Adjusts the contrast of an image

(PECL imagick 2.0.0)

Imagick::sigmoidalContrastImageAdjusts the contrast of an image


bool Imagick::sigmoidalContrastImage ( bool $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.

Список параметров


If true increase the contrast, if false decrease the contrast.


The amount of contrast to apply. 1 is very little, 5 is a significant amount, 20 is extreme.


Where the midpoint of the gradient will be. This value should be in the range 0 to 1 - mutliplied by the quantum value for ImageMagick.


Which color channels the contrast will be applied to.

Возвращаемые значения

В случае успешной работы возвращает TRUE.


Пример #1 Create a gradient image using Imagick::sigmoidalContrastImage() suitable for blending two images together smoothly, with the blending defined by $contrast and $the midpoint


function generateBlendImage($width$height$contrast 10$midpoint 0.5) {
$imagick = new Imagick();
$quanta $imagick->getQuantumRange();
$imagick->sigmoidalContrastImage(true$contrast$midpoint $quanta["quantumRangeLong"]);




Вызывает ImagickException при ошибке.