Histogram equalization in Computer Vision - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to read an image using OpenCV.

Computer Vision

import cv2

image = cv2.[1]('input.jpg', 0)

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Aimread

Bimshow

Cimwrite

DcvtColor

Attempts:

3 left

💡 Hint

Common Mistakes

Using cv2.imshow instead of cv2.imread

Using cv2.imwrite which saves images

Using cv2.cvtColor which converts color spaces

The cv2.imread function reads an image from a file. The second argument 0 means read as grayscale.

2fill in blank

medium

Complete the code to apply histogram equalization on a grayscale image.

Computer Vision

equalized_image = cv2.[1](image)

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Athreshold

BequalizeHist

CcvtColor

Dblur

Attempts:

3 left

💡 Hint

Common Mistakes

Using cv2.cvtColor which changes color spaces

Using cv2.threshold which applies thresholding

Using cv2.blur which blurs the image

The cv2.equalizeHist function performs histogram equalization on a grayscale image.

3fill in blank

hard

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

Computer Vision

cv2.[1]('Equalized Image', equalized_image)
cv2.waitKey(0)
cv2.destroyAllWindows()

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Aimread

Bimwrite

CequalizeHist

Dimshow

Attempts:

3 left

💡 Hint

Common Mistakes

Using cv2.imread which reads images

Using cv2.imwrite which saves images

Using cv2.equalizeHist which equalizes histograms

The cv2.imshow function displays an image in a window.

4fill in blank

hard

Fill both blanks to create a histogram equalization function for color images using OpenCV.

Computer Vision

def equalize_color_image(img):
    ycrcb = cv2.cvtColor(img, [1])
    ycrcb[:, :, 0] = cv2.[2](ycrcb[:, :, 0])
    return cv2.cvtColor(ycrcb, cv2.COLOR_YCrCb2BGR)

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ACOLOR_BGR2YCrCb

BCOLOR_BGR2GRAY

CequalizeHist

Dthreshold

Attempts:

3 left

💡 Hint

Common Mistakes

Using COLOR_BGR2GRAY which converts to grayscale

Applying threshold instead of equalizeHist

Not converting back to BGR color space

To equalize a color image, convert it to YCrCb color space (COLOR_BGR2YCrCb), equalize the Y channel using equalizeHist, then convert back.

5fill in blank

hard

Fill all three blanks to compute and plot the histogram of a grayscale image using matplotlib.

Computer Vision

import matplotlib.pyplot as plt

hist = cv2.calcHist([image], [[1]], None, [256], [0, 256])
plt.plot(hist)
plt.title('[2] Histogram')
plt.xlabel('[3]')
plt.ylabel('Frequency')
plt.show()

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A0

BGrayscale

CPixel Intensity

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using channel 1 which is invalid for grayscale

Wrong plot title or axis labels

Not calling plt.show() to display the plot

For grayscale images, the channel index is 0. The plot title is 'Grayscale Histogram' and the x-axis label is 'Pixel Intensity'.