Morphology Flashcards
What are connected components?
Connected set of (non-background) pixels that are labelled distinctly from other clusters
Explain the concept of 4-neighbour vs 8-neighbour.
In a 4-neighbour system, pixels are only connected to those horizontally or vertically adjacent. 8 pixels also includes diagonal neighbours.
- 8 neighbours will generally include more pixels in each component
What are two common negatives of connected component algorithms?
-Slow
- Often a bottleneck
What is Dilation?
It expands a foreground object A using structuring element B
What is erosion?
It shrinks a foreground object A using Element B
What depends on the structuring element in the processes of dilation and erosion?
The amount and the way objects grow and shrink
What normally happens to the boundaries of foreground and background during the process of dilation / erosion?
Typically smooth
What are the 2 inputs of dilation?
- binary input image
- structuring element
How would you do edge detection using dilation?
You would dilate an original image, subtract from the original and the edges would remain
What are the two inputs for erosion?
- binary input image to erode
- Set of points to be considered (the structuring element)
Which type of pixel do you superimpose the structuring element over in dilation and erosion?
Dilation: background
Erosion: Foreground
Erosion of foreground pixels is equivalent to what?
Dilation of background pixels by the same structuring element
What are some practical uses of erosion?
- separating touching objects to count them
- edge detection
What is the process of opening?
First erode A with B then dilate A with B
What does opening do?
Smoothes contours, eliminates protrusions
What is the process of closing?
First dilate A with B then erode A with B
What does closing do?
Smoothes sections of contours, fuses narrow breaks and long thin gulfs, eliminates small holes and ill gaps in contours
What happens when you apply opening or closing several times?
They will only have an effect the first time
To close holes you would perform closing with a diameter that’s….
Larger than the diameter of the holes you want to close (this will close all holes smaller)
What does ROI stand for?
Region of Interest, for applying a process only to certain parts of an image
What makes ROIs so powerful?
Code can be written to allow the output of one process to determine where another is applied.
