Image rotation and zoom in SciPy - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to rotate the image by 45 degrees using scipy.

SciPy

from scipy.ndimage import rotate
rotated_image = rotate(image, [1])

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

A45

B90

C30

D60

Attempts:

3 left

💡 Hint

Common Mistakes

Using radians instead of degrees.

Forgetting to import rotate from scipy.ndimage.

The rotate function takes the angle in degrees. To rotate by 45 degrees, use 45.

2fill in blank

medium

Complete the code to zoom the image by a factor of 2 using scipy.

SciPy

from scipy.ndimage import zoom
zoomed_image = zoom(image, [1])

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

A0.5

B1

C2

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using a zoom factor less than 1 to enlarge the image.

Confusing zoom factor with pixel dimensions.

The zoom function scales the image. A factor of 2 doubles the size.

3fill in blank

hard

Fix the error in the code to rotate the image without changing its shape.

SciPy

rotated_image = rotate(image, 30, [1]=False)

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

Amode

Border

Cprefilter

Dreshape

Attempts:

3 left

💡 Hint

Common Mistakes

Using mode or order instead of reshape.

Not setting reshape parameter at all.

The reshape parameter controls if the output shape changes. Setting reshape=False keeps the original shape.

4fill in blank

hard

Fill both blanks to zoom the image by 1.5 and rotate it by 90 degrees.

SciPy

zoomed_image = zoom(image, [1])
rotated_image = rotate(zoomed_image, [2])

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

A1.5

B90

C45

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up zoom factor and rotation angle.

Using 45 degrees instead of 90 for rotation.

Use 1.5 to zoom by 1.5 times and 90 to rotate by 90 degrees.

5fill in blank

hard

Fill all three blanks to rotate the image by 180 degrees, zoom by 0.75, and keep the original shape after rotation.

SciPy

rotated_image = rotate(image, [1], [2]=False)
final_image = zoom(rotated_image, [3])

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

Areshape

B180

C0.75

Dorder

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting reshape=False causes shape change.

Using zoom factor greater than 1 when shrinking is needed.

Rotate by 180 degrees, set reshape=False to keep shape, and zoom by 0.75 to reduce size.

Practice

1. What does the function scipy.ndimage.rotate do to an image?

easy

A. It adds noise to the image.

B. It turns the image by a specified angle.

C. It crops the image to a smaller size.

D. It changes the image colors.

Solution

1. Step 1: Understand the function purpose

   scipy.ndimage.rotate is designed to rotate images by a given angle in degrees.

2. Step 2: Compare options with function behavior

   Only turning or rotating the image matches the function's purpose; other options describe different image operations.

3. Final Answer:

   It turns the image by a specified angle. -> Option B

4. Quick Check:

   Rotate = Turn image [OK]

Hint: Rotate means turn image by angle [OK]

Common Mistakes:

• Confusing rotate with crop or color change
• Thinking rotate changes image size
• Assuming rotate adds effects like noise

2. Which of the following is the correct way to rotate an image array img by 45 degrees using scipy?

easy

A. scipy.ndimage.rotate(img, 45)

B. scipy.ndimage.zoom(img, 45)

C. scipy.ndimage.rotate(45, img)

D. scipy.ndimage.zoom(45, img)

Solution

1. Step 1: Check function signatures

   scipy.ndimage.rotate takes the image first, then the angle as the second argument.

2. Step 2: Validate correct argument order

   scipy.ndimage.rotate(img, 45) correctly uses rotate(img, 45). Options C and D swap arguments incorrectly, and B uses zoom instead of rotate.

3. Final Answer:

   scipy.ndimage.rotate(img, 45) -> Option A

4. Quick Check:

   rotate(image, angle) correct syntax [OK]

Hint: Image first, angle second in rotate() [OK]

Common Mistakes:

• Swapping argument order
• Using zoom instead of rotate
• Passing angle before image

3. What will be the shape of the output image after applying scipy.ndimage.zoom(img, 2) if img.shape is (100, 100)?

medium

A. (50, 50)

B. (100, 100)

C. (200, 200)

D. (100, 200)

Solution

1. Step 1: Understand zoom factor effect

   A zoom factor of 2 doubles the size of each dimension of the image.

2. Step 2: Calculate new shape

   Original shape is (100, 100). Doubling each dimension gives (200, 200).

3. Final Answer:

   (200, 200) -> Option C

4. Quick Check:

   Zoom 2x doubles shape [OK]

Hint: Zoom factor multiplies each dimension [OK]

Common Mistakes:

• Confusing zoom with cropping
• Thinking zoom keeps shape same
• Mixing width and height dimensions

4. You run this code but get an error:

scipy.ndimage.rotate(45, img)

What is the problem?

medium

A. The image should be the first argument.

B. The angle should be the first argument.

C. The rotate function does not accept two arguments.

D. The angle must be in radians, not degrees.

Solution

1. Step 1: Check argument order for rotate()

   scipy.ndimage.rotate expects the image array as the first argument, then the angle.

2. Step 2: Identify error cause

   Passing angle first and image second causes a type error because the function tries to treat the number as an array.

3. Final Answer:

   The image should be the first argument. -> Option A

4. Quick Check:

   Image first, angle second in rotate() [OK]

Hint: Image must come before angle in rotate() [OK]

Common Mistakes:

• Swapping argument order
• Assuming angle must be radians
• Thinking rotate takes only one argument

5. You want to rotate an image by 90 degrees and then zoom it to half its size. Which code sequence correctly does this?

hard

A. rotated = scipy.ndimage.rotate(img, 0.5)
zoomed = scipy.ndimage.zoom(rotated, 90)

B. zoomed = scipy.ndimage.zoom(img, 0.5)
rotated = scipy.ndimage.rotate(zoomed, 90)

C. zoomed = scipy.ndimage.zoom(img, 90)
rotated = scipy.ndimage.rotate(zoomed, 0.5)

D. rotated = scipy.ndimage.rotate(img, 90)
zoomed = scipy.ndimage.zoom(rotated, 0.5)

Solution

1. Step 1: Understand operation order

   First rotate by 90 degrees, then zoom by 0.5 to reduce size by half.

2. Step 2: Check code correctness

   rotated = scipy.ndimage.rotate(img, 90)
   zoomed = scipy.ndimage.zoom(rotated, 0.5)

   correctly rotates img by 90, then zooms the rotated image by 0.5. Other options mix argument order or use wrong values.

3. Final Answer:

   rotated = scipy.ndimage.rotate(img, 90) zoomed = scipy.ndimage.zoom(rotated, 0.5) -> Option D

4. Quick Check:

   Rotate 90°, then zoom 0.5 [OK]

Hint: Rotate first, then zoom with correct factors [OK]

Common Mistakes:

• Swapping zoom and rotate order
• Using zoom factor as angle
• Passing wrong argument order