Create jpgs from pdf with WordPress plugin - php

Question

I'm working on a plugin which creates jpgs from every page of an uploaded pdf file.
I use the wp_handle_upload action and check if the mime type is pdf.
After that, I use Imagick to get the page count and create a new jpg from every page. Then the file gets uploaded.
I think Wordpress doesn't support ImageMagick from scratch so I installed the ImageMagick Engine Plugin.
When I now upload a file in Wordpress I just get an error. I don't know what exactly doesn't work.
Any idea about what is going wrong?
Thanks, Oliver
function process_pdf($results) {
if( $results['type'] === 'application/pdf' ) {
$filename = $results[ 'file' ];
$filename_wo_extension = basename( $filename );
$url = $results[ 'url' ];
$im = new Imagick();
$im->setResolution(300, 300);
$pages = $im->getNumberImages();
for($p = 0; $p < $pages; $p++){
// http://stackoverflow.com/questions/467793/how-do-i-convert-a-pdf-document-to-a-preview-image-in-php
// http://stackoverflow.com/questions/1143841/count-the-number-of-pages-in-a-pdf-in-only-php
$im->readImage( $url.'['.p.']');
$im->setImageFormat('jpg');
$filename_neu = $filename_wo_extension .'_'. $p .'.jpg';
// https://codex.wordpress.org/Function_Reference/wp_insert_attachment
$upload_file = wp_upload_bits($filename_neu, null, $im);
if (!$upload_file['error']) {
$attachment = array(
'post_mime_type' => 'image/jpeg',
'post_title' => preg_replace('/\.[^.]+$/', '', $filename_neu),
'post_content' => '',
'post_status' => 'inherit'
);
$attachment_id = wp_insert_attachment( $attachment, $upload_file['file'] );
if (!is_wp_error($attachment_id)) {
require_once(ABSPATH . "wp-admin" . '/includes/image.php');
$attachment_data = wp_generate_attachment_metadata( $attachment_id, $upload_file['file'] );
wp_update_attachment_metadata( $attachment_id, $attachment_data );
}
}
}
}
}
add_action('wp_handle_upload', 'process_pdf');

Answer 1

Here is the code for achieving this.
The pdf file has to be uploaded to a post, otherwise there is no $post_id.
The only thing now is, that when clicking on save, the custom field (gallery) gets overwritten. When the post is not saved after uploading the pdf, the images are in the gallery.
function process_pdf( $file ) {
if( $file['type'] === 'application/pdf' ) {
// Get the parent post ID, if there is one
if( isset($_REQUEST['post_id']) ) {
$post_id = $_REQUEST['post_id'];
$filename = $file[ 'name' ];
$filename_wo_extension = basename( $filename, ".pdf" );
$im = new Imagick();
$im->setResolution(300, 300);
$im->readimage( $file[ 'tmp_name' ] );
$pages = $im->getNumberImages();
$attachments_array = array();
// iterate over pages of the pdf file
for($p = 1; $p <= $pages; $p++){
$im->setIteratorIndex( $p - 1 );
$im->setImageFormat('jpeg');
$filename_neu = $filename_wo_extension .'_'. $p .'.jpg';
// upload new image to wordpress
// https://codex.wordpress.org/Function_Reference/wp_insert_attachment
$upload_file = wp_upload_bits($filename_neu, null, $im);
if (!$upload_file['error']) {
$attachment = array(
'post_mime_type' => 'image/jpeg',
'post_title' => preg_replace( '/\.[^.]+$/', '', $filename_neu),
'post_content' => '',
'post_status' => 'inherit'
);
$attachment_id = wp_insert_attachment( $attachment, $upload_file['file'] );
if (!is_wp_error( $attachment_id )) {
require_once(ABSPATH . "wp-admin" . '/includes/image.php');
$attachment_data = wp_generate_attachment_metadata( $attachment_id, $upload_file['file'] );
wp_update_attachment_metadata( $attachment_id, $attachment_data );
$attachments_array[] = $attachment_id;
}
}
}
// add new images to a gallery (advanced custom fields plugin)
// http://www.advancedcustomfields.com/resources/update_field/
update_field( 'field_55b0a473da995', $attachments_array, $post_id );
$im->destroy();
}
}
return $file;
}
add_filter('wp_handle_upload_prefilter', 'process_pdf' );

Answer 2

I know this is an old thread, but anyway, I would like to say that there is a very fine WordPress plugin that deals with PDF files, converting the first page into an image, using either ImageMagick or IMagik (it let's you chose what you have installed on your site).
As the source code if freely available, I guess it might be of some help for whoever might be researching on this matter:
PDF IMAGE GENERATOR
https://wordpress.org/plugins/pdf-image-generator/