PHP's imagettftext creates black edges on transparent background

Question

I have this code:

$im = imagecreatetruecolor(70, 25);

$white = imagecolorallocate($im, 255, 255, 255);
$grey = imagecolorallocate($im, 128, 128, 128);
$black = imagecolorallocate($im, 0, 0, 0);

imagecolortransparent($im, imagecolorallocate($im, 0,0,0));

$font = 'font.ttf';

imagettftext($im, 20, 0, 3, 22, $white, $font, $randomnr);

header("Expires: Wed, 1 Jan 1997 00:00:00 GMT");
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
header("Cache-Control: no-store, no-cache, must-revalidate");
header("Cache-Control: post-check=0, pre-check=0", false);
header("Pragma: no-cache");

header ("Content-type: image/png");
imagepng($im);
imagedestroy($im);

And like I said in the title it creates some black edges around the text. I also tried with the imagealphablending/imagesavealpha and i've had the same result(i used the white text on transparent background so that you can see what i am talking about):

UPDATE: the solution is:

$im = imagecreatetruecolor(70, 25);
$font = 'font.ttf';
//antialiasing:
$almostblack = imagecolorallocate($im,254,254,254); 
imagefill($im,0,0,$almostblack);
$black = imagecolorallocate($im,0,0,0); 
imagecolortransparent($im,$almostblack);

imagettftext($im, 20, 0, 3, 22, $white, $font, $randomnr);
...

Answer 1

Something like this should do the work:

$width = 70;
$height = 25;

$im = imagecreatetruecolor($width, $height);

$white = imagecolorallocate($im, 255, 255, 255);
$grey = imagecolorallocate($im, 128, 128, 128);
$black = imagecolorallocate($im, 221, 221, 221);

imageSaveAlpha($im, true);
imageAlphaBlending($im, false);

$transparent = imageColorAllocateAlpha($im, 0, 0, 0, 127);
imagefilledrectangle($im, 0, 0, $width-1, $height-1, $transparent);
imageAlphaBlending($im, true);

$font = 'font.ttf';
$randomnr = "1234";
imagettftext($im, 20, 0, 3, 22, $white, $font, $randomnr);

header("Expires: Wed, 1 Jan 1997 00:00:00 GMT");
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
header("Cache-Control: no-store, no-cache, must-revalidate");
header("Cache-Control: post-check=0, pre-check=0", false);
header("Pragma: no-cache");

header ("Content-type: image/png");
imagepng($im);
imagedestroy($im);

Answer 2

That is what you have specified here:

imagecolortransparent($im, imagecolorallocate($im, 0,0,0));

If you want to use some other color for transparent, choose some other color. Right now you're using black.

See imagecolortransparent^Docs.

Also take note of this user's note on that same page:

A transparent background with text doesn't seem to work very well because of the antialiasing .