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Digital Image Fundamentals
1
Outline
briefly summarizes the mechanics of the human visual system
discussy) is digital image f(x,y), and f is a function that assigns a gray-level to each distinct pair of coordinates (x,y). This functional assignment obviously is the quantization process.
If the gray levels also are integers, then a digital image becomes a 2-D function whose coordinates and amplitude values are integers.
15
Representing Digital Images
due to processing, storage, and sampling hardware considerations, the number of gray levels typically is an integer power of 2：
Sometimes the range of values spanned by the gray scale is called the dynamic range of an image.
16
Representing Digital Images
The number b, of bits required to store a digitized image is
b=M×N×k. ()
When M=N, this equation becomes:
()
17
Spatial and Gray-Level Resolution
Sampling is the principal factor determining the spatial resolution of an image．Basically, spatial resolution is the smallest discernible detail in an image.
Gray-level resolution similarly refers to the smallest discernible changes in gray level. The most common number is 8 bits.
It is common to refer to an L-level digital image of size M*N as having a spatial resolution of M*N pixels and a gray-level resolution of L levels.
18
Spatial and Gray-Level Resolution
19
Spatial and Gray-Level Resolution
20
Spatial and Gray-Level Resolution
21
Spatial and Gray-Level Resolution
22
Zooming and Shrinking Digital Images
Zooming may be viewed as oversampling, while shrinking may be viewed as undersampling.
Zooming requires two steps：the creation of new pixel locations，and the assignment of gray levels to those new locations.
Image shrinking is done in a similar manner as just described for zooming．The equivalent process of pixel replication is row-column deletion.
23
2
1
Outline
briefly summarizes the mechanics of the human visual system
discussy) is digital image f(x,y), and f is a function that assigns a gray-level to each distinct pair of coordinates (x,y). This functional assignment obviously is the quantization process.
If the gray levels also are integers, then a digital image becomes a 2-D function whose coordinates and amplitude values are integers.
15
Representing Digital Images
due to processing, storage, and sampling hardware considerations, the number of gray levels typically is an integer power of 2：
Sometimes the range of values spanned by the gray scale is called the dynamic range of an image.
16
Representing Digital Images
The number b, of bits required to store a digitized image is
b=M×N×k. ()
When M=N, this equation becomes:
()
17
Spatial and Gray-Level Resolution
Sampling is the principal factor determining the spatial resolution of an image．Basically, spatial resolution is the smallest discernible detail in an image.
Gray-level resolution similarly refers to the smallest discernible changes in gray level. The most common number is 8 bits.
It is common to refer to an L-level digital image of size M*N as having a spatial resolution of M*N pixels and a gray-level resolution of L levels.
18
Spatial and Gray-Level Resolution
19
Spatial and Gray-Level Resolution
20
Spatial and Gray-Level Resolution
21
Spatial and Gray-Level Resolution
22
Zooming and Shrinking Digital Images
Zooming may be viewed as oversampling, while shrinking may be viewed as undersampling.
Zooming requires two steps：the creation of new pixel locations，and the assignment of gray levels to those new locations.
Image shrinking is done in a similar manner as just described for zooming．The equivalent process of pixel replication is row-column deletion.
23
2
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