Reading images (cv2.imread) in Computer Vision - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the function cv2.imread() do?

It reads an image file from your computer and loads it into memory as an array of pixels that your program can use.

beginner

What are the common flags used with cv2.imread() and what do they mean?

• cv2.IMREAD_COLOR: Loads the image in color (default).
• cv2.IMREAD_GRAYSCALE: Loads the image in black and white (grayscale).
• cv2.IMREAD_UNCHANGED: Loads the image including the alpha channel (transparency).

beginner

What type of data does cv2.imread() return?

It returns a NumPy array representing the image pixels. Each pixel has values for color channels depending on the flag used.

beginner

What happens if cv2.imread() cannot find or open the image file?

It returns None. This means the image was not loaded and you should check the file path or file existence.

beginner

Why is it important to check the result of cv2.imread() before using the image?

Because if the image failed to load, your program might crash or behave unexpectedly. Checking ensures your code handles missing files safely.

What does cv2.imread('image.jpg', cv2.IMREAD_GRAYSCALE) do?

A Saves the image to disk

B Loads the image in black and white

C Loads the image with transparency

D Loads the image in color

Using cv2.IMREAD_GRAYSCALE loads the image as a black and white (grayscale) image.

What type of object does cv2.imread() return?

A A NumPy array of pixel values

B A string with the image path

C A Python list of colors

D An integer representing image size

cv2.imread() returns a NumPy array representing the image pixels.

If cv2.imread() returns None, what does it mean?

A The image was loaded successfully

B The image is empty but loaded

C The image is corrupted but loaded

D The image file was not found or could not be opened

Returning None means the image file was not found or could not be opened.

Which flag loads an image including its transparency channel?

A cv2.IMREAD_UNCHANGED

B cv2.IMREAD_COLOR

C cv2.IMREAD_GRAYSCALE

D cv2.IMREAD_ALPHA

cv2.IMREAD_UNCHANGED loads the image including the alpha (transparency) channel.

What should you do after calling cv2.imread() before processing the image?

A Convert the image to text

B Immediately display the image

C Check if the returned value is not <code>None</code>

D Save the image again

Always check if the image loaded successfully by verifying the return is not None.

Explain how cv2.imread() works and what you need to check after using it.

Think about loading an image and what can go wrong.

Describe the difference between cv2.IMREAD_COLOR and cv2.IMREAD_GRAYSCALE flags.

Consider how images look in color vs black and white.