**DIGITAL IMAGE PROCESSING VIVA Questions :-**

**1. Define Image?**

An image may be defined as two dimensional light intensity function f(x, y) where x and y denote spatial co-ordinate and the amplitude or value of f at any point (x, y) is called intensity or gray scale or brightness of the image at that point.

**2. What is Dynamic Range?**

The range of values spanned by the gray scale is called dynamic range of an image. Image will have high contrast, if the dynamic range is high and image will have dull washed out gray look if the dynamic range is low.

**3. Define Brightness?**

Brightness of an object is the perceived luminance of the surround. Two objects with different surroundings would have identical luminance but different brightness.

**4. What do you meant by Gray level?**

Gray level refers to a scalar measure of intensity that ranges from black to grays and finally to white.

**5. What do you meant by Color model?**

A Color model is a specification of 3D-coordinates system and a subspace within that system where each color is represented by a single point.

**6. List the hardware oriented color models?**

1. RGB model

2. CMY model

3. YIQ model

4. HSI model

**7. What is Hue and saturation?**

Hue is a color attribute that describes a pure color where saturation gives a measure of the degree to which a pure color is diluted by white light.

**8. List the applications of color models?**

1. RGB model— used for color monitors & color video camera

2. CMY model—used for color printing

3. HIS model—-used for color image processing

4. YIQ model—used for color picture transmission

**9. What is Chromatic Adoption?**

The hue of a perceived color depends on the adoption of the viewer. For example,the American Flag will not immediately appear red, white, and blue of the viewer has been subjected to high intensity red light before viewing the flag. The color of the flag will appear to shift in hue toward the red component cyan.

**10. Define Resolutions?**

Resolution is defined as the smallest number of discernible detail in an image.Spatial resolution is the smallest discernible detail in an image and gray level resolution refers to the smallest discernible change is gray level.

**11. What is meant by pixel?**

A digital image is composed of a finite number of elements each of which has a particular location or value. These elements are referred to as pixels or image elements or picture elements or pixls elements.

**12. Define Digital image?**

When x, y and the amplitude values of f all are finite discrete quantities , we call the image digital image.

**13. What are the steps involved in DIP?**

1. Image Acquisition

2. Preprocessing

3. Segmentation

4. Representation and Description

5. Recognition and Interpretation

**14. What is recognition and Interpretation?**

Recognition means is a process that assigns a label to an object based on the information provided by its descriptors.Interpretation means assigning meaning to a recognized object.

**15. Specify the elements of DIP system?**

1. Image Acquisition

2. Storage

3. Processing

4. Display

**16. List the categories of digital storage?**

1. Short term storage for use during processing.

2. Online storage for relatively fast recall.

3. Archival storage for infrequent access.

**17. What are the types of light receptors?**

The two types of light receptors are

- Cones and
- Rods

**18. Differentiate photopic and scotopic vision ?**

Photopic vision Scotopic vision

1. The human being can resolve the fine details with these cones because each one is connected to its own nerve end.

2. This is also known as bright light vision.

**19. How cones and rods are distributed in retina?**

In each eye, cones are in the range 6-7 million and rods are in the range 75-150 million.

**20. Define subjective brightness and brightness adaptation?**

Subjective brightness means intensity as preserved by the human visual system.Brightness adaptation means the human visual system can operate only from scotopic to glare limit. It cannot operate over the range simultaneously. It accomplishes this large variation by changes in its overall intensity.

**21. Define weber ratio?**

The ratio of increment of illumination to background of illumination is called as web er ratio.(ie) Δi/i

If the ratio (Δi/i) is small, then small percentage of change in intensity is needed (ie) good brightness adaptation.

If the ratio (Δi/i) is large , then large percentage of change in intensity is needed (ie) poor brightness adaptation.

**22. What is meant by mach band effect?**

Mach band effect means the intensity of the stripes is constant. Therefore it preserves the brightness pattern near the boundaries, these bands are called as mach band effect.

**23. What is simultaneous contrast?**

The region reserved brightness not depend on its intensity but also on its background. All centre square have same intensity. However they appear to the eye to become darker as the background becomes lighter.

**24. What is meant by illumination and reflectance?**

Illumination is the amount of source light incident on the scene. It is represented as i(x, y).

