Edit:这似乎已在 PHP 中修复7.0.12 http://www.php.net/ChangeLog-7.php#7.0.12 (bug #53504 https://bugs.php.net/bug.php?id=53504)所以不需要下面的代码。
基于一个PHP手册中的注释 http://php.net/manual/en/function.imagettfbbox.php#97357我编写了以下函数来计算并返回 GD 认为边界框左侧的位置与找到最左侧像素的位置之间的差异:
function xadjust($size, $angle, $fontfile, $text)
{
$bbox = imagettfbbox($size, $angle, $fontfile, $text);
$width = $bbox[4] - $bbox[6]; // upper right x - upper left x;
$height = $bbox[1] - $bbox[7]; // lower left y - upper left y;
// create an image with height and width doubled to fit any 'swash'.
$im = imagecreatetruecolor($width * 2, $height * 2);
// set background color to opaque black.
imagefill($im, 0, 0, 0x00000000);
// draw the text in opaque white.
imagettftext(
$im,
$size,
0,
$width / 2,
$height,
0x00ffffff,
$fontfile,
$text
);
// set the min-width to its possible maximum.
$min_x = $width * 2;
for ($x = 0; $x < $width * 2; $x++) {
// each x-pixel (horizontal)
for ($y = 0; $y < $height * 2; $y++) {
// each y-pixel (vertical)
if (imagecolorat($im, $x, $y) > 0) {
// non-black pixel found!
$min_x = min($x, $min_x);
}
}
}
imagedestroy($im);
// return the difference between where GD thinks the bounding box is and
// where we found the leftmost non-black pixel.
return (($width / 2) - $min_x) - abs($bbox[0]);
}
这可以很容易地集成到您的脚本中:
$font = 'scriptin.ttf';
$text = 'Ipsum';
$size = 30;
$image = imagecreatetruecolor(200, 200);
$fontColour = imagecolorallocate($image, hexdec('11'), hexdec('11'), hexdec('11'));
$bgColour = imagecolorallocate($image, hexdec('CC'), hexdec('CC'), hexdec('CC'));
imagefilledrectangle($image, 0, 0, 200, 200, $bgColour);
$xadjust = xadjust($size, 0, $font, $text); // 1. get the adjust value.
$dimensions = imagettfbbox($size, 0, $font, $text);
imagefilledrectangle(
$image,
$dimensions[0] + 40 - $xadjust, // 2. move the left-side of the box to the left.
$dimensions[7] + 50,
$dimensions[2] + 40 - $xadjust, // 3. move the right-side of the box to the left.
$dimensions[3] + 50,
imagecolorallocate($image, mt_rand(1, 180), mt_rand(1, 180), mt_rand(1, 180))
);
imagettftext(
$image,
$size,
0,
40,
50,
$fontColour,
$font,
$text
);
header('Content-Type: image/png');
imagepng($image);
这给了我以下输出:
我用其他一些字体和大小运行过它,它似乎精确到 1 像素以内。