Image & Movie Compression W5

Question 1

Why are images and movies good candidates for compression?

Answer 1

They contain lots of redundancy; neighboring pixels or frames are often similar.

Question 2

What is run-length encoding (RLE)?

Answer 2

A method that stores the number of identical pixels in a run instead of each pixel.

Question 3

What is lossy compression?

Answer 3

Compression that removes less important data (e.g., fine image detail) to save space.

Question 4

How does JPEG compression work?

Answer 4

Uses a mix of lossy techniques (like Fourier transforms to remove detail) and lossless methods (like RLE).

Question 5

What is the difference between BMP, JPG, and PNG formats?

Answer 5

BMP: Uncompressed

JPG: Lossy and lossless compression

PNG: Lossless compression

Question 6

Why can lossy compression sometimes increase file size?

Answer 6

For simple images, the overhead of compression algorithms may outweigh savings.

Question 7

Can you recover the original BMP image from a PNG file?

Answer 7

Yes, because PNG is lossless.

Question 8

Can you recover the original BMP from a JPG file?

Answer 8

No, because JPG is lossy.

Question 9

Why is movie compression especially effective?

Answer 9

Because each frame is similar to the next, making differences predictable and compressible.