Microsoft Office Tutorials and References
In Depth Information
Chapter 3: Handling Graphics, Photos, and Clip Art
Figure 3-1:
A
highresolution
photo (left)
and the
same photo
at low
resolution
(right).
Compression
Compression refers to a mathematical algorithm by which bitmap graphic
files can be made smaller. In effect, compression enables your computer
to store a bitmap graphic with less disk space. Some bitmap graphic types
can’t be compressed; other bitmap graphic types are compressed using
either lossless or lossy compression:
Lossless compression: To maintain the picture’s integrity, the same
number of pixels are stored in the compressed file as in the original.
Because the pixels remain intact, you can change the size of a file that
has undergone lossless compression without losing picture quality.
Lossy compression: Without regard for the picture’s integrity, pixel data
in the original picture is lost during compression. Therefore, if you try
to enlarge a picture that has undergone lossy compression, the picture
loses quality.
Color depth
Color depth refers to the number of colors that can be displayed in a
graphics file. The larger the color depth, the larger the number of colors that can
be displayed, the richer the graphic looks, and the larger its file size is. Color
depth is measured in bits. To get technical on you, color depth is measured
in the number of bits that are needed to describe each pixel’s color in the
image. A bit, or “binary digit,” is the smallest unit of data measurement in
computing. These are the color-depth measurements:
 
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