imageconvolution
(PHP 5 >= 5.1.0RC1)
imageconvolution -- Apply a 3x3 convolution matrix, using coefficient and offset
Description
bool
imageconvolution ( resource image, array matrix, float div, float offset )
Applies a convolution matrix on the image, using the given coefficient and
offset.
Parameters
imageAn image resource, returned by one of the image creation functions,
such as imagecreatetruecolor().
matrix
A 3x3 matrix: an array of three arrays of three floats.
div
The divisor of the result of the convolution, used for normalization.
offset
Return Values
Returns TRUE on success or FALSE on failure.
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);
?>
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The above example will output: 
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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);
?>
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The above example will output: 
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Notes
Note: This function is only available if
PHP is compiled with the bundled version of the GD library.