Changing this from "documentation problem" to "change 
request".

As far as I can tell, there's currently no way in GMagick to 
calculate the "fit" of text annotations. There is no 
equivalent to the newPseudoImage function in IMagick to use 
the CAPTION pseudo format.

You guys are fast! Getting ready to test it now. One thing I 
noticed-- the version number in php_gmagick.h needs to be 
updated. Still has 1.0.1-b1 in the trunk.

http://svn.php.net/viewvc/pecl/gmagick/trunk/php_gmagick.h?
revision=292136&view=markup

Example:

    $image = new Gmagick();
    $image->newImage(200, 200, 'yellow', 'PNG');
    $draw = new GmagickDraw();
    $draw->setFontSize('12');
    $color = new GmagickPixel('blue');
    $draw->setFillColor($color);
    $draw->setFont('Vera.ttf');
    $metrics = $image->queryfontmetrics($draw, 'Hello');
    print_r($metrics);

Gmagick's interface is minimal. To do something similar to the newPseudoImage() method available in Imagick:

$gm = new Gmagick();
$gm->setSize(200, 200)
   ->read("caption:test")
   ->setImageFormat("png")
   ->write("pseudo_file.png");

Vito, that's great to know. I had a feeling there had to be a 
way to do that. After the new year I'm going to take a stab at 
documenting some of the functions like read() that have a lot 
more power in them than meets the eye. In the mean time, I 
started a users group on Google (that doesn't have many 
members yet, but should be nicely searchable as a 
knowledgebase) on which I'll post this tidbit and others can 
as well. http://groups.google.com/group/gmagick-php