CSCI 3162 Digital Media - Assignment 1: Dithering
CSCI 3162: Digital Media — Assignment 1
1. Digital Images: The lecture slides describe several techniques for dithering when reducing the bit depth of images to b = 1. Write MATLAB code that generalizes those techniques to allow dithering when reducing to a bit depth b ≥ 1. Consider at least thresholding, noise dithering, and FloydSteinberg dithering. Avoid using loops where possible and do not hardcode the bit depth. Please submit one function file for each dithering approach considered. Submit your code as well as the results of processing the test images available on Brightspace for b = 2 and b = 4.
2. Differential PCM: Read in the file piano.wav using its native format (int16; use ’native’ as dataType).
- What compression rate does bzip2 achieve on the file?
- Implement the simplest predictor from the lecture slides (l = a1 = 1). Avoid loops if possible. Apply the predictor to the same data and store the resulting error values using audiowrite. What compression rate does bzip2 achieve on this file? Also give code to reconstruct the original data from the error values and test it to make sure that no information is lost.
- Now implement the next simplest predictor (l = 2; a1 = 2 and a2 = −1) and proceed as above. What compression rate that bzip2 achieve?
- Try to build a better predictor by using l > 2. Describe what you did to come up with one, and test how well it works by measuring the compression rate achieved by bzip2 on the resulting file.
Hint: Try to quadratically extrapolate the preceding values.
Instructions: Please submit your solutions on Brightspace. Submit a single archive file (e.g., .zip) with one folder per problem. Remember that: • All work you submit must be your own. • Any questions you may have should be brought up during class time or posted on the Brightspace discussion board. • You must not share your calculations, ideas, or code with anyone. • You must not make use of any code you find on the web.
