OpenCV Interview Questions and Answers

Ques 1. what is OpenCV?

OpenCV stands for Open Source Computer Vision Library is an open-source library using which is used to develop real-time computer vision applications such as image processing, video capture, and analysis, for example, face detection and object detection.

Ques 2. List some sample applications of OpenCV?

Some of the applications of OpenCV are object detection, face recognition, medical diagnosis, etc.

Ques 3. How many types of image filters are available in OpenCV?

There are two types of image filters available in OpenCV:Linear filterNon-linear filter

Ques 4. In OpenCV which function is used to draw a line?

In the OpenCV line() function is used to draw the line.

Ques 5. 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.

Ques 6. 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.

Ques 7. What are Erosion and Dilation in OpenCV?

In OpenCV, Erosion and Dilation are the two very common morphological image processing operations which is a procedure for modifying the geometric structure in the image.

Ques 8. Which method of OpenCV is used to read image?

The cv2.imread() method of the Imgcodecs class is used in OpenCV to read an image.

Ques 9. What is OpenGL?

OpenGL stands for Open Graphics Library, it is an open-source cross-platform application programming interface (API) for rendering 2D and 3D vector graphics. The API is used to interact with GPU for achieving the hardware-accelerated rendering.

Ques 10. How many types of video filters are in OpenCV?

Different types of video filters available in OpenCV are Blurring, Smoothing, Distortion, Warp Stabilizer, alpha extract, bilateral, color matrix, chrome hold, etc.

Ques 11. Which method of OpenCV is used to save images?

cv2.imwrite() method is the method of OpenCV that is used to save an image.

Ques 12. Which method of OpenCV is used to show the image?

cv2.imshow() method is the method of OpenCV that is used to show an image.

Ques 13. What are computer vision libraries?

OpenCV – Python, Java

Ques 14. What Is Image Translation And Scaling?

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.

Ques 15. What Do You Meant By Shrinking Of Digital Images?

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.

Ques 16. Explain 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 performs large variation by changes in its overall intensity.

Ques 17. How can we Increase the Quality of an Image?

– Recognition and Interpretation

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.

Ques 18. What is CUDA?

CUDA is a parallel computing platform developed by Nvidia that is consists of its own GPU for general computing.

Ques 19. How to find threshold in images using OpenCV?

We can find the threshold of an image in OpenCV with the help of cv.threshold function.

Ques 20. What is Scharr Operator?

Scharr() Operator is an operator that is used to detect the second derivatives of an image in horizontal and vertical directions.

Ques 21. Enlist different types of filters available in OpenCV?

The different types of linear and non-linear filter that you can apply to a picture using OpenCV are, BaeColumn filter, Base filter, BaseRow filter, FilterEngine, Bilateral filter, AdaptiveBilateral Filter, Blur, BorderInterpolate, BoxFilter, BuildPyramid, copyMakeBorder, createBoxFilter, createDerivFilter, createGuassionFilter, createLinear filter, createMorphology filter, createSeparableLinear filter, dilate, erode, filter2D, GuassianBlur, getDerivKernels, getKernelType, getStructuringElement, medianBlur, morphologyEx, Laplacian, pyrDown, pyrUp, pyrMeanShiftFiltering, sepFilter2D, Smooth, Sobel, Scharr.

Ques 22. What is computer vision?

It's a Subset of AI. Computer vision is an interdisciplinary scientific field that deals with how computers can be made to gain a high-level understanding of images or videos.

Ques 23. What are machine learning algorithms available in OpenCV?

Normal Bayes ClassifierK-Nearest NeighborsSupport Vector MachinesDecision TreesBoostingGradient Boosted TreesRandom TreesExtremely randomized trees

Ques 24. How many types of image filters in OpenCV?

• Averaging 
• Gaussian Filtering 
• Median Filtering 
• Bilateral Filtering

Ques 25. How many types of video filters are in OpenCV?

Color ConversionThresholdingSmoothingMorphology Gradients CannyEdgeDetectionContoursHistograms

Ques 26. How can we Increase the Quality of an Image in OpenCV?

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.

Ques 27. What Is Image Transform in OpenCV?

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.

Ques 28. What do you mean by zooming of digital images?

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.

Ques 29. What Is The Need For Transform in OpenCV?

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.

Ques 30. List The Hardware Oriented Color Models?

They are as follows.– RGB model– CMY model– YIQ model– HSI model

Ques 31. Do You Know What Rectification Is In Image Processing in OpenCV?

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.

Ques 32. 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). Whereas, Reflectance is the amount of light reflected by the object on the scene. It is represented by r(x, y).

Ques 33. List The Categories Of Digital Storage in OpenCV?

They are as follows

– Short term storage for use during processing.

– Online storage for relatively fast recall.

– Archival storage for infrequent access.

Ques 34. What Are The Differences Between Structural Patterns & Morphological Structural Element?

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

Ques 35. What Are The Steps Involved In Dip?

They are as follows.

Ques 36. What Is Geometric Transformation?

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