Project 4: Arith

Authors: Claire Levin (slevin12), Aya Ismail (aismai02)

Purpose:

• Implements the bitpack interface which provides several functionalities to manipulate bit fields, serving as a tool to pack multiple bit fields into a single word and also unpacking a word into multiple bit fields.

• Uses the bitpack interface to compress a given ppm image to a binary image file and/or decompress the binary image back into a ppm, with the help of some computational conversions inspired from JPEG image compression (conversion from RGB to component video space and DCT).

Acknowledgments:

• TAs: Andrew, Sam, Jian, Charlie, Dan, Tim, Randy

About Implementation:

• 40image.c: Handles command line options and calls compress40 or decomoress40 accordingly (given code by course staff)

• compress40.c: reads in a pixmap, converts the RGB pixels into scaled integers (RGB values / denominator), converts the float RGB values into component video space pixels, uses DCT to convert luma values into cosine coefficiants (a, b, c, d), quantizes the component video space values of each 2 by 2 block of pixels and packs them into a 32-bit word and writes the binary compressed image to stdout.

            reads in the packed words, unpacks each word, dequantizes 
            the unpacked values back into component videa space values, 
            convert these back into float RGB and then back to integer
            RGB values and writes the final ppm image to stdout. 
  

• bitpack.c: correctly implements bit-field operations defined in bitpack.h: determines if a number fits in a certain number of bits (signed or unsigned), if not, it raises an overflow exception, extracts a bit field from a given word, and updates a word given a bit field.

Hours: Design (problem analysis) - 10 hours Implementation (solving the problem) - 20 hours