Digital signal and image processing
Guess first
Guess: what does dilation do to a hole?
Most students get this one wrong in the exam hall
Quick check · tap an answer to continue
Lesson notes
Key points
- Dilation slides a structuring element over a binary image and turns a pixel white if the element touches any white pixel.
- So white objects grow outward, and small black holes inside them shrink or get filled completely.
Definitions
- Dilation
- Output pixel is 1 if the structuring element overlaps at least one foreground pixel; objects grow.
Takeaway: Dilation grows white objects and shrinks the holes inside them.
Quick check: You dilate a white object that has a small black hole inside. What happens to the hole?
- The hole gets bigger
- The hole stays the same
- The hole shrinks or fills
Dilation grows the foreground, so background holes shrink.
DilationHoles shrink
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