# Exam - CS556 Final Exam Questions 1 What are the main steps...

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CS556: Final Exam Questions 1. What are the main steps in David Marr’s framework of computational vision? What are the key differences between Marr’s paradigm and “Intrinsic images”? 2. Specify the criterion for identifying brightness changes in a pixel neighborhood, used by the (a) Harris detector. (b) Hessian detector. (c) Kadir-Brady detector. 3. Derive the criterion for detecting interest points, used by the (a) Harris detector. (b) Hessian detector. (c) Kadir-Brady detector. 4. Specify the Difference-of-Gaussians (DoG) detector? 5. Specify the main steps of extracting Maximally Stable Extremal Regions? 6. Derive a linear transform that maps a detected interest point onto a canonical, normalized form. 7. Explain differences between the SIFT and DAISY descriptors. 8. Explain the main steps of the Canny edge detector. In one of the steps, the Canny detector connects broken edges in the image, by filling the gaps with straight lines. Why is this post- processing necessary? What is the underlying Gestalt principle for connecting the edges? 9. Suppose we applied the Canny edge detector to an image. Can we use intersections of detected Canny edges as interest points? 10. The goal is to extract scale invariant DAISY descriptors. Which of the following two algo- rithms would you use? Explain your choice. Algorithm 1: For each scale S Compute DAISY gradient field of the image; Detect interest points at scale S; Compute the DAISY descriptor for each detection; End 1

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Algorithm 2: Detect interest points that are stable over different scales; For each detected interest point Identify the scale of a region associated with the interest point; Use this scale to define the basic radius of the DAISY descriptor; Compute the DAISY descriptor; End 11. What is the difference between progressive scanning and interlaced scanning? 12. What is a vanishing point? Can there be more than one vanishing point in the image? 13. Homogeneous coordinates of point P in the image are P = [40 164 2] T . Which row and column contains P if homogeneous coordinates are measured from the top left corner of the image? 14. The intrinsic parameters of two cameras are given by K 1 = 0 . 6 0 . 3 1 . 4 0 0 . 4 0 . 9 0 0 1 , K 2 = 0 . 4 0 . 3 0 . 9 0 0 . 6 1 . 4 0 0 1 Which of the two cameras would you prefer to use? Explain your choice. 15. Point P in the image is mapped to point P by first translating P to P 1 15 rows in the same direction of y axis, and 102 columns in the opposite direction of x axis, then, by rotating P 1 to P 2 around the top left image corner by 30 counter clockwise, and finally by scaling the coordinates of P 2 to P by 1.3 along x axis, and 1 . 6 along y axis. Find the affine transformation matrix that captures these transformation steps from P to P . 16. Point
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## This note was uploaded on 04/17/2010 for the course CS 261 taught by Professor Staff during the Spring '08 term at Oregon State.

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Exam - CS556 Final Exam Questions 1 What are the main steps...

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