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Pros and Cons of Bitmap File Formats

Bitmap files are especially suited for the storage of real-world images; complex images can be rasterized in conjunction with video, scanning, and photographic equipment and stored in a bitmap format.

Advantages of bitmap files include the following:

Bitmap files may be easily created from existing pixel data stored in an array in memory.
Retrieving pixel data stored in a bitmap file may often be accomplished by using a set of coordinates that allows the data to be conceptualized as a grid.
Pixel values may be modified individually or as large groups by altering a palette if present.
Bitmap files may translate well to dot-format output devices such as CRTs and printers.

Bitmap files, however, do have drawbacks:

They can be very large, particularly if the image contains a large number of colors. Data compression can shrink the size of pixel data, but the data must be expanded before it can be used, and this can slow down the reading and rendering process considerably. Also, the more complex a bitmap image (large number of colors and minute detail), the less efficient the compression process will be.
They typically do not scale very well. Shrinking an image by decimation (throwing away pixels) can change the image in an unacceptable manner, as can expanding the image through pixel replication. Because of this, bitmap files must usually be printed at the resolution in which they were originally stored.

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This page is taken from the Encyclopedia of Graphics File Formats and is licensed by O'Reilly under the Creative Common/Attribution license.