On our D6 installation we have CAPTCHA 6.x-2.4 plus Captcha Riddler 6.x-1.1 and Image CAPTCH 6.X-2.4 (all from the same package I believe). All three are installed and enabled.
Although we have used this module before with success on other sites, it is not working on this site which is a subdomain on our staging server.
The configuration page (/admin/user/captcha/image_captcha) does not show the CAPTCHA in the preview example. Further the font previews are not shown in that section. The font files are there and should be readable by inspecting the permissions of the individual files and the directories which contain them. (I wonder if the standard D6 .htaccess protection causes a problem here). However, instead of a preview of the font, the text path to the font's .ttf file is shown.
Looking at other tickets related to this, I saw the suggestion that one display the output of settings for the GD library. I have done this and it looks OK:
'GD Version' => 'bundled (2.0.34 compatible)',
'FreeType Support' => true,
'FreeType Linkage' => 'with freetype',
'T1Lib Support' => false,
'GIF Read Support' => true,
'GIF Create Support' => true,
'JPG Support' => true,
'PNG Support' => true,
'WBMP Support' => true,
'XPM Support' => false,
'XBM Support' => true,
'JIS-mapped Japanese Font Support' => false,
It certainly is not missing any of the features which seem to be required for this function.
Looking at another ticket I saw reference to a user with uid=0. We have such a user but the name and mail fields are empty. Is this an issue?
Switching the contact form's CAPTCHA to math seems to work.
When I try to view the sample image from the admin page, Firefox gives me this message:
The image “.../image_captcha/5414/1310082595” cannot be displayed because it contains errors.
I saved the image and attached it to this ticket in case it helps any.
As near as I can tell, the module (and PHP) can't see the fonts so the CAPTCHA images are not being created. I would appreciate any suggestions of how to resolve this.