mirgcire

stianlik

This plugin hooks into the media manager and generates a thumbnail everytime a 
PDF is uploaded. Generated thumbnail is an image of the first page in the 
uploaded document and is named <code>PDFNAME-thumbnail</code>, where <code>PDFNAME</code> is replaced 
by uploaded document filename.
Generated thumbnails are equivalent to <a href="https://codex.wordpress.org/Post_Thumbnails" rel="nofollow ugc">featured 
images</a> so that common thumbnail 
functions like <code>get_post_thumbnail_id()</code> can be used for PDF attachments. See 
<a href="https://codex.wordpress.org/Post_Thumbnails" rel="nofollow ugc">Post Thumbnails</a> for information 
on how you can use thumbnails efficiently.
Integration with the javascript media API is not yet implemented, therefore, you 
may need to reload the page before you can see generated thumbnail after an 
upload.
<h4>Shortcodes</h4>
It is possible to display a thumbnail linking to an uploaded PDF using the <code>[pdf_thumbnails_link]</code> 
shortcode. The following attributes are supported:
<ul>
<li><code>id</code> – Attachment ID (required)</li>
<li><code>size</code> – <a href="https://codex.wordpress.org/Post_Thumbnails#Thumbnail_Sizes" rel="nofollow ugc">Thumbnail size</a> (optional)</li>
<li><code>title</code> – <a href="https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes#attr-title" rel="nofollow ugc">Anchor title attribute</a> (optional)</li>
<li><code>target</code> – <a href="https://developer.mozilla.org/en-US/docs/Web/HTML/Element/a#attr-target" rel="nofollow ugc">Anchor target attribute</a> (optional)</li>
<li><code>download</code> – <a href="https://developer.mozilla.org/en-US/docs/Web/HTML/Element/a#attr-download" rel="nofollow ugc">Anchor download attribute</a> (optional)</li>
</ul>
Example 1: Display link to PDF with ID = 172 using <a href="https://codex.wordpress.org/Post_Thumbnails#Thumbnail_Sizes" rel="nofollow ugc">default thumbnail size</a>
<pre><code>[pdf_thumbnails_link id="172"]
</code></pre>
Example 2: Display link to PDF with ID = 172 using thumbnail size (default 150×150)
<pre><code>[pdf_thumbnails_link id="172" size="thumbnail"]
</code></pre>
Thanks to <a href="https://wordpress.org/support/profile/mirgcire" rel="ugc">mirgcire</a> for providing the first 
version of the <code>[pdf_thumbnails_link]</code> shortcode.
<h4>Developer API</h4>
In most cases it should be sufficient to use built-in thumbnail functions from 
the WordPress API (<code>get_post_thumbnail</code> and similar). If you need to modify the 
way thumbnails are generated, you can override image generation with 
the <code>pdf_thumbnails_generate_image_blob</code> filter.
Example 1: Increase resolution for all generated PDF thumbnails
<pre><code>// $blob is the current image blob (defaults to null, can be used for chaining)
// $filename is the PDF filename
add_action('pdf_thumbnails_generate_image_blob', function ($blob, $filename) {
 $imagick = new Imagick();
 $imagick->setResolution(200,200);
 $imagick->readImage($filename);
 $imagick->setIteratorIndex(0);
 $imagick->setImageFormat('jpg');
 return $imagick->getImageBlob();
}, 10, 2);
</code></pre>
It is possible to modify generated thumbnail links using the <code>pdf_thumbnails_link_shortcode</code> 
filter. The following attributes are available:
<ul>
<li><code>$html</code> – Generated HTML code to be displayed</li>
<li><code>$attachmentId</code> – Sanitized ID of the PDF attachment</li>
<li><code>$size</code> – Sanitized thumbnail size</li>
<li><code>$atts</code> – <a href="https://codex.wordpress.org/Shortcode_API#Handling_Attributes" rel="nofollow ugc">Shortcode attributes (not sanitized)</a></li>
<li><code>$content</code> – Shortcode content (not sanitized)</li>
</ul>
Example 2: Wrap thumbnail link in figure and append caption
<pre><code>add_filter('pdf_thumbnails_link_shortcode', function ($html, $attachmentId, $size, $atts, $content) {
 return "<figure>$html <caption>Click to open image $attachmentId</caption></figure>";
}, 10, 5);
</code></pre>
<h3>TODO</h3>
Add generated image to media browser after upload.
Outline of an implementation based on the javascript media API:
<pre><code>// New uploads
wp.Uploader.queue.on('add', function (attachment) {

 if (attachment.subtype !== 'pdf') {
 return;
 }

 findThumbnailFor(attachment.ID).then(function (data) {

 // Add attachment thumbnail to browser
 var attachment = wp.media.model.Attachment.get(id)
 attachment.fetch().done(function () {
 wp.media.editor.open().state().get('library').add(generated attachment)
 });

