Steganography is the art of concealing one image inside another. I discussed the basics of the technique in a post: Hiding one surface inside another. It involves bit-shifting. In an 8-bit image each pixel is represented by an integer in RGB (red, green and blue). With 256 shades of RGB that provides over 16 million…More
Tag Archives: steganography
ASCII stereograms 101
In the 1990s, text email (without pictures) was the main channel for person-to-person communication. Mimicking early text printer graphics, arrays of evenly spaced characters could serve as simple pixels inside an email. Imaginative emailers followed this method to adorn their messages with emojis and ASCII pictures. Amongst such text-based imagery you can find ASCII stereograms,…More
What ever happened to autostereograms?
I recall the craze in the 1990s for Magic Eye posters and books. People would gaze and squint at these multicoloured, seemingly random, patterns to discern 3d images of dolphins, elephants, temples, and spaceships. The method of display was a variation on what I experienced as a child, as I gazed at my bedroom wallpaper…More
Crypto-conspiracy
CryptoArt is a term applied to artworks that are bought, sold and authenticated on a blockchain. In this sense, CryptoArt is no more a genre, sub-genre, style or movement in art than auction art, gallery art or collectible art. “Art” is not a protected or regulated noun and invites appendage to many other nouns. A…More
Visualising 2D Discrete Cosine Transforms
I’m interested in the Discrete Cosine Transform (DCT) method as a means of hiding one image inside another. It’s also a key technique in image compression. I’ve implemented the DCT method on an Excel spreadsheet. The image below is an 8×8 grid of pixel values, in grey ranging from 0 = black to 255 =…More
Beyond averages: DCT graphics
The visual field is full of smooth curves. Shadows don’t have sharp edges but fade out. Colours blend, sometimes imperceptibly. At some level of detail, most things transition smoothly, but to varying degrees. The variation across such transitions is noticeable in a high quality digital photograph, i.e. a pixel image. Here is a random row…More
The culture of the GIF
GIF image files have 8 bit colour for red (R), green (G) and blue (B), i.e. 256 shades each for RGB. Most smartphone cameras currently provide 10 bit colour. So if you convert your photographs to GIF format they will be of lower quality. Apart from that the GIF format provides lossless compression. So GIF…More
Hiding one surface inside another
What’s it like to get inside a surface? I’ve been reading Avron Stroll’s seminal philosophy book Surfaces. He exhausts most of the ways people use the word “surface” in everyday speech. E.g. you can be on a surface or under it, but it’s not usual to speak of a surface inside a surface. And some…More
Ornament and crime
The Austrian architect Adolf Loos (1870-1933) wrote Ornament and Crime. It is a celebrated polemic against the superfluity of ornament in the modern industrial age: “not only is ornament produced by criminals but also a crime is committed through the fact that ornament inflicts serious injury on people’s health, on the national budget and hence…More
Steganography for architects
Steganography is hiding one picture (a secret or data) inside another (a host or carrier) image. As with cryptography in general, there are several reasons someone might want to hide content in this way. The hidden image could serve as a digital watermark. That’s to assert your claim on a picture. If someone copies it…More