Top 50 Computer Vision Interview Questions & Answers 2021

1.What is computer vision?

Answer:Computer Vision uses images and videos to understand a real-world scene. Just like Humans use eyes for capturing light, receptors in the brain for accessing it, and the visual cortex for processing it. Similarly, a computer understands images, videos, or a real-world scenario through machine learning algorithms and AI self-learning programming.

2.What are machine learning algorithms available in OpenCV?

Answer:An OpenCV is open for all and free cross-platform where you get a library of real-time computer vision programming functions.

  • It is developed by Intel and is mostly written in the C++ programming language. A JavaScript version is also available as OpenCV.
  • js which is built for web platforms.

Some machine learning libraries available in OpenCV are:

  • Artificial Neural Networks, Random Forest, Support Vector Machine,
  • Decision Tree Learning, Convolution Neural Networks, Boosting and Gradient Boosting Trees,
  • Expectation-Maximization algorithm, Naive Bayes classifier, K-nearest neighboring algorithm.

3.How many types of image filters in OpenCV?

Answer:Image filters used in OpenCV are:

Bilateral Filter, Blur, Box Filter, Dilate, Build Pyramid, Erode, Filter2D, Gaussian Blur, Deriv, and Gabor Kernels, Laplacian, and Median Blur.

4.What are face recognition algorithms?

Answer:The face recognition algorithm is basically the computer application that is used for tracking, detecting, identifying, or verifying the human faces simply from the image or the video that has been captured using the digital camera.

Some popular but evolving algorithms are:

  • PCA- Principal Component Analysis
  • LBPH- Local Binary Pattern Histograms
  • k-NN (nearest neighbors) algorithm
  • Eigen’s faces
  • Fisher faces
  • SIFT- Scale Invariant Feature Transform
  • SURF- Speed Up Robust Features

5.What are languages supported by Computer vision?

Answer:LISP, Prolog, C/C++, Java, and Python.

6.What Do You Mean By Color Model?

Answer:A Color Model is a coordinate system and a subset of visible colors. With "Color Model" we create a whole range of colors from a limited set of primary colors like RGB (Red Green Blue). Color Models are of two types: Additive and Subtractive.

7.What Is Dynamic Range?

Answer:Dynamic Range is a ratio of small and large values that is assumed by a certain quantity. It is used in signals, photography, sounds, and light. From a photographic point of view, it is a ratio of minimum and maximum measuring light intensity or the lightest and darkest regions also called color contrast.

8.Define Digital Image?

Answer:A digital image is an image that is comprised of the elements of the picture, they are also admitted as pixels. Each pixel is with the finite and the discrete numbers of the numerical representation which belong to its intensity and the gray level which is considered as it’s output from the functions of the two-dimensions that is feed by the input of spatial coordinates those are denoted by the x-axis and y-axis.

9.What Is Meant By Mach Band Effect?

Answer:Mach Band Effect is an optical illusion. It emphasizes the differentiation between edges of the somewhat varying shades of grey when they reach each other. The extreme left side is dark grey and it converts into the lighter shades as they move to the right side of the plate.

10.What Are Sampling And Quantization?

Answer:We use sampling and Quantization to convert analog images to digital images. An image has two things.

1. Coordinates

Digitizing of coordinates is called Sampling. That is, converting the coordinates of the analog images to the digital images.

2. Intensity/Amplitude

Answer:Digitizing of Amplitude or Intensity is called Quantization. That is converting the Amplitude or Intensity of an analog image to a digital image.

11.What is Images stitching? How can you do with opencv ?

Answer:The idea is to transform one of the images so that both images merge as one. To do this, we can use the OpenCV warpPerspective() function. It takes an image and the homography as input. Then, it warps the source image to the destination based on the homography.

12.What is Computational Photography ? How can you do with opencv

Answer:The first allows us to perform computations on arrays very effectively (with surprisingly short code), while OpenCV handles reading/writing of the image files in this case, but is a lot more capable, providing many advanced graphics procedures

13.What Is Chromatic Adoption?

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

14.What Is Meant By Pixel?

Answer: 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.

15.What Is Geometric Transformation?

Answer: Transformation is used to alter the co-ordinate description of image.basic geometric transformations are:

  • Image translation
  • Scaling
  • Image rotation

16.What Is Meant By Mach Band Effect?

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

17.Define Digital Image?

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

18.What Do You Meant By Gray Level?

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

19.What Is Meant By Path?

Answer: Path from pixel p with co-ordinates (x, y) to pixel q with co-ordinates (s,t) is a sequence of distinct pixels with co-ordinates.

20.Give The Formula For Calculating D4 And D8 Distance.

Answer: D4 distance ( city block distance) is defined by D4(p, q) = |x-s| + |y-t| D8 distance(chess board distance) is defined by D8(p, q) = max(|x-s|, |y-t|).

21.Explain What Is Simultaneous Contrast?

Answer: The region reserved brightness not depend on its intensity but also on its background. All centers square have same intensity. Thus, they appear to the eye to become darker as the background becomes lighter.

22.In what way does Cones and Rods Are Distributed in Retina?

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

23.Define Brightness?

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

24.What Is Meant By Machband Effect?

Answer: Machband effect means the intensity of the stripes is constant. Thus, it preserves the brightness pattern near the boundaries, these bands are called as machband effect.

25.Define Sampling And Quantization?

