Page 229 - Green - Maritime Archaeology: A Technical Handbook. 2nd ed

208 Maritime Archaeology: A Technical Handbook, Second Edition
is a compressed format designed to minimize file size and electronic transfer time. BMP is a standard Windows image format on DOS and Windows-compatible computers. BMP format supports RGB, indexed color, grayscale, and bitmap color modes. Encapsulated PostScript (EPS) language file format can contain both vector and bitmap graphics and is supported by virtually all graphic, illustration, and page-layout programs. EPS format is used to transfer PostScript-language artwork between appli- cations. When you open an EPS file containing vector graphics, Photoshop rasterizes the image, converting the vector graphics to pixels. PICT format is widely used among Mac OS graphics and page-layout applications as an intermediary file format for transferring images between applications.
III. VECTOR GRAPHIC PACKAGES A. TWO-DIMENSIONAL PACKAGES
There are a number of two-dimensional packages, the best known are Adobe IllustratorTM, MacroMedia FreeHandTM, and AutoCADTM and its variants. These programs enable computer-aided drawing of a whole range of archaeological projects, from site plans to artifact drawings. There are great advantages to working electronically. The ability to work in a non-pen- and-ink environment is an obvious advantage, particularly as it is possible to produce hard copy at any scale, using A0 plotters through to A4 printers and e-mail these plans across the world in a blink of an eye. Because vector graphics are created by a series of equations which define lines, text, and fill, the files are small, for example, the plan shown in Figure 11.11b (below) is a scan with a file size is a 64 KB file whereas the relatively low resolution scan of the plan (Figure 11.11a) is 236 KB. In addition, scaling of a vector image has no effect on pixilation, because the lines are equations and can be infi- nitely scaleable. Figure 7.2 shows the effect of enlarging a letter created in raster and vector graphics. Often, vector graphic packages are used to trace over hand-drawn plans. For example, a drawing of a site plan can be scanned and imported into the vector graphics package in a background layer. This image can then be locked and the standard drawing tools used to trace around the drawing. Proper text and symbols can be inserted, and when the job is finished the underlying drawing can be deleted.
B. THREE-DIMENSIONAL PACKAGES
The three-dimensional package, Rhinoceros (Rhino), a NURBS three- dimensional modeling program, is typical of a range of similar packages that