Underline text using imagettftext

Question

My question is, how do I underline all the text in the image?

Code:

function createImage($text)
{
    $text .= "\n";
    $text = wordwrap($text, 40, "\n");
    $newlines = substr_count($text, "\n");
    if($newlines == 0)
    {
        $height = 30;
    }
    else
    {
        $height = 30*$newlines-$newlines*7;
    }
    putenv('GDFONTPATH=' . realpath('.'));
    header('Content-Type: image/png');

    $im = imagecreatetruecolor(315, $height);
    $white = imagecolorallocate($im, 255, 255, 255);
    $grey = imagecolorallocate($im, 128, 128, 128);
    $black = imagecolorallocate($im, 0, 0, 0);
    $purple = imagecolorallocate($im, 97, 26, 139);
    imagefilledrectangle($im, 0, 0, 399, $height, $white);
    $font = 'arialbd.ttf';

    imagettftext($im, 11, 0, 10, 20, $purple, $font, $text);
    imagepng($im);
    imagedestroy($im);
}

createImage("Stackoverflow Stackoverflow Stackoverflow Stackoverflow Stackoverflow Stackoverflow Stackoverflow Stackoverflow Stackoverflow Stackoverflow Stackoverflow Stackoverflow ");

RESULT http://i.imgur.com/Jdr7HPy.png

I want all the text to be underlined, I've found some solutions but they're only from left to right, not depending on words.

Answer 1

Use the Unicode underline combining character U+0332.

You will need a loop to or clever array merge to modify the text,

$e = explode(' ', $text);

for($i=0;$i<count($e);$i++) {
  $e[$i] = implode('&#x0332;', str_split($e[$i]));
}

$text = implode(' ', $e);

Answer 2

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.