1. What is the main goal of connected components labeling in digital image processing?
(A) Enhance image brightness
(B) Detect edges in an image
(C) Assign unique labels to connected regions
(D) Convert image to grayscale
2. Which type of image is typically used for connected components labeling?
(A) RGB image
(B) Grayscale image
(C) Binary image
(D) Color image
3. Which connectivity type considers horizontal and vertical neighbors only?
(A) 8-connectivity
(B) 6-connectivity
(C) 4-connectivity
(D) 2-connectivity
4. Which connectivity type includes diagonal neighbors?
(A) 2-connectivity
(B) 3-connectivity
(C) 4-connectivity
(D) 8-connectivity
5. What is the first step in the two-pass algorithm for connected components labeling?
(A) Relabel the components
(B) Assign provisional labels and record label equivalences
(C) Count the number of regions
(D) Apply edge detection
6. What is done in the second pass of the two-pass algorithm?
(A) Eliminate noise
(B) Apply thresholding
(C) Resolve label equivalences and assign final labels
(D) Resize image
7. Which data structure is commonly used to manage label equivalences?
(A) Queue
(B) Stack
(C) Union-Find (Disjoint Set)
(D) Heap
8. What does the Union operation do in the Union-Find algorithm?
(A) Finds the parent node
(B) Combines two disjoint sets
(C) Splits a set into two
(D) Sorts the labels
9. In connected components labeling, what does a label value represent?
(A) The size of the region
(B) The intensity of the region
(C) The region’s color
(D) A unique identifier for a connected region
10. Which scan order is commonly used in the first pass of labeling?
(A) Bottom-right to top-left
(B) Top-left to bottom-right
(C) Zigzag
(D) Spiral
11. Which neighborhood is examined during the first pass in 4-connectivity?
(A) Right and bottom
(B) Left and top
(C) Left, top, and bottom
(D) All eight surrounding pixels
12. What causes different regions to be assigned the same label in the first pass?
(A) Noise
(B) Label equivalence
(C) Thresholding
(D) Filtering
13. Which of the following can affect the labeling result?
(A) Bit depth
(B) Connectivity type
(C) Image size
(D) File format
14. Which operation can be used after labeling to determine region properties?
(A) Histogram equalization
(B) Region growing
(C) Region property analysis
(D) Fourier transform
15. What is the minimum number of passes required for the basic connected components labeling algorithm?
(A) One
(B) Two
(C) Three
(D) Four
16. Which labeling method is faster for hardware implementation?
(A) Two-pass
(B) One-pass
(C) Flood fill
(D) Region growing
17. Flood fill algorithm is an example of which labeling approach?
(A) Recursive
(B) Iterative
(C) Global
(D) Local
18. Which labeling algorithm is most suitable for small images and teaching purposes?
(A) Union-Find
(B) Flood fill
(C) Two-pass
(D) Adaptive thresholding
19. What is a potential disadvantage of recursive flood fill?
(A) Uses too much memory
(B) Misses diagonal connections
(C) Slower than two-pass
(D) Stack overflow in large images
20. Which of the following methods avoids recursion and is more memory-efficient?
(A) Recursive flood fill
(B) Iterative flood fill with queue
(C) Adaptive histogram
(D) Sobel edge detection
21. What is the role of equivalence table in connected components labeling?
(A) Counts the regions
(B) Stores provisional labels
(C) Merges equivalent labels
(D) Assigns binary values
22. Why might connected components labeling be used before region analysis?
(A) To enhance colors
(B) To convert the image to grayscale
(C) To isolate meaningful objects
(D) To compress the image
23. What is a typical application of connected components labeling?
(A) Edge detection
(B) Object counting
(C) Color balancing
(D) Histogram equalization
24. In which domain is connected components labeling most commonly used?
(A) Frequency domain
(B) Spatial domain
(C) Wavelet domain
(D) Time domain
