Hi,
I try to generate PDF thumbnails.
I tried to extend the thumb component for it, but it does not seem to be triggered when files are documents. Can someone confirm or disprove this?
Thanks
I based my experiments on those topics:
Extend core component thumb
Create Preview from PDF-File
Hi!
Thumbs generation is a bit “magic” in Kirby3 and I am trying to explain how I think it works.
Please correct me if my steps below are wrong!
The first part of thumb generation:
$file->thumb() , you are calling the thumb method of the file class. This method is defined in the FileModifications trait.file::version component is called (here)The second part of thumb creation:
Long story short: Your pdf thumb generation fails in the second step of part 1. file::version checks if a file is resizable and a pdf is not.
You’ll need to adjust the file::version component aswell or use another solution, e.g. an after upload hook.
Thank you for this!
I keep digging and I’ll post some updates if reach something worthy enough.
That’s how I create thumbs for my pdf files:
'file.create:after' => function (Kirby\Cms\File $file) {
if ($file->template() == "flyer") {
$im = new Imagick();
$im->setResolution(72,72);
$im->readimage($file->root() . '[0]');
$im->setImageFormat('jpeg');
$im->writeImage(dirname($file->root()) . '/' . $file->name() . '.jpg'); // temp
$im->clear();
$im->destroy();
Kirby\Cms\File::create([
'source' => dirname($file->root()) . '/' . $file->name() . '.jpg',
'parent' => $file->page(),
'filename' => $file->name() . '-preview.jpg',
'template' => 'preview'
]);
Kirby\Toolkit\F::remove(dirname($file->root()) . '/' . $file->name() . '.jpg'); // delete temp
}
},
And I realize that I am not checking if it actually is a pdf. So I might should do that before creating the thumb…
I went for a field methode for now 
<?php
use Kirby\Cms\File;
use Kirby\Cms\Filename;
use Kirby\Cms\FileVersion;
Kirby::plugin('julien-gargot/pdf-preview', [
'fileMethods' => [
'preview' => function ($page = 0) {
$extension = 'jpg';
$mediaRoot = dirname($this->mediaRoot());
$src = $this->root() . '.' . $extension;
$dst = $mediaRoot . '/{{ name }}.{{ extension }}';
$thumbRoot = (new Filename($src, $dst))->toString();
$thumbName = basename($thumbRoot);
if (!is_dir($mediaRoot)) mkdir( $mediaRoot );
if (f::exists($thumbRoot))
{
if ( (f::modified($thumbRoot) > $this->modified())) {
return new FileVersion([
'original' => $this,
'root' => $thumbRoot,
'url' => dirname($this->mediaUrl()) . '/' . $thumbName,
]);
} else {
f::remove($thumbRoot);
}
}
$im = new Imagick();
$im->setResolution(96,96);
$im->readImage($this->root().'['.$page.']');
$im->transparentPaintImage("rgb(255, 255, 255)", 0, Imagick::getQuantum() * 0.2, false);
$im = $im->mergeImageLayers(Imagick::LAYERMETHOD_FLATTEN);
$im->setImageFormat($extension);
$im->setImageCompression(Imagick::COMPRESSION_JPEG);
$im->writeImage($thumbRoot);
return new FileVersion([
'original' => $this,
'root' => $thumbRoot,
'url' => dirname($this->mediaUrl()) . '/' . $thumbName,
]);
}
]
]);
Is it possible to chain file methods with your approach?
e.g. $file->preview()->resize(200) ?
No. It was the purpose, but I have to continue to work on it.
So, I ended up in a simple field method that saves a preview as siblings of the original file. Like this, it became a regular image that you can chain or use as a preview for the original PDF in templates or panel.
But, as this, it is also listed when calling $page->files() and displayed in the panel page files section if you use templates on other files to be able to filter this list.
I would rather save the preview in the media folder so this file cannot be listed in the $page->files() method… But, if saving the preview in the media folder returns a file to display in front end, I didn’t manage to allow it to be chained like a regular Kirby File. Actually, you can’t even make a thumbnail of it.
Here a plugin anyway: https://github.com/julien-gargot/kirby-plugin-pdf-preview.
Am I right to assume that with your solution, Imagick parses the whole PDF even though it makes the thumb from the first page? That could be quite a problem for larger files (got some documents with 500+ pages).
I’m currently implementing this library to circumnavigate performance issues:
I would expect that Imagick is smart enough to only parse the page I defined in $im->readimage($file->root() . '[0]');
Have you tested with big files and experienced performance issues?
I got the idea from people replying to this gist, but didn’t test it myself - but now I see you already thought about that, nice!
I actually didnt. My files are just not big enough to run into that problem.
Be that as it may, I also think IM would be clever enough to only parse input being passed to it … 
Hello everyone !
I’m also interested for an automatic jpg/png thumbnail creation for my PDF’s… Anyone got a solution please ?
My programming skills are small… and I’m a “rookie” kirby user…
Thanks a lot !
You mean when the file is uploaded? Then you can use the code from the plugin code mentioned above (https://github.com/julien-gargot/kirby-plugin-pdf-preview/blob/master/index.php) with some little changes in a file.create:after hook.