(PECL imagick 2, PECL imagick 3)
Imagick::contrastStretchImage — Enhances the contrast of a color image
$black_point, float $white_point, int $channel = Imagick::CHANNEL_DEFAULT): boolEnhances the contrast of a color image by adjusting the pixels color to span the entire range of colors available. 此方法在Imagick基于ImageMagick 6.2.9以上版本编译时可用。
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.
成功时返回 true。