Using ImageCache, I can scale to 100x100 and then crop to 100x100 with settings Center:Center for the x and y offsets. This center/center option can be achieved in ImageMagick with the -gravity Center command line option.

but the function imageapi_imagemagick_image_crop doesnt have this -gravity option, so the imagecache x/y offset settings are not added to the command line.

I suggest the function should be changed to something more like this (not $gravity)

function imageapi_imagemagick_image_crop(&$image, $x, $y, $width, $height, $gravity) {
  $image->ops[]  = '-gravity '.$gravity.' -crop '. (int) $width .'x'. (int) $height .'+'. (int) $x .'+'. (int) $y .'!';
  $image->info['width'] = $width;
  $image->info['height'] = $height;
  return TRUE;
}

This way, ImageCache could add the correct gravity, e.g. Center, South, Southwest etc. The GD module does have this implemented. Seems "forgotten" in the ImageMagick module.