(PECL imagick 2 >= 2.1.0, PECL imagick 3)
Imagick::setImageAlphaChannel — Sets image alpha channel
Activate or deactivate image alpha channel. The mode is one of the Imagick::ALPHACHANNEL_* constants. This method is available if Imagick has been compiled against ImageMagick version 6.3.8 or newer.
modeOne of the Imagick::ALPHACHANNEL_* constants
Returns true on success.
Throws ImagickException on error.