Legacy ImageMagick Discussions Archive

How does one retrieve the Stegano from an image that has been given this treatment?

I input a small image, then output to the clipboard. Its dimensions are 130x122.

Then I created a black image, dimensions 300x300, and went to F/X.

The parameter I entered was 130x122 +300+300.

Since I got no error message when clicking on "effect," I assume that the smaller image had been embedded inside the black square.

So I output this final image to my file manager. Then I took this image back to (Arbor) iMagic. After input, I had to output again to the clipboard to avoid getting the stop sign. But when I input again and went to F/X, entered the stegano coords, all I got was my black image again.

Stegano can be used to prove ownership of an image. So how does one do this - retrieve the hidden image? The url of the black image is below.

http://tutes.tonebytone.com/black.jpg

TIA, Flo

Have you read http://www.imagemagick.org/Usage/transform/#stegano?

Thanks for responding. However, I use the interfaces, not the scripts - so, yes, I did try to read that, but it makes no sense to me. I can't figure out how to transfer the data from the scripts to the interfaces.

Flo

First of all you can NOT use JPG.

Stegno stored th image in the lower, least significant bits of an image. If those bits are lost you lose the hidden image. JPG compresses the image by modifying colors, that is ignoring the lower bits to get better compression. You can NOT use JPEG images!

If you read the notes in the link about you should have read that!

Thank you, Anthony. The "do not use jpegs" instruction is way down at the end of the instructions - and by that time I'd given up trying to understand the script.

However, I'm now forced to assume that there's really no such thing as a "lossless jpeg" - even though Image Magick now includes that output option? I've been outputting all my jpegs as lossless.

OK, I'll go back and try with a .png that hasn't been output as a grayscale.

lossless jpg only happens if you set -quality 100 and use J2K (JPEG2000) format. Or at least those are the conditions I know of.

Note you do also need the JASPER (JPEG2000) libraries! And such images are not very small. Sort of equivalent to PNG, so you may as well use that for lossless behavior.

I have added some warnings about it, at the top of BOTH Stegno and Encrypt.