Why OCR digitizes text from images in Computer Vision - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to load an image for OCR processing.

Computer Vision

image = cv2.imread([1])

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

A'text_image.png'

B12345

CTrue

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Using a number instead of a filename string

Passing None instead of a filename

The cv2.imread function loads an image file given its filename as a string.

2fill in blank

medium

Complete the code to convert the image to grayscale before OCR.

Computer Vision

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

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

Acv2.COLOR_BGR2RGB

Bcv2.COLOR_RGB2BGR

Ccv2.COLOR_GRAY2BGR

Dcv2.COLOR_BGR2GRAY

Attempts:

3 left

💡 Hint

Common Mistakes

Using color conversions that do not produce grayscale images

Converting to grayscale uses cv2.COLOR_BGR2GRAY to simplify the image for OCR.

3fill in blank

hard

Fix the error in the OCR text extraction line.

Computer Vision

text = pytesseract.image_to_string([1])

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

Agray_image

Bimage

Ccv2

Dpytesseract

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the original image instead of the grayscale

Passing the module name instead of an image

The OCR function should process the grayscale image, not the original color image or modules.

4fill in blank

hard

Fill both blanks to create a dictionary with word lengths greater than 3.

Computer Vision

word_lengths = {word: [1] for word in text.split() if len(word) [2] 3}

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Alen(word)

B>

C<

Dword

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong comparison operator

Storing the word instead of its length

This dictionary comprehension stores the length of each word only if the word length is greater than 3.

5fill in blank

hard

Fill all three blanks to filter words starting with 'a' and count them.

Computer Vision

filtered_words = [word[1] for word in text.split() if word[2]'a')]
count = [3](filtered_words)

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A.lower()

B.startswith(

Clen

D.endswith(

Attempts:

3 left

💡 Hint

Common Mistakes

Using endswith instead of startswith

Not converting to lowercase

Not counting the filtered list

This code filters words starting with 'a' (case-insensitive) and counts them using len().

Practice

1. Why does OCR (Optical Character Recognition) convert images of text into digital text?

easy

A. To make the text editable and searchable on computers

B. To change the image colors

C. To compress the image size

D. To create new images from text

Solution

1. Step 1: Understand OCR's main function

   OCR reads text from images and converts it into a format computers can edit and search.

2. Step 2: Identify the purpose of digitizing text

   Making text editable and searchable helps users work with written content easily on digital devices.

3. Final Answer:

   To make the text editable and searchable on computers -> Option A

4. Quick Check:

   OCR digitizes text to edit/search it [OK]

Hint: OCR turns pictures of words into editable text [OK]

Common Mistakes:

• Thinking OCR changes image colors
• Confusing OCR with image compression
• Believing OCR creates new images

2. Which of the following is the correct way to describe OCR's output?

easy

A. A new image with highlighted text

B. Editable and searchable text extracted from an image

C. A compressed version of the original image

D. A handwritten note scanned into a PDF

Solution

1. Step 1: Identify OCR output type

   OCR outputs text that can be edited and searched, not images or compressed files.

2. Step 2: Compare options to OCR output

   Only Editable and searchable text extracted from an image correctly describes OCR output as editable and searchable text.

3. Final Answer:

   Editable and searchable text extracted from an image -> Option B

4. Quick Check:

   OCR output = editable/searchable text [OK]

Hint: OCR outputs text, not images or compressed files [OK]

Common Mistakes:

• Confusing OCR output with image files
• Thinking OCR compresses images
• Assuming OCR creates PDFs

3. Consider this Python snippet using an OCR library:

import pytesseract
from PIL import Image
img = Image.open('receipt.jpg')
text = pytesseract.image_to_string(img)
print(text)

What will this code output?

medium

A. An error because 'image_to_string' is not a valid function

B. The image 'receipt.jpg' displayed on screen

C. The text content found in the image 'receipt.jpg'

D. A compressed version of 'receipt.jpg'

Solution

1. Step 1: Understand the code's purpose

   The code uses pytesseract to extract text from an image file named 'receipt.jpg'.

2. Step 2: Identify the output of image_to_string

   image_to_string returns the text found in the image, which is then printed.

3. Final Answer:

   The text content found in the image 'receipt.jpg' -> Option C

4. Quick Check:

   pytesseract.image_to_string outputs text [OK]

Hint: pytesseract.image_to_string extracts text from images [OK]

Common Mistakes:

• Thinking it displays the image
• Believing image_to_string is invalid
• Expecting image compression output

4. This code tries to extract text from an image but fails:

import pytesseract
from PIL import Image
img = Image.open('document.png')
text = pytesseract.image_to_text(img)
print(text)

What is the error and how to fix it?

medium

A. Image.open cannot open PNG files

B. Image file 'document.png' does not exist

C. Missing import for pytesseract

D. Function name is wrong; use image_to_string instead of image_to_text

Solution

1. Step 1: Identify the function error

   The function pytesseract.image_to_text does not exist; the correct function is image_to_string.

2. Step 2: Fix the function call

   Replace image_to_text with image_to_string to correctly extract text from the image.

3. Final Answer:

   Function name is wrong; use image_to_string instead of image_to_text -> Option D

4. Quick Check:

   Correct function = image_to_string [OK]

Hint: Use image_to_string, not image_to_text [OK]

Common Mistakes:

• Using wrong function name
• Assuming image file missing without checking
• Thinking PNG files can't be opened

5. You want to digitize a large collection of scanned books using OCR. Which of these steps is most important to improve OCR accuracy before digitizing?

hard

A. Enhance image quality by cleaning noise and adjusting brightness

B. Convert images to grayscale without any preprocessing

C. Resize images to very small dimensions to save space

D. Skip preprocessing and run OCR directly on raw images

Solution

1. Step 1: Understand OCR accuracy factors

   OCR works best on clear, clean images with good contrast and minimal noise.

2. Step 2: Identify preprocessing to improve OCR

   Enhancing image quality by removing noise and adjusting brightness helps OCR read text more accurately.

3. Final Answer:

   Enhance image quality by cleaning noise and adjusting brightness -> Option A

4. Quick Check:

   Better image quality = better OCR accuracy [OK]

Hint: Clean and brighten images before OCR for best results [OK]

Common Mistakes:

• Ignoring image preprocessing
• Reducing image size too much
• Assuming grayscale alone is enough