Code: T-14                                Subject: IMAGE PROCESSING & COMPUTER GRAPHICS

Time: 3 Hours                                                                                                     Max. Marks: 100

 

NOTE: There are 11 Questions in all.

 

·      Question 1 is compulsory and carries 16 marks. Answer to Q.1 (A) must be written in the space provided for it in the answer book supplied and nowhere else.

·      Answer any THREE Questions each from Part I and Part II. Each of these questions carries 14 marks.

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

 

Q.1      

   (A)     Choose the correct or best alternative in the following:                                         (2 x 4)

       

a.       Projection that does not preserve relative proportions of objects is

                  

                   (A)  Perspective                                  (B)  Orthoraphic

(C)    Isometric                                     (D)  Parallel

 

             b.   Height of the resized image of size  to one of 640 pixels wide with the same aspect ratio is

                  

                   (A)  864.                                             (B)  480.

(C)  1024.                                           (D)  800.

 

             c.   Low gray level resolution results in

 

(A)    False contouring.                          (B)  Checker board effect

(C)  Moire Patterns                             (D)  none of the above.

 

             d.   mask detects lines that are oriented at

                   (A) *                                                (B) 

(C)                                            (D) 

                                                                            

   (B)     Write brief notes on the following :-                                                             (2 x 4)

                  

(i)                  Elevation views.                                                                                   

(ii)                Resolution.             

(iii)               Histogram.                              

(iv)              Edge.

 

 

 

 

 

                                                                                                                

PART I

Answer any THREE Questions. Each question carries 14 marks.

 

  Q.2     a.   With neat diagrams, explain the two basic techniques used for producing colour displays with a CRT.                                                                    (8)

 

             b.   Consider a raster system with a resolution of . What is the size of the frame buffer in bytes needed to store 4 bits/pixel? How long would it take to load the frame buffer if bytes can be transferred per second? How many pixels are accessed per second by a display controller that refreshes the screen at a rate of 30 frames/second? What is the access time per pixel?                              (6)

 

  Q.3     a.   Describe the mid point circle generation algorithm by deriving necessary equations.             (6)       

             b.   Illustrate the mid point circle generation algorithm for drawing a circle centered at (0,0) and having radius of 5 units.                                                (8)

                  

  Q.4     a.   What is clipping? Explain Cohen and Sutherland line clipping technique with suitable figures.                        (8)

 

             b.   Show that the transformation for a reflection about the line y = x is equivalent to a reflection relative to the x-axis followed by a counter clockwise rotation of . Derive the similar relation for a reflection about the line y = -x.                                                 (6)

            

  Q.5     a.   Explain the parallel and perspective projections and the transformation matrix for each of them.                                                                  (8)

 

             b.   Explain the reflection and shear transformation in three dimensional graphics applications by providing the  matrix representation and example figures.                                                          (6)

 

  Q.6     a.   Give the back face detection algorithm and mention its application.                      (6)

 

             b.   Obtain the composite transformation to rotate a 3D object by an angle  about an arbitrary axis.                                                               (8)

 

PART II

Answer any THREE Questions. Each question carries 14 marks.

 

  Q.7     a.   Explain the different techniques used for image sensing and acquisition with suitable diagrams.                     (8)

 

b.      What is the purpose of a color model? Explain the RGB color model and also draw the RGB color cube.                                                              (6)

 

 

 

 

  Q.8     a.   Draw histograms for different types of images. Briefly explain the histogram specification technique with necessary equations and figures.           (8)

 

             b.   Mention some of the properties of the median filter. Find the median filter output for an input image {2, 3, 8, 4, 2} and with the window specified by     W = {-1, 0, 1}.                                                (6)                   

  Q.9     a.   The basic approach used to approximate a discrete derivative involves taking differences of the form f (x+1, y)-f (x, y). Obtain the filter transfer function H(u,v) for performing the equivalent process in the frequency domain. Show that H(u,v)is a high pass filter.                                                                      (6)

 

             b.   What is homomorphic filtering? Explain the filtering approach with a block diagram. Indicate where this filtering is used and the effect of using this filter on images.                                                   (8)

 

Q.10           a.                                                        Explain the JPEG Image compression standard with the aid of a neat block diagram.                                                                                                   (8)          

             b.  Consider the following four symbols with probabilities P(A)=0.2,  P(B)=0.2, P(C)=0.4, and P(D)=0.2. Encode the sequence ABCCD using Arithmetic  coding.  Calculate the average length of the code assuming that 3 decimal digits are used to represent the sequence and compare it with the entropy of  the source.                                                                  (6)

 

Q.11     a.   Explain the process of segmentation and describe the region growing algorithm for segmenting the image into different regions.                                  (8)

 

             b.   Suppose that an image has the gray level probability density functions shown in Fig. 1. Here  corresponds to objects and  corresponds to the background.   Assume that  and find the optimal threshold between object and background pixels.                                                                       (6)