1. Which technique is primarily used in edge-based segmentation to detect changes in intensity?
(A) Region growing
(B) Histogram equalization
(C) Gradient operators
(D) Thresholding
2. Which of the following is a commonly used edge detection operator?
(A) Gaussian
(B) Sobel
(C) Mean
(D) Laplace
3. Which edge detection method uses the second derivative of intensity?
(A) Prewitt
(B) Canny
(C) Laplacian
(D) Roberts
4. What is the primary goal of edge-based segmentation?
(A) Enhance image contrast
(B) Identify object boundaries
(C) Smooth image noise
(D) Convert image to binary
5. Which of the following operators is used to approximate the gradient magnitude?
(A) Fourier
(B) Median
(C) Sobel
(D) DCT
6. Which edge detector uses non-maximum suppression and double thresholding?
(A) Laplacian
(B) Canny
(C) Roberts
(D) Prewitt
7. Which of the following is NOT a first-order edge detector?
(A) Sobel
(B) Prewitt
(C) Roberts
(D) Laplacian
8. What does the Canny edge detector aim to optimize?
(A) Noise reduction only
(B) High contrast only
(C) Detection, localization, and minimal response
(D) Binary conversion
9. What is the first step in the Canny edge detection algorithm?
(A) Gradient calculation
(B) Smoothing with Gaussian filter
(C) Thresholding
(D) Non-maximum suppression
10. Which filter is commonly used before applying the Canny edge detector to reduce noise?
(A) Median
(B) Gaussian
(C) Laplacian
(D) Box
11. In edge-based segmentation, edges are detected based on what?
(A) Histogram peaks
(B) Pixel connectivity
(C) Intensity discontinuities
(D) Texture patterns
12. Which of the following is an isotropic edge detector?
(A) Prewitt
(B) Sobel
(C) Laplacian
(D) Roberts
13. Which operator calculates the difference between diagonally adjacent pixels?
(A) Sobel
(B) Roberts
(C) Canny
(D) Laplacian
14. Which technique is effective for detecting edges in noisy images?
(A) Laplacian
(B) Sobel
(C) Canny
(D) Roberts
15. The gradient magnitude is computed from which two components?
(A) Vertical and diagonal
(B) Vertical and horizontal
(C) High-pass and low-pass
(D) Red and green
16. Which of the following edge detectors uses a 3×3 convolution mask?
(A) Canny
(B) Sobel
(C) Fourier
(D) Histogram
17. Which step in Canny edge detection removes false edges caused by noise?
(A) Gaussian filtering
(B) Thresholding
(C) Edge linking
(D) Non-maximum suppression
18. Double thresholding in Canny edge detection is used to:
(A) Convert image to grayscale
(B) Connect strong and weak edges
(C) Smooth image
(D) Calculate gradients
19. Which operator performs best at detecting vertical edges?
(A) Prewitt
(B) Laplacian
(C) Canny
(D) Sobel
20. In Canny edge detection, which step ensures that edges are as thin as possible?
(A) Gaussian smoothing
(B) Thresholding
(C) Non-maximum suppression
(D) Edge linking
21. Edge-based segmentation fails in which of the following situations?
(A) High contrast regions
(B) Textured areas
(C) Noisy images
(D) Smooth gradients
22. Which of the following is a disadvantage of edge-based segmentation?
(A) Easy to implement
(B) Sensitive to noise
(C) Accurate detection
(D) Fast processing
23. What is the main advantage of the Sobel operator?
(A) Speed
(B) Diagonal edge detection
(C) Noise suppression
(D) Simplicity and smoothing
24. Which method is often combined with edge detection to form complete regions?
(A) Histogram equalization
(B) Morphological operations
(C) Region growing
(D) Color enhancement
25. What does the Laplacian operator detect?
(A) First-order intensity change
(B) Mean intensity
(C) Second-order intensity change
(D) Local threshold
26. Which is an example of a zero-crossing detector?
(A) Sobel
(B) Canny
(C) Laplacian of Gaussian
(D) Prewitt
27. What is the effect of increasing the threshold in edge detection?
(A) More edges detected
(B) Less edges detected
(C) Better noise suppression
(D) Brighter image
28. Which of the following edge detectors does not use convolution masks?
(A) Roberts
(B) Laplacian
(C) Canny
(D) Prewitt
29. Which method uses zero-crossings in the second derivative for edge detection?
(A) LoG
(B) Sobel
(C) Roberts
(D) Prewitt
30. In edge-based segmentation, what defines a closed region?
(A) Texture boundary
(B) Gradient edge
(C) Continuous edge loop
(D) Histogram bin
31. What does a large gradient magnitude indicate in an image?
(A) Constant region
(B) Smooth intensity
(C) Strong edge
(D) No edge
32. Which filter combines Laplacian and Gaussian smoothing?
(A) Prewitt
(B) LoG
(C) Sobel
(D) Median
33. What is the purpose of edge thinning in segmentation?
(A) Remove small objects
(B) Sharpen image
(C) Reduce edge thickness
(D) Smooth background
34. Which property is critical for a good edge detector?
(A) Low accuracy
(B) Low sensitivity
(C) High localization
(D) High saturation
35. The Laplacian operator is sensitive to:
(A) Uniform regions
(B) Gradual changes
(C) Sharp transitions
(D) Texture patterns
36. Which of the following helps in closing small gaps in edge maps?
(A) Morphological closing
(B) Histogram stretching
(C) Thresholding
(D) Filtering
37. The gradient direction is calculated using:
(A) Sum of derivatives
(B) Ratio of derivatives
(C) Average of intensity
(D) Standard deviation
38. What type of kernel is used in the Prewitt operator?
(A) Gaussian
(B) Median
(C) Averaging
(D) Derivative
39. Which step follows non-maximum suppression in Canny edge detection?
(A) Gradient calculation
(B) Thresholding
(C) Gaussian filtering
(D) Laplacian transformation
40. The direction of the edge is:
(A) Same as gradient
(B) Perpendicular to gradient
(C) Horizontal
(D) Vertical
41. Edge linking is used to:
(A) Remove noise
(B) Fill in gaps between edge pixels
(C) Segment texture
(D) Increase resolution
42. Which of the following affects edge detection the most?
(A) Contrast
(B) Brightness
(C) Histogram
(D) Saturation
43. The Roberts operator uses how many pixels for calculation?
(A) 4
(B) 6
(C) 9
(D) 16
44. The Laplacian is a:
(A) Non-linear operator
(B) Smoothing filter
(C) Second-order differential operator
(D) Histogram function
45. What shape is the kernel of the Gaussian filter?
(A) Square
(B) Circular
(C) Triangular
(D) Elliptical
46. What does non-maximum suppression do in edge detection?
(A) Removes weak edges
(B) Thins edges by suppressing non-maximum points
(C) Blurs edges
(D) Enhances contrast
47. Which edge detection technique performs multi-stage processing?
(A) Sobel
(B) Laplacian
(C) Canny
(D) Roberts
48. Why is edge detection important in image segmentation?
(A) Reduces size
(B) Identifies object boundaries
(C) Changes image color
(D) Improves compression
49. Which type of edge is easiest to detect?
(A) Gradual change
(B) Smooth curve
(C) Sharp edge
(D) Texture boundary
50. Which operator detects diagonal edges best?
(A) Sobel
(B) Roberts
(C) Laplacian
(D) Canny
