Code: AT14                                                                            Subject: IMAGE PROCESSING &

                                                                                                               COMPUTER GRAPHICS

Time: 3 Hours                                                                                                     Max. Marks: 100

NOTE: There are 9 Questions in all.

· Question 1 is compulsory and carries 20 marks. Answer to Q. 1. must be written in the space provided for it in the answer book supplied and nowhere else.

· Out of the remaining EIGHT Questions answer any FIVE Questions. Each question carries 16 marks.

· Any required data not explicitly given, may be suitably assumed and stated.

Q.1       Choose the correct or best alternative in the following:                                         (2x10)

a. These are pencil shaped devices used to select screen positions by detecting the light coming from points on the CRT screen.

(A)  Light Pens                                    (B)  Data Gloves

(C)   Mouse                                         (D)  Scanners

b. This algorithm for circle generation sets up decision parameters for finding the closest pixel to the circumference at each sampling step.

(A)  Parallel curve algorithm                 (B)  Bresenham algorithm

(C)  DDA algorithm                             (D)  Midpoint circle algorithm

c.   To express any two-dimensional transformation as a matrix multiplication, the Cartesian coordinate position are represented with the ___________.   

(A) Parallel coordinates                      (B)  Perpendicular coordinates

(C) Homogeneous coordinates             (D)  Perspective coordinates

             d.   Number of regions in Cohen Sutherland algorithm is

(A)  3                                                 (B)   8

(C)  9                                                 (D)  10

             e.   Engineering and architectural drawings commonly employ this projection.

(A) Parallel                                          (B)  Oblique

(C) Cavalier                                        (D)  Isometric

             f.    The effect caused by the use of an insufficient number of gray levels in smooth areas of a digital image is called _________

(A) Graininess                                     (B) False contouring

(C) Blurring                                         (D) Checker board pattern

             g.   This process results in an image with reduced sharp transitions in gray levels.

(A)  Sharpening                                   (B)  Spatial averaging

(C)  Edge detection                             (D)  Image segmentation

h.   In transform coding, if the retained coefficients are selected on the basis of maximum variance, it is termed as ____________

(A) Threshold coding                          (B) Adaptive coding

(C)  Zonal coding (D) Quantization

             i.    If the threshold T in a thresholding technique for image segmentation depends on the gray value of the pixel and also some local property of that point, then it is ___________

(A) Global thresholding                       (B) Adaptive thresholding

(C) Optimal thresholding                      (D) Local thresholding

             j.    Edge detection algorithms are followed by this procedure to assemble edge pixels into meaningful edges.

(A)  Homomorphic filtering                  (B)  Smoothing

(C)  Edge linking                                  (D)  Sharpening

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

Q.2     a.   Write short notes on

(i)  Raster-Scan displays                     

                   (ii) Random-Scan displays.                                                                                (8)

             b.   What are line-drawing algorithms?  Explain the steps involved in the DDA algorithm for scan-conversion of lines.                                                    (8)

Q.3     a.   Derive the transformation for scaling an object in other directions instead of x- and y- directions.                                                                (8)

             b.   Determine a sequence of basic transformations that are equivalent to the x-directions shear matrix and y-direction shear matrix.                          (8)

Q.4     a.   Explain Cohen Sutherland line clipping algorithm.                                                (8)

b.   Derive the rotation matrix when an object is to be rotated about an axis that is not parallel to one of the coordinate axes using composite transformations.                                                               (8)

Q.5     a.   Explain the transformation pipeline required for generating the views of a scene given the spatial position, orientation and aperture size of the camera.                                                                        (8)

b.   Describe the depth-buffer or the z-buffer method for detecting visible surfaces.                   (8)

Q.6     a. What is image acquisition?  Explain different techniques employed for image sensing and acquisition with suitable diagrams.                                (8)

             b.   What is a histogram?  Explain how histogram statistics are used for image enhancement.                  (8)

Q.7     a.   Explain the following filters

                   (i)   Butterworth filters.                         (ii)  Unsharp masking filter.

                   (iii) High-Boost filter.                                                                                        (8)

b.   Explain Discrete Fourier transform along with its properties.                                (8)

Q.8     a.   Explain the terms (i)  Error-Free compression (ii)  Variable-Length coding.  Encode the symbols {A, B, C, D, E, F} with probabilities {0.1, 0.4, 0.06, 0.1, 0.04, 0.3} using Huffman coding technique.  Calculate the average length of the code, entropy of the source and code efficiency.                 (8)

             b.   Explain the JPEG continuous tone still image compression standard in detail with a block diagram.                                                              (8)

Q.9     a.   Describe edge detection.  Provide examples of different operators used for detecting edges.                                                                      (8)

b.   What is the objective of segmentation?  Describe the basic formulation of a region.  Explain the region growing technique of  region segmentation.                                                        (8)