[ers35]

> If the string is readable over only some background colors, then it's written on a transparent-backed image, so the whole background-changing script can be ignored. Just OCR the image with the transparent background.

The CAPTCHA image contains false values for misdirection, hence the requirement of running the background changing script.

Here is a list of claims made on the example CAPTCHA page:

  BG                     Ability
  color                  to
  generation             solve (as defined by the author)
  ----------             ---------
  mouse cursor hovering  difficult
  previous state         impossible
  input
  shared secret  

I have no way to know precisely what the author means by those words since the given example does not demonstrate any of them. I cannot match the left and right columns.

For example, if I claimed that a CAPTCHA based off a "shared secret" only a trusted user has is impossible to solve, then one might ask the question, "Why is a CAPTCHA needed for a trusted user?". Is this what the author of the CAPTCHA example meant? I do not know.

My only purpose of posting in this thread was to show that the OP's premise that "this is the best example of how not to implement it." is flawed because no such example was given in the first place.