JPEG Encoder

JPEG Encoding with Discrete Cosine Transform, Quantisation & Run-Length Compression

JPEG Image Encoder

This repository contains a JPEG image encoder implemented in C. It takes a BMP image as input and encodes it using Discrete Cosine Transform (DCT), quantisation, and Run-Length Encoding (RLE), producing a compressed output file.

Functionality

The encoder performs the following steps:

1. Image Loading: Loads a BMP image from the specified input file using the image_load function.
2. Color Conversion: Converts the RGB color space to YCbCr.
3. DCT: Applies the Discrete Cosine Transform (DCT) on 8x8 blocks of the image using the forward_dct function.
4. Quantisation: Quantizes the DCT coefficients using predefined quantisation matrices and the quantize_block function.
5. RLE: Encodes the quantized coefficients using Run-Length Encoding (RLE).
6. File Output: Writes the encoded data to the specified output file, including a header, quantisation tables, and RLE encoded data.

Repository Structure

The repository has the following structure:

• include/: Contains header files, including encoder.h, which defines the image and encoder structures and function prototypes.
• src/: Contains the source code files.
  • jpeg_encoder.c: Implements the JPEG encoding logic, including color conversion, DCT, quantisation, and RLE. The main encoding function is jpeg_encode.
  • dct.c: Implements the Discrete Cosine Transform (DCT) and quantisation functions, including forward_dct, quantize_block, and related utility functions.
  • main.c: Contains the main function that parses command-line arguments, loads the image, performs the encoding, and saves the output.
  • utils/: Contains utility functions.
    • bitstream.c: Implements bitstream reading and writing functions (currently not used in this encoder).
    • image.c: Implements image loading and saving functions, including image_load and image_save.
• Makefile: Defines the build process for the project.
• README.md: This file, providing an overview of the project.

Building the Encoder

To build the encoder, you need a C compiler (e.g., GCC) and the make build tool.

1. Clone the repository.
2. Navigate to the repository's root directory.
3. Run the make command.

make