数字图像处理-冈萨雷斯-课件(英文)Chapter11-表示与描述-50页PPT资料
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What kind of information we can use? - Boundary, shape - Region - Texture - Relation between regions
Shape Representation by Using Chain Codes
Why we focus on a boundary? The boundary is a good representation of an object shape and also requires a few memory.
(Images from Rafael C. Gonzalez and Richard E. Wood, Digital Image Processing, 2nd Edition.
Distance-Versus-Angle Signatures Represent an 2-D object boundary in term of a 1-D function
1
difference - a chain code: 10103322
01
1
- The first difference = 3133030
2
0 02
2
- Treating a chain code as a
03
3
ຫໍສະໝຸດ Baidu
circular sequence, we get
3
23
1
20
2
the first difference = 33133030
of radial distance with respect to q.
(Images from Rafael C. Gonzalez and Richard E. Wood, Digital Image Processing, 2nd Edition.
Chain codes: represent an object boundary by a connected sequence of straight line segments of specified length and direction.
4-directional chain code
The First Difference of a Chain Codes
Problem of a chain code: a chain code sequence depends on a starting point.
Solution: treat a chain code as a circular sequence and redefine the starting point so that the resulting sequence of numbers forms an integer of minimum magnitude.
Minimum perimeter polygon consists of line segments that
minimize distances between boundary pixels.
(Images from Rafael C. Gonzalez and Richard E. Wood, Digital Image Processing, 2nd Edition.
an image in other forms that are more suitable than the image itself.
Benefits: - Easier to understand - Require fewer memory, faster to be processed - More “ready to be used”
The first difference of a chain code: counting the number of direction change (in counterclockwise) between 2 adjacent elements of the code.
Example: Chain code : The first Example:
8-directional chain code
(Images from Rafael C. Gonzalez and Richard E. Wood, Digital Image Processing, 2nd Edition.
Examples of Chain Codes
Object boundary (resampling)
Boundary vertices
4-directional chain code
8-directional chain code
(Images from Rafael C. Gonzalez and Richard E. Wood, Digital Image Processing, 2nd Edition.
Polygon Approximation:Splitting Techniques
0. Object boundary
1. Find the line joining two extreme points
2. Find the farthest points from the line
3. Draw a polygon
Digital Image Processing
Chapter 11:
Image Description and Representation
12 September 2019
Image Representation and Description?
Objective: To represent and describe information embedded in
21
3 The first difference is rotational
invariant.
Polygon Approximation Represent an object boundary by a polygon
Object boundary
Minimum perimeter polygon
Shape Representation by Using Chain Codes
Why we focus on a boundary? The boundary is a good representation of an object shape and also requires a few memory.
(Images from Rafael C. Gonzalez and Richard E. Wood, Digital Image Processing, 2nd Edition.
Distance-Versus-Angle Signatures Represent an 2-D object boundary in term of a 1-D function
1
difference - a chain code: 10103322
01
1
- The first difference = 3133030
2
0 02
2
- Treating a chain code as a
03
3
ຫໍສະໝຸດ Baidu
circular sequence, we get
3
23
1
20
2
the first difference = 33133030
of radial distance with respect to q.
(Images from Rafael C. Gonzalez and Richard E. Wood, Digital Image Processing, 2nd Edition.
Chain codes: represent an object boundary by a connected sequence of straight line segments of specified length and direction.
4-directional chain code
The First Difference of a Chain Codes
Problem of a chain code: a chain code sequence depends on a starting point.
Solution: treat a chain code as a circular sequence and redefine the starting point so that the resulting sequence of numbers forms an integer of minimum magnitude.
Minimum perimeter polygon consists of line segments that
minimize distances between boundary pixels.
(Images from Rafael C. Gonzalez and Richard E. Wood, Digital Image Processing, 2nd Edition.
an image in other forms that are more suitable than the image itself.
Benefits: - Easier to understand - Require fewer memory, faster to be processed - More “ready to be used”
The first difference of a chain code: counting the number of direction change (in counterclockwise) between 2 adjacent elements of the code.
Example: Chain code : The first Example:
8-directional chain code
(Images from Rafael C. Gonzalez and Richard E. Wood, Digital Image Processing, 2nd Edition.
Examples of Chain Codes
Object boundary (resampling)
Boundary vertices
4-directional chain code
8-directional chain code
(Images from Rafael C. Gonzalez and Richard E. Wood, Digital Image Processing, 2nd Edition.
Polygon Approximation:Splitting Techniques
0. Object boundary
1. Find the line joining two extreme points
2. Find the farthest points from the line
3. Draw a polygon
Digital Image Processing
Chapter 11:
Image Description and Representation
12 September 2019
Image Representation and Description?
Objective: To represent and describe information embedded in
21
3 The first difference is rotational
invariant.
Polygon Approximation Represent an object boundary by a polygon
Object boundary
Minimum perimeter polygon