COMP 9517 WK2
2021 T1
Contrast Stretching
• Produces images of higher contrast
• Puts values below L in the input to black in the output • Puts values above H in the input to white in the output
• Linearly scales values between L and H in the input to the maximum range in the output
Intensity thresholding
Intensity thresholding
• Limiting case of contrast stretching
• Produces binary images of gray-scale images
• Puts values below the threshold to black in the output
• Puts values equal / above the threshold to white in the output
• Popular method for image segmentation
• Useful only if object and background intensities are very different
Automatic intensity thresholding
Otsu thresholding
Automatic intensity thresholding
Iso-data thresholding
Histogram of pixel intensities
Histogram processing
Histogram processing
Histogram Equalization
Histogram Equalization (discrete)
Histogram matching (discrete)
Example – HE
Example – HM
Arithmetic and logical operations
Arithmetic and logical operations
Arithmetic and logical operations
Spatial Filtering
Spatial Filtering
Smoothing Spatial Filters
Gaussian Filter
Non-linear Spatial Filters
Pooling
Sharpening Spatial Filters-Edge Detection
Derivative definitions
Basic idea – Derivatives
Summary – Derivatives
Gradient Operator
The Laplacian
Padding