Emboss

Usually, given a grayscale image (e.g. black text on a white background), doing an emboss will create an image which makes it look like the original image was indeed embossed, rather than just being a "flat" surface. It does this by faking the way light would be reflected off the surface if it was really embossed. Effectively, it is hacked 2D bump mapping.

Implementing an emboss is trivial. The algorithm is:

1. Take a grayscale image A.
2. Make a copy called B.
3. Offset the image B by one pixel in both the vertical and the horizontal. (Note: By using different offsets -- even non-integer offsets -- you can make it look like the "light" is coming from a different direction).
4. Subtract B from A.
5. Adjust the range so you don't get negative colors.

Things can get a little bit tricky in practice, because frequently images are stored as unsigned values, and the above can lead to negative values. This isn't too tricky to solve, basically you can get around it by using scale and bias adjustments.

Em*boss" (?; 115), v. t. [imp. & p. p. Embossed (?; 115); p. pr. & vb. n. Embossing.] [Pref. em- (L. in) + boss: cf. OF. embosser to swell in bunches.]

1.

To arise the surface of into bosses or protuberances; particularly, to ornament with raised work.

Botches and blains must all his flesh emboss. Milton.

2.

To raise in relief from a surface, as an ornament, a head on a coin, or the like.

Then o'er the lofty gate his art embossed Androgeo's death. Dryden.

Exhibiting flowers in their natural color embossed upon a purple ground. Sir W. Scott.

© Webster 1913.

Em*boss", v. t. [Etymology uncertain.]

To make to foam at the mouth, like a hunted animal.

© Webster 1913.

Em*boss", v. t. [Cf. Pr. & Sp. emboscar, It. imboscare, F. embusquer, and E. imbosk.]

1.

To hide or conceal in a thicket; to imbosk; to inclose, shelter, or shroud in a wood.

In the Arabian woods embossed. Milton.

2.

To surround; to ensheath; to immerse; to beset.

A knight her met in mighty arms embossed. Spenser.

© Webster 1913.

Em*boss", v. i.

To seek the bushy forest; to hide in the woods.

S. Butler.

© Webster 1913.