This is using the negative kerning but keeping the original captcha algorithm otherwise. Except we also prevent some letters like i and l for appearing next to each other
Note, this uses the DejaVuSans font, instead of the FreeMonoBoldOblique.ttf that Wikipedia currently uses
View other captcha tests: Current captcha | Tim's proposal | Tim's captcha without gradiant | Current captcha with OCR rejection | Using negative kerning and less harriness [Bawolff's proposal] | Negative kerning and harriness
Tesseract (off the shelf. No special training) success on this set is 7 (out of 200) or 3.5 %
