Making text difficult for OCR?

[Sampo Syreeni]

On 9 Aug 2001, Dr. Evil wrote:

>I have a question for you c'punks.  If you wanted to generate some bitmaps
>of text which would be difficult or impossible to OCR, but not too
>difficult for humans to read, how would you do that?  Basically, I want to
>create GIFs of text which can't be OCRed in a reliable way. I've thought
>about some things: I can put in noise pixels, I can blur the text, I can
>rotate, shear, and otherwise distort it.

Some ideas: Start with a highly ornate script font. Anti-alias. Try a font
with lots of gaps and other topology breaking features. Pluck out a decent
perceptual model from one of the better image compressors and try doing
maximum modifications beneath a given perceptual error bound. Low contrast,
with information encoded in the hue channel.

(Dead trees: Use a colorless, fluorescent ink, or a combination of such inks
to throw off the scanner. Print your stuff on extremely heat and/or light
sensitive paper.)

Sampo Syreeni, aka decoy, mailto:decoy at iki.fi, gsm: +358-50-5756111
student/math+cs/helsinki university, http://www.iki.fi/~decoy/front