Draw text with GD with transparent background

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