Gamma Steganography

I remember this trick was used years ago on 4Chan /b/

It was known how a thumbnail looked when it was generated by 4chan, so knowing that could be used to generate the appropriate compressed image with a 'bait' thumbnail.

It was common to show sexy females in the thumbnail image, and then when opened, you'd be greeted by goatse (guy naked, with his hands pulling apart his buttocks).

Nobody knew what it was called, but someone created an informal script, attached it to a zip file, and appended the zip to the end of an image. Then said image was uploaded to 4chan /b/.. And the jokes commenced.

I still have a few of them, but they're at home and I'm at work. And lets say they're nsfw/nsfl.

The trick does not work on Safari, but you can click and drag the first image and the drag preview will reveal what other browsers show.

this is a really cool trick. I don't think steganography is the right term though, when the 'hidden' image is viewable in most browsers

Stenography is a recording something in real-time, e.g., taking minutes, court-reporting, taking dictation, etc.

Steganography is entirely different, referring to the hiding of information inside other information.

Please correct the title. s/Stenography/Steganography/