PHP Manual: Apply a 3x3 convolution matrix, using coefficient and offset

Description

bool imageconvolution(
    GdImage $image,
    array $matrix,
    float $divisor,
    float $offset
)

Applies a convolution matrix on the image, using the given coefficient and offset.

Parameters

image: A GdImage object, returned by one of the image creation functions, such as imagecreatetruecolor.
matrix: A 3x3 matrix: an array of three arrays of three floats.
divisor: The divisor of the result of the convolution, used for normalization.
offset: Color offset.

Return Values

Returns true on success or false on failure.

Changelog

Version	Description
8.0.0	`image` expects a GdImage instance now; previously, a valid `gd` resource was expected.

Examples

Example #1 Embossing the PHP.net logo

<?php
$image = imagecreatefromgif('http://www.php.net/images/php.gif');

$emboss = array(array(2, 0, 0), array(0, -1, 0), array(0, 0, -1));
imageconvolution($image, $emboss, 1, 127);

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

The above example will output:

Example #2 Gaussian blur

<?php
$image = imagecreatetruecolor(180,40);

// Writes the text and apply a gaussian blur on the image
imagestring($image, 5, 10, 8, 'Gaussian Blur Text', 0x00ff00);
$gaussian = array(array(1.0, 2.0, 1.0), array(2.0, 4.0, 2.0), array(1.0, 2.0, 1.0));
imageconvolution($image, $gaussian, 16, 0);

// Rewrites the text for comparison
imagestring($image, 5, 10, 18, 'Gaussian Blur Text', 0x00ff00);

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