Answer: Sampling means digitizing the co-ordinate value (x, y).Quantization means digitizing the amplitude value.

26.What Are Sampling And Quantization?

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

27.Differentiate Photopic And Scotopic Vision?

Answer: Photopic vision /Scotopic vision

  • The human being can resolve the fine details with these cones because each one is connected to its own nerve end.
  • This is also known as bright light vision.

28.Define Resolutions?

Answer: 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.

29.What Is Image Translation And Scaling?

Answer: Image translation means reposition the image from one co-ordinate location to another along straight line path. Whereas, Scaling refers to alter the size of the object or image (ie) a co-ordinate system is scaled by a factor.

30.What Do You Meant By Shrinking Of Digital Images?

Answer: Shrinking may be viewed as under sampling. If an image is been shrinked by one half, we delete every row and column. To reduce possible aliasing effect, it is a good idea to blue an image slightly before shrinking it.

31.Explain Subjective Brightness And Brightness Adaptation?

Answer: 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 performs large variation by changes in its overall intensity.

32.What Are The Steps Involved In Dip?

Answer:They are as follows.

  • Image Acquisition
  • Preprocessing
  • Segmentation
  • Representation and Description
  • Recognition and Interpretation

33.Do You Know What Rectification Is In Image Processing?

Answer: They are as follows.

  • Rectification in Image Processing is a transformation process used to project two-or-more images onto a common image plane.
  • It corrects image distortion by transforming the image into a standard coordinate system.
  • It is used in computer stereo vision to simplify the problem of finding matching points between images.
  • It is used in geographic information systems to merge images taken from multiple perspectives into a common map coordinate system.

34.What Is Meant By Illumination And Reflectance?

Answer: Illumination is the amount of source light incident on the scene. It is represented as i(x, y). Whereas, Reflectance is the amount of light reflected by the object on the scene. It is represented by r(x, y).

35.List The Categories Of Digital Storage?

Answer: They are as follows.

  • Short term storage for use during processing.
  • Online storage for relatively fast recall.
  • Archival storage for infrequent access.

36.What Are The Differences Between Structural Patterns & Morphological Structural Element?

Answer: In software engineering, structural design patterns are design patterns that ease the design by identifying a simple way to realize relationships between entities.

37.Write Short Notes On Neighbours Of A Pixel?

Answer: They are follows.

  • The pixel p at co-ordinates (x, y) has 4 neighbors (ie) 2 horizontal and 2 vertical neighbors whose co-ordinates is given by (x+1, y), (x-1,y), (x,y-1), (x, y+1). This is called as direct neighbors. It is denoted by N4(P)
  • Four diagonal neighbors of p have co-ordinates (x+1, y+1), (x+1,y-1), (x-1, y-1),(x-1, y+1). It is denoted by ND(4).
  • Is a combination of 4 direct neighbors and 4 diagonal neighbors. Eight neighbors of p denoted by N8(P)

38.Specify The Elements Of Dip System?

Answer: They are as follows.

  • Image Acquisition
  • Storage
  • Processing
  • Display

39.What Is Hue And Saturation?

Answer: 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.

40.What Is Luminance?

Answer: Luminance measured in lumens (lm), gives a measure of the amount of energy an observer perceiver from a light source.

41.What Is Simultaneous Contrast?

Answer: The region reserved brightness not depends on its intensity but also on its background. All centre square have same intensity. Hence, they appear to the eye to become darker as the background becomes lighter.

42.What Is Recognition And Interpretation?

Answer: 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.

43.How can we Increase the Quality of an Image?

Answer: Image enhancement process is purely dependent on the application where we need to use the enhanced image and the type of degradation in the image. Few solutions from my basic knowledge

  • If image contain so much noises, apply filtering operations such as mean/median etc.
  • If the image is looking too dark or too bright apply histogram equalization process to improve the contrast.
  • If the image is blurred apply sharpening operations in the image.

44.What Is Image Transform?

Answer: An image can be expanded in terms of a discrete set of basis arrays called basis images. Hence, these basis images can be generated by unitary matrices. An NxN image can be viewed as an N^2×1 vectors. It provides a set of coordinates or basis vectors for vector space.

45.What Do You Meant By Zooming Of Digital Images?

Answer: Zooming may be viewed as over sampling. Zooming involves the creation of new pixel locations and the assignment of gray levels to those new locations.

46.What Is The Need For Transform?

Answer: The need for transform is most of the signals or images are time domain signal (ie) signals can be measured with a function of time. This representation is not always best. Any person of the mathematical transformations is applied to the signal or images to obtain further information from that signal. Particularly, for image processing.

47.List The Hardware Oriented Color Models?

Answer: They are as follows.

  • RGB model
  • CMY model
  • YIQ model
  • HSI model

48.Explain What Are The Differences Between The Books Digital Image Processing And Digital Image Processing?

Answer: Digital Image Processing (DIP) deals primarily with the theoretical foundation of digital image processing, while Digital Image Processing Using MATLAB (DIPUM) is a book whose main focus is the use of MATLAB for image processing. The Digital Image Processing Using MATLAB (DIPUM)is a book that covers essentially the same topics as DIP, but the theoretical treatment is not as detailed.

49.What Do You Meant By Color Model?

Answer: 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.

50.What Are The Types Of Light Receptors?

Answer: The two types of light receptors are

  • Cones
  • Rods

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