Imagick::sigmoidalContrastImage
(PECL imagick 2.0.0)
Imagick::sigmoidalContrastImage — Adjusts the contrast of an image
Description
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.
Parameters
sharpen
If true increase the contrast, if false decrease the contrast.
alpha
The amount of contrast to apply. 1 is very little, 5 is a significant amount, 20 is extreme.
beta
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.
channel
Which color channels the contrast will be applied to.
Return Values
Returns TRUE on success.
Examples
Example #1 Create a gradient image using Imagick::sigmoidalContrastImage() suitable for blending two images together smoothly, with the blending defined by $contrast and $the midpoint
<?php
function generateBlendImage($width, $height, $contrast = 10, $midpoint = 0.5) {
$imagick = new Imagick();
$imagick->newPseudoImage($width, $height, 'gradient:black-white');
$quanta = $imagick->getQuantumRange();
$imagick->sigmoidalContrastImage(true, $contrast, $midpoint * $quanta["quantumRangeLong"]);
return $imagick;
}
?>Errors/Exceptions
Throws ImagickException on error.
← Imagick::shearImage
Imagick::sketchImage →
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