(PECL imagick 2.0.0)
Imagick::contrastStretchImage — Enhances the contrast of a color image
$black_point
   , float $white_point
   [, int $channel = Imagick::CHANNEL_DEFAULT
  ] )Enhances the contrast of a color image by adjusting the pixels color to span the entire range of colors available. Diese Funktion ist verfügbar, wenn Imagick gegen die ImageMagick-Version 6.2.9 oder höher kompiliert wurde.
black_pointThe black point.
white_pointThe white point.
channel
       Provide any channel constant that is valid for your channel mode. To
       apply to more than one channel, combine channeltype constants using
       bitwise operators. Imagick::CHANNEL_ALL. Refer to this
       list of  channel constants.
      
   Liefert TRUE bei Erfolg.