Reflectance is the amount of light reflected by the object in the scene. It is represented by r(x, y).

**26. Define sampling and quantization?**

Sampling means digitizing the co-ordinate value (x, y).Quantization means digitizing the amplitude value. Several rods are connected to one nerve end. So it gives the overall picture of the image.This is also known as thin lightvision.

**30. What Are The Properties Of Haar Transform?**

- Haar transform is real and orthogonal.
- Haar transform is a very fast transform
- Haar transform has very poor energy compaction for images
- The basic vectors of Haar matrix sequency ordered.

**31. What Are The Properties Of Slant Transform?**

- Slant transform is real and orthogonal.
- Slant transform is a fast transform
- Slant transform has very good energy compaction for images
- The basic vectors of Slant matrix are not sequency ordered.

**32. Define Of Kl Transform?**

KL Transform is an optimal in the sense that it minimizes the mean square error between the vectors X and their approximations X^. Due to this idea of using the Eigenvectors corresponding to largest Eigen values. It is also known as principal component transform.

**33. Justify That Klt Is An Optimal Transform?**

Since mean square error of reconstructed image and original image is minimum and the mean value of transformed image is zero so that uncorrelated.

**34. Explain The Term Digital Image?**

The digital image is an array of real or complex numbers that is represented by a finite no of bits.

**35. Write Any Four Applications Of Dip?**

- Remote sensing
- Image transmission and storage for business application
- Medical imaging
- Astronomy

**36. What Is The Effect Of Mach Band Pattern?**

The intensity or the brightness pattern perceive a darker stribe in region D and brighter stribe in region B.This effect is called Mach band pattern or effect.

**37. Write Down The Properties Of 2d Fourier Transform?**

- Separability
- Translation
- Periodicity and Conjugate property
- Rotation
- Distributivity and scaling
- Average value
- Convolution and Correlation
- Laplacian

**38.Obtain The Hadamard Transformation For N = 4?**

N = 4 = 2n

=> n = 2

**39. Write Down The Properties Of Haar Transform?**

- Real and orthogonal
- Very fast transform
- Basis vectors are sequentially ordered
- Has fair energy compaction for image
- Useful in feature extraction,image coding and image analysis problem

**40. What Is Image Enhancement?**

Image enhancement is to process an image so that the output is more suitable for specific application.

**41. Name The Categories Of Image Enhancement And Explain?**

The categories of Image Enhancement are

- Spatial domain
- Frequency domain Spatial domain: It refers to the image plane, itself and it is based on direct manipulation of pixels of an image.
- Frequency domain techniques are based on modifying the Fourier transform of an image.

**42. What Do You Mean By Point Processing?**

Image enhancement at any Point in an image depends only on the gray level at that point is often referred to as Point processing.

**43. Explain Mask Or Kernels?**

A Mask is a small two-dimensional array, in which the value of the mask coefficient determines the nature of the process, such as image sharpening.

**44. What Is Image Negatives?**

The negative of an image with gray levels in the range [0, L-1] is obtained by using the negative transformation, which is given by the expression.

s = L-1-r

Where s is output pixel.

r is input pixel.

**45. Define Histogram?**

The histogram of a digital image with gray levels in the range [0, L-1] is a discrete function h (rk) = nk, where rk is the kth gray level and nk is the number of pixels in the image having gray level rk.

**46. Define Derivative Filter?**

For a function f (x, y), the gradient f at co-ordinate (x, y) is defined as the

vector_f = _f/_x

_f/_y

_f = mag (_f) = {[(_f/_x) 2 +(_f/_y) 2 ]} ½

**47. Explain Spatial Filtering?**

Spatial filtering is the process of moving the filter mask from point to point in an image. For linear spatial filter, the response is given by a sum of products of the filter coefficients, and the corresponding image pixels in the area spanned by the filter mask.

**48. Define Averaging Filters?**

The output of a smoothing, linear spatial filter is the average of the pixels contain in the neighborhood of the filter mask. These filters are called averaging filters.

**49. What Is A Median Filter?**

The median filter replaces the value of a pixel by the median of the gray levels in the neighborhood of that pixel.

**50. What Is Maximum Filter And Minimum Filter?**

The 100th percentile is maximum filter is used in finding brightest points in an image. The 0th percentile filter is minimum filter used for finding darkest points in an image.

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