Can't get perfect thumbnail sizes with image editor

[smerriman]

In the media settings, I have the thumbnail set to a fixed size (218x145), and set to crop to these exact dimensions.

Sometimes the automatic thumbnail crops off people's heads, etc, so I use the Image Editor to manually adjust the thumbnail. I select a rectangle, set the aspect ratio to 218x145, click crop, apply to thumbnail only, and save.

However, sometimes that results in an image slightly off in dimensions - for example, 215x145.

I expect this is a rounding error. However, it happens even if I select an area much bigger than this when cropping in the Image Editor - eg 300x200. After I click crop and see the 300x200 image, I would expect the thumbnail to be automatically be created at 218x145 like it does normally based on this adjusted image - however, it appears the checkbox for using exact dimensions doesn't apply here. (In fact, if I select, say 300x300, it will make my thumbnail 145x145).

This feels like a bug to me, and makes it very hard to generate thumbnails at the size I want.

[smerriman]

Update: this appears to be caused by line 615 of wp-admin/includes/image-edit.php:

	} elseif ( 'thumbnail' == $target ) {
		$sizes = array( 'thumbnail' );
		$success = $delete = $nocrop = true;
	}

I don't know why $nocrop is set to true, but I can't see any reason for doing so, and removing it fixes the problem.

[gcorne]

I have confirmed that when cropping in the image editor that the Setting > Media > Crop thumbnail to exact dimensions setting is not honored when cropping images via the image editor. I am not sure why $nocrop is being set to true, but if I was to guess, it is to give make sure that the user's crop size based on the selection in the image editor is honored. While more work to design/build, I wonder if it would be better if the image editor's UX communicated and respected the setting when cropping just the thumbnail.

Either way, I think it would be nice to fix this.

[Presskopp]

Related: #32282

[gaisma22]

Tested on WordPress 6.9.1 using a fresh install (Docker environment), no plugins, default theme (Twenty Twenty-Four).

Steps to reproduce:

1. Uploaded an image (2400 × 1350) to the Media Library
2. Opened the image and clicked “Edit Image”
3. Performed a manual crop and saved the edits
4. Returned to Media Library (Grid view) to inspect the thumbnail

Results:
After applying and saving the crop, the generated thumbnail correctly reflected the cropped image and respected the configured thumbnail cropping behavior from Media Settings.

The thumbnail preview displayed a cropped square representation rather than the original full image, which matches expected behavior.

Could not reproduce the issue on WordPress 6.9.1.