On Mon, 16 Oct 2006 12:17:50 +0200, Dave Long wrote: > > It would be cool to print out a black-and-white image on, say, a laser > > printer, which contained an unobtrusive embedded "watermark" or > > "barcode" that contained chroma information for the image --- rather > > like what the Apple II did to get NTSC color just by producing a > > pattern of 1's and 0's. > > Come to think of it, the Apple II scheme turns a well known broadcast > bug (there are dress codes for on-air appearances, as houndstooth and > similar high-frequency fabrics alias into color) into a feature. I > wonder how much the use of gradients in web graphics is due to > recent-featurism, and how much is in imitation of broadcast graphics, > which have to have smooth gradients -- they'd bleed if one tried to > make a crisp transition.
That's an interesting question. My preferred hypothesis is that it's the age of calm technology --- one of the disadvantages of the Apple ][ scheme was that it could only produce bright, garish colors with sharp boundaries between them, and gradients are much more soothing. > > Then you could point, say, a cellphone camera at the image, and push a > > button, and see the image in color. > > Unfortunately (fortunately?) the information between a cellphone camera > and a printout isn't mediated by NTSC, but by regular photons, so it > seems unlikely this would work. I didn't mean it would work by accident --- I meant that software in the cellphone could decode a chroma signal from a barcode "hidden" in the image, for example in the angle and spacing of patterns of parallel lines used to approximate a grayscale as in an engraving. Venezuelan paper money has areas that appear from a distance to be one solid color, but consist of many areas of fine parallel lines at different angles. Presumably the idea is that each area would appear a different brightness by raster aliasing if scanned with a poor-quality scanner, or printed with a poor-quality printer. But the same scheme could be applied to encode more interesting information subliminally into the print; perhaps the frequency of the lines could represent saturation, and their angle could represent hue.
