WebP image compression

[theamnesic]

Expected behavior

Timber WebP lossless quality is lossless quality.

Actual behavior

Seems like the towebp filter with quality 100 don't make lossless quality, compared to ImageMagick command.
When I use Timber with an original image at 381ko, Timber generate a 66ko image, ImageMagick a 232ko image.

Original: https://www.dropbox.com/s/7evk7rrfqsbj6x9/original.png?dl=0
Timber WebP: https://www.dropbox.com/s/oj8gdqf6qnaqtjs/timber.webp?dl=0
ImageMagick WebP: https://www.dropbox.com/s/cgfgklf013xttg4/imagemagick.webp?dl=0

(Sorry for using Dropbox, Github doesn't support WebP upload)

Steps to reproduce behavior

Generate a WebP with Timber:
TimberImage(my_image).src('full')|towebp(100)

Generate a WebP with ImageMagick:
magick original.png -quality 100 generated.webp

The image is lossless with ImageMagick, not with Timber.

What version of WordPress, PHP and Timber are you using?

PHP 7.4 with Mamp Pro, Timber 1.19.1, WP 5.8.2.

Thanks!

[EpicKau]

The |towebp filter use the php 'imagewebp' function.
Timber
PHP
So I gues they just handle it different.
Your results should also be different with cwebp, gd, gmagick, ...

[theamnesic]

The difference of the size is very important, 66ko (Timber) versus 232ko (ImageMagick).
There is lossless parameter in the ImageMagick documentation, maybe PHP ignore this?

[theamnesic]

Ok, it's a new feature:

In PHP 8.1, the GD extension supports lossless encoding, and declares a new PHP constant IMG_WEBP_LOSSLESS which can be passed to imagewebp function to enable lossless encoding of a GdImage object.

TimberImage(my_image).src('full')|towebp(101) in the future?