I wrote a simple function that calculates the *exact* bounding box (single pixel precision).

The function returns an associative array with these keys:

left, top:  coordinates you will pass to imagettftext 

width, height: dimension of the image you have to create



 black => empty)

  $rleft  = $w4 = $width<<2;

  $rright = 0;

  $rbottom   = 0;

  $rtop = $h4 = $height<<2;

  for( $x = 0; $x < $w4; $x++ )

    for( $y = 0; $y < $h4; $y++ )

      if( imagecolorat( $img, $x, $y ) ){

        $rleft   = min( $rleft, $x );

        $rright  = max( $rright, $x );

        $rtop    = min( $rtop, $y );

        $rbottom = max( $rbottom, $y );

      }

  // destroy img and serve the result

  imagedestroy( $img );

  return array( "left"   => $left - $rleft,

                "top"    => $top  - $rtop,

                "width"  => $rright - $rleft + 1,

                "height" => $rbottom - $rtop + 1 );

}

?>