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Last updated: Sat, 27 Jan 2007

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# imageconvolution

(PHP 5 >= 5.1.0RC1)

imageconvolution -- Apply a 3x3 convolution matrix, using coefficient and offset

## Описание

bool imageconvolution ( resource image, array matrix, float div, float offset )

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

## Список параметров

`image`

  An 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`

## Возвращаемые значения

Возвращает `TRUE` в случае успешного завершения или `FALSE` в случае возникновения ошибки.

## Примеры

Пример 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);
?>`

Результат выполнения данного примера:

Пример 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);
?>`

Результат выполнения данного примера:

## Примечания

> Замечание: Эта функция доступна только в том случае, если PHP был скомпилирован со встроенной библиотекой GD.

## Смотрите также

imagefilter()

add a note User Contributed Notes
imageconvolution
mgcclx at gmail dot com
28-Feb-2007 07:55
`imageconvolution() does not appear in PHP with non-bundled GD libraries. It is a rare situation, but it still happens. That's why I wrote a replication of imageconvolution() in PHP. Compare to the post below, this one makes the use of offset and 30% faster.
Because it's written in PHP, it is 50 times slower than the bundled version.
Actually, this is a replication of gdimageconvolutaion() of GD library, it does not support data validating feature imageconvolution() have. But I guess people who uses this function knows their stuff.
THE SCRIPT:
<?php
//include this file whenever you have to use imageconvolution...
//you can use in your project, but keep the comment below :)
//great for any image manipulation library
//Made by Chao Xu(Mgccl) 2/28/07
//www.webdevlogs.com
//V 1.0
if(!function_exists('imageconvolution')){
function imageconvolution($src, $filter, $filter_div, $offset){
if ($src==NULL) {
return 0;
}
$sx = imagesx($src);
$sy = imagesy($src);
$srcback = ImageCreateTrueColor ($sx, $sy);
ImageCopy($srcback, $src,0,0,0,0,$sx,$sy);
if($srcback==NULL){
return 0;
}
for ($y=0; $y<$sy; ++$y){
for($x=0; $x<$sx; ++$x){
$new_r = $new_g = $new_b = 0;
$alpha = imagecolorat($srcback, $pxl[0], $pxl[1]);
$new_a = $alpha >> 24;
for ($j=0; $j<3; ++$j) {
$yv = min(max($y - 1 + $j, 0), $sy - 1);
for ($i=0; $i<3; ++$i) {
$pxl = array(min(max($x - 1 + $i, 0), $sx - 1), $yv);
$rgb = imagecolorat($srcback, $pxl[0], $pxl[1]);
$new_r += (($rgb >> 16) & 0xFF) * $filter[$j][$i];
$new_g += (($rgb >> 8) & 0xFF) * $filter[$j][$i];
$new_b += ($rgb & 0xFF) * $filter[$j][$i];
}
}
$new_r = ($new_r/$filter_div)+$offset;
$new_g = ($new_g/$filter_div)+$offset;
$new_b = ($new_b/$filter_div)+$offset;
$new_r = ($new_r > 255)? 255 : (($new_r < 0)? 0:$new_r);
$new_g = ($new_g > 255)? 255 : (($new_g < 0)? 0:$new_g);
$new_b = ($new_b > 255)? 255 : (($new_b < 0)? 0:$new_b);
$new_pxl = ImageColorAllocateAlpha($src, (int)$new_r, (int)$new_g, (int)$new_b, $new_a);
if ($new_pxl == -1) {
$new_pxl = ImageColorClosestAlpha($src, (int)$new_r, (int)$new_g, (int)$new_b, $new_a);
}
if (($y >= 0) && ($y < $sy)) {
imagesetpixel($src, $x, $y, $new_pxl);
}
}
}
imagedestroy($srcback);
return 1;
}
}
?>`
interghost at crovortex dot com
31-Mar-2006 11:26
`an implementation of this function for PHP versions <5.1
