I use Tank Auth a lot for my CodeIgniter development work. It’s nice & flexible and since I’ve used it a number of times, I’m much more familiar with it now than before. One of the nice features of this tool is that it comes with the CAPTCHA feature. However, the default settings for Tank Auth captcha sometimes renders the image in such a way that is hard to read for users. So it is always good if you can modify it (e.g. change the colours, option of using numbers, small or capital letters).

Such modification can be made in captcha_helper.php file. Look for this file and then go all the way down to around line 111 and 150. In line 111, I changed it to following

$pool = ‘ABCDEFGHIJKLMNOPQRSTUVWXYZ’;

Because sometimes numbers and letters are hard to differentiate. On line 150, I changed the colours involved in CAPTCHA image.

$bg_color        = imagecolorallocate ($im, 240, 240, 240);
$border_color    = imagecolorallocate ($im, 210, 210, 213);
$text_color        = imagecolorallocate ($im, 134, 156, 178);
$grid_color        = imagecolorallocate($im, 179, 207, 235);
$shadow_color    = imagecolorallocate($im, 255, 240, 240);

Now the letters in the images are clearer and easier to recognize for users.