ARCHIVED: What are bitmap and vector graphics, and how are they different?
A bitmap (also called "raster") graphic is created from rows of different colored pixels that together form an image. In their simplest form, bitmaps have only two colors, with each pixel being either black or white. With increasing complexity, an image can include more colors; photograph-quality images may have millions. Examples of bitmap graphic formats include GIF, JPEG, PNG, TIFF, XBM, BMP, and PCX as well as bitmap (i.e., screen) fonts. The image displayed on a computer monitor is also a bitmap, as are the outputs of printers, scanners, and similar devices. They are created using paint programs like Adobe Photoshop.
Vector (also known as "object-oriented") graphics are constructed using 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 bitmap image contains information about the color of each pixel, a vector graphic contains instructions about where to place each of the components. It is even possible to embed a bitmap graphic within a vector graphic, which is how vector-bitmap hybrid graphics work. It is not possible, however, to embed vector information within a bitmap. Examples of vector graphic formats are PICT, EPS, and WMF as well as PostScript and TrueType fonts. These are created with GIS and CAD applications as well as drawing programs like FreeHand.
SVG, or Scalable Vector Graphics, is a language for describing vector graphics in XML. With SVG, you can code graphics directly into 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 their strengths and weaknesses:
- In general, a bitmap graphic is much larger than a similar vector
graphic.
- Bitmap graphics are affected by resolution. If you enlarge a
bitmap graphic, it will look jagged. When shrunk, its features become
indistinct and fuzzy. This does not happen with vector graphics as
their shapes are redrawn to compensate for changes in resolution.
- Altering vector graphics is easy because the shapes within them
can be ungrouped and edited individually. However, vector graphics
are difficult to modify or even display when they are not opened in
programs that understand their rendering languages. For example,
while many Mac OS drawing programs easily display and edit PICT
files, few are able to do anything at all with WMF files. Most paint
applications, however, are capable of opening many different kinds of
bitmap 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 a
bitmap graphic into a true vector graphic. It is even difficult to
convert one kind of vector graphic into another (e.g., PICT to WMF).
- Vector graphics are not appropriate for complex images (e.g., digitized photographs).
Last modified on November 01, 2008.
