不完全确定你的要求......你能举个例子吗?也许imagettfbbox是你需要的?
// get bounding box dims
$dims = imagettfbbox($fontsize, 0, $font, $quote);
// do some math to find out the actual width and height
$width = $dims[4] - $dims[6]; // upper-right x minus upper-left x
$height = $dims[3] - $dims[5]; // lower-right y minus upper-right y
编辑:这是垂直居中文本的示例
<?php
$font = 'arial.ttf';
$fontsize = 100;
$imageX = 500;
$imageY = 500;
// text
$text = "FOOBAR";
// create a bounding box for the text
$dims = imagettfbbox($fontsize, 0, $font, $text);
// height of bounding box (your text)
$bbox_height = $dims[3] - $dims[5]; // lower-right y minus upper-right y
// Create image
$image = imagecreatetruecolor($imageX,$imageY);
// background color
$bgcolor = imagecolorallocate($image, 0, 0, 0);
// text color
$fontcolor = imagecolorallocate($image, 255, 255, 255);
// fill in the background with the background color
imagefilledrectangle($image, 0, 0, $imageX, $imageY, $bgcolor);
$x = 0;
$y = (($imageY/2) - ($bbox_height/2)) + $fontsize;
imagettftext($image, $fontsize, 0, $x, $y , $fontcolor, $font, $text);
// tell the browser that the content is an image
header('Content-type: image/png');
// output image to the browser
imagepng($image);
// delete the image resource
imagedestroy($image);
?>