[magick-users] convert -size bug resulting wrong font size using ttf font file

[John]

Hi,
  I'm using the cygwin port of convert tool on a windows machine to
add caption to my photos, the version of convert I use is:
 convert -version
Version: ImageMagick 6.3.0 11/05/06 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2006 ImageMagick Studio LLC

The problem I found is that sometimes the font size chosen by convert
is actually larger than the -size constraints I impose, resulting a
wrong caption image:
$ convert -size x55 -font ~/arial.ttf label:"A test label" wrong.png

the font file arial.ttf is the one (Arial) found on my window/fonts directory.

However, I found this problem is size related, if I slightly change
the size to x54, it looks all right:
$ convert -size x54 -font ~/arial.ttf label:"A test label" right.png

I tried different ttf fonts on my system and found they all have
similar problem, but each at different sizes. As I need to generate
caption image at variable sizes (only constrain height, I want the
width grows automatically to the label string length), there is no
one-stop solution to this problem at the moment and I suspect this is
indeed a bug.

I attached two image files generated.

Any tips?

John