[Mousewaffle]

Reproduction of black-and-white illustrations in an ebook apparently baffles even the biggest and best mainstream publishers. Since I date back to the Ancient Times of hot-metal type, letterpress printing and halftone zinc illustrations, let me offer the following:

In the days of letterpress (from which most of our scans are derived), printing was (surprise! surprise!) binary. It was black ink on white paper... black or not-black... 1 or 0. Shades of gray were derived by a trompe l'oeil or persistence-of-vision effect. In wood or steel engravings, it came from the hand of the engraver varying the width of a line. In photographs, it came from halftone dots created by projecting the image onto a chemically sensitized metal plate through a screen which focused the image into dots. Big dots were blacker; small dots were whiter (grayer). The finer the mesh of the screen, the higher the resolution.

To reproduce that pure black-white in a scan, you'd have to scan at the same scale as the original — translation: huge file, huge image. Anything less, and the scanning algorithm will throw away anything it doesn't read as pure black or pure white — translation: jagged lines, pixilated image. Scanning in grayscale lets the scanning algorithms do what your eye does on a printed engraving or halftone: assign shades of gray. So far so good.

A problem arises from the fact that "white" paper in old books that scans come from is almost never "white" anymore. It has aged to shades of yellow, ranging from pale to deep tan — which the grayscale scanner reads as a shade of gray. The original black-on-white illustration scans as a low-contrast black-on-muddy gray (or muddy tan, if it's in colour). I don't know how many ebooks I've spent good money on arrive with illustrations that look like a closeup of mouldy bread.

Photoshop (or whatever) to the rescue! By fiddling with the "levels" menu, and sometimes even the "lighten shadows" menu, you can lighten the lights, darken the darks and increase or decrease the contrast of the midrange. (Oddly, I find the "brightness/contrast" menu is fairly ineffective.) The closer you get to a high-contrast image without losing too much detail, the better it will look in a e-reader.

Some archives try to control file size by scanning in bit-map, black-and-white, which gives you really crisp type but illustrations that look like shadow-puppets made wearing boxing gloves. There's really no way to recover from that except to find a colour or grayscale scan, save or screen-capture the illustrations and fiddle with them.

Hope at least some of that has been useful.