Computer vision basics in Intro to Computing - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to load an image using OpenCV.

Intro to Computing

import cv2
image = cv2.[1]('image.jpg')

Drag options to blanks, or click blank then click option'

Aimshow

Bresize

Cimwrite

Dimread

Attempts:

3 left

💡 Hint

Common Mistakes

Using imshow instead of imread

Using imwrite which saves images

Using resize which changes image size

The imread function loads an image from a file into memory.

2fill in blank

medium

Complete the code to convert a color image to grayscale using OpenCV.

Intro to Computing

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

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ACOLOR_BGR2GRAY

BCOLOR_GRAY2BGR

CCOLOR_BGR2RGB

DCOLOR_RGB2BGR

Attempts:

3 left

💡 Hint

Common Mistakes

Using COLOR_BGR2RGB which changes color space but not to grayscale

Using COLOR_GRAY2BGR which converts grayscale to color

Using COLOR_RGB2BGR which swaps color channels

COLOR_BGR2GRAY converts a color image from BGR to grayscale.

3fill in blank

hard

Fix the error in the code to display an image using OpenCV.

Intro to Computing

cv2.[1]('Image Window', image)
cv2.waitKey(0)
cv2.destroyAllWindows()

Drag options to blanks, or click blank then click option'

Aimread

Bimshow

Cresize

Dimwrite

Attempts:

3 left

💡 Hint

Common Mistakes

Using imread which loads images

Using imwrite which saves images

Using resize which changes image size

The imshow function displays an image in a window.

4fill in blank

hard

Fill both blanks to create a binary threshold on a grayscale image.

Intro to Computing

_, binary_image = cv2.threshold(gray_image, [1], [2], cv2.THRESH_BINARY)

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A127

B255

C128

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 as threshold which makes all pixels black

Using 128 as max value which is not standard

Swapping threshold and max value

The threshold value is 127 and the max value for the binary image is 255.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps image filenames to their grayscale shapes.

Intro to Computing

shapes = {filename: cv2.imread(filename, [1]).shape[:[2]] for filename in files if cv2.imread(filename, [3]) is not None}

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Acv2.IMREAD_GRAYSCALE

B2

Ccv2.IMREAD_COLOR

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using IMREAD_COLOR which loads 3 channels

Using 3 for slicing shape which is for color images

Using different flags for loading images in comprehension

Images are loaded in grayscale mode (IMREAD_GRAYSCALE), so shape has 2 dimensions (height, width).