PHP | Imagick sigmoidalContrastImage() Function

The Imagick::sigmoidalContrastImage() function is an inbuilt function in PHP which is used to adjust the contrast of an image with a non-linear sigmoidal contrast algorithm.

Syntax:

bool Imagick::sigmoidalContrastImage( bool $sharpen, float $alpha,
                 float $beta, int $channel = Imagick::CHANNEL_DEFAULT)

Parameters: This function accepts four parameters as mentioned above and described below:

• $sharpen: It specifies whether to increase or decrease the contrast. The true value increases the contrast and the false value decreases the contrast.
• $alpha: It specifies the amount of contrast to apply.
• $beta: It specifies the midpoint of the gradient.
• $channel: It is optional parameter that hold the channel constant. The default value is Imagick::CHANNEL_DEFAULT.

Return Value: This function returns TRUE on success.

Exceptions: This function throws ImagickException on error.

Below programs illustrate the Imagick::sigmoidalContrastImage() function in PHP:

Program 1:

<?php

// Create a new imagick object
$imagick = new Imagick(
'https://media.geeksforgeeks.org/wp-content/uploads/geeksforgeeks-13.png');

// Adjust the contrast
$imagick->sigmoidalContrastImage(true, 10, 32000);

// Show the output
header("Content-Type: image/png");
echo $imagick->getImageBlob();
?>

Output:

Program 2:

<?php

// Create a new imagick object
$imagick = new Imagick(
'https://media.geeksforgeeks.org/wp-content/uploads/geeksforgeeks-13.png');

// Adjust the contrast
$imagick->sigmoidalContrastImage(false, 10, 31000);

// Show the output
header("Content-Type: image/png");
echo $imagick->getImageBlob();
?>

Output:

Reference: https://www.php.net/manual/en/imagick.sigmoidalcontrastimage.php