25. What is the label assigned to background pixels in binary images during labeling?
(A) 0
(B) 1
(C) 255
(D) 100
26. Which step is performed after labeling to extract each component?
(A) Segmentation
(B) Object extraction
(C) Label mapping
(D) Region analysis
27. Which type of connectivity often leads to over-segmentation?
(A) 4-connectivity
(B) 6-connectivity
(C) 8-connectivity
(D) 2-connectivity
28. Which algorithm is NOT commonly used for connected components labeling?
(A) Two-pass
(B) Union-Find
(C) Flood fill
(D) Canny edge detection
29. How many neighbors does a pixel have in 8-connectivity?
(A) 2
(B) 4
(C) 6
(D) 8
30. Which of the following is true about 4-connectivity?
(A) Includes diagonal neighbors
(B) Considers pixels in cross pattern
(C) Leads to better segmentation in all cases
(D) Is slower than 8-connectivity
31. What happens if you apply 8-connectivity on a cross-shaped object?
(A) It will break it into parts
(B) It may merge nearby objects diagonally
(C) It will sharpen the image
(D) It performs thresholding
32. Which is more sensitive to diagonal connections?
(A) 4-connectivity
(B) 8-connectivity
(C) 2-connectivity
(D) None of these
33. What does a label collision indicate?
(A) Same object detected twice
(B) Edge not detected
(C) Multiple labels assigned to same region
(D) Object count is reduced
34. What is one way to improve labeling accuracy?
(A) Use smaller images
(B) Apply smoothing before labeling
(C) Increase brightness
(D) Use histogram equalization
35. Connected components labeling is not suitable for:
(A) Noisy binary images
(B) Object detection
(C) Region analysis
(D) Image compression
36. Which component is NOT part of two-pass algorithm?
(A) Provisional labeling
(B) Label equivalence table
(C) Final labeling
(D) Color enhancement
37. Which method ensures that equivalent labels are correctly assigned to connected regions?
(A) Region growing
(B) Thresholding
(C) Union-Find
(D) Histogram matching
38. Which property can be measured after labeling a component?
(A) Edge sharpness
(B) Average intensity
(C) Area and centroid
(D) Compression ratio
39. Which operation might precede connected components labeling to reduce false regions?
(A) Filtering
(B) Cropping
(C) Compression
(D) Color conversion
40. The two-pass algorithm avoids recursion by:
(A) Using BFS
(B) Using forward-backward scan
(C) Using edge detection
(D) Using histogram equalization
41. What is the complexity of connected components labeling using Union-Find?
(A) Linear
(B) Exponential
(C) Logarithmic
(D) Quadratic
42. What does a connected component consist of?
(A) Isolated pixels
(B) All pixels with same intensity
(C) All connected foreground pixels
(D) All background pixels
43. Which format is best for applying connected components labeling?
(A) PNG
(B) RGB
(C) Binary
(D) CMYK
44. Which of the following is true about the one-pass algorithm?
(A) It requires recursion
(B) It labels in multiple passes
(C) It uses decision trees or hardware-specific logic
(D) It cannot handle equivalences
45. What is the major drawback of two-pass algorithm?
(A) Too complex
(B) Too slow for real-time
(C) Requires color input
(D) Needs frequent histogram updates
46. In a labeled image, how are components typically visualized?
(A) With binary values
(B) With different colors for each label
(C) As grayscale
(D) As histogram
47. What ensures uniqueness of each region in labeling?
(A) Different pixel values
(B) Unique label assignment
(C) Threshold level
(D) Region growing
48. Which field benefits from connected components labeling for counting cells?
(A) Astronomy
(B) Agriculture
(C) Medical imaging
(D) Cryptography
49. What happens when two regions are mistakenly merged?
(A) They appear darker
(B) They form one larger region
(C) Labeling is skipped
(D) They turn into background
50. Which process follows labeling in object tracking tasks?
(A) Morphological dilation
(B) Edge enhancement
(C) Feature extraction
(D) Compression