<?php
if(!function_exists("imageconvolution"))
{
function imageconvolution(&$img,$mat,$div,$off)
{
if(!imageistruecolor($img) || !is_array($mat) || count($mat)!=3 || count($mat[0])!=3 || count($mat[1])!=3 || count($mat[2])!=3) return FALSE;
unset($bojainfo);
for($nx=0;$nx<imagesx($img)-1;$nx++)
{
for($ny=0;$ny<imagesy($img)-1;$ny++)
{
$rgb=imagecolorat($img,$nx,$ny);
$bojainfo[$nx][$ny][r]=($rgb>>16)&0xFF;
$bojainfo[$nx][$ny][g]=($rgb>>8)&0xFF;
$bojainfo[$nx][$ny][b]=$rgb&0xFF;
}
}
for($nx=1;$nx<imagesx($img)-1;$nx++)
{
for($ny=1;$ny<imagesy($img)-1;$ny++)
{
$nr=$mat[0][0]*$bojainfo[$nx-1][$ny-1][r] + $mat[0][1]*$bojainfo[$nx][$ny-1][r] + $mat[0][2]*$bojainfo[$nx+1][$ny-1][r] + $mat[1][0]*$bojainfo[$nx-1][$ny][r] + $mat[1][1]*$bojainfo[$nx][$ny][r] + $mat[1][2]*$bojainfo[$nx+1][$ny][r] + $mat[2][0]*$bojainfo[$nx-1][$ny+1][r] + $mat[2][1]*$bojainfo[$nx][$ny+1][r] + $mat[2][2]*$bojainfo[$nx+1][$ny+1][r];
$nr=intval(round($nr/$div));
if($nr<0) $nr=0;
elseif($nr>255) $nr=255;
$ng=$mat[0][0]*$bojainfo[$nx-1][$ny-1][g] + $mat[0][1]*$bojainfo[$nx][$ny-1][g] + $mat[0][2]*$bojainfo[$nx+1][$ny-1][g] + $mat[1][0]*$bojainfo[$nx-1][$ny][g] + $mat[1][1]*$bojainfo[$nx][$ny][g] + $mat[1][2]*$bojainfo[$nx+1][$ny][g] + $mat[2][0]*$bojainfo[$nx-1][$ny+1][g] + $mat[2][1]*$bojainfo[$nx][$ny+1][g] + $mat[2][2]*$bojainfo[$nx+1][$ny+1][g];
$ng=intval(round($ng/$div));
if($ng<0) $ng=0;
elseif($ng>255) $ng=255;
$nb=$mat[0][0]*$bojainfo[$nx-1][$ny-1][b] + $mat[0][1]*$bojainfo[$nx][$ny-1][b] + $mat[0][2]*$bojainfo[$nx+1][$ny-1][b] + $mat[1][0]*$bojainfo[$nx-1][$ny][b] + $mat[1][1]*$bojainfo[$nx][$ny][b] + $mat[1][2]*$bojainfo[$nx+1][$ny][b] + $mat[2][0]*$bojainfo[$nx-1][$ny+1][b] + $mat[2][1]*$bojainfo[$nx][$ny+1][b] + $mat[2][2]*$bojainfo[$nx+1][$ny+1][b];
$nb=intval(round($nb/$div));
if($nb<0) $nb=0;
elseif($nb>255) $nb=255;
$nrgb=($nr<<16)+($ng<<8)+$nb;
if(!imagesetpixel($img,$nx,$ny,$nrgb)) return FALSE;
}
}
return TRUE;
}
}
?>
it's a bit slowish so I wouldn't recommend big images, also offset is not implemented (don't know what it's suppose to do)`
mlconnor at yahoo dot com
21-Mar-2006 09:00
`I've seen many people come up with ways to do a drop shadow behind a rectangle such as a picture. I haven't found one yet that was fast, PHP 4 complaint, and nice looking. Here is one I came up with last night. It takes an image, fills it with the background, and creates a blurred drop shadow at the specified coords using the colors and the distance offset specified. It looks great!!!
function blurRect(&$image, $distance, $rectX1, $rectY1, $rectX2, $rectY2, $shadowR, $shadowG, $shadowB, $backR, $backG, $backB) {
$potentialOverlap = ($distance * 2) * ($distance * 2);
$backgroundColor = imagecolorallocate($image, $backR, $backG, $backB);
$shadowColor = imagecolorallocate($image, $shadowR, $shadowG, $shadowB);
$imageWidth = imagesx($image);
$imageHeight = imagesy($image);
imageFilledRectangle($image, 0, 0, $imageWidth - 1, $imageHeight - 1, $backgroundColor);
imageFilledRectangle($image, $rectX1, $rectY1, $rectX2, $rectY2, $shadowColor);
for ( $pointX = $rectX1 - $distance; $pointX < $imageWidth; $pointX++ ) {
for ( $pointY = $rectY1 - $distance; $pointY < $imageHeight; $pointY++ ) {
if ( $pointX > $rectX1 + $distance &&
$pointX < $rectX2 - $distance &&
$pointY > $rectY1 + $distance &&
$pointY < $rectY2 - $distance ) {
$pointY = $rectY2 - $distance;
