PHP's imagettftext creates black edges on transparent background

G

2

5

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):

black edges

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);
...

Galling answered 1/10, 2012 at 12:5 Comment(0)

G

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 .

Goodloe answered 1/10, 2012 at 12:13 Comment(5)

yes i think that the antialiasing is the problem... is ther a way to fix that? I want the black color to be transparent. and as i said in the image is a transparent bg with white text on it so the image should be completely white. – Galling 1/10, 2012 at 12:18

You could try to first fill the image with the transparent color. Also when you create the output image, ensure it has got an 8-bit alpha-channel. – Goodloe 1/10, 2012 at 12:21

How to output with 8-bit alpha? – Galling 1/10, 2012 at 12:25

You seem weak in search, this was asked already back in 2009: PHP gdLib 8-Bit PNG with alpha - also take a look at the difference between transparency and alpha. You might want to try with an alphacolor, not a transparent one. You see? – Goodloe 1/10, 2012 at 12:26

Accepted for the antialiasing solution in the link you gave. – Galling 1/10, 2012 at 12:38

C

6

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);

Canvass answered 1/10, 2012 at 12:26 Comment(0)

G

2