This test consists in detecting captcha canvas and thus defining the applicability of the test.
Human check will be then needed to determine whether the alternative is pertinent.
For each bitmap image (canvas tag), used as a CAPTCHA or test image, with a text alternative, does this alternative describe the nature and purpose of the image?
<canvas> tags of the page not within a link with a not empty content (css selector : canvas:not(a canvas):not(:matchesOwn(^\s*$)))
All the elements of Set1 identified as a CAPTCHA (see Notes for details about CAPTCHA characterisation).
For each element of Set2, raise a MessageA
MessageA : Check captcha alternative
- code : CheckCaptchaAlternative
- status: Pre-Qualified
- parameter : text tag name, snippet
- present in source : yes
The page has no
<canvas> tag with a not empty content identified as a captcha (Set2 is empty)
In all other cases
An element is identified as a CAPTCHA when the “captcha” occurrence is found :
- on one attribute of the element
- or within the text of the element
- or on one attribute of one parent of the element
- or within the text of one parent of the element
- or on one attribute of a sibling of the element
- or within the text of a sibling of the element