|
|
Safeguarding your images
By Doug Stewart
Mark of success. A test in Think Research proved that IBM's digital watermarks
can survive various image manipulations and the printing process. The original
image (#1) was invisibly watermarked by a technique that used a unique
string of numbers to subtly modify the brightness of each pixel.  The image then
underwent common graphic-arts processes: it was cropped on three sides, mirrored
left to right, color corrected, contrast enhanced, and overlaid with multicolored
type before being reproduced through photo-offset printing. After printing, the
watermarking program restored the image to its original orientation (#2).
When the program examined the image, it recovered a watermark (#3a)
that was almost as clear as the watermark recovered from the unprocessed image
(#3b). For comparison, an unmarked image returns only a random pattern (#3c).
|
|
|
