Draw text with GD with transparent background - php

Question

I have this code to write some text on a new created image:
class ImageCreator
{
public function Draw($string)
{
$font = "lg.ttf";
$txtsize = imagettfbbox(20, 0, $font, $string);
$image = imagecreatetruecolor($txtsize[2], $txtsize[4]);
imagealphablending($image, false);
$c = imagecolorallocatealpha($image,0,0,0,127);
imagefilledrectangle($image,0,0,$txtsize[2],$txtsize[4], $c);
imagealphablending($image, true);
$c = ImageCreator::hexcol2dec("#FFFFFF");
$white = imagecolorallocate($image, $c[0], $c[1], $c[2]);
$c = ImageCreator::hexcol2dec("#000000");
$black = imagecolorallocate($image, $c[0], $c[1], $c[2]);
$c = ImageCreator::hexcol2dec("#044D8F");
$tcolor = imagecolorallocate($image, $c[0], $c[1], $c[2]);
imagettftext($image, 20, 0, 0, 0, $black, $font, $string);
imagettftext($image, 20, 0, 1, 0, $tcolor, $font, $string);
imagettftext($image, 20, 0, 2, 0, $white, $font, $string);
imagealphablending($image,false);
imagesavealpha($image,true);
ob_start();
imagepng($image);
$imgData = ob_get_contents();
ob_end_clean();
return $imgData;
}
public function hexcol2dec($hexColor)
{
$R=0;
$G=0;
$B=0;
for($i = 0; $i < strlen($hexColor);$i++)
{
if($hexColor[$i] == "#")
{
}
else if($hexColor[$i] == 'A' || $hexColor[$i] == 'a')
{
$dec[$i] = 10;
}
else if($hexColor[$i] == 'B' || $hexColor[$i] == 'b')
{
$dec[$i] = 11;
}
else if($hexColor[$i] == 'C' || $hexColor[$i] == 'c')
{
$dec[$i] = 12;
}
else if($hexColor[$i] == 'D' || $hexColor[$i] == 'd')
{
$dec[$i] = 13;
}
else if($hexColor[$i] == 'E' || $hexColor[$i] == 'e')
{
$dec[$i] = 14;
}
else if($hexColor[$i] == 'F' || $hexColor[$i] == 'f')
{
$dec[$i] = 15;
}
else
{
$dec[$i] = $hexColor[$i];
}
}
if($hexColor[0] == "#")
{
$R = 16*$dec[1]+$dec[2];
$G = 16*$dec[3]+$dec[4];
$B = 16*$dec[5]+$dec[6];
}
else
{
$R = 16*$dec[0]+$dec[1];
$G = 16*$dec[2]+$dec[3];
$B = 16*$dec[4]+$dec[5];
}
return array ($R, $G, $B);
}
}
and i get just the transparent background none of the text is showed. I am new at PHP GD and i can't figure out why isn't writing the text. Please help me figure out
Thanks.

Answer 1

The coordinates returned by imagettfbbox are relative to the basepoint, and as such, can be negative.
So when the angle is 0, the upper Y and left X are negative, and you need to subtract them from the lower Y and right X to get the box size.
$width = $txtsize[2] - $txtsize[0];
$height = $txtsize[1] - $txtsize[5];
$image = imagecreatetruecolor($width, $height);
And then you have then to use the absolute values of the negative coordinates as the basepoint coordinate for drawing the text:
imagettftext($image, 20, 0, -$txtsize[0], -$txtsize[5], $black, $font, $string);

Answer 2

Do you have warnings enabled? There could be an issue with PHP locating the font file, since I noticed it is not a complete path.
Does your server have the FreeType library installed? Use phpinfo() to verify. http://www.freetype.org/
You can use this sandbox to test if your coordinates are right: http://ruquay.com/sandbox/imagettf/.
Remember, the basepoint is the x, y coordsinates you use to draw text with imagettftext. A useful thing to do is take a string like...
ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789
and use the "aboveBasepoint" value for the height of your font. Now you can draw lines and use "the height of your font * leading" as the distance between lines of text, where leading is a number such as 1.45 (for 45% leading).
Look in the comments at the bottom of the PHP Manual entry for this function for many useful functions: http://php.net/manual/en/function.imagettfbbox.php