How to apply a gamma correction to a Graphics Draw (GD) image in PHP?

imagegammacorrect() is an inbuilt function in PHP that is used to apply a gamma correction to a given Graphics Draw (GD) input image and an output gamma.

Syntax

bool imagegammacorrect(resource $image, float $inputgamma, float $outputgamma)

Parameters

imagegammacorrect() takes three different parameters: $image, $inputgamma and $outputgamma.

• $image − Specifies the image to be worked.

• $inputgamma − Specifies the input gamma.

• $outputgamma − Specifies the output gamma.

Return Values

imagegammacorrect() returns True on success and False on failure.

Example 1

<?php
   // load an image from the local drive folder
   $img = imagecreatefrompng('C:\xampp\htdocs\Images\img58.png');

   // Change the image gamma by using imagegammacorrect
   imagegammacorrect($img, 15, 1.5);

   // Output image to the browser
   header('Content-Type: image/png');
   imagepng($img);
   imagedestroy($img);
?>

Output

Input image before using imagegammacorrect() PHP function

Output image after using imagegammacorrect() PHP function

Explanation − In this example, we loaded the image from the local drive folder by using the imagecreatefrompng() function or we can also use the URL of an image. After that, we applied imagegammacorrect() with the values 5 and 1.5. We can see the difference between the two images in the output.