function image_etendre_alpha($im, $coul='000000', $trait=2)
{
	$image = valeurs_image_trans($im, "etendre-$coul-$trait");
	if (!$image) return("");

	include_ecrire("filtres");
	$couleurs = couleur_hex_to_dec($coul);
	$dr= $couleurs["red"];
	$dv= $couleurs["green"];
	$db= $couleurs["blue"];
	
	$x_i = $image["largeur"];
	$y_i = $image["hauteur"];
	
	$im = $image["fichier"];
	$dest = $image["fichier_dest"];
	
	$creer = $image["creer"];

	if ($creer) {
		$im = $image["fonction_imagecreatefrom"]($im);
		$im_ = imagecreatetruecolor($x_i, $y_i);
		@imagealphablending($im_, false);
		@imagesavealpha($im_,true);
		$color_t = ImageColorAllocateAlpha( $im_, 255, 255, 255 , 127 );
		imagefill ($im_, 0, 0, $color_t);

		$dist = abs($trait);
		for ($x = 0; $x < $x_i; $x++) {
			for ($y=0; $y < $y_i; $y++) {
			
				$rgb = ImageColorAt($im, $x, $y);
				$a = ($rgb >> 24) & 0xFF;
				$r = ($rgb >> 16) & 0xFF;
				$g = ($rgb >> 8) & 0xFF;
				$b = $rgb & 0xFF;
				
				$dif = false;
				if ($trait > 0) $m = 127;
				else $m = 0;
				$t = 0;

				for ($ix = -1*$dist; $ix <= $dist; $ix++) {
					for ($iy = -1*$dist; $iy <= $dist; $iy++) {
						$x2 = max(min($x+$ix, $x_i-1),0);
						$y2 = max(min($y+$iy, $y_i-1),0);
					
						$rgb2 = ImageColorAt($im, $x2, $y2);
						$a2 = ($rgb2 >> 24) & 0xFF;
						$r2 = ($rgb2 >> 16) & 0xFF;
						$g2 = ($rgb2 >> 8) & 0xFF;
						$b2 = $rgb2 & 0xFF;

						$dx = $x2-$x;
						$dy = $y2-$y;
						
						if ($dx == 0 AND $dy == 0) {
							$d = 0;
						}
						else if (!$mem[$dx][$dy]) {
							$d = sqrt(($dx)*($dx)+($dy)*($dy)) / 1.4;
							$mem[$dx][$dy] = $d;				
						} else {
							$d = $mem[$dx][$dy];
						}

						if ($d <= abs($trait)) {
							if ($trait > 0) $m = min($m, $a2);
							else $m = max($m, $a2);
						}						
					}
				}

				$color = ImageColorAllocateAlpha( $im_, $dr, $dv, $db , round($m) );
				imagesetpixel ($im_, $x, $y, $color);				}
		}
		$image["fonction_image"]($im_, "$dest");
	}

	$class = $image["class"];
	if (strlen($class) > 1) $tags=" class='$class'";
	$tags = "$tags alt='".$image["alt"]."'";
	$style = $image["style"];
	
	return "<img src='$dest'$tags />";
}</code>

Le filtre s'utilise, essentiellement, sur une image typographique. Par exemple:

<cadre>
[(#TITRE
	|image_typo{police=big_noodle_titling.ttf,taille=80})]
[(#TITRE
	|image_typo{police=big_noodle_titling.ttf,taille=80}
		|image_etendre_alpha{ffffff,2})]
[(#TITRE
	|image_typo{police=big_noodle_titling.ttf,taille=80}
		|image_etendre_alpha{ffffff,-2})]