be carefully arranged, not mixing anything up. All meta fields are added to the $post->meta array, and files into an $post->files array and files are immediately sorted by number order (when downloading it, you can specify the sort order).<br />
In addition, for each file, if it is an image, the full path to the thumbnails is calculated: small (thumbnail), average (medium) and the complete picture (full).</p>
<h4>WordPres 4:</h4>
<p>The default filter is only connected to the main query using is_main_query().<br />
Does not work in is_admin() or is_page().</p>
<p><a href="http://bugacms.com/wpEn/all-inclusive/" rel="nofollow ugc">Home page</a><br />
<a href="http://bugacms.com/wpRu/all-inclusive/" rel="nofollow ugc">Русская страница</a></p>
<h3>A brief Markdown Example</h3>
<p><a href="http://bugacms.com/wpEn/all-inclusive/" rel="nofollow ugc">More PHP code Examples</a><br />
<a href="http://bugacms.com/wpRu/all-inclusive/" rel="nofollow ugc">Больше примеров</a></p>


All Inclusive

The pluginplug-in, with two additional SQL queries, joins the original data sample $wp_query->posts all meta fields, all files and images.

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.

All Inclusive vs PDF Image Generator