Hi guys, How to create random image that have some text on it radomly. so that automatic form submission can be prevented. Generally it is in registration form. like in digitalpoint forum registration http://forums.digitalpoint.com/register.php - > Image Verification How to make these kind of image using programming?
You are talking about captcha images. There are several libraries, in various programming languages, available around internet. Basically, they generate a random string of text made up of letters and.or numbers and print this on top of a picture. When the user enters what they saw, it is compared to the string used by the machine. If it is the same, the user proceeds. If it is different, the user is shown a new image with a new random string. To make it harder for machines to guess the string, the text is often skewed in some direction and the baseline for the text shifted up and down. Further confusion is added by applying a random texture to the image. More confusion by imbedding nearly invisible letters in the image. The idea is that a program capable of finding text in the image, will also find the hidden text that a human would not see. I hope this helps point you in the right direction.
if you are using Joomla, you can get a component that easily adds this functionality to your site here: http://extensions.joomla.org/component/option,com_mtree/task,viewlink/link_id,116/Itemid,35/