It's up to you of course, but I think that's too big of an API change right now. To make the behaviour consistent it should be done for any and all methods. But then it would make much more sense to rebuild `Imagine\Imagick\Image` to make sure this is done consistently without having to add the same ugly condition inside each method. There's a reason Imagick itself doesn't apply everything to layers either. When you load the animated GIF I added to the repo in Imagick directly (sample below), you still have to iterate over each frame and resize the frame (which is an Imagick object itself too) rather than resizing the top object.

```php
$image = new \Imagick('animated.gif');
$image = $image->coalesceImages();

foreach ($image as $frame) {
    /** @var \Imagick $frame */
    $frame->resizeImage(100, 100, Imagick::FILTER_BOX, 0, true);
}

$image = $image->deconstructImages();
$image->writeImages('test.gif', true);
```

If you just do `$image->resizeImage(100, 100, Imagick::FILTER_BOX, 0, true);` the image will still come out as 400x400 if there's any frame at that size.

If I may make a suggestion; perhaps the change I proposed (supportCoalescing()) is one fit for the scope of this pull request, whereas the bigger rethinking of dealing with layers is something for a separate branch/PR? I just think that it's a fairly big API change to make in case, one that should be documented and thought through fully. Like I said, animated GIFs are probably the most common multi-layered images Imagine is used with, but they're not the only ones.

Or maybe I'm overthinking it :P