You can do this by finding out dimensions of the text in pixels using imagettfbbox()
, then use it as reference to draw lines beneath the text. I've played around with it and here's my try:
function createImage($text){
putenv('GDFONTPATH=' . realpath('.'));
$text = wordwrap($text, 40, "\n");
$padding = 10; // padding around text
$uOffs = 2; // distance between the line and the text above it
$uHeight = 1; // height of the under-line
$lines = explode("\n", $text); // split text in lines
$lineLengths = array(); // will store length of each line
$textSize = 11;
$font = 'arialbd.ttf';
// bounding box of all text
$textBoundingBox = array_map('abs', imagettfbbox($textSize, 0, $font, $text));
list($blx, $bly, $brx, $bry, $trx, $try, $tlx, $tly) = $textBoundingBox;
// calculate image dimensions based on the bounding box data
$x = max($brx, $trx) + ($padding * 4);
$y = max($blx, $bly) + ($padding * 4);
$img = imagecreatetruecolor($x, $y);
// determine length of each line of text
foreach($lines as $i => $line){
$box = imagettfbbox($textSize, 0, $font, $line);
$lineLengths[$i] = max($box[2], $box[4]);
}
$white = imagecolorallocate($img, 255, 255, 255);
$grey = imagecolorallocate($img, 128, 128, 128);
$black = imagecolorallocate($img, 0, 0, 0);
$purple = imagecolorallocate($img, 97, 26, 139);
imagefilledrectangle($img, 0, 0, $x - 1, $y - 1, $white);
imagettftext($img, $textSize, 0, $padding + min($tlx, $blx), $padding + min($tly, $bly), $purple, $font, $text);
// starting Y position of the under-line
$uY = $padding + min($tly, $bly);
// underline text...
foreach($lineLengths as $length){
imagefilledrectangle($img, $padding + min($tlx, $blx), $uY + $uOffs, $padding + $length, $uY + $uOffs + $uHeight, $purple);
$uY += 19;
}
header('Content-Type: image/png');
imagepng($img);
imagedestroy($img);
}
Result:
This is a little more flexible that using Unicode chars because you have control over the line height, and position relative to the text above it.