imagick thumb driver: Requesting animated resized gifs from srcsets only applies alot of transforms (resize, crop etc) to the first frame

[mrckzgl]

Description

I encountered a bug where if requesting an animated resized gif only its first frame is resized but the contents of the other frames is not resized.

This is caused by this code:

kirby/src/Image/Darkroom/Imagick.php

Lines 126 to 148 in 8006161

	public function process(string $file, array $options = []): array
	{
	$options = $this->preprocess($file, $options);
	$image = new Image($file);
	$image = $this->threads($image, $options);
	$image = $this->interlace($image, $options);
	$image = $this->coalesce($image);
	$image = $this->grayscale($image, $options);
	$image = $this->autoOrient($image);
	$image = $this->resize($image, $options);
	$image = $this->quality($image, $options);
	$image = $this->blur($image, $options);
	$image = $this->sharpen($image, $options);
	$image = $this->strip($image, $options);
	if ($this->save($image, $file, $options) === false) {
	// @codeCoverageIgnoreStart
	throw new Exception(message: 'The imagemagick result could not be generated');
	// @codeCoverageIgnoreEnd
	}
	return $options;

and

kirby/src/Image/Darkroom/Imagick.php

Lines 74 to 81 in 8006161

	protected function coalesce(Image $image): Image
	{
	if ($image->getImageMimeType() === 'image/gif') {
	return $image->coalesceImages();
	}
	return $image;
	}

$image->coalesceImages(); will return an Imagick instance where its first frame is 'selected' and one needs to do all image transformation for all frames, but the driver is currently only doing it for the first.

Here is a (just briefly tested) fixed preprocess function:

	public function process(string $file, array $options = []): array
	{
		$options = $this->preprocess($file, $options);

		$image = new Image($file);
		$image = $this->threads($image, $options);
		$image = $this->interlace($image, $options);
		$image = $this->coalesce($image);
		foreach ($image as $frame) {
			$frame = $this->grayscale($image, $options);
			$frame = $this->autoOrient($image);
			$frame = $this->resize($image, $options);
			$frame = $this->quality($image, $options);
			$frame = $this->blur($image, $options);
			$frame = $this->sharpen($image, $options);
			$frame = $this->strip($image, $options);		
		}

		if ($this->save($image, $file, $options) === false) {
			// @codeCoverageIgnoreStart
			throw new Exception(message: 'The imagemagick result could not be generated');
			// @codeCoverageIgnoreEnd
		}

		return $options;
	}

Is there a way to register a custom / own thumb driver, such that we can patch this until a fix is released?

[mrckzgl]

I figured I could modify

kirby/src/Image/Darkroom.php

Lines 22 to 26 in 8006161

	public static array $types = [
	'gd' => GdLib::class,
	'imagick' => Imagick::class,
	'im' => ImageMagick::class
	];

for example at plugin initialization time:

\Kirby\Image\Darkroom::$types['mythumbdriver'] = '\MyNamespace\MyThumbDriverClassname';

and then use

    'thumbs' => [
        'driver' => 'mythumbdriver',
    ],

in the config.php

[lukasbestle]

Yes, see our reference: https://getkirby.com/docs/reference/plugins/extensions/darkroom-drivers

[mrckzgl]

@lukasbestle Thnk for the reference to the docs. It seems, I just did it like mentioned intuitively as well. I am a bit puzzled by the "Enhancement" label. For me, having incorrect resized animations is a bug ... 🤔🤪

EDIT: I just tested my above proposed solution for jpegs and gifs, and it seems to work fine for both file types, making me a bit more confident that this could be a good proposal.

[lukasbestle]

It's somewhere in between. Resizing GIFs with multiple frames was not a supported feature of the thumb engine for a long time and we are only starting to support it more. But you are right, in the end it's more towards being a bug :)