It took me some time to make full use of imagettfbbox. Hopefully the following function makes it much easier to use for others.
<?php
function convertBoundingBox ($bbox) {
if ($bbox[0] >= -1)
$leftOfBasepoint = -abs($bbox[0] + 1);
else
$leftOfBasepoint = abs($bbox[0] + 2);
$rightOfBasepoint = abs($bbox[2] - $bbox[0]);
if ($bbox[0] < -1) $rightOfBasepoint = abs($bbox[2]) + abs($bbox[0]) - 1;
$aboveBasepoint = abs($bbox[5] + 1);
$height = abs($bbox[7]) - abs($bbox[1]);
if ($bbox[3] > 0) $height = abs($bbox[7] - $bbox[1]) - 1;
$width = $leftOfBasepoint + $rightOfBasepoint;
$belowBasepoint = $height - $aboveBasepoint;
return array(
'width' => $width,
'height' => $height,
'leftOfBasepoint' => $leftOfBasepoint,
'rightOfBasepoint' => $rightOfBasepoint,
'aboveBasepoint' => $aboveBasepoint,
'belowBasepoint' => $belowBasepoint
);
}
?>
Thanks goes to mike at mikeleigh dot com for providing the core of this function.
Remember, the basepoint is the x, y coords you use to draw text with imagettftext. A useful thing to do is take a string like...
ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz01234567890
...and use the "aboveBasepoint" value for the height of your font. Now you can draw lines and use "the height of your font * leading" as the distance between lines of text, where leading is a number like 1.45 (for 45% leading).
