$file = 'orignal.png';
$file_cmyk = str_replace('.png', '_cmyk.jpg', $file);
$icc1 = '/imagine/imagine/lib/Imagine/resources/color.org/sRGB_IEC61966-2-1_black_scaled.icc';
$icc2 = '/imagine/imagine/lib/Imagine/resources/Adobe/CMYK/USWebUncoated.icc';
$cmd = "convert $file -intent relative -black-point-compensation -profile $icc1 -profile $icc2 -quality 100 $file_cmyk";
system($cmd);