PHP | imageconvolution() Function

Last Updated : 11 Jul, 2025

The imageconvolution() function is an inbuilt function in PHP which is used to modify the image content. It applies a 3 x 3 convolution matrix in the image, using the given coefficient and offset. This function returns true on success or false on failure. Syntax:

bool imageconvolution ( $image, $matrix, $div, $offset )

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

$image: It is returned by one of the image creation functions, such as imagecreatetruecolor(). It is used to create size of image.
$matrix: It contains an array of 3 x 3 (3 x 3 matrix) of floats.
$div: It is divisor of result of the convolution, used for normalization.
$offset: It is used to set the color offset.

Return Value: This function returns True on success or False on failure. Below programs illustrate the imageconvolution() function in PHP: Program 1:

php

<?php

// Create a gif image 
$image = imagecreatefromgif(
'https://media.geeksforgeeks.org/wp-content/uploads/animateImages.gif');
 
// Declare a 3X3 matrix
$matrix = array(
        array(2, 0, 0), 
        array(0, -1, 0), 
        array(0, 0, -1)
);
 
// imageconvolution function to modify image elements
imageconvolution($image, $matrix, 1, 127);
 
// Output of image content
header('Content-Type: image/png');
imagepng($image, null, 9);
?>

Output:

Program 2:

php

<?php

// Create a gif image 
$image = imagecreatefrompng(
'https://media.geeksforgeeks.org/wp-content/uploads/geeksforgeeks-9.png');
 
// Declare a 3X3 matrix
$emboss = array(        
        array(0, -1, 2), 
        array(2, 0, 0),
        array(2, 0, -2)
);
 
// imageconvolution function to modify image elements
imageconvolution($image, $emboss, 1, 127);

// Output of image content
header('Content-Type: image/png');
imagepng($image, null, 9);
?>