Watermark font problem in codeigniter

[eluser]zombica[/eluser]
Hey Guys i am displaying the water mark image containing some text over it but it doesn't display any thing.

Here is my code

Code:

$config['image_library'] = 'GD2';
            $config['source_image'] = 'images/watermark.png';
            $config['wm_text'] = 'Negotiable';
            $config['wm_type'] = 'text';
            $config['wm_font_path'] = './system/fonts/texb.ttf';
            $config['wm_font_size'] = '35';
            $config['wm_font_color'] = '000000';
            $config['wm_vrt_alignment'] = 'bottom';
            $config['wm_hor_alignment'] = 'center';
            $config['wm_padding'] = '20';
        
            $this->image_lib->initialize($config);

If i display with this font it throws me following error:

A PHP Error was encountered
Severity: Warning
Message: imagettftext() [function.imagettftext]: Could not read font
Filename: libraries/Image_lib.php
Line Number: 1094

i have updated the font folder and applied some more fonts but in that case it displays nothing.

Whats the real issue behind this. i have found no solution regarding this on internet.

Regards,
Zombica.