Size and Shape Analysis of Objects Size Measurements
Size and Shape Analysis of Objects
Size Measurements - Area - Perimeter - Length - Width
OBJECT BOUNDARY
OBJECT Area = b(x, y) x y (of object) Basically, count the pixels in the object b(x, y) = 1, if object b(x, y) = 0, if background
BOUNDARY Perimeter = b(x, y) x y (of boundary image)
BOUNDARY Boundary definition issue: Are boundary pixels completely or partially contained in the object?
BOUNDARY Polygon Perimeter: establishes boundary at center of each boundary pixel
BOUNDARY Polygon Perimeter: establishes boundary at center of each boundary pixel Perimeter = # lateral transitions + # diagonal transitions * 2
BOUNDARY Polygon Perimeter: establishes boundary at center of each boundary pixel Perimeter = # lateral + # diagonal 2 if chain coded boundary: Perimeter = (# even directions) + 2 (# odd directions)
BOUNDARY Polygon Area: area inside polygon perimeter Polygon Area = Pixel count - 1/2 boundary pixel count - 1
BOUNDARY Polygon Area: area inside polygon perimeter Polygon Area = Pixel count - 1/2 boundary pixel count - 1
Length & Width - Easy to find the horizontal and vertical extents
Length & Width - Easy to find the horizontal and vertical extents 6 pixels 7 pixels What is wrong with this approach?
Length & Width - Identification of length and width requires location of vertical axis
Length & Width - Identification of length and width requires location of vertical axis
Length & Width - Identification of length and width requires location of vertical axis
Shape Analysis - compactness (circularity) - eccentricity
Shape Analysis Compactness (circularity) 2 Compactness = Perimeter / Area (for a circle Compactness = 4 p)
Shape Analysis Eccentricity = Length / Width (as defined by the major axis) (for a circle Eccentricity = 1)
- Slides: 19