(PECL imagick 2.0.0)
Imagick::sigmoidalContrastImage — Adjusts the contrast of an image
$sharpen
, float $alpha
, float $beta
[, int $channel = Imagick::CHANNEL_ALL
] )
Adjusts the contrast of an image with a non-linear sigmoidal contrast
algorithm. Increase the contrast of the image using a sigmoidal transfer
function without saturating highlights or shadows. Contrast indicates
how much to increase the contrast (0 is none; 3 is typical; 20 is
pushing it); mid-point indicates where midtones fall in the resultant
image (0 is white; 50 is middle-gray; 100 is black). Set sharpen to
TRUE to increase the image contrast otherwise the contrast is reduced.
sharpen
alpha
beta
channel
成功时返回 TRUE。
错误时抛出 ImagickException。