Why face analysis is a core CV application in Computer Vision - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to load an image using OpenCV for face analysis.

Computer Vision

import cv2
image = cv2.imread([1])

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Aimage.jpg

B'face.jpg'

Ccv2.imread

Dface.jpg

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around the filename

Passing a variable name instead of a string

The cv2.imread function requires the file path as a string, so the filename must be in quotes.

2fill in blank

medium

Complete the code to convert the image to grayscale, which is common in face analysis.

Computer Vision

gray_image = cv2.cvtColor(image, [1])

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Acv2.COLOR_BGR2RGB

Bcv2.COLOR_RGB2GRAY

Ccv2.COLOR_BGR2GRAY

Dcv2.COLOR_GRAY2BGR

Attempts:

3 left

💡 Hint

Common Mistakes

Using RGB instead of BGR

Using conversion codes for wrong color spaces

To convert a color image to grayscale, use cv2.COLOR_BGR2GRAY because OpenCV loads images in BGR format.

3fill in blank

hard

Fix the error in the code to detect faces using a Haar cascade classifier.

Computer Vision

face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')
facedetected = face_cascade.[1](gray_image, scaleFactor=1.1, minNeighbors=5)

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AdetectMultiScale

BdetectFaces

CdetectFace

DdetectScale

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect method names

Typo in method name

The correct method to detect objects with Haar cascades in OpenCV is detectMultiScale.

4fill in blank

hard

Fill both blanks to draw rectangles around detected faces and display the image.

Computer Vision

for (x, y, w, h) in facedetected:
    cv2.rectangle(image, (x, y), ([1], [2]), (255, 0, 0), 2)
cv2.imshow('Faces', image)
cv2.waitKey(0)
cv2.destroyAllWindows()

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Ax + w

By + h

Cx - w

Dy - h

Attempts:

3 left

💡 Hint

Common Mistakes

Subtracting width or height instead of adding

Swapping x and y coordinates

The rectangle's bottom-right corner is at (x + w, y + h), which marks the face boundary.

5fill in blank

hard

Fill all three blanks to create a dictionary of face bounding boxes with keys as face IDs.

Computer Vision

faces_dict = {f'face_[1]': (x, y, [2], [3]) for [1], (x, y, w, h) in enumerate(facedetected)}

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Ai

Bw

Ch

Dindex

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong variable names

Mixing up width and height

Use i from enumerate for keys, and w, h for width and height values.