(PECL imagick 2.0.0)
Imagick::addNoiseImage — Adds random noise to the image
$noise_type
   [, int $channel = Imagick::CHANNEL_DEFAULT
  ] )Adds random noise to the image.
noise_type
     The type of the noise. Refer to this list of noise constants.
channel
     
       Provide any channel constant that is valid for your channel mode. To apply to more than one channel, combine channel constants using bitwise operators. Defaults to Imagick::CHANNEL_DEFAULT. Refer to this list of channel constants
      
   Returns TRUE on success.