Image ?¬?les can be either
bitmaps, which are generally best for computer viewing, or vector graphics, which are
better suited to printing or print-like formats such as PDF.
For bitmap ?¬?les of models, compression artifacts make JPEG a nonstarter. While
the 256 color palette in GIF ?¬?les is not a problem in most modeling languages, it
becomes a limitation if the symbols contain photographic bitmaps or fountain ?¬?lls.
Perhaps the best format is Portable Network Graphics (PNG), since it offers small ?¬?le
size, lossless compression, and a 24-bit color palette. Until recently PNG support in
other software such as browsers was weak, but now almost all support the PNG
features needed for models.
Up until a few years ago, there was no satisfactory, platform-independent
format for vector graphics. PostScript ?¬?les, and for stand-alone images Encapsulated
PostScript, was one possibility, but application support was poor. Most applications
could not show the vector content of an EPS ?¬?le, which would only appear
when interpreted by a PostScript printer, but instead only displayed the bitmap
thumbnail (if the generator had included one).Windows Meta?¬?les, bothWMFand the
enhanced EMF, were only supported on Windows. The ancient Macintosh Paint
program??™s format, PICT, became rather surprisingly one of the better choices.
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