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PHP Manual :: Imagick::sigmoidalContrastImage

Imagick::shearImage || Imagick::sketchImage || Imagick || PHP Manual

(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.

See also » ImageMagick v6 Examples - Image Transformations — Sigmoidal Non-linearity Contrast



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.

Return Values

Returns TRUE on success.


Example #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"]);




Throws ImagickException on error.

Imagick::shearImage || Imagick::sketchImage || Imagick || PHP Manual
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