Digital signal and image processing
Kid → expert
Thresholding at 3 levels: kid to professor
Explain thresholding to a 5-year-old, a student and a professor
Quick check · tap an answer to continue
Lesson notes
Key points
- Imagine sorting pebbles: anything lighter than your chosen grey goes in one bucket, anything darker goes in the other.
- Global thresholding maps each pixel to 1 if its intensity exceeds T, else 0, producing a binary image that separates object from background.
- Otsu's method chooses T automatically by maximising between-class variance of the histogram, but fails under uneven lighting, where adaptive thresholds work better.
Takeaway: Thresholding splits pixels into object and background using a cut-off T.
Quick check: Which quantity does Otsu's method maximise to choose its threshold?
- Within-class variance
- Between-class variance
- Mean pixel intensity
Otsu picks T where the two classes are most separated: maximum between-class variance.
Sorting by brightnessGlobal threshold TOtsu's method
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