}
$boxX1 = $pointX - $distance;
$boxY1 = $pointY - $distance;
$boxX2 = $pointX + $distance;
$boxY2 = $pointY + $distance;
$xOverlap = max(0, min($boxX2, $rectX2) - max($boxX1, $rectX1));
$yOverlap = max(0, min($boxY2, $rectY2) - max($boxY1, $rectY1));
$totalOverlap = $xOverlap * $yOverlap;
$shadowPcnt = $totalOverlap / $potentialOverlap;
$backPcnt = 1.0 - $shadowPcnt;
$newR = $shadowR * $shadowPcnt + $backR * $backPcnt;
$newG = $shadowG * $shadowPcnt + $backG * $backPcnt;
$newB = $shadowB * $shadowPcnt + $backB * $backPcnt;
$newcol = imagecolorallocate($image, $newR, $newG, $newB);
imagesetpixel($image, $pointX, $pointY, $newcol);
}
}
}`
jonathan dot aquino at gmail dot com
17-Jan-2006 09:30
`For those who don't have PHP 5.1 and thus don't have imageconvolution, I found some code to do blurring: http://www.hudzilla.org/php/11_2_25.php Works quite nicely.`
dyer85 at gmail dot com
07-Jan-2006 02:24
`Took me a while, but thanks to a couple of the user notes on the array_values PHP documentation page, I was able to come up with a way to dynamically compute the divisor.
I'm using PHP 5.1.0b2 on Win32 with the bundled GD library. When I try and use the imageconvolution function, whether normally, or via the functions below, the resulting image (I've only tried JPEGs and GIFs), always comes out far too bright, even when the divisor makes matrix sum equal to 1. The only thing that would reduce the brightness was to make the offset argument ridiculously large. So, I'm not sure if this effects anyone else.
Here are the functions with an example:
<?php
$im = imagecreatefromjpeg('path/to/pic.jpg');
$matrix = array( array(5,5,5),
array(5,15,5),
array(5,5,5) );
makeFilter($im, $matrix);
header ( 'Content-Type: image/jpeg' );
imagejpeg($im);
imagedestroy($im);
/**
* functions
*/
// This flattens the 3X3 array matrix, so we can get the sum of all the values
function array_flatten($array) {
(array)$tempArray = array();
foreach ( $array as $value ) {
if ( is_array($value) ) {
$tempArray = array_merge($tempArray, array_flatten($value));
} else {
$tempArray[] = $value;
}
}
return $tempArray;
}
// Creates the divisor value dynamically, and passes offset
function makeFilter($resource, $matrix, $offset=1.0) {
global $$resource;
(float)$divisor = array_sum(array_flatten($matrix));
return imageconvolution($resource, $matrix, $divisor, $offset) ? true : false;
}
?>`
26-Oct-2005 05:32
`The example below didn't provide a 3x3 matrix. Correctly, it's a multidimensional array.
<?php
$matrix = array( array( -1, -1, -1 ),
array( -1, 16, -1 ),
array( -1, -1, -1 ) );
?>`
timeshifting at gmail dot com
24-Aug-2005 03:40
`Matrices can be used for sharpening, blurring, edge detection, etc, ala Photoshop.
A sharpening example:
<?php
$sharpenMatrix = array(-1,-1,-1,-1,16,-1,-1,-1,-1);
$divisor = 8;
$offset = 0;
imageconvolution($myImage, $sharpenMatrix, $divisor, $offset);
?>
Below is some information on building different kinds of matrices. (If you have photoshop (or PSP, GIMP) you can test out your matrices before applying them in PHP)
http://loriweb.pair.com/8udf-basics.html (covers blurs)
http://loriweb.pair.com/8udf-sharpen.html
http://loriweb.pair.com/8udf-edges.html
http://loriweb.pair.com/8udf-emboss.html`
add a note
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Last updated: Sat, 27 Jan 2007
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