重心常數非常有用，因為它們可以省去計算可變文字字串和字型大小的放置。
例如
$draw->setGravity (Imagick::GRAVITY_CENTER);
$image->annotateImage($draw, 0, 0, 0, 'The quick brown fox jumps over the lazy dog');
將會水平和垂直置中文字字串。
注意，有幾個重心常數可用。請參閱 常數 — Imagick 類別常數
(PECL imagick 2, PECL imagick 3)
ImagickDraw::setGravity — 設定文字放置重心
不回傳值。
範例 #1 ImagickDraw::setGravity() 範例
<?php
function setGravity($fillColor, $strokeColor, $backgroundColor) {
$draw = new \ImagickDraw();
$draw->setStrokeColor($strokeColor);
$draw->setFillColor($fillColor);
$draw->setStrokeWidth(1);
$draw->setFontSize(24);
$gravitySettings = array(
\Imagick::GRAVITY_NORTHWEST => 'NorthWest',
\Imagick::GRAVITY_NORTH => 'North',
\Imagick::GRAVITY_NORTHEAST => 'NorthEast',
\Imagick::GRAVITY_WEST => 'West',
\Imagick::GRAVITY_CENTER => 'Centre',
\Imagick::GRAVITY_SOUTHWEST => 'SouthWest',
\Imagick::GRAVITY_SOUTH => 'South',
\Imagick::GRAVITY_SOUTHEAST => 'SouthEast',
\Imagick::GRAVITY_EAST => 'East'
);
$draw->setFont("../fonts/Arial.ttf");
foreach ($gravitySettings as $type => $description) {
$draw->setGravity($type);
$draw->annotation(50, 50, '"' . $description . '"');
}
$imagick = new \Imagick();
$imagick->newImage(500, 500, $backgroundColor);
$imagick->setImageFormat("png");
$imagick->drawImage($draw);
header("Content-Type: image/png");
echo $imagick->getImageBlob();
}
?>重心常數非常有用，因為它們可以省去計算可變文字字串和字型大小的放置。
例如
$draw->setGravity (Imagick::GRAVITY_CENTER);
$image->annotateImage($draw, 0, 0, 0, 'The quick brown fox jumps over the lazy dog');
將會水平和垂直置中文字字串。
注意，有幾個重心常數可用。請參閱 常數 — Imagick 類別常數看來 GRAVITY 常數具有整數等效值
NORTHWEST = 1
NORTH = 2
NORTHEAST = 3
WEST = 4
CENTER = 5
EAST = 6
SOUTHWEST = 7
SOUTH = 8
SOUTHEAST = 9