Image interpolation methods in Matplotlib - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to display an image using nearest neighbor interpolation.

Matplotlib

import matplotlib.pyplot as plt
import numpy as np

image = np.random.rand(5, 5)
plt.imshow(image, interpolation='[1]')
plt.show()

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

Abicubic

Bbilinear

Cnearest

Dspline16

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'bilinear' or 'bicubic' which smooth the image instead of nearest neighbor.

Misspelling the interpolation method name.

The 'nearest' interpolation method displays the image by picking the nearest pixel value without smoothing.

2fill in blank

medium

Complete the code to display an image using bilinear interpolation.

Matplotlib

import matplotlib.pyplot as plt
import numpy as np

image = np.random.rand(10, 10)
plt.imshow(image, interpolation='[1]')
plt.show()

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

Abilinear

Bnone

Channing

Dnearest

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'nearest' which does not smooth the image.

Using 'none' which disables interpolation.

Bilinear interpolation smooths the image by averaging the nearest 2x2 pixels.

3fill in blank

hard

Fix the error in the code to use bicubic interpolation correctly.

Matplotlib

import matplotlib.pyplot as plt
import numpy as np

image = np.random.rand(8, 8)
plt.imshow(image, interpolation=[1])
plt.show()

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

A'bilinear'

Bbicubic

C'nearest'

D'bicubic'

Attempts:

3 left

💡 Hint

Common Mistakes

Not using quotes around the interpolation method name.

Using an unsupported interpolation method.

The interpolation parameter must be a string in quotes, so 'bicubic' is correct.

4fill in blank

hard

Fill both blanks to create a dictionary of images with their interpolation methods.

Matplotlib

images = {'img1': np.random.rand(4, 4), 'img2': np.random.rand(6, 6)}
methods = ['[1]', '[2]']
image_dict = {k: (v, m) for k, v, m in zip(images.keys(), images.values(), methods)}

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

Anearest

Bbilinear

Cbicubic

Dnone

Attempts:

3 left

💡 Hint

Common Mistakes

Using unsupported interpolation method names.

Mixing up the order of methods.

This creates a dictionary pairing each image with its interpolation method: 'nearest' for 'img1' and 'bilinear' for 'img2'.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension filtering images with interpolation 'nearest' and size > 5.

Matplotlib

images = {'a': np.random.rand(3, 3), 'b': np.random.rand(7, 7), 'c': np.random.rand(10, 10)}
methods = {'a': '[1]', 'b': '[2]', 'c': '[3]'}
filtered = {k: v for k, v in images.items() if methods[k] == 'nearest' and v.shape[0] > 5}

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

Anearest

Bbilinear

Cbicubic

Dnone

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning 'nearest' to all images.

Not checking image size correctly.

Only images 'b' and 'c' have interpolation 'nearest' and size > 5. 'b' and 'c' are assigned 'nearest', 'a' is 'bilinear'.

Practice

1. Which matplotlib image interpolation method uses the closest pixel value without any smoothing?

easy

A. bilinear

B. nearest

C. bicubic

D. spline16

Solution

1. Step 1: Understand interpolation basics

   Interpolation fills in pixels when resizing images by estimating new pixel values.

2. Step 2: Identify method characteristics

   Nearest neighbor picks the closest pixel value directly, causing no smoothing.

3. Final Answer:

   nearest -> Option B

4. Quick Check:

   Nearest = closest pixel, no smoothing [OK]

Hint: Nearest means pick closest pixel, no blur or smoothing [OK]

Common Mistakes:

• Confusing bilinear or bicubic as nearest
• Thinking spline16 is the simplest method
• Assuming nearest does smoothing

2. Which of the following is the correct way to set bilinear interpolation in matplotlib.pyplot.imshow()?

easy

A. imshow(image, interpolation='bilinear')

B. imshow(image, interp='bilinear')

C. imshow(image, interpolation_method='bilinear')

D. imshow(image, method='bilinear')

Solution

1. Step 1: Recall imshow parameters

   The correct parameter name for interpolation is interpolation.

2. Step 2: Match correct syntax

   Only interpolation='bilinear' matches the official syntax.

3. Final Answer:

   imshow(image, interpolation='bilinear') -> Option A

4. Quick Check:

   Parameter name is 'interpolation' [OK]

Hint: Use 'interpolation' parameter exactly in imshow [OK]

Common Mistakes:

• Using 'interp' instead of 'interpolation'
• Using 'method' or 'interpolation_method' which are invalid
• Misspelling 'bilinear'

3. What interpolation method will produce the smoothest image when zooming in using imshow?

medium

A. bicubic

B. bilinear

C. nearest

D. none

Solution

1. Step 1: Understand interpolation smoothness

   Nearest is blocky, bilinear is smoother, bicubic is even smoother with better curves.

2. Step 2: Compare methods for zooming

   Bicubic interpolation uses cubic polynomials to create smooth transitions, best for zoomed images.

3. Final Answer:

   bicubic -> Option A

4. Quick Check:

   Bicubic = smoothest zoom [OK]

Hint: Bicubic gives smoothest zoomed images [OK]

Common Mistakes:

• Choosing nearest for smoothness
• Confusing bilinear as smoother than bicubic
• Selecting 'none' which disables interpolation

4. Given this code snippet, what is the error?

import matplotlib.pyplot as plt
import numpy as np
image = np.random.rand(10,10)
plt.imshow(image, interpolation='bicubicc')
plt.show()

medium

A. plt.show() is missing parentheses

B. Missing import for numpy

C. imshow does not accept interpolation parameter

D. Typo in interpolation method name

Solution

1. Step 1: Check interpolation parameter spelling

   The string 'bicubicc' has an extra 'c' and is not a valid method.

2. Step 2: Validate other code parts

   Imports and plt.show() are correct; imshow accepts interpolation parameter.

3. Final Answer:

   Typo in interpolation method name -> Option D

4. Quick Check:

   Correct spelling needed for interpolation [OK]

Hint: Check spelling of interpolation strings carefully [OK]

Common Mistakes:

• Assuming plt.show() missing parentheses
• Thinking numpy import is missing
• Believing imshow lacks interpolation parameter

5. You want to display a small image enlarged by 5 times with the smoothest edges possible using matplotlib. Which interpolation method should you choose and why?

hard

A. nearest, because it is fastest and simplest

B. bilinear, because it balances speed and smoothness

C. bicubic, because it produces the smoothest edges when enlarging

D. none, to avoid any interpolation artifacts

Solution

1. Step 1: Understand enlargement effects

   Enlarging a small image requires interpolation to fill new pixels smoothly.

2. Step 2: Compare interpolation methods for smooth edges

   Bicubic interpolation uses cubic polynomials to create smooth transitions and edges, best for enlarging.

3. Step 3: Evaluate other options

   Nearest is blocky, bilinear is smoother but less than bicubic, none disables interpolation causing pixelation.

4. Final Answer:

   bicubic, because it produces the smoothest edges when enlarging -> Option C

5. Quick Check:

   Enlarge + smooth edges = bicubic [OK]

Hint: For smooth large images, pick bicubic interpolation [OK]

Common Mistakes:

• Choosing nearest for quality over speed
• Thinking 'none' avoids artifacts but causes pixelation
• Assuming bilinear is as smooth as bicubic