 });
});
</code></pre>
Filter: ajax_query_attachments_args

PDF Thumbnails

The plugin does just what it says and the author is very helpful.  My only suggestion would be to add a short code that would insert a clickable thumbnail into a webpage.  Clicking on that would open the PDF in a viewer.
For example: [pdf-thumbnail id="1234" size="medium"]
... naturally this functionality would require host support for imagick.



Nice Job

Works just like it should. Can't believe this functionality isn't in the WP core. Thanks!

Excellent

This plugin generates a thumbnail everytime you upload a PDF attachment. Generated thumbnail is an image of the first page in uploaded document.

sebastianbarria

This plugin is made for developers.
It creates a function named thumbGen() that allows to show any image in the specified size. Additionally you can specify values like crop, center, rotation and effects.
It saves all generated thumbs in a cache folder, so it won’t overload your server at all.
<h3>Usage</h3>
To use this function you just need to use this line code:
<pre><code><?php thumbGen(image,width,height,additional_parameters); ?>
</code></pre>
[image:] the URL of the original image you need to create a thumbnail from (needed).
[width:] the width you need for the generated thumbnail (default=0 – if not specified it gets the 
proportional value from the specified height).
[height:] the height you need for the generated thumbnail (default=0 – if not specified it gets the proportional value from the specified width).
note: if you don’t specify the with AND height (or if you set both to 0), the image will be generated in the source size.
<h4>Additional parameters</h4>
[filename:] some people have troubles with duplicated names, so I’ve added this parameter for you to specify a new filename (or ID or something like that) in order to differentiate each file (if not set it will use the source filename).
[md5:] by default, the images are generated with an md5 encode filename. If you don’t want the generated file to have an encoded name set this to 0
[force:] force thumb creation, even if it already exists (default=0) (NOT RECOMENDED! – use it just for testing or debugging)
[crop:] if you want the thumbnail to be cropped (no image deformation) if the width and height are different from the original image, set this value as 1 or true. If you want the content of the thumbnail to be resized to fit the space (image deformation) set this to 0 or false (default=1).
[halign:] horizontal align of the croped image. You can set it to left, center or right (default=center)
[valign:] vertical align of the croped image. You can set it to top, center or bottom (default=center)
[effect:] you can apply two effects: grayscale and sephia
[rotate:] you can specify a rotation angle
[background:] hex color (like #ffffff) to apply on the background ONLY when you rotate the image. If you don’t want a color applied you can set this to transparent (default=transparent)
[return:] if set to 1 (or true) the image name will be returned instead of printed (default=0).
[preserveAnimation:] if set to 1 (or true) it will show animated gif’s with motion but without applying other parameters. Otherwise, it will show the first frame of the animated gif resized.
[quality:] you can chooos from 0 to 9, where 0 is the worst quality (lower file size) and 9 is the best (bigger file size). The default value is 7.
<h3>Examples of usage</h3>
In this example I will not explain detailed how this WordPress code works, but I will show this as an example of this plugin usage:
<pre><code><?php
$img="";
$args = array(
'post_parent' => $post->ID,
'post_type' => 'attachment',
'numberposts' => 1,
'post_mime_type' => 'image'
);
$attachs = get_posts($args);
if ($attachs) {
$img=wp_get_attachment_image_src($attachs[0]->ID,'full');
}
if(!empty($img)){
?>
<img src='<?php thumbGen($img[0],171,56,"effect=grayscale&halign=left&valign=top"); ?>' alt='' />
<?php
}
?>
</code></pre>
This example reads the first attached image of a post and save it’s information in a variable called $img. In the thumbGen function the first parameter is $img[0] and that’s the image URL. The second and third parameters are the width and height of the generated thumbnail we need. The rest of the parameters are defined in the string in the format parameter=value, concatenated with an &. the values not specified will use their default value.

thumbGen

This plugin creates a function named thumbGen() that allows to show any image in the specified size (plus many other things).

PDF Thumbnails vs thumbGen