Digital Signal Processing Reference
In-Depth Information
10
VIDEO ROTATION
CHAPTER OUTLINE
10.1 Interpolation
68
Video images can be rotated, as well as scaled. Common
applications involve surveillance, heads-up displays, military and
industrial usages. Images are rotated about a reference point in
the image. This can be seen in the image rotation below.
Depending upon the location of the reference point, the rotation
may also cause the image to move to a different location.
Figure 10.1
Image rotation.
The mathematical relationship is quite simple. To perform
a rotation of
, with a normalized reference point (0,0), a pixel at
location (
x
,
y
) is translated to (
x'
,
y'
).
x'
q
¼
cos(
)
x
sin(
)
y
q
e
q
y
y
This can be expressed in matrix form as:
¼
sin(
)
x
þ
sin(
)
q
q
