Bitmap vs.
Vector-Based Graphics
Bitmap images
Bitmap images, also referred to as raster
images, are pixel-based. This means that
location and color information about the image
is stored in individual pixels within a grid.
Arrow Image, Actual Size
Magnified Arrow Image with Pixel Grid
As the figure illustrates, each pixel has an assigned
color; some pixels are white, while other pixels are blue.
The information stored in a bitmap image regarding
pixel location and color is what forms the image. Bitmap
images are edited at the pixel level; in other words, the
color of any one pixel can be changed. Additional
attributes of bitmap images include:
Additional attributes of bitmap images
• Bitmap images are usually created and edited in
"photo" or "paint" programs such as Adobe
Photoshop.
• Bitmap images are mapped to a grid.
• The size of the image is based on the image's
resolution.
• Bitmap images are not easily scalable.
• Bitmap images are used for photorealistic
images and, therefore, may involve complex
color variations.
Vector images
Vector images are mathematically-based. All lines,
shapes, etc. (also called objects) of a vector-based
image are independent of one another
one leaf of the same rose magnified, along with the paths and
handles used within vector images
Additional attributes of vector-based images
• Vector-based images are usually created and
edited in "draw" or "illustrate" programs such as
Adobe Illustrator.
• Vector-based images have smooth edges.
• Vector-based images create curves or shapes.
• Vector-based images are good for precise
illustrations, but are not as good for
photorealistic images.
• Vector-based images are easily scalable, due to
their use of mathematic formulas.
Bit Depth
Bit depth refers to the number of
colors that can be displayed.
The higher the bit depth, the more
colors used in the image, therefore, the
larger the file size.
Bit Depth Formula Number of Colors
1-bit 21 2
2-bit 22 4
3-bit 23 8
4-bit 24 16
5-bit 25 32
6-bit 26 64
7-bit 27 128
8-bit 28 256
24-bit 224 16,777,216
Bit Depth Number of Colors File Size Bit Depth Number of Colors File Size
1-bit 2 colors 2 KB 4-bit 16 colors 21 KB
Bit Depth Number of Colors File Size Bit Depth Number of Colors File Size
8-bit 256 colors 53 KB 24-bit 16.7 million colors 224 KB
Resolution
Resolution is the number of pixels in a linear inch
(i.e. pixels per inch or ppi).
More pixels means higher resolution, which creates
better image quality because you end up with more
realistic representations of color, better gradations
of both individual colors and gray tones, and crisper
images in general.
Graphic File Formats
File formats help to identify what kind of file is being
worked with and are usually distinguished by the file
extension.
Most computer applications have a native file format
i.e., a default format for files created in that program.
Adobe InDesign saves files with an .indd extension
Adobe Illustrator saves files with an .ai extension
In addition, many applications allow the user to save files
in formats other than the application's native format.
It is a good idea to save files in the native format & non-
native format.
