I am on latest Mountain Lion, I reinstalled IM with same command as you used, earlier I had used - 'sudo port -p install ImageMagick'.
Now i used - 'sudo port -p install ImageMagick +graphviz+hdri+jbig+jpeg2+lqr+mpeg+pango+perl+q16+rsvg+wmf'
My version:
Version: ImageMagick 6.7.9-0 2012-08-22 Q16
http://www.imagemagick.org
Copyright: Copyright (C) 1999-2012 ImageMagick Studio LLC
Features: OpenCL HDRI
Output from:
$convert -list configure
Path: /opt/local/lib/ImageMagick-6.7.9/config/configure.xml
Name Value
-------------------------------------------------------------------------------
CC /usr/bin/clang
CFLAGS -I/opt/local/include/lqr-1 -I/opt/local/include/glib-2.0 -I/opt/local/lib/glib-2.0/include -I/opt/local/include -pipe -O2 -arch x86_64 -Wall -D_THREAD_SAFE -pthread
CODER_PATH /opt/local/lib/ImageMagick-6.7.9/modules-Q16/coders
CONFIGURE ./configure '--prefix=/opt/local' '--enable-shared' '--enable-static' '--disable-ltdl-install' '--with-frozenpaths' '--with-dps' '--with-bzlib' '--with-fontconfig' '--with-gslib' '--with-jpeg' '--with-lcms' '--with-png' '--with-tiff' '--with-webp' '--with-zlib' '--with-modules' '--with-xml' '--with-x' '--without-fpx' '--with-gs-font-dir=/opt/local/share/fonts/urw-fonts' '--with-gvc' '--with-openexr' '--enable-hdri' '--with-jbig' '--with-jp2' '--with-lqr' '--with-pango' '--with-perl=/opt/local/bin/perl' '--with-quantum-depth=16' '--with-rsvg' '--with-wmf' 'CC=/usr/bin/clang' 'CFLAGS=-pipe -O2 -arch x86_64' 'LDFLAGS=-L/opt/local/lib -arch x86_64' 'CPPFLAGS=-I/opt/local/include' 'CXX=/usr/bin/clang++' 'CXXFLAGS=-pipe -O2 -arch x86_64'
CONFIGURE_PATH /opt/local/etc/ImageMagick/
COPYRIGHT Copyright (C) 1999-2012 ImageMagick Studio LLC
CPPFLAGS -I/opt/local/include/ImageMagick
CXX /usr/bin/clang++
CXXFLAGS -pipe -O2 -arch x86_64 -D_THREAD_SAFE -pthread
DEFS -DHAVE_CONFIG_H
DELEGATES bzlib fftw fontconfig freetype gs gvc jbig jpeg jng jp2 lcms2 lqr lzma openexr pango png rsvg tiff x11 xml wmf zlib
DISTCHECK_CONFIG_FLAGS 'CC=/usr/bin/clang' 'CFLAGS=-pipe -O2 -arch x86_64' 'CPPFLAGS=-I/opt/local/include' 'CXX=/usr/bin/clang++' 'LDFLAGS=-L/opt/local/lib -arch x86_64' --disable-deprecated --with-quantum-depth=16 --with-umem=no --with-autotrace=no --with-fpx=no --with-fontpath= --with-gs-font-dir=/opt/local/share/fonts/urw-fonts --with-perl=/opt/local/bin/perl
DOCUMENTATION_PATH /opt/local/share/doc/ImageMagick-6.7.9
EXEC-PREFIX /opt/local
EXECUTABLE_PATH /opt/local/bin
FEATURES HDRI OpenCL
FILTER_PATH /opt/local/lib/ImageMagick-6.7.9/modules-Q16/filters
HOST x86_64-apple-darwin12.0.0
INCLUDE_PATH /opt/local/include/ImageMagick
LDFLAGS -L/opt/local/lib -L/opt/local/lib -arch x86_64 -L/opt/local/lib -L/opt/local/lib
LIB_VERSION 0x679
LIB_VERSION_NUMBER 6,7,9,0
LIBRARY_PATH /opt/local/lib/ImageMagick-6.7.9
LIBS -lMagickCore -llcms2 -ltiff -lfreetype -ljpeg -L/opt/local/lib -llqr-1 -lglib-2.0 -lintl -lfftw3 -L/opt/local/lib -lfontconfig -lXext -lSM -lICE -lX11 -lXt -L/opt/local/lib -llzma -lbz2 -lz -lm -Wl,-framework,OpenCL -lpthread -lltdl
NAME ImageMagick
PCFLAGS
PREFIX /opt/local
QuantumDepth 16
RELEASE_DATE 2012-08-22
SHARE_PATH /opt/local/share/ImageMagick-6.7.9
SVN_REVISION 8971
TARGET_CPU x86_64
TARGET_OS darwin12.0.0
TARGET_VENDOR apple
VERSION 6.7.9
WEBSITE
http://www.imagemagick.org
Path: [built-in]
Name Value
-------------------------------------------------------------------------------
NAME ImageMagick
Ran this command as is -
$convert pokemon.gif -alpha on \( +clone -flip -size 64x28 gradient:gray40-black -alpha off -compose CopyOpacity -composite \) -append -gravity North -crop 100x100+0-5\! -background black -compose Over -flatten reflect_attenuated.png
It generates this image -
http://www.tiikoni.com/tis/view/?id=446537b
This image doesn't show any reflection in preview.app or any other viewers.