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A bitmap (also called "raster") graphic is created from rows ofdifferent colored pixels that together form an image. In theirsimplest form, bitmaps have only two colors, with each pixel beingeither black or white. With increasing complexity, an image caninclude more colors; photograph-quality images may havemillions. Examples of bitmap graphic formats include GIF,JPEG, PNG, TIFF, XBM, BMP,and PCX as well as bitmap (i.e., screen) fonts. The image displayedon a computer monitor is also a bitmap, as are the outputs ofprinters, scanners, and similar devices. They are created using paintprograms like Adobe Photoshop.
Vector (also known as "object-oriented") graphics are constructedusing mathematical formulas describing shapes, colors, and placement.Rather than a grid of pixels, a vector graphic consists of shapes,curves, lines, and text which together make a picture. While a bitmapimage contains information about the color of each pixel, a vectorgraphic contains instructions about where to place each of thecomponents. It is even possible to embed a bitmap graphic within avector graphic, which is how vector-bitmap hybrid graphics work. Itis not possible, however, to embed vector information within a bitmap.Examples of vector graphic formats are PICT, EPS, and WMF as well asPostScript and TrueType fonts. These are created with GISand CAD applications as well as drawing programs like FreeHand.
SVG, or Scalable Vector Graphics, is a language for describing vectorgraphics in XML. With SVG, you can code graphics directlyinto an XML document. For more information about SVG, see:
http://www.wdvl.com/Authoring/Languages/XML/SVG/
As described below, bitmap and vector graphics both have theirstrengths and weaknesses:
- In general, a bitmap graphic is much larger than a similar vectorgraphic.
- Bitmap graphics are affected by resolution. If you enlarge abitmap graphic, it will look jagged. When shrunk, its features becomeindistinct and fuzzy. This does not happen with vector graphics astheir shapes are redrawn to compensate for changes in resolution.
- Altering vector graphics is easy because the shapes within themcan be ungrouped and edited individually. However, vector graphicsare difficult to modify or even display when they are not opened inprograms that understand their rendering languages. For example,while many Mac OS drawing programs easily display and edit PICTfiles, few are able to do anything at all with WMF files. Most paintapplications, however, are capable of opening many different kinds ofbitmap graphic formats.
- You can easily convert one kind of bitmap file into another.You can also convert a vector graphic into a bitmap.However, it is very difficult to convert abitmap graphic into a true vector graphic. It is even difficult toconvert one kind of vector graphic into another (e.g., PICT to WMF).
- Vector graphics are not appropriate for complex images (e.g.,digitized photographs).
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Last modified on 2023-09-22 16:58:56.
