The Imagick::contrastStretchImage() function is an inbuilt function in PHP which is used to enhance the contrast of the image. This function the enhances the contrast of a color image by adjusting the pixels color to span the entire range of colors available.
Syntax:
bool Imagick::contrastStretchImage( float $black_point,
float $white_point, int $channel = Imagick::CHANNEL_DEFAULT)
Parameters: This function accepts three parameters as mentioned above and described below:
- $black_point: This parameter holds the black point.
- $white_point: This parameter holds the white point.
- $channel: This parameter holds the Imagick channel constants that provide any channel constant which is valid for channel mode. More than one channel can be combined using bitwise operators. The default value of channel constant is CHANNEL_DEFAULT.
Return Value: This function returns TRUE on success.
Below programs illustrate the Imagick::contrastStretchImage() function in PHP:
Program 1:
<?php   // Create new Imagick object $imagick = new Imagick(   // Apply the contrastStretchImage() function $imagick->contrastStretchImage(10, 20);   header("Content-Type: image/png");   // Display the output image echo $imagick->getImageBlob(); ?> |
Output:
Program 2:
<?php   // Create new Imagick object $imagick = new Imagick(   // Apply the contrastStretchImage() function $imagick->contrastStretchImage(100, 50);   header("Content-Type: image/png");   // Display the output image echo $imagick->getImageBlob(); ?> |
Output:
Program 3:
<?php   // Create new Imagick object $imagick = new Imagick(   // Apply the contrastStretchImage() function $imagick->contrastStretchImage(5000, 100);   header("Content-Type: image/png");   // Display the output image echo $imagick->getImageBlob(); ?> |
Output:
Reference: https://www.php.net/manual/en/imagick.contraststretchimage.php
