为什么Imagick的缩略图失败？

Question

I try to make a thumbnail image with Imagick. To make the question simpler, I have the following test code:

//loading picture
$image = new Imagick('/home/ytg/temp/blank.png');
//checking image size
echo "width: {$image->getimagewidth()}\n";
echo "height: {$image->getimageheight()}\n";
//creating thumbnail
$image->thumbnailImage(220, 220, true);
//checking image size
echo "new width: {$image->getimagewidth()}\n";
echo "new height: {$image->getimageheight()}\n";

Which gives me the following result:

width: 300
height: 300
new width: 219
new height: 220

Why does it make the thumbnail image width a pixel smaller? How could I prevent this from happening? I wouldn't like to use the last $fill parameter of thumbnailImage() , because the input image does not always have the same width and height and I wouldn't like if it filled the thumbnail in those cases.

( PHP Version => 5.4.6-1ubuntu1.1; imagick module version => 3.1.0RC1 )

Answer 1

Right now I'm settling with this solution:

$image = new Imagick('/home/ytg/temp/blank.png');
//checking image size
echo "width: {$image->getimagewidth()}\n";
echo "height: {$image->getimageheight()}\n";
//creating thumbnail
$image->thumbnailImage(220, 220, true);
//checking image size
echo "new width: {$image->getimagewidth()}\n";
echo "new height: {$image->getimageheight()}\n";        
$image->thumbnailImage($width, $height, true);                                                
if (($width == $height) && ($image->getImageWidth() != $image->getImageHeight())) {
    $image->thumbnailImage($width, $height, true, true);            
}

It's not perfect though because it works only with the specific case of square images. But in that special case it solves my problem.