Project 1 - LZW Compression for Text and Images

This project was developed for COMP204 – Programming Studio. It implements Lempel-Ziv-Welch (LZW) compression and decompression for text files and image files, and provides a Tkinter-based graphical user interface (GUI) to test all implemented levels.

Project Overview

The project consists of five functional levels and one GUI level:

• Level 1: LZW compression and decompression for text files
• Level 2: LZW compression and decompression for grayscale images
• Level 3: LZW compression and decompression for grayscale difference images
• Level 4: LZW compression and decompression for RGB color images
• Level 5: LZW compression and decompression for RGB difference images
• Level 6: Graphical User Interface (GUI) for running all levels

The aim of the project is to understand how dictionary-based lossless compression works, how image data can be transformed into compressible sequences, and how preprocessing methods such as difference images affect compression performance.

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Features

• Text file compression and decompression using LZW
• Grayscale image compression and decompression
• Difference-image based compression for grayscale images
• RGB channel-based compression and decompression
• Difference-image based compression for RGB images
• GUI for selecting:
  • file
  • compression level
  • compress/decompress operation
  • output path
• File size comparison support through the GUI
• Original vs decompressed file checking
• BMP-based restoration support for image levels

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File Descriptions

• lzw_core.py: Core LZW compression/decompression implementation. Includes encoding, decoding, bit-packing, padding, and binary conversion utilities.

• image_lzw_utils.py: Utility functions for packing encoded LZW codes into byte streams, unpacking them, and writing/reading custom headers for compressed image files.

• basic_image_operations.py: Basic image processing functions such as reading, writing, grayscale conversion, flattening, and reshaping arrays.

• image_tools.py: Additional helper functions for image reading and channel operations.

• level1_text.py: Implements Level 1 text compression and decompression.

• level2_gray.py: Implements grayscale image compression and decompression.

• level3_diff.py: Implements grayscale difference-image compression and decompression.

• level4_color.py: Implements RGB image compression and decompression by compressing each color channel separately.

• level5_color_diff.py: Implements RGB difference-image compression and decompression.

• level6_gui.py: Tkinter-based graphical user interface to run all levels interactively.

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Requirements

The project uses Python and the following libraries:

• Pillow

• numpy

• tkinter

Install required libraries with:

pip install pillow numpy

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How to Run

Run the GUI

cd Project1
python level6_gui.py

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Project Structure

Project1/
│
├── lzw_core.py
├── image_lzw_utils.py
├── basic_image_operations.py
├── image_tools.py
│
├── level1_text.py
├── level2_gray.py
├── level3_diff.py
├── level4_color.py
├── level5_color_diff.py
├── level6_gui.py
│
└── README.md

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Learning Outcomes

This project helped demonstrate:

• how dictionary-based compression works

• how bit-packing affects compressed file size

• how image data can be transformed for compression

• how grayscale and RGB data differ in representation

• how preprocessing techniques such as difference coding affect redundancy

• how to build a GUI for testing and demonstrating algorithms

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