Graphics Gems III (IBM Version)

1.7

COMPOSITING BLACK-AND-WHITE BITMAPS

David Salesin,     Cornell University, Ithaca, New York and

Ronen Barzel,     California Institute of Technology, Pasadena, California

Publisher Summary

A typical bitmap encodes pixels that are black and white. Adding an auxiliary bitmap allows to represent pixels that are transparent. The two-bit representation is useful for black-and-white images that are non-rectangular or that have holes. It also leads to a richer set of operations for combining bitmaps. This chapter discusses the three possible pixel values by the Boolean pair (α, β) and explains the effects of the operations on two sample bitmaps—P and Q. The Boolean operations can be executed for an entire bitmap at once, using a sequence of ...