I've got a very weird bug which I've yet to find a solution. UPDATE see solution below What I am trying to do is convert a full size picture into a 160x120 thumbnail. It works great with jpg and jpeg files of any size, but not with png. ImageMagick command: /opt/local/bin/convert '/WEBSERVER/images/img_0003-192-10.png' -thumbnail x320 -resize '320x<' -resize 50% -gravity center -crop 160x120+0+0 +repage -quality 91 '/WEBSERVER/thumbs/small_img_0003-192-10.png' PHP function (shortened) ... $cmd = "/opt/local/bin/convert '/WEBSERVER/images/img_0003-192-10.png' -thumbnail x320 -resize '320x<' -resize 50% -gravity center -crop 160x120+0+0 +repage -quality 91 '/WEBSERVER/thumbs/small_img_0003-192-10.png'"; exec($cmd, $output, $retval); $errors += $retval; if ($errors > 0) { die(print_r($output)); } When this function runs $retval equal 1 which means the convert command failed (thumbnail isn't created). This is where it gets interesting, if I run the exact same command in my shell, it works. wedbook:~ wedix$ /opt/local/bin/convert '/WEBSERVER/images/img_0003-192-10.png' -thumbnail x320 -resize '320x<' -resize 50% -gravity center -crop 160x120+0+0 +repage -quality 91 '/WEBSERVER/thumbs/small_img_0003-192-10.png' wedbook:~ wedix$ I've tried using different PHP function such as system, passthru but it didn't work. I thought maybe someone here knew the solution. I'm using MAMP 1.7.2 Apache/2.0.59 PHP/5.2.6 Thanks! UPDATE I updated the following dependencies libpng from 1.2.35 to 1.2.37 libiconv from 1.12_2 to 1.13_0 ImageMagick 6.5.2-4_1 to 6.5.2-9_0 However, it did not fix my problem. 2nd UPDATE I finally found something that might help, when the function runs this is what gets printed in the Apache logs: dyld: Library not loaded: /opt/local/lib/libiconv.2.dylib Referenced from: /opt/local/bin/convert Reason: Incompatible library version: convert requires version 8.0.0 or later, but libiconv.2.dylib provides version 7.0.0 3rd UPDATE libiconv.2.dylib is version 8.0.0... bash-3.2$ otool -L /opt/local/lib/libiconv.2.dylib /opt/local/lib/libiconv.2.dylib: /opt/local/lib/libiconv.2.dylib (compatibility version 8.0.0, current version 8.0.0) /usr/lib/libgcc_s.1.dylib (compatibility version 1.0.0, current version 1.0.0) /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 111.1.4) 4th UPDATE Problem was related to MAMP, see solution below