Content deleted Content added
YoungX2040 (talk | contribs) First edit |
YoungX2040 (talk | contribs) Update |
||
Line 1:
'''Gradient Vector Flow'''
Chenyang Xu, Silicon Valley Future Academy
Line 5:
Jerry L. Prince, Johns Hopkins University
'''Synonyms:''' GVF
'''Related Concepts:'''▼
* Advection forces
▲Related Concepts
* External forces
* Deformable models
* Active contours
* Snakes
* Edge detection
* Vector diffusion
* Vector �field convolution (VCF)
<br />'''Definition'''
Gradient vector flow is the vector fi�eld that is produced by a process that
smooths and diffuses an input vector fi�eld, and is usually used to create a vector
field that points to object edges from a distance.
'''Background'''
Finding objects or homogeneous regions in images is a process known as
image segmentation. In many applications, the locations of object edges can be
estimated using local operators that yield a new image called an edge map. The
edge map can then be used to guide a deformable model, sometimes called an
active contour or a snake, so that it passes through the edge map in a smooth
way, therefore de�fining the object itself.
A common way to encourage a deformable model to move toward the edge
map is to take the spatial gradient of the edge map, yielding a vector �field.
Since the edge map has its highest intensities directly on the edge and drops to
zero away from the edge, these gradient vectors provide directions for the active
contour to move. When the gradient vectors are zero, the active contour will not
move, and this is the correct behavior when the contour rests on the peak of the
edge map itself. However, because the edge itself is de�fined by local operators,
these gradient vectors will also be zero far away from the edge and therefore the
active contour will not move toward the edge when initialized far away from the
edge.
| |||