[4.4.15]: Quality setting does not work for transforms of png images

What happened?

Description

Transforms of png images to any format always result in the same file size, irrespective of the quality setting.

The file size is large, so I assume the output quality is always maximum.

This happens both on local (latest DDEV) and on a server provisioned with Ploi with all the latest updates.

ImageMagick version from system report: Imagick 3.7.0 (ImageMagick 6.9.11-60)

Steps to reproduce

1. Upload a png image file to any asset folder.
2. Output a transform of this asset in a template, either with a named transform or with a template defined transform, with a quality of 100.
3. Take note of the file size.
4. Change the transform quality setting to a lower quality.
5. Check the new file size.

Expected behavior

The file size should be lower, due to lower quality

Actual behavior

The file size remains exactly the same, no matter how low the quality setting.

Craft CMS version

4.4.15

PHP version

8.2.8

Operating system and version

No response

Database type and version

No response

Image driver and version

Imagick 3.7.0 (ImageMagick 6.9.11-60)

Installed plugins and versions

Start by reproducing the transform with a PNG asset and compare output sizes while changing the quality setting, using the reported Imagick 3.7.0 and ImageMagick 6.9.11-60 versions. Check both named and template-defined transforms; done means lower quality produces a correspondingly smaller output file.